Surface area increases a lot more than just friction. Attracative forces. Stickiness and adhesion. etc etc. Anyway, drag cars have larger tyres and lower pressures to increase surface area and allow more power to enter the ground.I'm actually not sure why friction is taught the way it is. It is incorrect.
@Marcin J. A few cars have larger rear disc diameters than the front. BMW 330 for example. More than just the disc diameter determines the brake torque, and obviously hydraulic pressure is also less on the rear with smaller caliper pistons. But rear discs are always thinner as they have less heat to absorb.
Such a great explanation. You make it so intuitive to understand but at the same time keep it technical enough to make sure no detail is missed. Great stuff mate!
great video. I engineered the braking system on an FSAE car a while back and this reflects what I learned through doing that. It's worth mentioning how different caliper and master cylinder piston sizes can also have an effect on braking forces. Pressure equals force divided by area, so changing the total area of the various pistons in a given hydraulic loop will change how much hydraulic pressure and force at the caliper will result from a given pedal input force. This is also impacted by pedal ratio, brake bias, rotor diameter, etc. So you can have a car with equal-sized front and rear rotors, but bigger calipers on the front, and the car will still have an overall front-biased braking system (see the Porsche 911 as an example of this)
Please send this simple information to Yamaha Motorcycle corporate offices ...they seem very slow on the uptake....someone there just year after year fails to "get it"
The tendency for a car to go straight when you brake is why about the most important thing an anti-skid school teaches you is letting go of the brakes when this happens (and yes, even ABS can't always help there). Without this, many instinctively 'freeze' on the brake when the car no longer reacts as expected, thus losing the chance to correct course. By changing that default reaction, you open more options for a potential better outcome in emergencies. I absolutely *love* how this is explained here.
one important hing about disc diameter: heat dissipation isn't really a big factor here, the brakes almost always heat up more quickly than they cool down and while a larger brake has more surface area to loose heat over, that difference isn't significant. what is significant is the larger mass of a larger brake disc. A larger mass of anything can absorb more energy before its absolute temperature increases to the critical limit of the material, and since we're not constantly braking, loosing heat slowly is ok, on the other hand, heating up quickly is very much an issue we worry about.
I already knew why the front were larger but still clicked because I knew you'd breakdown and deliver even more information for better understanding. Good thing I did! Everythingfrom brake bias on was new to me, never would have guessed that there were electronic brake bias-ers. Keep delivering these HQ vids man you have a great way of divulging lots of important info in digestable and understandable formats
Thanks for another interesting video. 😊 F=µN doesn't apply to viscoelastic friction, and is generally a poor friction model. The EBD devices are great. A common failure is the linkage in the rear suspension - a good thing to check if your car is getting older.
Very interesting to see. My 1991 Honda Beat has slightly more rear brake than front, which surprised me. Especially with both being single piston unventilated disc brakes.
No words to explain my excitement I wish i had this guy as my teacher in school I would have became an Auto engineer. What a wonderful opportunity TH-cam is giving us to reach this kind of master teacher Thank You So Much Sir I'm grateful to TH-cam algorithm
Everytime I watch one of your videos I learn 2 things : - The Content in the video - I'm literally at the top of the iceberg and there's so much knowledge to be acquired.
Excellent explanation - thank you. In the late sixties, I used to have the van version of the Morris Mini. It was pretty light in the rear end, and not even a pressure reduction valve for the rear brakes. Under heavy breaking (yeah, I was young and stupid) I put that thing sideways a fair number of times. On the plus side, it was great for handbrake turns.
As usual, you covered everything important we need to understand about automobile brakes, and illustrated them perfectly. I am a visual learner, have always been, and understand concepts more completely with visual representations of the theory. Thank you! The Brake Biasing technology was something I had completely forgot about. Its no wonder you have over 800K subscribers!
Really nice video and explained everything clearly to everyone. Other channels regarding changing tyre width and changing caliper size looks stupid now after this.
On your last video about bigger brakes not being better I read a comment about bigger brakes having more leverage, completely ignoring that even tiny brakes have enough force to lock the wheels, And ignoring the fact that with smaller brakes you can fit smaller (and lighter) wheels and low profile tires that require less braking force, resulting in cooler brakes, better pad life etc win win
It's not the first time he's not made that distinction. You remember he made a video earlier about how bigger breaks don't stop you faster, and then went on about how they're not needed. His perspective is that he is only talking about regular street cars, small European ones at that, so he tends to ignore performance aspects down to the point of saying things don't matter that do matter when you get to those levels.
@@potatopobobot4231 probably... But to be honest I didn't even watch all of this one. Lol Like most things in life, things tend to be application specific when you want to get down to the details. In the applications I'm interested in are so different from what he's describing that sometimes it's not worth watching. For example, with the street tires he's talking about going to a wider tire he isn't changing the coefficient of friction. But I know if I'm going to a wider tire I'm also going to get a much stickier tire. So the coefficient of friction between the tire and the road would be dramatically different. So again I can just kind of ignore what he's saying there. Or in the case of my street car, I actually use a rear brake that is the same diameter (but not the same width) as my front brakes. But that's because that application is a large station wagon with electronically controlled dynamic brake bias that allows the car to use maximum rear braking before engaging the fronts more... So by decreasing the weight transfer to the front with my car being much lower than stock and my antidive being modified in my suspension, I can now use a lot more rear brake because there's more weight in the back of a wagon to begin with. So while weight is transferring forward and providing more pressure on the front wheels, all of this is moot. But of course that doesn't apply to any of the stuff he's showing here because it's very application specific. You would have to have a vehicle that has a large amount of weight on the rear, lower to the ground, with atypical suspension geometry and electronically controlled brake bias... That's very specific.
@@TravisFabel Mr. Fable, We would like to see your explanations in your next video. I don't doubt anyone's expertise, but I'm personally (guilty through personal experience) turned off by hints of arrogance. Fortunately, for me, I learned that sitting in comfort taking on air of superiority is detrimental on the whole. We could all benefit if you could "start from the beginning".
Philosophy... This is philosophy... Every child, past present & future, should see this video - Every year of their lives... The world is a better place because of this video.
