Crank length query - sorry for another topic on this

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Joined: Mon Feb 12, 2018 10:48 pm

by Vowles

Hi there, I know this is covered all the time and there is no direct answer to my question but I thought that I would ask anyway.

I have always used a 172.5mm crankset 50/34 with 11-25 10 speed. I have just bought a new groupset that has 175mm crank length 52/36 with 11-28 11 speed. My question is do I need to swap the crank length over to a 172.5mm or will I not notice the extra 2.5mm?

I am 177cm tall with and inseam of 83cm.


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Location: The Grim North.

by mattr

The only way to find out is to ride the bike.
Height and inseam are only of secondary importance. Flexibility and range of movement are the main drivers.

Either build it and try it, or if you are of a nervous disposition, swap the crankset while it's new and you can maximise the sale cost.

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Joined: Wed Jan 24, 2018 12:31 am

by cassard


there is not enough scientific evidences of performance/biomecanical health changes between crank arm length. It's to specific to do a general assumption.

I'd try the new one first, then change it if there is something you don't like.

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Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

A 2.5mm jump is small. You can get used to it.

I'm taller than you (183cm) and while I rode 175mm cranks for decades I've switched back to 170mm cranks in recent years. I like the reduced hip angle and I like to spin.

There's no right/wrong answer.
Last edited by AJS914 on Tue Mar 20, 2018 2:51 pm, edited 1 time in total.

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Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

AJS914 wrote:
Thu Mar 15, 2018 6:35 pm
A 2.5mm jump is small. You can get used to it.
Unless you are already a borderline case, as i found out that i was.

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Location: Canada

by Geoff

Personally, I have never been able to 'get used' to cranks that are different than my 'normal' cranks. Strangely, I find shorter cranks 'worse' than longer ones. I have even had to go to 172.5 track cranks. On the weekend, I was getting a bike ready for the season and could not understand why it felt so strange. After much fretting with the saddle, I noticed that one of the Trek Segafredo mechanics accidentally put on a set of 175s!

I think everyone is different. I know some guys who use 165s for track, 172.5s for road, and 175s for TT and think nothing of it. You'll justneed to try it and see.

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