Surprisingly, the stem length is also vitally important and it was not mentioned. Hmm. I ride a 55cm Pinarello Dogma frame with obviously an extremely short reach measurement (I like short, instant, left and right turning which makes it nice for bursting out of a paceline or dropping off the lead quickly) and run a 90mm Cinelli stem -- any longer and the Dog will wobble at high speed like a drunken sailor. And so goes bike geometry, this topic is a great one and could go on forever. Thanks for the great ditty!
short trail bikes: we are talinking 30-35mm. It can be a very useful trick on randoneur bike as the shot trail tends to mute the steering when riding with a front load like a rando bag. This is also to be considered for gravelbikes and does further complicate the idea of havinga gravel bike designed for 40mm 700 and putting on 25mm 700c for road rideing
it's helped me a lot because I couldn't tell if it was just the low handlebars on my aero road bike, or the skinny tyres meaning I couldn't ride no hands.
@@devinfahada4880 I think he's saying that using less trail can be useful on bikes which have a load on the front (front bags ahead of the steering axis, etc) because in those cases the angular momentum has a similar stabilizing effect. With a long trail bike, with front bags, it can feel like steering a freight train, so you make a twitchier bike and it will feel normal when its loaded up.
Years ago I went on a 2 week cycle tour on my tourer. When I got back I went for a ride on my racing bike and it was so twitchy for the first few minutes, I was all over the shop! What a difference geometry makes.
This is really helpful. My old boardman Alu bike is incredibly stable you can ride uphill no hands and stuff. My ribble is incredibly difficult on any terrain to ride no handed, makes eating whilst riding so hard.
Just changed my old alu 15y frame, to a new era carbon frame. Amazed is not enough to say how much difference there is in handling going downhill 50+kph hour. I thought that there would be a change, but to me it is a game changer
I get and mostly appreciate GCN's production style of warmly blanketing bite-size information with pretty B-roll, background music, and charismatic positivity. But please more and deeper dives to interesting themes like bike geometry. People like Tom, and most of the presenters surely have enough insightful knowledge to make a whole series on geometry alone
This was a fantastic video. I would love to watch a series on geometry to help cyclists identify what to look for in geometry charts when selecting bikes. What geometry for what conditions, needs or preferences. Thanks team!
GCN Tech: I think you meant to say, in your explanation at 1:45, that trail is how far *behind* the steering axis the contact point of the tyre is. The tire's contact patch with the road is *behind* the imaginary line where the steering axis intersects the road. Great video, and great topic!
As a poor descender I've always been interested in the relationship between trail and handling on technical descents. I've come to the conclusion that the "standard" trail of 55-60mm is actually best for this. Shorter trail feels frighteningly unstable, longer trail seems to reduce confidence in sharp bends. Front-end Stiffness is also really important
This is one of my most favourite topic of bike. And why most modern gravel bike have multiple wheel size compatibly. When the bike has say clearance for 700cx40 mm the trail is around 69 mm but when you switch it to say 700x28 mm or 650b x 48 mm the trail went Round 64 to 66 mm not much but it will Make the bike felt more different when you switch tyre or wheel size. Just like on the geek edition 700c vs 650b wheel on this channel. Keep up the great content GCN.
Stem length -> not as much as trail value. Fork rake -> already included in trail value. 71.2deg head tube angle+55mm fork rake and 73deg head tube angle+45mm fork rake both result in trail=58mm and will handle very similarly. Fork rake alone doesn't tell how it'll handling without head tube angle and wheel (and tire) size. Which, from three factors combined compute trail value anyway.
Very much appreciated!. Could you do a couple more of these, like for example the differences in ride qualities between ‘double diamond classic geometry’ versus ‘sloped top tube’ geometry? Or is that just to limit the amount of different frame sizes during production?
very good question, some people claim the longer seat post on a sloped top tube bike creates a more comfortable ride whereas some people say that sloped top tube bikes are stiffer, as well as horizontal top tube frames. Personally comfort doesn't mean anything to me and I much prefer the look of horizontal top tube bikes with dropped seatstays like TT bikes.
On the "sloped tube" geometry "Giant's" contribution to cycling world. I think it basically allowed for a better or easier fit among all riders. Using the S, M, L frame standard you could easily fit a rider by using different length of components, such as bar width, crank arm length, stem length, and so on.
I've always preferred a twitchy bike, but the 'Speed Wobble' comment hit home. In the last RR I did I caught a speed wobble right out of the neutral zone that turned my RR into a 60mi ITT.
Hi Ollie , Ken here . cool video . I went back and checked " trail" of my new bike , (Specialized Tarmac Pro with Sram shifting with hydraulic disc brakes 2020) , since getting my new bike when I'm going in a straight line the bike is so stable compared to my old bike and around the turns at speed are awesome . At first it thought it had more to do with the 50mm deep wheels and then I watch this video , again TankX Ollie .
Jan Heine, the publisher of Bicycle Quarterly, studied trail and published his findings around 2007. Kogswell Cycles supplied him with three forks of varying offset and he test all three at once. He would be a great person to interview. His understanding of geometry is well considered.
