The basics of Crank Length (Effect on power, cadence, comfort)
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- เผยแพร่เมื่อ 30 มิ.ย. 2016
- Here is a basic explanation of Crank Length. A more in depth analysis is here: • How to find the best C... .
ps. sorry I muddled up rpm and pedal velocity at one point. doh!
1:04 crank length vs power
5:02 crank length vs acceleration
5:30 crank length vs gear ratio
7:30 crank length vs fit
10:00 crank length vs cadence
This video has been updated here: th-cam.com/video/ydePgGR1Lu8/w-d-xo.html ps. please join us on our accredited strava club here: fft.tips/strava
I went from 172.5 to 165mm. I am 5'11 with a 32" inseam. Due to arthritis in my right hip, I shortened my crank length because of pain in my hip on the up stoke while pedaling. After doing so, I saw an increase in speed, due to the lack of pain!!...so, yes crank length does matter! Bottom line, everyone is different, so find what works for you! Smooth is fast!!!
Very interesting. Since I starting cycling 2 years ago, I've had off and on right hip/flexor pain. I'm 5'9 with proportionally shorter legs and I have 170mm crank. I'll look into switching to 165mm.
Angus, I'm very interested in whether shorter cranks can cause a decrease in hip pain, and am happy your hip pain is improving. Did you adjust your saddle height, however, when you shortened your cranks? If not, is it possible that the decreased saddle height due to your shorter cranks has something to do with your decreased hip pain?
I also went from 172.5 to 165mm. I'm 31yo, 5' 10", 32in inseam. I have used 3 different crank sizes 172.5, 170, and 165mm. I use 165mm because it definitely feels best of the 3 sizes. I don't have arthritis but it still feels better and more fluid with the shorter cranks. I ride over 600 miles a month. I also put 145mm cobb cranks on my girls bike,she likes it sooo much better than the 165's that came on her bike originally. Hope this helps somebody make the decision to go to shorter cranks. Worth it 100% imo. www.strava.com/athletes/3853032
For those that want to buy short cranks this is the guy I have bought from,
bikesmithdesign.com/Short_Cranks/index.html
I ride a recumbent and I went through various sizes till I found the ones that I feel fast and comfortable with. I am now riding on 153 mm crank arms and I am 6'1" all the power and no pain in the knees, the same knees I have trouble with climbing stairs because one of them has a torn meniscus within. The recumbent came with 170 mm cranks and a different seat. Comfort is available for your body or just your knees/ hips.
I have also went from 170 mm to 165 mm to try solve some hip/gluteos pain. It did not work and I was very worried about it. I finally find out that the problem is when you ride a lot your "vastus lateralis" and "rectus femoris" muscles develop to much and you can have pain in your rip or your gluteos. After several months making some specific exercises to stretch all muscles I solved the problem.
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How does crang length effect out of saddle pedaling?
@@vaugr1917Very good question: too small and you cannot develop enough power, too large and you get rocking of hips and body and ultimately instability.
Sorry, but your calculation with the Gear ratio is wrong. It is 11/53=0.2 not 53/11=4.8. If you calculate with torque its maybe easier to understand. If you put down 100Nm with your foot you have 100Nm *0.2=20Nm on the wheel/street. Cadence is the other way around 100rpm(crank)/0.2 =500rpm(wheel).
You explain things very well. Thanks.
This is one of the best videos on crank length out there.!
Thanks, easy to understand. Thanks Angus below as well. I've got a similar problem at age 72. Might try the shorter cranks and keep on pedaling.
From 172.5 down to 165 on my TT bike and i'm 6f1inch (185.4cm). Theres's a huge diference on my position on the TT bike and my cadence is up... I like it!! On my computrainer I still put the same power (ftp) but I'm more aero and stay easy at 95-97 rpm for a long period... really better for me. I hope this will help some who are hesitant at least for TT bike. (excuse my english, I'm french speaking)
Nice work on a tough subject, I'm an older rider and I discovered a few years ago that I have less knee pain with shorter cranks, even when bike fit is adjusted.
Very good explanation. I am about to order a Falkenjagd Hoplit titanium bike, and given the expense, it really cleared some issues. Thanks a lot! Congrats!
Best explanation yet on crank length. 5 stars! Seems awash in the middle ranges of crank length as the multitude of gear choices dominates most rides anyway. Thanks!
Excellent video! Love this explanation
Thanks for a great explanation
I have several road bikes with same gearing 53/39 and 13-29 and different crank lengths 170 &172.5 mm
Same frame geometry & stem length
I really notice the pick- up and speed with the longer crank which suits my riding style - not a spinner but long distance recreational cyclist these days :)
68 yo riding steel
This is a great idea and you should really do this video again, it is certainly worth while! You acknowledge the confusion between Cadence and Pedal speed in the notes you added, but it is not clear when you are using the right terminology and when you are not (thus I suggest a redo!)
At the same time, the analysis needs to go both directions. A longer crank gives you more ability to climb steeper hills (by creating a lower gear so to speak); a shorter crank allows higher maximum velocity for a given foot speed( though it requires more force on the pedals)
In addition, air resistance is always highly relevant. It would seem that shorter cranks should reduce wind resistance (less overall average frontage because the foot does not go as far from the hip)
In addition, there is likely an optimum length for muscle efficiency, as other comments have suggested.