Excellent video and explanation! The only thing to add is that the reason why understeer is more predictable is that most people, when going around a corner too fast and experiencing understeer, will apply the brakes. This gives the front tyres more grip, allowing the car to go in the direction they are pointing - ie. around the corner.
this only works if you brake hard enough to engage ABS. Otherwise a tire already at the limit (understeering) cannot provide any more force (braking). to regain traction you just lift the throttle, but of course most people won't have this instinct.
So that's what those braking power regulators are... This channel is an excellent source of knowledge! But this made me thinking about my '91 Skoda Favorit I use for LONG distance tourism. I swapped the original unventilated 230mm front discs with ventilated 256mm Kia discs controlled by Mondeo brake calipers, and yes, it skids on the dry tarmac easily now, which is suboptimal :) But then they didn't even catch a sweat going down the Transalpina pass, which is a nice tradeoff. But I left both the regulators unchanged, and I didn't change the rear drum brakes. Car is most of the time loaded quite heavily at the back with the camping stuff etc., so basically I should A) get rid of the bigger brakes in front? B) replace the regulators somehow finding the fitting ones C) swap rear brakes for the discs at least (Polo 6n2 fit AFAIK) D) do both B and C?
As a 1990 MKII MR2 Turbo owner I have to emphasize “Usually” larger. This is true of my 1994 Celica Turbo and my 1993 Soarer GT-T. However, the front and rear discs and pads are nearly identical in size on my early MR2. Later MKII Turbos got a big front brake upgrade with dual piston calipers from factory. Looking at your 1987, I can see that your brake system is very similar to the system on my 1990. Great video as usual!
I have a 1993 Citroen ZX Volcane, and the front and rear brake discs are identical in diameter too. Although the rear ones arent ventillated and the pads are smaller. Weird setup.
@@negativeindustrial yes it is bertone. it might look dull on the outside, but i am really fond of the interior (i have it with leather seats as well) and the single wiper on the front windshield just reminds me of DTM racing haha. It is very fun due to the manufacturer pushing and tilting the engine backwards to the firewall as much as they could so the balance is better. Also it has pasive rear wheel steering which is truly noticable under spirited driving. I once could keep up with a car with twice as much power on a short racetrack with lot of turns.
Amazing sir!! Its a great explanation to your last video about braking in which you claimed that surface area doesn't count and that got so much people confused.
OH MY KANSEI DORIFTO!! Thank you so much!!! This topic has always eluded me, and I never really got why brake bias was that important, especially in endurance or GT racing. This video is beautiful!
Great Video! Explained in common terms without losing the science behind it. Regarding getting surprised by oversteer, i did experience this in a front wheel city car. Went into an exit of an interstate with about 100km/h bout an 180° turn with rather large radius. Was slowing down because of a car infront of me. (no real emergency breaking or stuff like that but from 100 - 70 over maybe 5 seconds) Suddently i realize i dont have to keep the steering wheel turned in like i did seconds before.... then i even had to counter steer... that is when i noticed the rear end of the car has gotten so light, i was actually drifting it *rolf. Drifiting in a 54PS FWD Fiat Punto. Since it happened so gradually, it was totally cool and controlled. When i went off the break, the car came back to neutral within an instant.
Could you make a video about 'drifting'? What happens during a drift maneuver, how camber, toe, caster angles, sway bars, suspension stiffnesses and tires act during a corner in countersteer, and how they are usually set in a drift car....also the differences between a drift and a conventional (or racing) suspension settings. I know it's not an easy and simple topic, but I think you're the best person on TH-cam that could explain these things in a precise and clear way. Thank you
According to Google: “Will wider wheels and tires affect your ability to brake and accelerate? That's an easy one to answer. Yes, those wider wheels will help you brake harder and take off faster. Wider wheels provide more traction and create higher acceleration.” Your explanation as to why wider tires won’t help is purely theoretical but in practice it does help a bit to have wider tires. 👍🏼 The rest of the video is great. Thanks for explaining. 😊
th-cam.com/video/CyH5xOcsXxs/w-d-xo.html I never said wider tires don't do anything. I said that increasing the front surface area during braking isn't relevant.
Another great video. Thanks for doing such an interesting and educational clips. One thing to point though is that in many modern cars and particularly Toyota hybrids rear brake pads wear faster than front one as a result of ebd and the fact that in some stopping situations rear brakes are engaged while front ones are still off as the cars relays on regenerative braking plus the traction control constantly applies brake force in turns. 👍
This was the best video I've seen about Electronic Brakeforce Distribution! Thanks for teaching us so many fun and useful things! I've added this video to my favorites. 😎👍🚗🚙
On my car (Holden VE Commodore), the rears are larger diameter than fronts, but the front has more friction surface area than rear. I would say that is because of the handbrake drum design taking up more area, making the overall rotor diameter larger. I have since changed this with a police pack upgrade, using the Chevy Caprice PPV front brakes, changing the front rotors from 298mm to 345mm and from 2 piston to 1 piston per caliper. Definitely stops a lot better now. I know of one other car with this style setup (Toyota 200 series Lancruiser) I've also noticed, as a mechanic, a lot of cars, mainly cars fitted with EBD and from around 2005 onwards, they tend to wear out the rear brakes a lot quicker than fronts too.
I have a VF v8 and went with the 345 rotors but Brembo calipers from the caddilac cts-v iirc. Only because I couldn't get the steel calipers in Australia and the brembos were the same price. It kinda sucks you can only buy DBA rotors for it. Tiny vs the VF gts-r at 410mm rotors though!
I swear I will never fully understand how understeer is easier or less terrifying than oversteer especially in a FWD vehicle. Got into a argument with a tire review channel once over this in fact.
One VERY important thing to note here is the chaps comment about ABS. Modern cars fool you into thinking you're a much better driver than you actually are. @10:30. I remember a 1 - Series I had on hire, and switching off the Traction Control made a bigger difference than I could have ever imagined. Completely exposed my lack of skill behind the wheel.
I personally think it's not so much a lack of skill as the fact that most new cars are developed and set up around traction control being enabled. If you take an older fully analog car you might discover that you're skills aren't poor at all.