Loved this. I'd watch anything you did with this formula--pick a characteristic, isolate it with two extreme examples, and try to explain what the difference feels like. Stem length (short TT & long stem vs. opposite), for example.
Yip, I feel I have experienced this with the two bikes I own.... The one is too twitchy and for me feels unstable, while the other handles to me feels far more stable, I will measure the trail on both bikes. Thanks For this info.
A fascinating discussion! When I got my first drop-bar bike last year (a Devinci Hatchet gravel bike) I couldn't help but notice that it felt sluggish in sharper, slow-speed maneuvers but very stable at high speeds (to the extent that I was sometimes shocked at the speeds I reached on descents). Turns out the trail is almost the same as the high value in this test.
Great presentation Ollie. As 60 year old rider I was just trying to decide whether my next bike will be have race or endurance geometry. Endurance it is 👍🏼
Finally. Geometry (beyond stack and reach) has been ignored by the average punter for so long now, when it used to be such a commonly understood concept as recently as 10-12 years ago. Great to see someone re-educating people on this front.
A great study of the aspects of frame design that affect handling. I learned to build frames by reading and practicing ideas. The most help I got was several articles in the mountain bike design field written by Scott Nicol of Ibis Bikes I believe.
It would be so great to have some links and files in the description to all your videos whenever it makes sense. Like a geometry chart with names for the specific lengths. Or in diy disc wheel the dimensions of the plastic and cut outs, glue. It would make learning much better after watching a video. Thanks!
So in Summary @Ollie What your saying is for a flat straight Time Trial I should get a fork with Longer trail But for Alley Cat races in the city, I should get a shorter trail fork
Watch out a bit when saying short and long. Some people can be confuse. Fork that'll create long trail have low offset (low rake). Then fork that'll create short trail have high offset (high rake). This can blow some people's mind because fork with high offset increase wheelbase length, but it reduce trail and make bike more agile.
Wow. Didn't expect this video to be THAT helpful! Thanks, GCN. I'm actually quite good at riding no handed. But after my last year's accidents I lost a bit confidence in doing things like that. Had a look at my Canyon's specs -> very long trail. So I'll definitely up my no handed cycling game next season. :-)
Great insight to how geometry effects the bike. Best one liner goes to Tom when talking about choosing a bike, at 1400. Try and build a frame of reference, That's easy for him as a bike builder 😂👍
Super helpful. I always wondered why my Fuji is difficult to ride without hands, and it feels very twitchy on the rollers. I'm going to look up the geometry now, but I bet I know the answer
wow great video, it'd be interesting on the next time you do a comparison video (road, gravel, cyclocross, tourer, time trial, cross country, (and please include track) to include the difference in trail and other geometry to understand how each discipline benefits from different characteristics! Not just the tire width and gears lol. awesome content!
Thank you. Very informative and presented in a very creative and interesting way (love the different tests). Please produce more videos explaining how the various components of geometry effect bike handling and rider experience.
This video was great! Something that I'd find really helpful along these lines would be some video(s) on how to measure the geometry of a bike yourself. I have a couple bikes that I've bought second hand and I'd love to better understand how their ride feel relates to the geometry of other bikes.
Very informative. The bike I own now rides differently than any other bike I've ever owned, for example I find it very difficult to ride without hands on the bar, I am actually scared to let go even to unzip my jacket because the bike will lose it's line very quikly. I thought something was wrong with this frame to be honest. I paid $8K for this bike so it is a dilemma I am stuck with. But I will investigate the possibility of changing the fork to change the trail.
Great subject and testing, Ollie...helped immensely by TBA's two bikes. Could have donned your Tweed Teaching Jacket and used that whiteboard to draw up the differences.
Went from a CX bike with steeper head angle and more trail to a gravel bike with slacker head angle and less trail. Only ridden on road so far for winter, but preferred the CX bike on the road. Can imagine less trail will be better offroad on the gravel bike to aid quickly adjusting line choice on trails.
With the same fork and wheel diameter, the steeper head angle would give a shorter trail and vice versa. Typically a gravel bike would have longer trail than the CX bike.
while more trail makes the bike more stable from the standpoint of the bike/wheels encountering external forces.... the converse is that more trail makes the bike more sensitive to the riders handlebar inputs... balancing those two factors makes for the desired feel which can be highly personal preference!
the geometry of a bike tells a lot - i went from a redline 26pl ( 26inch bmx) to a salsa journeyman flat bar large frame - i chose a flat bar large frame after sitting on a drop bar and realizing the geometry was completely different and went and looked at the numbers, and got it right based on what i knew i liked. it felt sketchy buying a bike online based on the numbers, but it worked.
Living in Eastern Canada (super flat) half of the year and in south of France (super hilly) the other half, I can tell you trail makes a huge difference in hairpin downhills. You need to fight with the bike - as opposed to the bike almost leading you - with a longer trail bike in handling lacets .