You are probably right, at some point we need to revisit this topic!
Here goes something no body has heard, train on bike with smaller cranks to improve speed, then when you race go with the longer cranks to generate peak power
Thank you for your videos
Thanks for a nice explanation.
The main benefit of a longer crank (longer end of "normal" range) is when "jumping" in to an acceleration. IOW, when operating at peak torque. This is rare for most athletes. And it's a compromise because you might be losing top end (high cadence) power development. Study power and torque curves of internal combustion engines to understand the torque/power dynamics and then remember that with your own "engine" you risk over-stressing your muscles - an additional risk.
OTOH, if you're really fine tuning your form for sub-maximal performance over long periods getting the length optimized can theoretically help with endurance/economy. The bottom line is to err on the side of the shorter crank unless you have lots of testing to validate your reasoning for extending the length.
Started riding 12 years ago with 175's. I am 5'9".s 31.5 inseam. Use 170's now and could no the happier. 53 x 39
Thank you very informative.
Very educational, I use 172.5 for this reason. I find, for me, it’s the best combination of leverage, cadence and torque effectiveness. I have long legs compared to a short torso, and tend to power my gears, but love to spin to unload my muscles as well as when climbing then apply more power cresting the hill.
It also depends on the type of use or discipline of biking you do. Most MTBers go for longer cranks and the reasons are obvious. You need more torque and the longer arm helps in that. Plus in many instances, you don't really need to spin as fast.
RB's may be more demanding and if I were a serious or advanced rider, this should already be included in the bike fitting. That may not be 100% or even 90% in some instances. Only long rides and actual intended use will one eventually find out what is good for them. Riding only for 1-2 hours and not for the intended use, may not reveal the problems or issues that can crop up. It's not like any different with saddles. You really have to ride 3-6 hours and do that several times to find weed out issues with your saddle. And one must take it to the conditions one intends to use it or the terrain one is often exposed to. It's really a long repetitive use that brings out the kinks if there are any. And a single ride may not to be smart to conclude anything, especially if one is still adapting to a new crank arm length.
Smaller wheels like in folding bikes, means it will be harder to consider longer crank arms simply because those arms can be limiting due to the lower bike stance. Though I have used 172.5mm ones, in 20" tires, it can be tricky not to prevent them from hitting the ground in speed bumps, or some road anomalies. Most folding bikes also tend to be more upright, so those hip and knee angles tend to be not an issue. RB's are usually make the riders lean forward in aggressive aero position which makes those angles smaller. But this is not true for folding bikes, or even other recreational bikes. Hence the issues raised here my not be applicable for some types of bikes.
Recreational riders, may not concern themselves with this. If you just ride maybe less than 50km or even 100km, leisurely you can opt out of finding out what's good for you, unless you have long or overly short legs, or some other problem (arthritis, one leg shorter, et ) and the like. Most bikes normally come in 170mm and likely 90-95% of the population will have no problems with those.
Of course, the bottom line is for you to experiment for yourself. Everybody is different as well. My guess is if you are a pro, or serious racer, or advanced enthusiast logging in hundreds of km a week, finding out the right crank length can maximize or optimize your potential. It can even help avoid getting injuries.
Great info. Thank you.
Cycling Bio-mechanics equals muscular considerations (bio) and non muscular(mechanical) considerations.
You need to consider what is lost not just what is gained.
A longer crank length gives a mechanical advantage of strength (force).
A shorter crank length gives a mechanical advantage of cadence (velocity).
Power is Force (strength) x Velocity (cadence).
As crank length goes up - force goes up and velocity goes down (say 2FxV.)
As crank length goes down - force goes down and velocity goes up (say Fx2V).
2 F x V = F x 2V .
In practice the power is the same.
The dominant factor here is the muscular considerations: muscle length, tendon length, ligament length, the length of the limbs and feet, the speed of contraction and where the maximum power is in the contraction.
There is no difference in efficiency because muscle shortening velocities are the same.
British cycling have experimented with this and found that there is only a difference at the extremes 1120mm and 220mm. length cranks.
The main purpose for different crank lengths is to change the bike fit position - hip closure and hip angle without changing other fit coordinate. Riding a smaller crank will open the hip angle allowing a more prone (aerodynamic) position.
In track cycling a crank length of 165mm is used for safety reasons and nothing else. No-one can spin a 165mm crank faster than say a 170mm length. Not even Chris Hoy.
Cyclists get good at what they use. Train with 170mm you will get good at this length and so on.
E Merckx used a 175mm crank length for time trials and 180mm crank length for hill climbs in the Tour of France.So longer crank length use is not new in pro cycling. I read M Cavendish is using a 182mm down from 187mm.
Another cycling myth on the internet.
Sorry guys 120mm to 220mm.
There needs to be a change of 30mm in crank length for a noticeable change in pedalling efficiency.
Think of crank length as a gear.
So 200mm is gear 1, 170mm is gear 2 and 140mm is gear 3.
For the nerds.
Power 170 = F x v.
Power 180mm = aF x 1/aV = Fv.