@@d4a i disagree with this one or at least in this form maybe if you unfold it more. However i know a car which can not brake in a straight line straight without abs but this is more the exception than the rule. Also there is an aspect that more powerful cars especially with electric engines (including hybrids) "needs" traction control. It is hard even for experienced drivers to handle the instantaneous torque and if you release the pedal you (can) have the same amount in the "opposite direction". In the recent (G2x) BMW cars in sport mode you can "drift" (at least in snow) with full throttle change direction only with steering. So i completely agree that "Modern cars fool you into thinking you're a much better driver than you actually are"
@@d4a Maybe in my case a lack of practice certainly. I don't make a habit of putting my car in positions where I think I am going to bend it so never get the chance to practice what might be needed if the proverbial ever does meet the fan. Or.............maybe I have but the car has fooled me into thinking my application of throttle brakes and steering were reasonable ones?
This friction thing. I know a few of those formulas and remember some from things physics in school. Now some context from "MY" POV. Surface area does matter in the real world and here is why. Consider the illustration at 02:45. Imagine they are little hooks grabbing valleys and troughs in the road surface. The amount of force is spread across each little hook and it's easy to imagine one single hook being overwhelmed by force and heat and breaking itself and therefore breaking traction. More surface area means more hooks and less load per hook. That's what happens with a tyre - bits of it break off, hence they wear out. Discuss. Very useful series of videos though. All of them. Strangely enough, more context. 08:45. The subject of bigger brakes is applies here too, (I remember this guys video about it) and he says here that bigger brake capacity can absorb more heat. In a one off you'll not notice any difference but as bigger brakes can dissipate more energy, in the real world with repeated stops they can fade less quickly and hence stop you more quickly. Great to learn about the theory behind all of this though.
you forgot to add "*in ideal world" in part about friction, in reality everybody knows that wider tire = more friction and better grip, as we don't live in perfect world and equation you showed is true only till some point, where increasing mass doesn't increase friction in linear way anymore
Btw nice explanation with Mazda i have a cx-3 and last year i changed front brake pads, i wanted to change rear omes this year but my mechanic said they are almost brand new. So the 80%/20% braking force is so true
Great channel, great videos! Just to clarify, there’s no ‘weight transfer’ in breaking, but a torque moment (tendency to rotate about the front wheel contact point with the ground) So, yes there’s higher normal load on the front tires due to this moment, but the CG is still fixed, there is NO weight transfer!
I love your channel and the way you explain complex subjects in a simple way that anyone can understand. It is one of the hallmarks of truly mastering a subject. That said, I'm pretty sure the CX-30 comes standard with AWD.
Simple layman terms summary: Because when you brake the vehicle's weight shifts forward so having equal size brakes doesn't make you stop any better. They can be a bit smaller to save a little weight.
Amazing my friend. Wonderful information. As an automotive service advisor of 24 years, you even taught me something to help me guide my customers during sales. Awesome! Now, if by commenting I don't get those phishing 'you just won' youtube alerts I usually get when commenting on your vids my visit will be complete! LOL😂
On a motorbike and bicycle you will always perform this biasing thing automatically. You can really feel, how applying more brakes on the front or rear tire will impact your overall braking performance. And yeah, the rear tire will always lock first. But because you know to never break hard while cornering, this will never be a problem.
I'm concerned about your comment. Frankly, you absolutely have to consider rear wheel locking while braking in a straight line. I believe most fatal accidents occur from failure to use the front brake. Under emergency braking almost 90 percent of the braking should be done by the front. If you need to practice, go to and empty parking lot and practice safely. Learn how to stop correctly.
Please keep doing these excellent videos! I like to understand how things really work, and I love the detailed explanation you do about everything in your videos. Congratulations and keep up with your excellent work. Cheers! 😉🥂✨
If you do not (yet) work in some kind of school or university as a teacher, you definitely should! You have so much fluency in the way you are passing a knowledge to the audience. God bless you, and don't ever stop what you are doing. 🙂
Another good reason to have a larger rear diameter disc (despite perhaps having a lower mass rear disc) is for cars using a disc parking brake. Most cars these days use mini drum P-brakes inside the disc hat, but for a long time the hydraulic rear caliper was actuated mechanically for the P-brake. Disc brakes make poor P-brakes due to their smaller friction surface area compared to drums, and the need for high application pressures that cables and levers couldn't provide. So having more brake torque from a larger diameter gave them a little help.
Very interesting. Now I know as a fact that my old Vitara had a leaver indicating the proportional valve how much weight is on the rear suspension and so change the proportion accordingly....
In trucks, the rear rotors are often larger in diameter than the fronts. The front brakes will be thicker with more mass and larger calipers, but the rear brakes need to be strong due to towing requirements.
Great video as usual. Could you do a video on the best/easiest/most serviceable cars of the last 20 years (ish)? I’d love to know which manufacturers and models are designed with the humble mechanic in mind!
I didn't know about EBD. The way you explained it, it sounds like an inverted electronic traction control system. i.e. it maximizes tire friction whereas the latter maximizes traction. neat!
Great channel, good job. I've been following for a long time. Regarding the brakes - all my previous cars were as you say but the current car has 345mm front discs and 350mm rear discs, both ventilated (Dodge charger police version). I was surprised myself when I changed tires for the first time.
@@d4a It's 2011 fleet car (Called the police version in the US). This particular example was never used by the police. I brought him to Poland a few years ago.
Coefficient of friction also decreases with the normal force. That's why a wider tyre has more grip than a narrow one, all within some limits where tyre tread is homogeneus due tyre pressure.
Great Video as usual! I'm always impressed how much I learn about a topic which I thought I knew completely😅 Little thing I find missing is that mechanical break force distribution was/is a thing since the 60's. Just some levers on the rear suspension opening and closing the valve to the rear breaks 👍🏻
I just bought a ford puma. Another compensation to add some braking percentage back to the rear is tyre pressures 35psi front, 31psi rear. First car I had that differentiates tyre pressure.