Thanks for this video and explanation of trail. However, looking at geometry charts usually displayed on websites of bike-builders, de trail is rarely indicated. They often do indicate the "head tube angle". So it might useful make a video about that as well (y)
What would help / would have helped is to overlay the design of both frames to see the differences in construction, angles, lengths, etc. Next time ? ;-) At the end however, although surprised that millimeters can have such an impact on handling, I understand what makes my Giant TCR feel so different from my old Trek. Thx guys for another great informative clip.
Hi GCN , could you please make Q&A videos on GCN tech channel with the bicycle academy ?. Please, please, please, we would like have some of our unanswered questions in bike geometry . Like fiting a smaller bike that has a trail 70 mm with a 100 to 110 mm stem .
Awesome stuff Ollie. Sorry word explaination doesnt work for me and maybe others so please drawings and side by side comparisons would be cool.... Plus now with this info I will have to convince my hubby that i need another bike.... Thank you GCN 😋👍😁
Great video! Tom? The builder was too smart at geo for the average Joe. When a guy says. “There is no one answer.” I know I’m talking to a true craftsman of his/her trade. The visual tests were great at explaining Trail.
Can you please do a topic about all bikes having the same wheel base. How is that normal for a 160cm tall and 200cm tall person to have the same wheelbase bike???!!! Being 194cm tall I find that very strange.
Actually it comes to seat tube angle and head tube angle when the bike has the same wheel base but has different size and fit different height rider. There's an actual tool online that you can use to play around the geometry. By changing some value on the geometry chart
Interesting that in car/kart racing geometry the same thing is know as castor, so positive and negative can affect the setup in exactly the same way. Always think of it like a shopping trolley, easy to steer, but unstable :-)
ah this explains why one of my bikes isn't able to be pushed along by the seat, as the wheel just spins round which I always found super annoying. I'm guessing it must have very short trail. I have also felt that the steering feels incredibly direct compared to some other bikes.
Could you do a video on what contributes to speed wobble? I have a beautiful titanium bike that was left in the shed for years due to one-too-many speed-wobble incidents when descending. I very nearly sold it, but before I did, I changed the stem and hey presto! No more wobble!
When a tall person pats your head and calls you shorty, then it's because appreciation and envy, because the trail on small frame that the short person rides is much longer and thus he can ride fast much easier. So many reason why being short is better than too tall. :D
Can you guys make a GCN Science channel? Ollie's Videos like this with bike engineering and other videos like sports science and nutrition are some of my favourite content 😂
Pretty good video. Did any of the GCN retired pro racers ever play with trail and various geometries for specific events with custom bikes. I know in modern times it is hard for that to happen with everyone on carbon bikes that are super expensive to build. Not that long ago this was easier with Ti, Aluminum and steel frames. I would like to know the experiences of maybe say using a long trail bike on the cobbles due to lower speed and needing more stable steering. Perhaps a short trail bike on race courses that were fairly straight with lots of break always and a brutal final sprint where snappy steering in a crowded peloton was needed. ????
Size 52 and smaller is where the difference in trail between models and brands starts to show. Because they don't want high amount of toe overlap on small sizes so the head tube angle and/or fork offset need to be change. Some brands treat small riders nicely by developing small size specific fork with higher offset to counteract the slack head tube angle. Resulting in small size have same/similar trail value to larger sizes. Most notable examples are Cannondale CAAD13 and new SS Evo (two forks, size 48-63 all have the same trail=58), newer Cervelo (three forks), Specialized (two forks, but trail is not so consistent). Then there are lazier brands (Giant, Canyon, and many other) who use single fork offset for every sizes despite deviate their head tube angle for small sizes. Look at Giant TCR, size XS has trail=71. S' trail=63, M larger are 58: any review of how TCR handle in size M does not apply to TCR size S and XS at all.
Please include information on the geometry for the best time trial bike that would travel in a straight line for maximum time trial speed on a flat straight out and buy course. I’ve noticed how hard it is to go in a straight line time trailing when you’re applying maximum force, especially towards the end of the time trial When you’re exhausted. I typically weave a lot.
I absolutely love this channel so in the interests of helping people grasp the principle of trail, I have to point out that that statement, written on screen at the start, was all backwards, which was a shame because Ollie is usually so precise. Trail is in fact the distance that the contact patch "trails" BEHIND the steering axis..... Not the other way around! (Hence the name, eh!?) As I say, I'm a huge fan and so I don't want to be seen as trolling in any way but to get this wrong at the start of a video attempting to explain such a misunderstood topic was such a shame. The rest of it was pretty good.... When emphasising the influence of trail, someone once said, think of going down from a large trail right through to a negative tral (which you could technically build but would be impossible/near impossible to ride).... it would be like going from trying to pull a piece of string where you wanted it to go, to trying to push it where you wanted it to go!
it' crazy how much an inch can make such a huge difference. I got hit by an electric scooterist in the city and bent back the rake my steel forks. I tried cold bending them into place; nontheless, the handling has been compromised-much twitchier.