Power 160mm = 1/aF x aV = FV.
So power 170mm = 180mm = 160mm.
a is the factor of change for the mechanical advantages of force and velocity.
Very nice, and also for those with physical limitations, if shorter cranks help with relief...then they may improve in areas they suffered in...no?
6 foot 1. Swapped from 175 to 165 on my aero road bike. Have noticed a lot less knee pain and things just seem to feel better. Have not noticed any power differences on rolling terrain.
im a mountainbiker and im 1.87m tall, but i prefer 170 cranks instead of 175 because my knees feel better with the shorter cranks on longer rides
11:30 If you're spinning out a 53x11 Sir Brailsford would like to talk to you.
yep exposes the bollox perfectly
My current bike is 172.5 and I have 29 in inseam. I think I will benefit from 167.5 cranks in my next bike mainly because my knees won't be forced up into my gut like they were with the 172.5 and I will be able to ride more comfortably with a lower bar position.
Excellent video. Explains my recent power average drop since going from 172.5 to 165mm crank. Reason I went down was comfort / bike fit. I'm 5'8 but have long legs and shorter torso. I had a hard time on the flats on a complete aero tuck. My knees would hit my chest so I couldn't get my body low enough. Sadly I seem to have a hard time averaging big cadance numbers (shoots my heart rate to sky) hence the little power drop on my rides. Hopefully I can make it up with getting a little stronger or just practice spinning fast more / improve endurance.
just curious, what happens exactly when your heartrate goes to sky? do you gas out?
Basically if I spin fast cadance my HR goes up but my legs get some relief from grinding (slow high torque)
If I grind slow high torque my legs get too tired while my HR is fine.
So you find a balance. Once my HR goes to the sky I slow my cadence down a bit to adjust and get my HR 2-3 bpm lower which keeps me going.
If neither of these help you stop and rest. I generally don't have to stop during a climb. I'm at a decent fitness level where I can choose to take a 10% hill easy (relatively) and get through it even if it means I go slow as hell. My HR shooting up is when I'm trying to get a good time on a climb etc.
I just thought crank length was correlated for inseam length, short legs get a short crank set..
I'm 30 in inseam so I switched to 165mm from the standard 170mm, and it feels great now.
Crank length is important. As a keen cross country unicyclist, I find choice of crank length is vital. Shorter means I can spin faster but with less leverage; longer gives me more leverage for hills, but a slower cadence. A unicycle is direct drive (fixed gear) so crank length and wheel diameter are the main two variables, and crank length is the easier one to change. However, with very short cranks, you use a smaller part of your range of muscle contraction, and with very long cranks, you move the mass of your legs further. On a bicycle, you are able to choose the gear ratio between the chain ring and the rear wheel. Therefore, it makes sense to choose the crank length solely for what gives you the best, most comfortable and most efficient pedalling action. About 170 mm for a typical adult male, a bit shorter for someone who is shorter, and possibly a bit longer for someone who is very tall. Think of the legs/cranks as the engine. Optimise the engine, then use the gears to direct that power to the rear wheel.
The shorter you are, the more sensitivity you have to crank length. I swapped 170 for 165 mm cranks on my track bike and found improvement in comfort and position. I am now accelerate seated faster while seated (essential for track racing) so it's totally worth it if you're 173 cm or shorter in height
this was the best discussion on the issue of crank length that I have encountered, mostly because it is universally ignored. I wish the subject of leg length had been brought into the discussion. I am 6'3" and usually ride 175s, but I am a grinder, not a spinner, perhaps longer cranks would suit my riding style. being over 50, my cadence ain't exactly speeding up.
WELL l did find going from 170 to 175 very odd at first but after proper adjustment of my seat to fit better ,l really liked it along with changing out chainring from 53/39T to a straight 46T with a 12-32 8spd rear cassette on my old steel road bike making a 1x system to simplify my drive train .AS my commuter bike this works great and simplified riding around my relatively flat city ,along with 32c tires to smooth out the bumps :)
i tested 172 and 175 and difference is noticable, shorter gives more ability to accelerate, it easly rotate on higher rpm.
with longer i felt centrifugal force on legs and it accelerate slower, and is not good for high rpm but is better for lower rpm on uphill and if tilt too much in corner longer will touch ground earlier when rotates
I just found your channel and really enjoy this series; excellent work! Could you please consider creating a video about types of chain rings including osymetric and q-rings?
Nice idea will have a think about that; we have extensively tested Q-rings.
Super happy with my upgrade to 180mm
Your video is very in depth and scientific in its analysis. With the growing advent of one by cranks on gravel racing bikes it makes things dificult to choose crank length, size of front sprocket and cassette range. Many riders buying or building a gravel bike are coming from traditional r oh ad bikes. Can you do a video on how you would best take a riders road gearing ( 2x10, 2x11) they are used to and how to best choose crank length, drive gear and cassette range for a gravel bike? Riding off road you obviously want lower gearing than you do on the road but I see riders all the time choose too small of a drive gear and too wide a range of cassette for gravel. There has to be a way of equating a riders road gearing and power output to a gravel equivalent to at least be closer than a guess.
I have used cranks between 165 mm and 175 mm. I found that in effect the main advantage of a longer crank was in hill-climbing.
