Crank Length?

Discuss light weight issues concerning road bikes & parts.
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SuperSix2018
Posts: 25
Joined: Mon May 06, 2019 8:00 am

by SuperSix2018

Evening all,

Apart from seat height will changing from a 170mm to 172.5mm cranks alter much in bike fit / physical power etc.

Im 170cm tall and have an inseam of 810mm.

I can get hold of a new Power Meter which is the 172.5mm cranks cheap.

I spin a 175mm on my MTB.

Cheers

by Weenie


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pdlpsher1
Posts: 2424
Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

You have very long legs for your height. Is your saddle height sound 75cm? I’m also 170cm tall but with a saddle height of 70cm and 170mm cranks.

If you go with 172.5mm cranks you should lower your seat and stem by 2.5mm.

Crank length can be dependent upon the position of the rider. The new trend in the Pro peloton is to use shorter cranks so they could get a more aero position by lowering the torso. There are many Pro riders who are over 180cm tall and use 170 cranks (Jasper Stuyven, Alex Dowsett, just to name a few).


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TobinHatesYou
Posts: 4196
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

I am 178cm with an 81.8cm inseam and use 165mm cranks on one road bike, 170mm on another road bike and 172.5mm on my junker/trainer bike. I have no problem switching between them on a daily basis, but I prefer I do prefer the 165mm cranks.

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Beaver
Posts: 720
Joined: Wed Aug 18, 2004 6:06 pm
Location: Lower Saxony - Germany

by Beaver

Some pros are now getting back to longer cranks again... it's just a matter of taste and your muscles adopt to it.

Currently I am running 170mm regulary as I am testing a smaller bike for someone and run 172,5mm on my bike parallel. It feels a bit odd in the beginning but I run the same speed and cadence, when I check afterwards. Don't overestimate this topic. It's just 2,5mm of 170mm after all...

TobinHatesYou
Posts: 4196
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Smaller cranks are doubly beneficial for opening up your hip at TDC. Not only are you not lifting your foot as high, but you are also opening up your hips more with a higher saddle position. They”re also beneficial for allowing you to pedal through tighter corners.

Since it’s mostly just adaptation, I think it makes sense to adopt shorter cranks...especially if one has an aggressive fit or races crits.

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