Something that has been puzzling me for some time. I have two front wheel drive vehicles, a 1990 SAAB 900, and a 2011 VW sportwagen. BOTH of these vehicles consume rear brake pads about 30K to 40K miles, but I have NEVER had to change the front pads on either one of them! I've had the SAAB 900 since 2004, and the Volkswagen since it was new. I also have a 2000 Chevy van, a rear wheel drive vehicle. It has needed front pads twice since I purchased it in 2008, but has never needed a set of rear drum shoes. I primarily use the van for work, and it gets city driving, along with towing a camping trailer. I am typically a light, early, easy braker, My wife drives the VW mostly, and has never driven the SAAB. she is more of a late, harder braker, so I'm not thinking it's driving habits that make these two vehicles burn rear pads more often. The VW is new enough to have EBD, whereas the SAAB has an older TEVES Mark III ABS system. The only reason I can come up with is that the SAAB and the VW are both European cars, and European cars must have a bit more bias to the rear brakes than American ones do. Does anyone have any thoughts on this? sorta goes opposite of what he says in the video, and what I would expect
great vid as always. I always enjoy watching your explanations even if its on something I'm already familiar with. At worst I become more confident in what I already knew, best case scenario I learn something I didn't realize I didn't! Hope you're getting some time in the dirt on the new Honda as well
Another consideration: even on purely hydraulic systems without electronics, front/rear brake bias doesn't have to be fixed by a proportioning valve in the front, either. I believe even the Mk4 Golf had EBD, but earlier Golfs (at least as far back as Mk2, on some models) went for a different approach, a proportioning valve mounted at the *rear*, attached to the torsion beam. As the rear suspension unloads due to weight transfer, the proportioning valve is adjusted to reduce rear braking force. Approaches like this - especially once Mk4s had EBD, but even before that - also let you start out with an extreme rear bias under gentle braking to reduce weight transfer and make the vehicle feel more stable, and as brake force increases, shift braking forward for maximum braking force. (I want to say my Mk4 Golf actually wore out the rear brakes first, because most of the braking it saw was quite gentle.)
It's interesting that as a mechanic for a dealership I've seen how the cars deteriorate from oil service to oil service. Ive always seen the rear brakes need to be replaced as early as 40k miles but front ones as early as 80k. I've never seen a car's first set of brakes wear faster in the front. I'm not disagreeing with the facts you've presented, but it should be noted.
I made a mistake recently. I searched Google for the answer to "why do some brake systems use 1/4" line to the rear brakes?", and I was inundated with vast quantities of the most clueless replies in countless forums. It almost made my brain explode. I "think" I know and understand the answer to the question, but I'd really love a well-researched definitive answer, if that's something you're inclined to tackle and you think your viewers would appreciate. You'll probably see some of the more common clueless answers appended as replies to this comment... 😂
I like your videos, very good content. I need to say my objection to ABS because is not for shorter brake distance, you need it because if you slide no steering will help you. And someone already says F=µN doesn't work for rubber because is viscoelastic...
hi mate, great channel! Really helped me understand complex topics quickly.... Please do a video on oil pressure(low oil pressure light) especially on boosted applications
dynamic stability control also requires more rear brake as the rear brakes are utilised to arrest wheel spin and aid in stability while hard cornering and can over heat rear brakes even without braking. did a v8 conversion and found the brake bias was fine until I upgraded the rear differential to a ford 9", with the extra mass of the heaver rear end more rear brake was required, I believe it was more the inertia of the heaver rotating mass.
I just gonna left this piece of knowledge here. After getting a ton of opinion and information on the subject, I arrived to the conclusion that: The normal car is made for bad drivers. Yes, that is the true, and makes perfect sense when you think about it. Most people are not out there to be a better driver, some find take the driving license test and school a chore. Not that is not annoying to do. But overall, most people driving do not seek to improve their driving skills, they just wanna get from place A to B in a safe, fast and convenient way.
th-cam.com/video/CyH5xOcsXxs/w-d-xo.html
Please watch this before commenting how and where surface area matters
Mahindra xuv 500
Is it true that wider ones can handle more pressure force? So more grip or more pressure for the same grip??
There is one exception of this rule. Cadillac STS-V has bigger brake disks in the rear thanks those in the front. 🤷♂️
Surface area increases a lot more than just friction. Attracative forces. Stickiness and adhesion. etc etc. Anyway, drag cars have larger tyres and lower pressures to increase surface area and allow more power to enter the ground.I'm actually not sure why friction is taught the way it is. It is incorrect.
@Marcin J. A few cars have larger rear disc diameters than the front. BMW 330 for example. More than just the disc diameter determines the brake torque, and obviously hydraulic pressure is also less on the rear with smaller caliper pistons. But rear discs are always thinner as they have less heat to absorb.
Such a great explanation. You make it so intuitive to understand but at the same time keep it technical enough to make sure no detail is missed. Great stuff mate!
Very well said!
Read a book....
@@ShainAndrews youtube: am i a joke to you?
great video. I engineered the braking system on an FSAE car a while back and this reflects what I learned through doing that. It's worth mentioning how different caliper and master cylinder piston sizes can also have an effect on braking forces. Pressure equals force divided by area, so changing the total area of the various pistons in a given hydraulic loop will change how much hydraulic pressure and force at the caliper will result from a given pedal input force. This is also impacted by pedal ratio, brake bias, rotor diameter, etc. So you can have a car with equal-sized front and rear rotors, but bigger calipers on the front, and the car will still have an overall front-biased braking system (see the Porsche 911 as an example of this)
Please send this simple information to Yamaha Motorcycle corporate offices ...they seem very slow on the uptake....someone there just year after year fails to "get it"
Thank you for your passion in making these videos. You always deliver a great and simple explanation. Keep it up! ❤
The tendency for a car to go straight when you brake is why about the most important thing an anti-skid school teaches you is letting go of the brakes when this happens (and yes, even ABS can't always help there). Without this, many instinctively 'freeze' on the brake when the car no longer reacts as expected, thus losing the chance to correct course. By changing that default reaction, you open more options for a potential better outcome in emergencies. I absolutely *love* how this is explained here.
casually continuing to provide the most well-informed explanations of car things on youtube is such a flex
one important hing about disc diameter:
heat dissipation isn't really a big factor here, the brakes almost always heat up more quickly than they cool down and while a larger brake has more surface area to loose heat over, that difference isn't significant.
what is significant is the larger mass of a larger brake disc. A larger mass of anything can absorb more energy before its absolute temperature increases to the critical limit of the material, and since we're not constantly braking, loosing heat slowly is ok, on the other hand, heating up quickly is very much an issue we worry about.
