Crank Size Difference Help

General cycling advice ( NOT technical ! )
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andr000ide
Posts: 1
Joined: 24 May 2020, 4:05pm

Crank Size Difference Help

Post by andr000ide »

Hello guys. I'm thinking of buying a power meter on the left crank.
But the thing is, my cranks are 170mm, and I can only find 172.5mm, do you think it's okay if I use 172.5 on one side and 170 on the other?
Thanks.
Brucey
Posts: 44522
Joined: 4 Jan 2012, 6:25pm

Re: Crank Size Difference Help

Post by Brucey »

some folk won't notice the difference, but I think I would.

Probably best to get a 172.5mm crankset or to think about using a power measuring hub or pedals instead.

cheers
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thatsnotmyname
Posts: 595
Joined: 23 Jan 2020, 10:23am

Re: Crank Size Difference Help

Post by thatsnotmyname »

andr000ide wrote:Hello guys. I'm thinking of buying a power meter on the left crank.
But the thing is, my cranks are 170mm, and I can only find 172.5mm, do you think it's okay if I use 172.5 on one side and 170 on the other?
Thanks.


The question is - do you think it's ok? I personally wouldn't do it. Assuming you are interested enough in performance to want to be able to record and monitor your power output, I'd assume you'd be interested enough to have two matching cranks..
Nebulous
Posts: 126
Joined: 14 May 2019, 10:01pm

Re: Crank Size Difference Help

Post by Nebulous »

andr000ide wrote:Hello guys. I'm thinking of buying a power meter on the left crank.
But the thing is, my cranks are 170mm, and I can only find 172.5mm, do you think it's okay if I use 172.5 on one side and 170 on the other?
Thanks.


You'll definitely notice it for the first ride, not so much thereafter and probably not at all after half a dozen rides. If in doubt try putting a thicker insole in one shoe for a test ride. This only affects the vertical component of each revolution obviously.
Ride, Eat, Sleep. Repeat
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iow
Posts: 416
Joined: 27 Jul 2010, 11:01am
Location: isle of wight

Re: Crank Size Difference Help

Post by iow »

I did a similar thing - 177.5mm nds power meter crank on a 175 ds crank. Didn't notice any difference, but I'm not normally sensitive to small changes and I think my left leg is fractionally longer anyway. My choice was purely financial - brand new, but unpopular size stages pm for £110.00. I think the pm will misread by a similar fraction, but my priority is consistency.
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