Crank Size Difference Help

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

Crank Size Difference Help

Postby andr000ide » 24 May 2020, 4:08pm

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: 42931
Joined: 4 Jan 2012, 6:25pm

Re: Crank Size Difference Help

Postby Brucey » 24 May 2020, 4:40pm

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
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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

Re: Crank Size Difference Help

Postby thatsnotmyname » 24 May 2020, 4:42pm

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

Postby Nebulous » 24 May 2020, 6:47pm

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

User avatar
iow
Posts: 411
Joined: 27 Jul 2010, 11:01am
Location: isle of wight

Re: Crank Size Difference Help

Postby iow » 25 May 2020, 9:59am

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.
mark