Oh no!!! You gave us trail numbers, but no information on head tube angle and rake. I can increase trail by increasing the head tube angle or rake and these two approaches give very different results. Please let us know the numbers for the test. Thanks!
trail is a combinakion of head tube angle, fork lengt, fork rake and tyre diameter - for this test rake, lenght and headtube angle is irrelevant. BB drop is relevant though.
In my experience, increasing trail with a steep head tube and shortening rake is quick and linear. Increasing trail by slackening head tube and going with long rake is quite different. It’s more stable when straight but less stable at high steering angles. It’s not just the trail; it’s how you create the trail.
Lots of geometry suggestions below. Here's one more in the GCN does science realm: I would be very interested in knowing the actual loss in wattage due to bad tarmac surface. We know there is a huge difference between perfectly smooth tarmac and a cobbled street... How about everything in between ?
Good one ! Thanks ! That wheel/shoe overlap can be a nuisance with short trail bikes. Recently, I had a new track bike built, and mentioned to the fabricator that I would prefer no wheel/shoe overlap, if possible -- by increasing the trail if necessary. The wheel/shoe overlap issue is worse on a track bike, because you can't move your foot out of the way on a fixie, when making a low speed turning maneuver (ie. U-turn). But he was only willing to go so far, so my new bike still has wheel/shoe overlap, although not a lot (it almost clears). He added that going beyond that would make the bike unstable, and it's also against their trademark geometry. That seems very odd, considering Ollie's tests & conclusion that bikes with more trail are more stable at high speed -- presumably what we do on a banked oval. Have they got it backwards ? Thnx.
All things being considered when it comes to bikes and handling you have to look at everything over all. Using the off the shelf geometry which you will find on many manufactures with only slight differences. You as a consumer must really look at what is best suited for your type of riding you will be doing. Maybe that's why I have so many bikes? LOL Could be! or I just like to buy bikes. N+1 you can never go wrong.
I would have likes to know what exactly where the 'tweeks' on steering tube angle and top tube length that where made to have these bikes end up with the same wheelbase. Not explaining that is a strange omission. I assume the bike with the longer trail has a slacker steering angle and a shorter top tube.. I never really understood what exactly it is that makes a bike more stable: longer trail, slacker steering angle, longer wheelbase, top tube length, lengt of the stem... Or how these (and other) factors interrelate.
Given trail is one of the main geometry figures that impact how a bike handles I have a question relating to the relationship between trail and bike size. Should it change? For example BMC (Roadmachine its 63 on all frame sizes) and Cannondale (System Six it's either 58 or 57) seem to keep a reasonable consistent trail figure. However, the Specialized SL7 ranges from 52 to 71. So do bikes of a similar trail handle similarly regardless of wheelbase or do larger bikes with longer wheelbased need less trail to make them feel as 'lively' or 'agile' as the shorter wheelbased smaller versions?
More videos explaining other parts of geometry too!
I love the science of geometry in bicycles. Had I known that when I was in High School I would have done better in class! More videos please!
Surprisingly, the stem length is also vitally important and it was not mentioned. Hmm. I ride a 55cm Pinarello Dogma frame with obviously an extremely short reach measurement (I like short, instant, left and right turning which makes it nice for bursting out of a paceline or dropping off the lead quickly) and run a 90mm Cinelli stem -- any longer and the Dog will wobble at high speed like a drunken sailor. And so goes bike geometry, this topic is a great one and could go on forever. Thanks for the great ditty!
Such an interesting and forgotten topic. Please more videos on other geometry measures! 👍
I have an endurance bike: long trail and a race bike; short trail. The handling is VERY different! Excellent job of illustrating those differences!
short trail bikes: we are talinking 30-35mm. It can be a very useful trick on randoneur bike as the shot trail tends to mute the steering when riding with a front load like a rando bag. This is also to be considered for gravelbikes and does further complicate the idea of havinga gravel bike designed for 40mm 700 and putting on 25mm 700c for road rideing
it's helped me a lot because I couldn't tell if it was just the low handlebars on my aero road bike, or the skinny tyres meaning I couldn't ride no hands.
@@mortenreippuertknudsen3576 english please.. I need further information
@@devinfahada4880 I think he's saying that using less trail can be useful on bikes which have a load on the front (front bags ahead of the steering axis, etc) because in those cases the angular momentum has a similar stabilizing effect. With a long trail bike, with front bags, it can feel like steering a freight train, so you make a twitchier bike and it will feel normal when its loaded up.
Years ago I went on a 2 week cycle tour on my tourer. When I got back I went for a ride on my racing bike and it was so twitchy for the first few minutes, I was all over the shop! What a difference geometry makes.
This is really helpful.
My old boardman Alu bike is incredibly stable you can ride uphill no hands and stuff.
My ribble is incredibly difficult on any terrain to ride no handed, makes eating whilst riding so hard.
It would have helped to See a shot of both bikes lined up in Front of each other... Interesting topic any way
BTW, Ollie has been a great addition to the team. Love his video and his crazy personality.
I could watch this type of video for hours! please explore more aspects of geometry on bike frames!