Sir, I have never known of any source which explains mechanics as efficiently as you do! Thank you!
I already knew why the front were larger but still clicked because I knew you'd breakdown and deliver even more information for better understanding. Good thing I did! Everythingfrom brake bias on was new to me, never would have guessed that there were electronic brake bias-ers. Keep delivering these HQ vids man you have a great way of divulging lots of important info in digestable and understandable formats
Thanks for another interesting video. 😊
F=µN doesn't apply to viscoelastic friction, and is generally a poor friction model.
The EBD devices are great. A common failure is the linkage in the rear suspension - a good thing to check if your car is getting older.
F=µN only apply to ideal body in school assignments.
Amazing how you make these concepts very simple to understand. Even for a non native English speaker like me. Thank you!
Very interesting to see. My 1991 Honda Beat has slightly more rear brake than front, which surprised me. Especially with both being single piston unventilated disc brakes.
sir thats my dream car
d4a always has the best explanations. a 6 y/o could understand this man's visualizations
No words to explain my excitement
I wish i had this guy as my teacher in school
I would have became an Auto engineer.
What a wonderful opportunity TH-cam is giving us to reach this kind of master teacher
Thank You So Much Sir
I'm grateful to TH-cam algorithm
I start watching your videos and before I know it I am at the end. They never get boring and are informative throughout. Excellent work.
Everytime I watch one of your videos I learn 2 things :
- The Content in the video
- I'm literally at the top of the iceberg and there's so much knowledge to be acquired.
Excellent explanation - thank you. In the late sixties, I used to have the van version of the Morris Mini. It was pretty light in the rear end, and not even a pressure reduction valve for the rear brakes. Under heavy breaking (yeah, I was young and stupid) I put that thing sideways a fair number of times. On the plus side, it was great for handbrake turns.
As usual, you covered everything important we need to understand about automobile brakes, and illustrated them perfectly. I am a visual learner, have always been, and understand concepts more completely with visual representations of the theory. Thank you! The Brake Biasing technology was something I had completely forgot about. Its no wonder you have over 800K subscribers!
Really nice video and explained everything clearly to everyone. Other channels regarding changing tyre width and changing caliper size looks stupid now after this.
On your last video about bigger brakes not being better I read a comment about bigger brakes having more leverage, completely ignoring that even tiny brakes have enough force to lock the wheels, And ignoring the fact that with smaller brakes you can fit smaller (and lighter) wheels and low profile tires that require less braking force, resulting in cooler brakes, better pad life etc win win
Holy crap! I'm a BIG nerd about cars, but somehow I didn't know that EBD's even exist until today. You taught me something new today!
In short, they need to be bigger in front to take more punishment, not because they "grab harder." Great content as usual!
It's not the first time he's not made that distinction.
You remember he made a video earlier about how bigger breaks don't stop you faster, and then went on about how they're not needed.
His perspective is that he is only talking about regular street cars, small European ones at that, so he tends to ignore performance aspects down to the point of saying things don't matter that do matter when you get to those levels.
@@TravisFabel did u even watch that whole video ur referencing?
@@potatopobobot4231 probably... But to be honest I didn't even watch all of this one. Lol
Like most things in life, things tend to be application specific when you want to get down to the details. In the applications I'm interested in are so different from what he's describing that sometimes it's not worth watching.
For example, with the street tires he's talking about going to a wider tire he isn't changing the coefficient of friction. But I know if I'm going to a wider tire I'm also going to get a much stickier tire. So the coefficient of friction between the tire and the road would be dramatically different. So again I can just kind of ignore what he's saying there.
Or in the case of my street car, I actually use a rear brake that is the same diameter (but not the same width) as my front brakes. But that's because that application is a large station wagon with electronically controlled dynamic brake bias that allows the car to use maximum rear braking before engaging the fronts more... So by decreasing the weight transfer to the front with my car being much lower than stock and my antidive being modified in my suspension, I can now use a lot more rear brake because there's more weight in the back of a wagon to begin with. So while weight is transferring forward and providing more pressure on the front wheels, all of this is moot. But of course that doesn't apply to any of the stuff he's showing here because it's very application specific. You would have to have a vehicle that has a large amount of weight on the rear, lower to the ground, with atypical suspension geometry and electronically controlled brake bias... That's very specific.
They grab harder too. The braking force they are producing is much higher since most of the weight is there and friction force is larger.
@@TravisFabel Mr. Fable,
We would like to see your explanations in your next video. I don't doubt anyone's expertise, but I'm personally (guilty through personal experience) turned off by hints of arrogance. Fortunately, for me, I learned that sitting in comfort taking on air of superiority is detrimental on the whole.
We could all benefit if you could "start from the beginning".
I had to explain this to a friend sometime ago, but this video helped me understand the concept even further. Great videos as always
Cheers. Something I thought was so simple and basic, yet I managed to learn more about it.
Honestly he just made this video to show off that awesome MR2 Project.
I know they are hard to work on but i have always loved them
Philosophy... This is philosophy...
Every child, past present & future, should see this video - Every year of their lives...
The world is a better place because of this video.
Excellent video and explanation!
The only thing to add is that the reason why understeer is more predictable is that most people, when going around a corner too fast and experiencing understeer, will apply the brakes. This gives the front tyres more grip, allowing the car to go in the direction they are pointing - ie. around the corner.
this only works if you brake hard enough to engage ABS. Otherwise a tire already at the limit (understeering) cannot provide any more force (braking). to regain traction you just lift the throttle, but of course most people won't have this instinct.