In the end I settled on 172.5 mm as a less tall than average cyclist at 1.68 m. I find with the longer the crank that, within reason, similar results can be achieved in terms of speed [progress with similar effort] with a slightly lower cadence, or as you might observe, a gear one higher than you might manage with a shorter crank.
A disadvantage of longer cranks is that you can more easily hit the road with a pedal when cornering at a road junction ... for example. You live and learn on that!
But short cranks seem to stress the knees more over a long ride, or even, when weary, starting off.
Off course it is all down to personal taste. But if you ride a bike every day, then experimenting is fully worth the effort. Give it a week and decide what option is more “comfortable.”
My lowest gear is 44 over 24, which is not really a low gear at all!
George Johnson but did you adjust your saddle setback? If you didn't you placed your knee more in front of the pedal axle with the shorter cranks which potentially could be causing knee pain
I wish I could like this video a dozen times, this was so well explained
Good explanation
I'm 75 inches tall. I switched to a 180 mm crank from a 175 mm crank, and my regular cadence dropped from 92 to 89. I think it is more comfortable for me, and I feel my leg muscles are working more powerfully. I have always felt inefficient in higher cadences, such as 100, and lower cadences feel more satisfying.
A mishmash of facts and info, some of the comments are on point. Changing crank length effects gearing choice. Shorter cranks allow a more aero position and can open up the hip angle which is generally a good thing. I used 170 for years tried 172.5 and 175. Hated them. Am 6' 1''. Am going to 165. Had 167.5 on my track bike I used a few times on undulating super hard training rides. Put something like a 92 inch gear on the bike. Uphills were a grind, steep fast downhills had to break a bit. It is a single speed fix gear track bike! Very efficient feeling on the flats. Get to the front to take a pull spin like hell and just seemed so fast. This is in non aero days, did affix both front and rear rim brakes for group street riding.
I'm 5'7" and wear a 30" inseam pant....I use 170mm cranks. I tried 172.5mm with my last bike, and spinning at higher cadences was much more of a chore - plus my hip angle was more acute as my seat was slightly lower (and overall more uncomfortable as well). I haven't noticed any real differences in overall power output however between the 170's and 172'5's with my power meter...however, it was marginally easier to climb steeper grades with the 172.5's.
There are two more considerations for me. I ride both a road bike and a mountain bike. Mountain bikes typically historically come with a 175 mm crank. I want my road bike to be the same so I'm in no discomfort going from one to the other. The other thing is where does my knee align when my cranks are parallel to the ground. This takes into account both upper and lower leg lengths and should require that a longer leg use a longer crank. In my case I'm 33 inch inseam (838 mm) that also guides me to the 175 mm crank based on using a plumb bob and fit kit.
I've done many back to back tests on my mountain bike with 175, 180, 195, and 210 mm cranks. The 210 mm cranks result in 5% faster hill climbs compared with the 175 mm cranks (210/175=1.20 more torque). I'm 6'0" with a 32" inseam. I've worried that the extra leg angle and movement might result in some wear or injury. After 30 years of hard riding with 210 mm cranks I'm still going strong.
I have gone to 170mm cranks on my TT, Road and Track bike. However have just gone to 172.5 on my TT bike and I use a 60T chainring. The shorter crank length gives me more aero abilities via open hip angle.... I set my fastest flying 200 of 10.9 on a 172.5 track crank.... on a 127” gear (57/12) I find no real issues with 170 or 172.5 in regards to getting on top of a big gear. I have found that I really like 170mm even though I am 6”0.
The cadence or rpm stays the same but the foot has to travel faster along a larger arc with a longer crank hence foot speed has to increase to maintain a given cadence with longer crank and and slower foot speed with a shorter crank. Foot speed and cadence are 2 different metrics!
I have SHIMANO, Claris, 50t, 34t, 8 Speed 12-30 Cassette. 170 CRANK. So far so good, never had any problems.
All this are fairly important to me. I have to race my neighbour to the market and see who get the freshest fish every day.
Or using an Italian-style frame pump, 'Cinzano' your neighbor = problem solved.
So short crank is good for crits because you will accelerate faster, but it will take a bigger toll on your legs.
I'm a short guy and I want to get aero. I want to get smaller cranks because my stem is slammed and I can't get the saddle any higher. But I should also get easier gearing along with the shorter crank so that pedaling doesn't get any harder than it is at this point. Am I getting this right?
Thank you sir very informative,, 🙏
Also rembember shorter cranks can produce less max torque but more even torque throughout pedal stroke. And also it's easier to lift on the upstroke on shorter cranks. Another thing you didn't mention is that if you have poor flexibility its harder to get power through the stroke on longer cranks because the muscles can't fire properly.
thanks David yes some useful additions, appreciated
there is an error at final on both situations the benefit is from long cranks you can apply more power with longer cranks the cost is on long time efforts when you use longer cranks the push effort is less but since the travel is more the cost you pay is an earlier fatigue.
I read somewhere that as a rough general rule, a longer crank lets you better sustain ave power over time but a shorter crank allows you to produce a higher peak power. Not sure how accurate that is. It might explain why they opt for shorter cranks on the track and for bmx. I've also heard the same thing said about small wheels which would also make sense for bmx. That smaller wheels accelerate quicker for a given power output but aren't as efficient for maintaining high speeds.