Just changed my old alu 15y frame, to a new era carbon frame. Amazed is not enough to say how much difference there is in handling going downhill 50+kph hour. I thought that there would be a change, but to me it is a game changer
Whoa, that was very interesting. Had no idea the difference trail really makes on a bikes handling. Food for thought.
I get and mostly appreciate GCN's production style of warmly blanketing bite-size information with pretty B-roll, background music, and charismatic positivity.
But please more and deeper dives to interesting themes like bike geometry. People like Tom, and most of the presenters surely have enough insightful knowledge to make a whole series on geometry alone
Cheers Pythonesque, we'll see what else we can do - what specifically would you like to know?
This was a fantastic video. I would love to watch a series on geometry to help cyclists identify what to look for in geometry charts when selecting bikes. What geometry for what conditions, needs or preferences. Thanks team!
GCN Tech: I think you meant to say, in your explanation at 1:45, that trail is how far *behind* the steering axis the contact point of the tyre is. The tire's contact patch with the road is *behind* the imaginary line where the steering axis intersects the road. Great video, and great topic!
Here's Ollie opening a can of worms (label on can, bike geometry).... Great video, keep the series rolling.
I love all of Ollie’s more scientific content. Keep it up, Ollie and GCN!
Love the geeky stuff, by far my favourite videos!! Thanks
As a poor descender I've always been interested in the relationship between trail and handling on technical descents. I've come to the conclusion that the "standard" trail of 55-60mm is actually best for this. Shorter trail feels frighteningly unstable, longer trail seems to reduce confidence in sharp bends. Front-end Stiffness is also really important
This is one of my most favourite topic of bike. And why most modern gravel bike have multiple wheel size compatibly. When the bike has say clearance for 700cx40 mm the trail is around 69 mm but when you switch it to say 700x28 mm or 650b x 48 mm the trail went Round 64 to 66 mm not much but it will Make the bike felt more different when you switch tyre or wheel size. Just like on the geek edition 700c vs 650b wheel on this channel.
Keep up the great content GCN.
Stem length and fork rake also contribute greatly to handling. This should be the subject of a video. Thanks.
Stem length -> not as much as trail value.
Fork rake -> already included in trail value. 71.2deg head tube angle+55mm fork rake and 73deg head tube angle+45mm fork rake both result in trail=58mm and will handle very similarly. Fork rake alone doesn't tell how it'll handling without head tube angle and wheel (and tire) size. Which, from three factors combined compute trail value anyway.
Very much appreciated!. Could you do a couple more of these, like for example the differences in ride qualities between ‘double diamond classic geometry’ versus ‘sloped top tube’ geometry? Or is that just to limit the amount of different frame sizes during production?
very good question, some people claim the longer seat post on a sloped top tube bike creates a more comfortable ride whereas some people say that sloped top tube bikes are stiffer, as well as horizontal top tube frames. Personally comfort doesn't mean anything to me and I much prefer the look of horizontal top tube bikes with dropped seatstays like TT bikes.
On the "sloped tube" geometry "Giant's" contribution to cycling world. I think it basically allowed for a better or easier fit among all riders. Using the S, M, L frame standard you could easily fit a rider by using different length of components, such as bar width, crank arm length, stem length, and so on.
I've always preferred a twitchy bike, but the 'Speed Wobble' comment hit home. In the last RR I did I caught a speed wobble right out of the neutral zone that turned my RR into a 60mi ITT.
Hi Ollie , Ken here . cool video . I went back and checked " trail" of my new bike , (Specialized Tarmac Pro with Sram shifting with hydraulic disc brakes 2020) , since getting my new bike when I'm going in a straight line the bike is so stable compared to my old bike and around the turns at speed are awesome . At first it thought it had more to do with the 50mm deep wheels and then I watch this video , again TankX Ollie .
Yes! More geometry videos would be awesome!
Andrew Felix agreed
Great video...Ollie was really serious this time...more videos on geometry specifically explaining different parts would be great
This is a great explanation of what seemed like voodoo before. More like this?
Check out the Geometry Flavor Wheel over at PathLessPedaled, awesome breakdown and explanation of trail, chainstay length etc.
th-cam.com/video/l7D1XhoZ90E/w-d-xo.html
@@benjaminnorland2110 I was about to mention the tasty wheel of bike geometry myself.
Jan Heine, the publisher of Bicycle Quarterly, studied trail and published his findings around 2007. Kogswell Cycles supplied him with three forks of varying offset and he test all three at once. He would be a great person to interview. His understanding of geometry is well considered.
Loved this. I'd watch anything you did with this formula--pick a characteristic, isolate it with two extreme examples, and try to explain what the difference feels like. Stem length (short TT & long stem vs. opposite), for example.
Yip, I feel I have experienced this with the two bikes I own.... The one is too twitchy and for me feels unstable, while the other handles to me feels far more stable, I will measure the trail on both bikes. Thanks For this info.
A fascinating discussion! When I got my first drop-bar bike last year (a Devinci Hatchet gravel bike) I couldn't help but notice that it felt sluggish in sharper, slow-speed maneuvers but very stable at high speeds (to the extent that I was sometimes shocked at the speeds I reached on descents). Turns out the trail is almost the same as the high value in this test.
