Cranklengths: school me about long vs short (Road, Track, TT)

[istigatrice]

Hey everyone,

not sure if there's already been a topic for this (not in the first few pages of search), but would like to start one if there isn't.

So I think Cervelo and Sky/TeamGB are pushing towards shorter cranks, while a few pros (Adam Hansen) prefer longer cranks. I used to use 170mm cranks but 'felt' that 172.5mm cranks were more comfortable (though 2.5mm seems like such a small difference to notice). I'd like to ask what other people have noticed, and what their body proportions are. What crank lengths have you experimented with, and what length have you stuck with?

[Rick]

This has been discussed extensively, and there is also a LOT of stuff on the internet about it.
I have experimented with 170, 172.5, 175, and 180.
I ended up going to 170
That is 20.6% of inseam
I have seen recommended formulas that range from about 18% to 21.6% of inseam, Others claim optimal crank length is not really related to inseam at all. My personal opinion is that it is "related", but a lot of other factors also influence the final choice.
I was surprised at how little difference the various lengths made (to me). It is a very subtle difference in the ability to spin, even with the longest.

[istigatrice]

A lot on the internet, but was hoping just to just get a few 'observations' from people. Most sites seem to 'recommend' shorter cranks though. Thanks for the reply though.

Interesting that you found the 170mm 'nice'. Your inseam is longer than mine but I felt more comfortable on 172.5, not sure if it's because of our riding style (I like to climb out of the saddle a lot).

[AJS914]

After being on 175s for years, I decided to try shorter. I tried 170s. I really like them. What I notice is that they force me to climb at a higher cadence and I need one gear higher than 175s to maintain a good cadence.

The bigger difference is with the hip angle. I raised my saddle 5mm and left my stem the same. It was more comfortable overall.

[User Name]

I'm 182cm and my inseam is about 88 or 89cm, and I've tried everything from 165 to 180.

The short answer: longer cranks may have more leverage, but they're harder to push, mostly because the hip and knee angles are increased, but also because the circle being pushed is larger (I don't fully understand this bit about torque and 'work'. Check out page 20 on the link below for an explanation), so it kinda balances out.

The extra length, coupled with having to lower the saddle, doubles the increase that your knee reaches at the top of the stroke. In other words, you're sitting relatively lower, so it's a little harder to start pushing down.

Long cranks can be less comfortable if your thighs hit your stomach. Also, you may have read that shorter cranks usually make riders more aero, due to being able to get the upper body lower without the knees getting in the way.

After using 180s for a year or so, I had sore knees (medial) for what ever reason, so I switched back to 175s for some relief and felt, if anything, a little faster and more powerful. I was initially sold on 180s, but after feeling good on 175s, I've dubious about long cranks ever since.

I now mostly use 172.5s, but in recent months I've been using 165s due to another knee injury, and they feel fine; I don't feel any slower or less powerful. Now I don't even notice that I'm using shorter cranks.

I feel that long cranks do have some small leverage advantage when riding off the saddle, because I'm not restricted by being seated, but how much time do we spend riding off the saddle? And doing so is less aero.

http://www.arniebakercycling.com/pubs/F ... 0pages.pdf

[istigatrice]

Interesting that your perception is that longer cranks offer a leverage advantage riding out of the saddle - I agree with this observation, it's my main argument for being more comfortable on 172.5mm cranks.

I climb out of the saddle a lot, I think it is less aero, but it just feels 'right' compared to climbing in the saddle. Perhaps being a smaller rider (170cm) there's less aero disadvantage (I'd still be tucked in behind taller riders who are seated)... However I have registered (solo) PRs on climbs when I made the effort to stay in the saddle for the whole climb in a pseudo aero tuck, even on climbs averaging 10%. I've never been game enough to try this while racing though (usually climb out of the saddle when it's crunch time).

Also interesting that on the Track I use 165mm cranks and I switch between my 172.5mm road cranks to 165mm track cranks without even noticing it - perhaps because on the track my cadence is much higher and there's little/no climbing involved (not sure if rolling up the banking counts as climbing tbh).

[cyclespeed]

Vid discussing this subject here; https://www.youtube.com/watch?v=nu5L_GrXo5E