I appreciate you refining your accent for us Americans some TH-camrs I can’t watch for such reason
This channel is incredible! Best explanation I have seen about brakes ever
Thanks a lot for this, keep doing this fenomenal job
So that's what those braking power regulators are... This channel is an excellent source of knowledge! But this made me thinking about my '91 Skoda Favorit I use for LONG distance tourism. I swapped the original unventilated 230mm front discs with ventilated 256mm Kia discs controlled by Mondeo brake calipers, and yes, it skids on the dry tarmac easily now, which is suboptimal :) But then they didn't even catch a sweat going down the Transalpina pass, which is a nice tradeoff. But I left both the regulators unchanged, and I didn't change the rear drum brakes. Car is most of the time loaded quite heavily at the back with the camping stuff etc., so basically I should A) get rid of the bigger brakes in front? B) replace the regulators somehow finding the fitting ones C) swap rear brakes for the discs at least (Polo 6n2 fit AFAIK) D) do both B and C?
Amazing teacher and really a must watch for anyone interested in cars, automotive engineer, or mechanics
As a 1990 MKII MR2 Turbo owner I have to emphasize “Usually” larger. This is true of my 1994 Celica Turbo and my 1993 Soarer GT-T. However, the front and rear discs and pads are nearly identical in size on my early MR2. Later MKII Turbos got a big front brake upgrade with dual piston calipers from factory.
Looking at your 1987, I can see that your brake system is very similar to the system on my 1990. Great video as usual!
I have a 1993 Citroen ZX Volcane, and the front and rear brake discs are identical in diameter too. Although the rear ones arent ventillated and the pads are smaller. Weird setup.
@@TC-zf1ji
Nice troll 👍
@@TiborSzarvas
Cool car. Bertone designed? We didn’t get them in my country. Is it fun to drive?
@@negativeindustrial yes it is bertone. it might look dull on the outside, but i am really fond of the interior (i have it with leather seats as well) and the single wiper on the front windshield just reminds me of DTM racing haha. It is very fun due to the manufacturer pushing and tilting the engine backwards to the firewall as much as they could so the balance is better. Also it has pasive rear wheel steering which is truly noticable under spirited driving. I once could keep up with a car with twice as much power on a short racetrack with lot of turns.
@@TiborSzarvas
That’s what’s up. Nice car, sir.
Amazing sir!!
Its a great explanation to your last video about braking in which you claimed that surface area doesn't count and that got so much people confused.
OH MY KANSEI DORIFTO!! Thank you so much!!! This topic has always eluded me, and I never really got why brake bias was that important, especially in endurance or GT racing. This video is beautiful!
Thank you so much for your support. I sincerely appreciate it.
Great Video! Explained in common terms without losing the science behind it.
Regarding getting surprised by oversteer, i did experience this in a front wheel city car. Went into an exit of an interstate with about 100km/h bout an 180° turn with rather large radius. Was slowing down because of a car infront of me. (no real emergency breaking or stuff like that but from 100 - 70 over maybe 5 seconds) Suddently i realize i dont have to keep the steering wheel turned in like i did seconds before.... then i even had to counter steer... that is when i noticed the rear end of the car has gotten so light, i was actually drifting it *rolf. Drifiting in a 54PS FWD Fiat Punto. Since it happened so gradually, it was totally cool and controlled. When i went off the break, the car came back to neutral within an instant.
Could you make a video about 'drifting'? What happens during a drift maneuver, how camber, toe, caster angles, sway bars, suspension stiffnesses and tires act during a corner in countersteer, and how they are usually set in a drift car....also the differences between a drift and a conventional (or racing) suspension settings.
I know it's not an easy and simple topic, but I think you're the best person on TH-cam that could explain these things in a precise and clear way. Thank you
According to Google:
“Will wider wheels and tires affect your ability to brake and accelerate? That's an easy one to answer. Yes, those wider wheels will help you brake harder and take off faster. Wider wheels provide more traction and create higher acceleration.”
Your explanation as to why wider tires won’t help is purely theoretical but in practice it does help a bit to have wider tires. 👍🏼
The rest of the video is great. Thanks for explaining. 😊
th-cam.com/video/CyH5xOcsXxs/w-d-xo.html
I never said wider tires don't do anything. I said that increasing the front surface area during braking isn't relevant.
Another great video. Thanks for doing such an interesting and educational clips. One thing to point though is that in many modern cars and particularly Toyota hybrids rear brake pads wear faster than front one as a result of ebd and the fact that in some stopping situations rear brakes are engaged while front ones are still off as the cars relays on regenerative braking plus the traction control constantly applies brake force in turns. 👍
This was the best video I've seen about Electronic Brakeforce Distribution! Thanks for teaching us so many fun and useful things! I've added this video to my favorites. 😎👍🚗🚙
The most mind-blowing fact about breaking for me is that it is a process of transferring a kinetic energy into heat.
On my car (Holden VE Commodore), the rears are larger diameter than fronts, but the front has more friction surface area than rear. I would say that is because of the handbrake drum design taking up more area, making the overall rotor diameter larger.
I have since changed this with a police pack upgrade, using the Chevy Caprice PPV front brakes, changing the front rotors from 298mm to 345mm and from 2 piston to 1 piston per caliper. Definitely stops a lot better now.
I know of one other car with this style setup (Toyota 200 series Lancruiser)
I've also noticed, as a mechanic, a lot of cars, mainly cars fitted with EBD and from around 2005 onwards, they tend to wear out the rear brakes a lot quicker than fronts too.
I have a VF v8 and went with the 345 rotors but Brembo calipers from the caddilac cts-v iirc. Only because I couldn't get the steel calipers in Australia and the brembos were the same price. It kinda sucks you can only buy DBA rotors for it. Tiny vs the VF gts-r at 410mm rotors though!
I swear I will never fully understand how understeer is easier or less terrifying than oversteer especially in a FWD vehicle. Got into a argument with a tire review channel once over this in fact.
One VERY important thing to note here is the chaps comment about ABS. Modern cars fool you into thinking you're a much better driver than you actually are. @10:30.
I remember a 1 - Series I had on hire, and switching off the Traction Control made a bigger difference than I could have ever imagined. Completely exposed my lack of skill behind the wheel.
I personally think it's not so much a lack of skill as the fact that most new cars are developed and set up around traction control being enabled. If you take an older fully analog car you might discover that you're skills aren't poor at all.
@@d4a i disagree with this one or at least in this form maybe if you unfold it more. However i know a car which can not brake in a straight line straight without abs but this is more the exception than the rule.