You need to go back and do a downhill test on these two bikes.
Great presentation Ollie. As 60 year old rider I was just trying to decide whether my next bike will be have race or endurance geometry. Endurance it is 👍🏼
Finally. Geometry (beyond stack and reach) has been ignored by the average punter for so long now, when it used to be such a commonly understood concept as recently as 10-12 years ago.
Great to see someone re-educating people on this front.
A great study of the aspects of frame design that affect handling. I learned to build frames by reading and practicing ideas. The most help I got was several articles in the mountain bike design field written by Scott Nicol of Ibis Bikes I believe.
It would be so great to have some links and files in the description to all your videos whenever it makes sense. Like a geometry chart with names for the specific lengths. Or in diy disc wheel the dimensions of the plastic and cut outs, glue. It would make learning much better after watching a video. Thanks!
I love this kind of content. I really learned something here. Thanks!
Gosh darn those bikes look amaaaaaazing
Great video. Please make another one that uses the stack to reach ratio and it’s impact on speed keeping all other things equal.
One of the best GCN Tech videos!
Thanks for watching, Tracy.
GCN Tech never miss an episode. Although due to work a times it may be a binge of GCN on Saturday
So in Summary @Ollie
What your saying is for a flat straight Time Trial I should get a fork with Longer trail
But for Alley Cat races in the city, I should get a shorter trail fork
Exactly!
It's not only a matter of the fork but also the steering head angle. That means a different frame.
Watch out a bit when saying short and long. Some people can be confuse.
Fork that'll create long trail have low offset (low rake).
Then fork that'll create short trail have high offset (high rake).
This can blow some people's mind because fork with high offset increase wheelbase length, but it reduce trail and make bike more agile.
AWESOME vid guys!! thanks, more of this please!
Wow. Didn't expect this video to be THAT helpful! Thanks, GCN. I'm actually quite good at riding no handed. But after my last year's accidents I lost a bit confidence in doing things like that. Had a look at my Canyon's specs -> very long trail. So I'll definitely up my no handed cycling game next season. :-)
Please do a video on stem size and handlebar width effect on handling and chainstay length/wheel base also!
GCN video on stem length. Enjoy. th-cam.com/video/B69I_uayeMA/w-d-xo.html
Great insight to how geometry effects the bike.
Best one liner goes to Tom when talking about choosing a bike, at 1400. Try and build a frame of reference,
That's easy for him as a bike builder 😂👍
Super helpful. I always wondered why my Fuji is difficult to ride without hands, and it feels very twitchy on the rollers. I'm going to look up the geometry now, but I bet I know the answer
The internet needed this video, thank you!
Excellent video! I hope this is the first of many videos on bicycle geometry.
wow great video, it'd be interesting on the next time you do a comparison video (road, gravel, cyclocross, tourer, time trial, cross country, (and please include track) to include the difference in trail and other geometry to understand how each discipline benefits from different characteristics! Not just the tire width and gears lol. awesome content!
Awesome video. Geometrie is everything. Have a good work, GCN.
very Egg-sperimental info! Thank you GCN :D
Thank you. Very informative and presented in a very creative and interesting way (love the different tests). Please produce more videos explaining how the various components of geometry effect bike handling and rider experience.
This video was great! Something that I'd find really helpful along these lines would be some video(s) on how to measure the geometry of a bike yourself. I have a couple bikes that I've bought second hand and I'd love to better understand how their ride feel relates to the geometry of other bikes.
Unless your bike predates the internet you should be able to get hold of geometry charts for most bikes fairly easily
@@justinkimber9456 key word there is most, I have tried.
Ollie is as the bigger trail. Always stable always do high level of videos!
the best way to understand the importance of trail is to ride a brompton 😁
No doubt about it. GCN, do a Brompton no hands demo.
trail and wheelbase are not the same
@@ianiscaratti4924 that's not what they are saying, the brompton practically has a negative trail
My thoughts exactly . . . could never do no hands on mine . . .
8:15 Mr Magoo approved straight line... xD
Very informative. The bike I own now rides differently than any other bike I've ever owned, for example I find it very difficult to ride without hands on the bar, I am actually scared to let go even to unzip my jacket because the bike will lose it's line very quikly. I thought something was wrong with this frame to be honest. I paid $8K for this bike so it is a dilemma I am stuck with. But I will investigate the possibility of changing the fork to change the trail.
Great subject and testing, Ollie...helped immensely by TBA's two bikes.
Could have donned your Tweed Teaching Jacket and used that whiteboard to draw up the differences.
Went from a CX bike with steeper head angle and more trail to a gravel bike with slacker head angle and less trail. Only ridden on road so far for winter, but preferred the CX bike on the road. Can imagine less trail will be better offroad on the gravel bike to aid quickly adjusting line choice on trails.
With the same fork and wheel diameter, the steeper head angle would give a shorter trail and vice versa. Typically a gravel bike would have longer trail than the CX bike.
