TT - Do you think I'd benefit from 170mm cranks? (picture included)

Currently using 172.5 and got the opportunity to get 170’s. Judging from this picture, do you think I’d benefit from going shorter or is it a ‘feel’ thing?

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Probably, if it feels ok without raising the saddle.

Are you saying that because my back is relatively flat already?

more that staying low closer to the bike is a good aero bet

edit: and people often say you should raise saddle to compensate for the higher pedal at 6 o clock - I dont see any good reason to make that the reference point.

I don’t really see a benefit here….shorter cranks help open your hip angle, which allows you to rotate forward more to get lower.

You are already really low and look like you have a great position. Assuming you are happy with your power numbers, I wouldn’t bother, honestly.


This is something that I didn’t take into account actually…. The power numbers! I did a 10mile TT the other night and my weight average power was 276 and my FTP is around 285. Position feels good but I didn’t know if I could get better. I wonder if 2.5mm will make all that much difference I’ve ordered it an anyway as there was only one left. I can always send it back

I would install the cranks and not make any other adjustments. Test it and see.
Shorter cranks will not only allow you to open up your hips but allow for more room to expand your lungs. Makes it easier to get the feet over the top, better spinning but a loss in leverage. It will be minor and you may not even notice much of a change. Let us know how it works out.

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2.5mm would be too small a difference for me to buy. I went from 172.5mm to 165mm and love that.


I’m considering making this same change – what do you love about it?

If that was a maximal effort, then something is not right. Either you have grossly overestimated your FTP, or you’re giving up a lot of power in your current TT position.

Ouch, that looks uncomfortable.

Nope, you should go even shorter. I gotta agree with @JT_34, a difference of 2.5 mm is not enough given the picture you posted.

I went from 172.5 mm to 165 mm cranks on a road bike and it made a world of difference. Where my knees were massaging my stomach on my old bike with 172.5 mm cranks, I breathe much more comfortably on my new bike with shorter 165 mm cranks even though it is an aggressive aero road bike instead of an endurance road bike.

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I would probably go with the latter to be honest. I know my FTP is around that number so I’m gonna go with TT position is causing a lack of power

I don’t think you’re going to notice 2.5mm.

Maybe raise your aero bars to close the arm to face gap.