Great video, the issue I have after a knee replacement I'm unable mechanically to bend more than approx 75° so I have to have a crank shortener on one side so that I can ride, without it I'm not able to cycle.
Is this better for you than two shorter cranks....ie the same length? does it cause any problems with asymmetry of the pedal circumference?
I ride with an above-knee prosthesis and use a custom made 85mm crank on the prosthesis side,
it basically just acts as a counterweight to complete the full rotation after the power stroke.
Thank you sir.
Where can I get shorter cranks sets from they really are like rocking horse droppings!! I live in Essex uk
hi i am 5'9 with a inseam between 78 79 cm i am currently running 172.2 mm cranks that came with my bike i have toe overlap in my bike and am planing to change my cranks to resolve it and maybe to get more comfortable ..also running 50 34 planing on getting 52 36 cranks because in 34 plate i spinn to fast and has to cross chain will i notice any negative effect on this changes if u can help me please ?? or it will better just to get 165 mm cranks with 50 34
With shorter cranks you mostly pedal fast, and long - slow, i could ride a 165 but do 170's for all-round use, hills etc... spinners are winners, literally tho at some point you have to push slow gears on a bike, if you go up a rise/false-flat hill...so you have to get back the momentum if in a competitive group sitiuation. Cycles are sold with waaay too long cranks and SHOULD BE selectable, i even dismissed a buy of a bike in a shop once as they didnt have my length of crank and they looked at me like i was crazy!
Does the non drive side crank require the same force as the drive side or is there any loss in power due to it being further from the chain ring
Great video on a difficult subject. It makes sense to me now why my track coach set my crank length shorter than my road bike 160 v 170, as a juvenile we were restricted with the gearing 45/14. We were coached to spin fast and smooth, something I was unable to replicate with a longer crank. Crank length and gearing in track cycling is very important. This video sorta proves track cycling tried and tested the science way before it was challenged by the biomechanics and engineers. I tried longer crank lengths later but I just found them uncomfortable. It just comes down to what you feel is good and I guess what your body prefers or is used to.
thanks for the comment and very interesting perspective on track riding.
Track has shorter cranks to avoid pedalstrike.
The reason is for quicker/faster spool up, not pedal strike concern. In track so much is about getting the quick spool up - jump. Bottom bracket is routinely 10mm to 10.7mm higher to that of most road bike which elevates the crank/pedal.
death2pc Even on the banking, your bike tends to stay perpendicular to the track. ....I you lean with the banking. ...
Jason Ward but the straights have to be banked so there's not a huge climb into the corners. if you're riding quickly, you don't need as much clearance in the corners, but you still need it on the straights.
I absolutley love your no BS approach. One thing I'm missing here is the biomechanical part. What part does leg length play? And especially what part does the length of the upper leg play?
Well spotted; I was saving this for a future "science of the bike fit" type video. Clearly its important but I have a question for you...is leg length based fitting more important than a. subjective comfort and b. power numbers. Which comes first?
Lots of great information...I also wonder what effect a 5 pound ballast weight at the end of a crank arm would accomplish...Wouldn't that turn your crankset into a pendulum...Making it easier to maintain momentum...Which theoretically should translate into climbing hills easier...Just curious...
Very interesting.
You do realize that there are those of us who do not race but happen to like speed and less knee problems? I ride with 153 mm crank arms and they are fabulous for my 6'1" body. Higher rpm, less flex of the knee, and all the power I require.
My bike fit guy reduced my 172.5 to 170 as I am too crowded (top of pedal stroke) when in the drops. Thigh hits chest etc. My case is I have long legs and short torso, so although my long legs can push the larger crank (175mm on MTB) my upper body is short so the upper body angle is compressed due to a higher seat relative to drops. Its all a compromise.
Best fit for road bikes are DUCKS. short legs/long body means you can get 'low as' and not have a ridiculous seat to bar drop.
I'd prefer longer cranks as I am less of a 'spinner' but the bike fit says otherwise. SO I had to learn to spin.
Oh... that was a true epiphany. I am on my way to a long adventure and all of a sudden I realize why I have always hated cykling, what it is that is wrong. Only time I really felt comfortable was when I had a huge 28" Kenhill. I sold it because it was to big for me but it probably had the right crank length for me because ever since I have had that feeling of driving this little kids bike.
im around 5'10.5", with 32" inseam and i went from something around 165 to 175mm, and luckily i really nailed it. if i used the currently favored formulas (height x .095 or (inseam x 1.25) + 65) i should supposedly do 170mm.. maybe its because im a pedal masher but 175 really feels optimal to me
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There is a benefit to shorter in mtb' ing In that a shorter crank gives better ground clearance when pedalling through rocky sections and later pedalling into a corner and earlier pedalling out of a corner - this would also affect fixed wheel bikes when cornering on road as you - whether this advantage would outweigh the leverage ratio difference would be down to your body dimensions and riding style - there is one other difference more relative singlespeed and fixed wheel riders in that with shorter cranks there is less vertical movement of the legs which would affect rear stability when spinning out a gear - marginal of course but still a difference nonetheless relatable to the engine stability difference of a rotary engine vs a conventional V shaped piston layout.