Also there is an aspect that more powerful cars especially with electric engines (including hybrids) "needs" traction control. It is hard even for experienced drivers to handle the instantaneous torque and if you release the pedal you (can) have the same amount in the "opposite direction".
In the recent (G2x) BMW cars in sport mode you can "drift" (at least in snow) with full throttle change direction only with steering. So i completely agree that "Modern cars fool you into thinking you're a much better driver than you actually are"
@@d4a Maybe in my case a lack of practice certainly. I don't make a habit of putting my car in positions where I think I am going to bend it so never get the chance to practice what might be needed if the proverbial ever does meet the fan.
Or.............maybe I have but the car has fooled me into thinking my application of throttle brakes and steering were reasonable ones?
This friction thing. I know a few of those formulas and remember some from things physics in school. Now some context from "MY" POV.
Surface area does matter in the real world and here is why. Consider the illustration at 02:45. Imagine they are little hooks grabbing valleys and troughs in the road surface. The amount of force is spread across each little hook and it's easy to imagine one single hook being overwhelmed by force and heat and breaking itself and therefore breaking traction. More surface area means more hooks and less load per hook.
That's what happens with a tyre - bits of it break off, hence they wear out.
Discuss.
Very useful series of videos though. All of them.
Strangely enough, more context. 08:45. The subject of bigger brakes is applies here too, (I remember this guys video about it) and he says here that bigger brake capacity can absorb more heat.
In a one off you'll not notice any difference but as bigger brakes can dissipate more energy, in the real world with repeated stops they can fade less quickly and hence stop you more quickly.
Great to learn about the theory behind all of this though.
This is as good as it gets, amazing explanation.
Really love all the recent video about brakes.
Thank you and keep it up!
Always a good day when D4A videos are in my recommendations
you forgot to add "*in ideal world" in part about friction, in reality everybody knows that wider tire = more friction and better grip, as we don't live in perfect world and equation you showed is true only till some point, where increasing mass doesn't increase friction in linear way anymore
So much more interesting than I was expecting! Thanks for sharing!
Btw nice explanation with Mazda i have a cx-3 and last year i changed front brake pads, i wanted to change rear omes this year but my mechanic said they are almost brand new. So the 80%/20% braking force is so true
Great channel, great videos! Just to clarify, there’s no ‘weight transfer’ in breaking, but a torque moment (tendency to rotate about the front wheel contact point with the ground) So, yes there’s higher normal load on the front tires due to this moment, but the CG is still fixed, there is NO weight transfer!
but oversteer is way more cool
Go try it urself going 150kmh then lock the rear
I love your channel and the way you explain complex subjects in a simple way that anyone can understand. It is one of the hallmarks of truly mastering a subject. That said, I'm pretty sure the CX-30 comes standard with AWD.
Simple layman terms summary: Because when you brake the vehicle's weight shifts forward so having equal size brakes doesn't make you stop any better. They can be a bit smaller to save a little weight.
Nice explanation and easy to understand. On 6:55 think that stiffer suspension does not change weight transfer by a significant amount
Amazing my friend. Wonderful information. As an automotive service advisor of 24 years, you even taught me something to help me guide my customers during sales. Awesome! Now, if by commenting I don't get those phishing 'you just won' youtube alerts I usually get when commenting on your vids my visit will be complete! LOL😂
So far so good on the phishers 🥸
On a motorbike and bicycle you will always perform this biasing thing automatically. You can really feel, how applying more brakes on the front or rear tire will impact your overall braking performance.
And yeah, the rear tire will always lock first. But because you know to never break hard while cornering, this will never be a problem.
I'm concerned about your comment. Frankly, you absolutely have to consider rear wheel locking while braking in a straight line. I believe most fatal accidents occur from failure to use the front brake.
Under emergency braking almost 90 percent of the braking should be done by the front.
If you need to practice, go to and empty parking lot and practice safely. Learn how to stop correctly.
Great explanation.seeing Indian xuv500
Please keep doing these excellent videos! I like to understand how things really work, and I love the detailed explanation you do about everything in your videos. Congratulations and keep up with your excellent work. Cheers! 😉🥂✨
Seriously: Do you teach at any school or university? If not, you should!!! You are very clear.
He's got a little to learn before he could. He's not way off but he does have some mistakes in the video.
My first car! 1st gen Toyota MR2 (1987). AWESOME!
If you do not (yet) work in some kind of school or university as a teacher, you definitely should! You have so much fluency in the way you are passing a knowledge to the audience. God bless you, and don't ever stop what you are doing. 🙂
Back in DiRT3, all my cars had rear brake biases of 100%
The best way to play, strongest diff, no downforce, rear brakes only!
And in my NFS Underground I can make 180 degree turns by just slamming into the wall at 320 km/h.
Brilliant video, answered all my questions, more similar videos please!
Great explanation as always 👍
Another good reason to have a larger rear diameter disc (despite perhaps having a lower mass rear disc) is for cars using a disc parking brake. Most cars these days use mini drum P-brakes inside the disc hat, but for a long time the hydraulic rear caliper was actuated mechanically for the P-brake. Disc brakes make poor P-brakes due to their smaller friction surface area compared to drums, and the need for high application pressures that cables and levers couldn't provide. So having more brake torque from a larger diameter gave them a little help.
Well explained idol. The motorcycle does have a small rear and big front disc too but some motorcycles have both the same size of disc.
everytime d4agot a new video i got currious as to what would i learn next 😁
thanks d4a,
you shared another load of knowledge 👌
Very interesting. Now I know as a fact that my old Vitara had a leaver indicating the proportional valve how much weight is on the rear suspension and so change the proportion accordingly....
this channel answers questions i've always had. Thank you
In trucks, the rear rotors are often larger in diameter than the fronts. The front brakes will be thicker with more mass and larger calipers, but the rear brakes need to be strong due to towing requirements.
Great video as usual. Could you do a video on the best/easiest/most serviceable cars of the last 20 years (ish)? I’d love to know which manufacturers and models are designed with the humble mechanic in mind!
I didn't know about EBD. The way you explained it, it sounds like an inverted electronic traction control system. i.e. it maximizes tire friction whereas the latter maximizes traction. neat!
