Hi all,
I recently had TT bike fit and the fitter went to shorter cranks. It seems like it opens up hips more, makes spinning easier. Now I am getting shorter cranks on road bike. Do you think this is just a fad?
KK
Nope. My .02.
Nope. My .02.
Seconded. There is sound logic to the “fadâ€.
Nope. My .02.
Seconded. There is sound logic to the “fadâ€.
Although people said the same for the longer cranks ‘fad’ c2011.
Not saying I don’t see the logic, but jut mentioning that at any time there’s a great reason for all the design decisions. Not that long ago we thought the secret to aero was a blade edge widening to a wedge ahead of the tube on a frame, and all thin as possible with minimum gap from a wheel bearing a tyre at 120+psi. That had ‘evidence’ to support it. Now we have newer evidence to say the contrary.
For me I’ve gone slightly shorter to 172.5 on tt (was 177.5) and stayed at 175mm on the road bike. Works for me with my daddy long legs and long cycling background. I’m a spinner (natural cadence is 95rpm + for longer rides) and so shorter cranks would need some fairly funky gearing to work in the hilly area I live.
Fad… ehh. That’s a bit too far I think. Like most things in cycling, the first thing to use for context is…where did you start.
Cycling in general has had cranks in the ~170-180 range (as they come at the bike shop) for a long time now, and so simply based on that, most of us started riding on something in that range.
More recently as more information/studies became available, and as more actual options (that is, to buy) became available, it’s fairly obvious to see that in most situations, crank length doesn’t have a terribly meaningful impact on power (at least steady state) and so it opens the door to start using crank length as a fitting tool that was much harder to access a decade ago. So it’s become more popular. It does open the hip more, which is often beneficial.
The danger / fad part of it is when people/fitters start using it as a panacea. Every problem becomes a nail and the hammer is shorter cranks.
I see a lot of times people say “opens the hip, lets you get lower and more aerodynamic” - to which I say… it could. But could and does are miles apart in cycling.
I’m a spinner (natural cadence is 95rpm + for longer rides) ad so shorter cranks would need some fairly funky gearing to work in the hilly area I live.
Crank length has no effect on gear ratios.
It does. Longer arms means your feet travel a longer distance per rotation. So while the amount of work per revolution is the same, the moment force at any point is lower, and you effectively lose some gear ratios, gearing being equal.
Foot speed is what tends to stay constant as athletes change crank length, so yes rpm increase and you need shorter gearing if you go with shorter cranks.
I am 6’ 1" and have 160mm cranks. I got them after a fit with a very reputable fitter. We even talked about and toyed with 165’s, 160’s, and 155’s but I landed on 160mm because it was the middle-of-the-road with those options and at that time, Shimano had just released a 105 crankset in 160 which matched the group set (really not that important though)
I don’t see ever going back. I have 165mm on my road bike. It doesn’t feel awkward, at all. I feel like I needed the go-ahead from a fitter though.
I would definitely work with a reputable fitter since shortening cranks can have considerable implications on how steep you ride which can push your front end out more and more. I think on both of my bikes, I could have / should have gone a frame size up. I basically have maxed out the reach on both road and tri.
Hi KK,
If I had moved to a shorter crank because a fitter recommended it, I can understand entertaining that it is a fad.
When you have hip impingement and shorter crank arms relieve it, it’s certainly not a fad.
Any cycling intensity coupled with running left me with debilitating hip pain. New cranks on my TT bike, then followed by a set for the road bike, rendered the problem manageable with stretching and massage allowing me to be more competitive and training and racing is more fun now.
I’m a spinner (natural cadence is 95rpm + for longer rides) ad so shorter cranks would need some fairly funky gearing to work in the hilly area I live.
Crank length has no effect on gear ratios.
Crank length does however have an effect on the force needed to turn the crank. Literally this is leverage. So if you are pressing down with 500 newtons on the pedal attached to a 175mm crank then you’d need to apply about 545 newtons onto a pedal on 160mm cranks for the same force to get applied to the chain. Note that because your foot is not travelling as far per revolution then power stays the same. Power is work/time, work is force * time distance and you’re reducing the distance (that the pedal travels).
But anyway. short/long whatever your choice. But physics is physics.
That is awesome! So glad you figured out what works for you that is what makes things not a fad. Everything is a fad when you think about it. Triathlon is a fad.
I think it’s somewhat more complicated than that as we’d all be using longer cranks if (all else being equal) you it actually meant we use less newtons
For me, changing crank lengths just meant changing which gear I ride in (in a really really immaterial way). No change to cadence, power or HR
I’m not sure if it’s had any impact on performance in other ways (like reducing fatigue, for example)
I thought of going to a shorter crank at the track because of the gear restriction but lately they took away the restriction for me so I stuck with 165’s.
I would like to try 155’s just to see how it feels.
**I think it’s somewhat more complicated than that as we’d all be using longer cranks if (all else being equal) you it actually meant we use less newtons **
For me, changing crank lengths just meant changing which gear I ride in (in a really really immaterial way). No change to cadence, power or HR
I’m not sure if it’s had any impact on performance in other ways (like reducing fatigue, for example)
Newtons isn’t the entire issue, it’s the combination of speed of rotation (cadence) and force. So for a constant power, then you make the crank shorter and apply the same force then you would slow down the cadence. Or go the other way, keep the same force and cadence you’d end up increasing the power.
Why don’t we use really long cranks, well as per my first post, that was the ‘trend’/common belief 10 years ago - we should be riding 180/185mm. But it is more complex, and now the impact on fit and aero is trumping the logic of the long lever, slow cadence that was ‘vogue’ 10 years ago. Also there are practical reasons not to go too long other than fit - clearance to the front wheel, chainstay and when cornering for a start.
I switched to shorter crank arms to improve my position on my triathlon bike. I don’t see any similar need on my road bike. Hip angle doesn’t seem to be as much a critical factor for my road bike position, and I do have a healthy drop distance from my seat to my handlebars. Am I missing something?
Seems like you are dialed. Yahooo! Riding bikes is the best.
I thought of going to a shorter crank at the track because of the gear restriction but lately they took away the restriction for me so I stuck with 165’s.
I would like to try 155’s just to see how it feels.
I had a 172.5 wired SRM on the track, which was definitely too long for me in pursuit. I ended up upgrading to a P2M in the Aldhu cranks and decided to try 155’s. I feel like I went just a little too far with them and I’ve never felt like they were just right. I have 165’s on my TT bike… I will probably end up getting 160’s for the P2M eventually.
I’ve got the P2m in the Aldhu crank (24mm) as as well. I went with the 165’s because I was afraid to drop coin on something smaller and not like it.
I do think I can get crank arms in 160’s. If I come across a good deal I’ll probably pick them up.
PowerCranks go down to 90mm.