You can gear up and reduce the cadence as you increase the torque, which requires less oxygen and making more efficient, moreover there is a balance
I find longer cranks are less tiring,managed to do stelvio-gavia-mortirolo in one day in attrocious conditions. Just couldnt get power out with shorter cranks.used 175mm vs 165 ultegra which are hollow btw and flex. Im a big heavy guy but power is much better with 175. I rarely get out of saddle on climbs and keep it smooth to save energy particularly past 2300 meters .
I have a short crank and my wife has a very large ring . I am always very tired after a long ride but she hardly breaks a sweat .and she doesn't seem that interested in riding any more .Are we doing it wrong she said a new chain and some ceramic lube might help . I am afraid she will leave me for a man with a long crank and to be honest I find myself admiring women who ride fixies with very small rings . Any advice on this matter would be great thanks .
well i tried 175mm ones then 170mm and then 165 mm ones and i am not sure of anything .....my weight is 170 cm and 81 cm from foot to crotch ....but for sure i know with 165 mm i feel my knees in short of time maybe directly after 4h ride /depends on intesnsity/ .....but yeah my natural cadence is quite low 75-85 rpm
Well. My opinion is that crank length must be result of natural cadence. Natural cadence is result of BMI. I know that BMI is useless measure but in this case it help you. If you have high body fat or body muscle that need hi amount of oxygen. If you go hi cadence that also need hi oxygen. As consequence you will be out of power very fast. So, you must use muscle to sustain power for longer.
On the other side, if you are slim, low fat, low muscle you need hi cadence. You will have more oxygen to spend but no big muscle. It is better way to use oxygen to sustain power for longer.
You use what you have more to spend or only think you can.
Now I have 175 because I have hi BMI. OK, I'm fat. But back in time my ideal length for 53/25 was 170. I have that bike. That is only reason I can remember that. Also different body shape. I was really slim, fast and powerful.
That is result of GCN test. But you must interpret it correctly. If you are beginner, 175 or 177,5 will be ideal but you must know that it will change if you are become more fit.
Crank length is anything about comfort or height or leg length.
Love the video (and others that you do) and you are very close...at time=4:30 you refer to cadence where more accurately you should be referring to foot speed: To output the same power with more torque (because of longer cranks) the cadence is lower. You do discuss the larger pedaling circle but do not mention that obvious fact that at the same cadence with longer cranks the foot has to travel faster. Might also be worth discussing that many people are considering shorter cranks to allow lower torso due to lower leg lift, and this may improve aerodynamics...
True...we fixed most of the criticisms here....th-cam.com/video/ydePgGR1Lu8/w-d-xo.html
Hey I was wondering if I could get your opinion on something? I just bought a 52 cm 2018 Cannondale supersix Evo Dura-Ace and it comes with 172.5 crank arms semi compact crank and 28 cassette in the back. What do you think about keeping the semi compact shortening the crank arms to 165 or 167.5 (I'm 5 foot 8 and 1/2 in tall but have 28 inch inseam for pants, 30 to the floor with bare feet, and 32 with shoes) then running an seq Lite lightweight 42 tooth cassette in the rear with a wolf's tooth Road link to make it work?
Try this online bike fit calculator: pedalforce.com/online/bikefit.php. If you want to know more about ratio/gear choice email us.
I got a bit shorter 170mm cranks to avoid touching the street with the Pedal in corner
So, you should first decide on the crank length based on your personal pedalling "comfort". Given the selected crank size choose then the sprockets/ chain rings to not run out of gears.... The confusion is because people tend to think in reverse order.
This is Wilson X Bezerra. You are right if you are talking about the conventional bicycle but not our stepper bicycle. The convention bicycle will become obsolete within the next few years. Our 20 year patent has been approved and we are sec approved. Our crankarm is 20 inches long. We operate in the most efficient area of the circle when pedaling, 2 to 4 o’clock. The forces on the conventional bicycle goes into the frame ours goes into the wheel. No distortion of the frame or fork. Also, we use 2 of the strongest muscles to propel the stepper bicycle forward instead of 8. We eliminate muscle fatigue while riding. The chain always remain straight when shifting. Our pedals are directly on top of the crankarm and not on the side. This avoids jerking the frame from side to side. Our RPM exceeds 120. Even though all can ride our system, it also allows a person missing a limb or those who have mobility issues to ride. Please visit our website. Www.arc287bc.com we have been approved to sell shares by the Sec on Oct 24, 2017 at 4PM. Go to Sec.Gov at the search bar type
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Ergonomics of crank to leg length is key for maximum efficiency.
Would it be reasonable to say that the leg movement/motion is not too dissimilar to walking up stairs.
I compared the recommended Australian Stair height from the CSIRO Australia with that of crank lengths and it falls in the same range. It states that the step height is to be not less than 150 and not higher than 180. For health reasons alone - crank length should be considered.
just saw the reference to powercranks in this video (around 40s) - what are your thoughts on these? any data to support their use in training?
Very skeptical!
This is all new to me I just looked at my cranks to see that they are 175. No wonder I’m a grinder.