Great channel, good job. I've been following for a long time. Regarding the brakes - all my previous cars were as you say but the current car has 345mm front discs and 350mm rear discs, both ventilated (Dodge charger police version). I was surprised myself when I changed tires for the first time.
I'm curious, what year is that charger? Also, it might be expected to have a trunk full of police stuff all the time?
Those front disks are twice as thick tho...
@@d4a It's 2011 fleet car (Called the police version in the US). This particular example was never used by the police. I brought him to Poland a few years ago.
@@ifixem9585 front 28mm, rear 26mm
The front caliper is double-piston and the rear single-piston
@Daniel Cieśla Hmm...that's Chrysler for you. Seems weird
Coefficient of friction also decreases with the normal force. That's why a wider tyre has more grip than a narrow one, all within some limits where tyre tread is homogeneus due tyre pressure.
Great Video as usual! I'm always impressed how much I learn about a topic which I thought I knew completely😅
Little thing I find missing is that mechanical break force distribution was/is a thing since the 60's. Just some levers on the rear suspension opening and closing the valve to the rear breaks 👍🏻
I just bought a ford puma. Another compensation to add some braking percentage back to the rear is tyre pressures 35psi front, 31psi rear. First car I had that differentiates tyre pressure.
Something that has been puzzling me for some time. I have two front wheel drive vehicles, a 1990 SAAB 900, and a 2011 VW sportwagen. BOTH of these vehicles consume rear brake pads about 30K to 40K miles, but I have NEVER had to change the front pads on either one of them! I've had the SAAB 900 since 2004, and the Volkswagen since it was new. I also have a 2000 Chevy van, a rear wheel drive vehicle. It has needed front pads twice since I purchased it in 2008, but has never needed a set of rear drum shoes. I primarily use the van for work, and it gets city driving, along with towing a camping trailer. I am typically a light, early, easy braker, My wife drives the VW mostly, and has never driven the SAAB. she is more of a late, harder braker, so I'm not thinking it's driving habits that make these two vehicles burn rear pads more often. The VW is new enough to have EBD, whereas the SAAB has an older TEVES Mark III ABS system. The only reason I can come up with is that the SAAB and the VW are both European cars, and European cars must have a bit more bias to the rear brakes than American ones do. Does anyone have any thoughts on this? sorta goes opposite of what he says in the video, and what I would expect
great vid as always. I always enjoy watching your explanations even if its on something I'm already familiar with. At worst I become more confident in what I already knew, best case scenario I learn something I didn't realize I didn't! Hope you're getting some time in the dirt on the new Honda as well
Another consideration: even on purely hydraulic systems without electronics, front/rear brake bias doesn't have to be fixed by a proportioning valve in the front, either.
I believe even the Mk4 Golf had EBD, but earlier Golfs (at least as far back as Mk2, on some models) went for a different approach, a proportioning valve mounted at the *rear*, attached to the torsion beam. As the rear suspension unloads due to weight transfer, the proportioning valve is adjusted to reduce rear braking force.
Approaches like this - especially once Mk4s had EBD, but even before that - also let you start out with an extreme rear bias under gentle braking to reduce weight transfer and make the vehicle feel more stable, and as brake force increases, shift braking forward for maximum braking force. (I want to say my Mk4 Golf actually wore out the rear brakes first, because most of the braking it saw was quite gentle.)
@0:50 A first gen Mahindra XUV500 :)
Thanks a lot for these videos, it is so helpful to explain the basic concepts to others.
Could you make a video on how bike clutch and transmission works and how it differs from car's equivalent
Thank you very much! I'm learning a lot from your videos.
Great video, great set-up. I'm really impressed with your development of the channel as the subscriber and regular viewer. Really great man.
It's interesting that as a mechanic for a dealership I've seen how the cars deteriorate from oil service to oil service. Ive always seen the rear brakes need to be replaced as early as 40k miles but front ones as early as 80k. I've never seen a car's first set of brakes wear faster in the front. I'm not disagreeing with the facts you've presented, but it should be noted.
That happened with the advent of abs. Non abs cars wear the fronts first.
Nice to see you back 👍👍
really happy to see mahindra in you videos
from the land of mahindra was bron
love from chennai❤❤
Great explanation, a video about removing the booster and electronic systems would be great
stayed glued to the video the enitre time, great work!
I made a mistake recently. I searched Google for the answer to "why do some brake systems use 1/4" line to the rear brakes?", and I was inundated with vast quantities of the most clueless replies in countless forums. It almost made my brain explode. I "think" I know and understand the answer to the question, but I'd really love a well-researched definitive answer, if that's something you're inclined to tackle and you think your viewers would appreciate.
You'll probably see some of the more common clueless answers appended as replies to this comment... 😂
You are very great in explaining car parts ❤
Wow, great video again. I thought I knew it all, but I didn't.
i allready knew this but i love watching your videos anyway😄
Please make a video about car chassis strength and the impact of the car🙏
Still the best ... Keep it up man
Clear, thorough, without skipping a beat !
Great stuff as always :D
I like your videos, very good content. I need to say my objection to ABS because is not for shorter brake distance, you need it because if you slide no steering will help you.
And someone already says F=µN doesn't work for rubber because is viscoelastic...
hi mate, great channel! Really helped me understand complex topics quickly.... Please do a video on oil pressure(low oil pressure light) especially on boosted applications
dynamic stability control also requires more rear brake as the rear brakes are utilised to arrest wheel spin and aid in stability while hard cornering and can over heat rear brakes even without braking.
did a v8 conversion and found the brake bias was fine until I upgraded the rear differential to a ford 9", with the extra mass of the heaver rear end more rear brake was required, I believe it was more the inertia of the heaver rotating mass.
I just gonna left this piece of knowledge here.
After getting a ton of opinion and information on the subject, I arrived to the conclusion that:
The normal car is made for bad drivers.
Yes, that is the true, and makes perfect sense when you think about it. Most people are not out there to be a better driver, some find take the driving license test and school a chore.
Not that is not annoying to do. But overall, most people driving do not seek to improve their driving skills, they just wanna get from place A to B in a safe, fast and convenient way.