Great tests to show the differences and way to demystify the words. Curious to get Albert's take on it though.
while more trail makes the bike more stable from the standpoint of the bike/wheels encountering external forces.... the converse is that more trail makes the bike more sensitive to the riders handlebar inputs... balancing those two factors makes for the desired feel which can be highly personal preference!
the geometry of a bike tells a lot - i went from a redline 26pl ( 26inch bmx) to a salsa journeyman flat bar large frame - i chose a flat bar large frame after sitting on a drop bar and realizing the geometry was completely different and went and looked at the numbers, and got it right based on what i knew i liked. it felt sketchy buying a bike online based on the numbers, but it worked.
great content! thanks!
Living in Eastern Canada (super flat) half of the year and in south of France (super hilly) the other half, I can tell you trail makes a huge difference in hairpin downhills. You need to fight with the bike - as opposed to the bike almost leading you - with a longer trail bike in handling lacets .
You blinded me with science!! Great info and video Olie!!
Thanks for this video and explanation of trail. However, looking at geometry charts usually displayed on websites of bike-builders, de trail is rarely indicated. They often do indicate the "head tube angle". So it might useful make a video about that as well (y)
What would help / would have helped is to overlay the design of both frames to see the differences in construction, angles, lengths, etc. Next time ? ;-)
At the end however, although surprised that millimeters can have such an impact on handling, I understand what makes my Giant TCR feel so different from my old Trek. Thx guys for another great informative clip.
Thanks, this was really helpful. More geometry explainers, please!
Hi GCN , could you please make Q&A videos on GCN tech channel with the bicycle academy ?.
Please, please, please, we would like have some of our unanswered questions in bike geometry . Like fiting a smaller bike that has a trail 70 mm with a 100 to 110 mm stem .
Excellent job on this one GCN!
Awesome stuff Ollie. Sorry word explaination doesnt work for me and maybe others so please drawings and side by side comparisons would be cool....
Plus now with this info I will have to convince my hubby that i need another bike....
Thank you GCN 😋👍😁
Great video! Tom? The builder was too smart at geo for the average Joe. When a guy says. “There is no one answer.” I know I’m talking to a true craftsman of his/her trade. The visual tests were great at explaining Trail.
Can you please do a topic about all bikes having the same wheel base. How is that normal for a 160cm tall and 200cm tall person to have the same wheelbase bike???!!! Being 194cm tall I find that very strange.
Actually it comes to seat tube angle and head tube angle when the bike has the same wheel base but has different size and fit different height rider. There's an actual tool online that you can use to play around the geometry. By changing some value on the geometry chart
Really? I am pretty sure that in all geometry charts I have ever looked at wheelbase in increasing with frame size...
@@tecnociclista5342 yes, incrementally. Like 10 to 15 mm mostly on front center. The distance from your bb to the wheel axle.
Interesting that in car/kart racing geometry the same thing is know as castor, so positive and negative can affect the setup in exactly the same way. Always think of it like a shopping trolley, easy to steer, but unstable :-)
ah this explains why one of my bikes isn't able to be pushed along by the seat, as the wheel just spins round which I always found super annoying. I'm guessing it must have very short trail. I have also felt that the steering feels incredibly direct compared to some other bikes.
Could you do a video on what contributes to speed wobble? I have a beautiful titanium bike that was left in the shed for years due
to one-too-many speed-wobble incidents when descending. I very nearly sold it, but before I did, I changed the stem and hey presto! No more wobble!
please post more videos on bike geometry!
When a tall person pats your head and calls you shorty, then it's because appreciation and envy, because the trail on small frame that the short person rides is much longer and thus he can ride fast much easier. So many reason why being short is better than too tall. :D
Can you guys make a GCN Science channel? Ollie's Videos like this with bike engineering and other videos like sports science and nutrition are some of my favourite content 😂
I’m just happy to get on my bike and ride!!
Thanks, great great video. Makes it so clear and explains so much of what I've experienced. I am now wondering how this plays with wheel base?
Pretty good video. Did any of the GCN retired pro racers ever play with trail and various geometries for specific events with custom bikes. I know in modern times it is hard for that to happen with everyone on carbon bikes that are super expensive to build. Not that long ago this was easier with Ti, Aluminum and steel frames. I would like to know the experiences of maybe say using a long trail bike on the cobbles due to lower speed and needing more stable steering. Perhaps a short trail bike on race courses that were fairly straight with lots of break always and a brutal final sprint where snappy steering in a crowded peloton was needed.
????
Size 52 and smaller is where the difference in trail between models and brands starts to show. Because they don't want high amount of toe overlap on small sizes so the head tube angle and/or fork offset need to be change.
Some brands treat small riders nicely by developing small size specific fork with higher offset to counteract the slack head tube angle. Resulting in small size have same/similar trail value to larger sizes. Most notable examples are Cannondale CAAD13 and new SS Evo (two forks, size 48-63 all have the same trail=58), newer Cervelo (three forks), Specialized (two forks, but trail is not so consistent).
Then there are lazier brands (Giant, Canyon, and many other) who use single fork offset for every sizes despite deviate their head tube angle for small sizes.