Gd mrning i am asking regarding about cranck i am 5'3 ft.height what is a goid for me the size if cranck 1.75 or 1.65 thats all thank you..
160 to 165
Yeah Crank length matter because with lower and lower BB we hit roots much faster with those long 175mm cranks. 160 FTW
im guessing this is why pantani was running 180s in the mountains. easier to turn around the 39/25 on the steeper grades. i live in an area where you run out of gears even with a 34/32, so the longer cranks do help on the over 12% grades i find. not sure why gravel bikes come with 1x, just not enough gears, not easy enough and get spun out to easy also
Thanks fot the video. I'm 198cm tall, riding with a 175mm crank. I might fit with 177mm crank to use my legs for efficiently without too much pain.
Also, I would lower the saddle height. would it make more aero?
Crank length will not effect aero more than about 0.5w but saddle height will.....its hard the predict but as a rule of thumb *raising* the saddle makes a more aero experience because you rotate relative to the front and encourage a more crouched position, up at the saddle & down at the front is ideal for aero.
🚲👍 Excellent! Thank you!
short crank makes you climb faster?long crank makes you go faster on flat?
Yo utilizo manivelas muy cortas, 125 a 130mm y puedo decir que el pedaleo se convierte con ellas en auténtico placer, la cadencia puede subir hasta las 140 ppm (pedaladas por minuto), implica un ángulo de flexión de rodilla menos agudo, lo que resulta ser fisiológicamente más natural para el esfuerzo de su articulación, músculos y tendones.
Tengo que decir que uso una bicicleta reclinada pero creo que el acortamiento también sería conveniente en las verticales, es cuestión de probar, como hemos hecho los usuarios de bicicletas reclinadas
Pacomi says "I use very short cranks, 125 to 130mm and I can say that the pedaling with them is a pleasure, the cadence can rise until 140 ppm (pedals per minute), and gives a angle of knee flexion less acute, which results that are physiologically more natural for the effort of your joint, muscles and tendons. I have to say I use a recumbent bike but I think the shortening would also be convenient in the upright bikes, it's a matter of trying, as we have done (ie users of reclining bikes)." REPLY....... Comentarios útiles gracias
As a short rider i have come to the conclusion bike manufacturers don't want me . You make lot's of good points about 170mm v 160mm , but have you tried to find 160mm cranks on a bike ? Even small , extra small or even extra extra small bikes from the cheapest to the very expensive all come with 170mm cranks , if you are very lucky you might find 165mm , but anything less is custom or very rare. All bike manufacturers are very quick to tell us about their new shiny technology but fail to give us even the option of 160mm or 155mm on small or extra small bikes , this is my main gripe. Many short riders have bikes languishing in sheds after riders give up trying to push 170mm or worse 175mm cranks on their extra small bike .end of rant . Thanks i enjoyed your video .
Would this hold true in BMX racing?
h'mm I would've thought ground clearance of the bottom bracket would come up somewhere in this subject?
good call. next time.
I find the part at 4-5 min confusing. Seems cadence and foot travel distance is being mixed up. If torque and power is the same then cadence is also fixed. Only crank length and force could vary while maintain equal torque. A nice thing to analyze futher would be the ideal crank length to a certain inseam length. At which radius do we keep our leg muscles working in their optimum most efficient range? Seems to me the more we bend our legs the less power we have. But how short crank is too short then? Also what about the issue of hard accelration (sprinting) requiring maximum leverage (torque) compared to just maintaining even power output (tt?) requiring constant force (power). Maybe less energy is wasted with short cranks if the power is kept constant.
point is that if you increase D in order to increase the torque and you want to increase power thanks to that increased torque, you should keep the same cadence you were able to produce with a shorter crank. That is more difficult with longer cranks as the pedal velocity you have to produce to achieve a certain cadence must be higher than before, as the circumference of the pedal stroke is also increased.
In other words there is a trade off when you increase crank length. On one hand the immediate effect on Torque is clear: increase D and T increases. However, due to the fact that now you have to ravel a longer circumference, it will be harder to keep the same cadence.
To answer your questions: it depends on the rider, try different crank lengths and see what is optimal for you. I am 1.82 and for instance I ride 172.5. This obsession about long crank lengths is due to the fact that people analyse only the "torque" part of the argument.
I hope it is clearer now ;-)
Yes there are several errors in terminology at least here. At about the 4:50 mark the presenter misinterpreted (or misuses) the P=Tq X C(?) formula when he states that if Torque and Power remain the same when the crank length is changed, the Cadence must change(?). This is incorrect. As mentioned in the other reply, the variable that changes is the amount of distance the end of the crank travels (greater circumference) and therefore the speed of pedal/feet has to increase to cover the same amount of distance in the same time, when compared to a shorter crank. Not the cadence.
For a tall enough rider there is little difference in perceivable torque advantage between a 172.5 and a 175mm crank. The difference in pedal speed between 170mm and 175mm cranks at a cadence of 80rpm is less than a 3% increase. This doesn't directly correlate to a 3% increase in O2 use/energy input. Not nothing but not huge.
Mike H yes definitely confused
Any ideal formula to get pedal and crank
no no no, cadence is hot the speed your legs are moving but the number of revolutions. longer crank, same cadence, your feet are traveling faster, but you need to sit lower and your knees come higher, restriction the aero position. Therefore, it is beneficial for TT and tri to have a smaller crank. But easier to have longer cranks for hill climbs and more upright positions
You broke this subject down “Barney style”, a.k.a. clear&concise. Your analysis is on point! Thank you for your contributions!🙏🏾
Leonard Zinn SWEARS that taller riders need longer cranks. I am 6'3" with normal length legs for my build and I use a 175 on my road (race) bike and 180 on my TT bike and can't really tell a performance difference. I want the clearance during criteriums so I don't see any reason to go past 180 as I've scraped a pedal a few times just with 175s. And thats scary at 30 mph in the middle of a corner!
Right all this TH-cam videos only seams to mention road bikes. I ride MTB and my BB is 70mm lower than rear axle. This mean that I may hit a ground on bend because of that. How do I determine a length of my crank based on position of bottom bracket ?
I'm 6'1" and getting 165mm crank will be a bit short I think and now I have 175mm crank
I like to think about the problem in terms of force and radii only, since then you don't have to deal with power and cadences. I approach it as follows:
Let f_p = tangential force applied by your foot at the pedal.
Let r_p = the radius of the crank arm (i.e. crank length).
Let r_gp = the radius of the pedal gear (i.e. the chain-ring).
Let f_c = the tension force on the chain.
Let r_gw = the radius of the wheel gear (i.e. the rear wheel cog).
Let r_w = the radius of the rear wheel.
Let f_w = the tangential force the tire applies to the road, at the contact patch.
ANALYSIS:
Pushing on the pedals produces a torque (T_p = f_p * r_p) on the bottom bracket axle.
This pulls on the chain with some force (f_c = T_p / r_gp).
The chain, in turn, pulls on the rear wheel cog gear with the same force, producing a torque (T_w = f_c * r_gw).
This torque causes the tire to produce a backwards frictional force (f_w = T_w / r_w) on the road, and the road then produces and equal and opposite forward force on the bicycle.
The whole equation then becomes:
f_w = T_w / r_w
= f_c * r_gw / r_w
= (T_p * r_gw) / (r_gp * r_w)
= (f_p * r_p * r_gw) / (r_gp * r_w)
= f_p * (r_p / r_w) * (r_gw / r_gp)
Where I've deliberately grouped the radii together in the last line in a rather suggestive way.
Let's look at a simple example, where the front and the rear gears have the same radius. My Trek 520's middle chain-ring and its biggest freewheel cog both have 36 teeth, so this isn't just academic.
Then the equation becomes:
f_w = f_p * (r_p / r_w)
If I have 700c wheels with a radius of 350 mm, and my crank-arms are 175mm, then the relationship between the forces is:
f_w = f_p * (175 / 350)
= f_p / 2
So the force pushing my bike forward is exactly half the force I'm pushing on the pedals with, at any given instant. That's when the gears are both the same size.
This implies that a longer crank-arm (or a smaller rear wheel!) will give a bigger wheel push for a given pedal force. Of course, changing the crank length affects body mechanics, and shrinking the wheel radius reduces how far you roll per revolution, so those are the tradeoffs.
Next, let's change gears.
When the gears were the same size, their ratio was 1. But the bigger the (back to front) ratio, the bigger the push will be, so we want to maximize this ratio. This means we'll get the biggest push on the smallest chain-ring (r_gp) and the biggest rear cog (r_gw).
My smallest chain-ring has 26 teeth, and my biggest cog is 36 teeth, so the ratio is:
36 / 26 =~ 1.38
and therefore my maximum push on the Trek is:
f_w = f_p * 1.38 / 2
= f_p * .69
So the highest force transfer I can get is about 69% of my input.
Now, let's turn it around and see what it looks like at the other end of the gears.
My weakest gear ratio (back to front) is:
11/48 = ~ .23
so:
f_w = f_p * .23 / 2
= f_p * .11
When I'm grinding, the bike is only getting pushed at 11% of my input force! To get the same push as my strongest gearing, I have to crank about 6 times as hard:
69% / 11% =~ 6.3
The conclusion to all this is that smaller front to rear gear ratios push the bike harder, but you have to spin faster to keep up with the wheels. That's the trade-off for gearing.
Incidentally, that's probably where that clickbait ad about the maximum cycling speed being 60kph comes from:
100 rpm * (48 / 11) * .7m * 3.14 = 959 m/min = 57.5km/hr
Guy probably just looked at a typical road bike and plugged in what he thought was a super fast cadence. :P
NOW on my carbon race bike l have a 172.5mm crank mated now to a 50/39T chainring and 12-28T cassette .Being fighter bike l can use a higher gear ratio than the bike below overall but l spin them faster and l get pretty much the same top speed between the two at around 46km/hr which is more than quick enough .AND on windy days around 35-39km/hr ,which is also fine . Funny how both bikes with different set ups end up same results BUT different feel between the two. RACE bike feels zippier and old steel more relaxed :)
PS l am looking to change out rear cassette to a 11/32 soon ,l intend to do some climbing with it in future...."RIDE UP GRADES " :)