Look at Giant TCR, size XS has trail=71. S' trail=63, M larger are 58: any review of how TCR handle in size M does not apply to TCR size S and XS at all.
Damn! That's really good looking bike! I'm sucker for nice classic round steal tubes.
Please include information on the geometry for the best time trial bike that would travel in a straight line for maximum time trial speed on a flat straight out and buy course. I’ve noticed how hard it is to go in a straight line time trailing when you’re applying maximum force, especially towards the end of the time trial
When you’re exhausted. I typically weave a lot.
With this newfound information :D I am now looking at trail a bit more in the geometry charts :D
Most geo don't include it, but if you know wheel/tire size, HTA and fork offset, it is easily computable:
yojimg.net/bike/web_tools/trailcalc.php
Those bikes look so beautiful and classy.
I absolutely love this channel so in the interests of helping people grasp the principle of trail, I have to point out that that statement, written on screen at the start, was all backwards, which was a shame because Ollie is usually so precise. Trail is in fact the distance that the contact patch "trails" BEHIND the steering axis..... Not the other way around! (Hence the name, eh!?)
As I say, I'm a huge fan and so I don't want to be seen as trolling in any way but to get this wrong at the start of a video attempting to explain such a misunderstood topic was such a shame. The rest of it was pretty good....
When emphasising the influence of trail, someone once said, think of going down from a large trail right through to a negative tral (which you could technically build but would be impossible/near impossible to ride).... it would be like going from trying to pull a piece of string where you wanted it to go, to trying to push it where you wanted it to go!
Great video! Love those bikes!!!! Please do wheelbase next.
it' crazy how much an inch can make such a huge difference. I got hit by an electric scooterist in the city and bent back the rake my steel forks. I tried cold bending them into place; nontheless, the handling has been compromised-much twitchier.
Oh no!!! You gave us trail numbers, but no information on head tube angle and rake. I can increase trail by increasing the head tube angle or rake and these two approaches give very different results. Please let us know the numbers for the test. Thanks!
trail is a combinakion of head tube angle, fork lengt, fork rake and tyre diameter - for this test rake, lenght and headtube angle is irrelevant. BB drop is relevant though.
In my experience, increasing trail with a steep head tube and shortening rake is quick and linear. Increasing trail by slackening head tube and going with long rake is quite different. It’s more stable when straight but less stable at high steering angles. It’s not just the trail; it’s how you create the trail.
Great stuff! More of this please.
Be interesting to look at cyclo cross, and the variations in mt bikes
Lots of geometry suggestions below.
Here's one more in the GCN does science realm: I would be very interested in knowing the actual loss in wattage due to bad tarmac surface. We know there is a huge difference between perfectly smooth tarmac and a cobbled street... How about everything in between ?
Now I hope Olly will do a video about stack and reach and how they work on aero-endurance-gravel-… bikes😅 I need it to buy my new bike!
Good one ! Thanks !
That wheel/shoe overlap can be a nuisance with short trail bikes.
Recently, I had a new track bike built, and mentioned to the fabricator that I would prefer no wheel/shoe overlap, if possible -- by increasing the trail if necessary.
The wheel/shoe overlap issue is worse on a track bike, because you can't move your foot out of the way on a fixie, when making a low speed turning maneuver (ie. U-turn).
But he was only willing to go so far, so my new bike still has wheel/shoe overlap, although not a lot (it almost clears).
He added that going beyond that would make the bike unstable, and it's also against their trademark geometry.
That seems very odd, considering Ollie's tests & conclusion that bikes with more trail are more stable at high speed -- presumably what we do on a banked oval.
Have they got it backwards ?
Thnx.
All things being considered when it comes to bikes and handling you have to look at everything over all. Using the off the shelf geometry which you will find on many manufactures with only slight differences. You as a consumer must really look at what is best suited for your type of riding you will be doing. Maybe that's why I have so many bikes? LOL Could be! or I just like to buy bikes. N+1 you can never go wrong.
What's the best geometry should I look for descending? I need stable going 50mph+
I would have likes to know what exactly where the 'tweeks' on steering tube angle and top tube length that where made to have these bikes end up with the same wheelbase. Not explaining that is a strange omission. I assume the bike with the longer trail has a slacker steering angle and a shorter top tube.. I never really understood what exactly it is that makes a bike more stable: longer trail, slacker steering angle, longer wheelbase, top tube length, lengt of the stem... Or how these (and other) factors interrelate.
The Top tube would have been made shorter and the headtube angle slackened to increasethe trail.
Given trail is one of the main geometry figures that impact how a bike handles I have a question relating to the relationship between trail and bike size. Should it change?
For example BMC (Roadmachine its 63 on all frame sizes) and Cannondale (System Six it's either 58 or 57) seem to keep a reasonable consistent trail figure. However, the Specialized SL7 ranges from 52 to 71.
So do bikes of a similar trail handle similarly regardless of wheelbase or do larger bikes with longer wheelbased need less trail to make them feel as 'lively' or 'agile' as the shorter wheelbased smaller versions?