How tall are you?

Me. 172.5 on road 155 on tri. 5’9

5'9

165 on tri and 172.5 on road bike for me. I wouldn’t bother changing.

Your tri bike should probably have 155mm cranks.

170mm for the road bike should be good.

175 on my road bike. 170 on my tri bikes.

I’m 72.25” tall.

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Favorite Gear: Dimond | Cadex | Desoto Sport | Hoka One One

I also use 165 TT 170 road. Just under 6' tall.

I just had a fitting and was suggested trying 160 on TT.

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24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Was that a TT fitting or a Tri fitting? At "just under 6' tall", 160 seems short for a TT.

165 on tri, road, gravel and mtb.

5'7"

I don't know why I made the switch to the same cranks on everything other than attempting to replicate the cycling motion in all disciplines. Most of my time is spent on my road bike but when I go to another bike, I don't want the slightly different peddling mechanics of different cranks to ask differing things of my muscles. For a short ride or event, no big deal, but as the ride gets longer and longer I want the trained muscles to do their thing and not ask them to stretch just that little bit further 20,000x during an event leading to something unexpected happening.

TT fitting for a 24 HOUR race. Fitting by Chris Balser. He is the best.

Perhaps you know this but taller doesn't mean longer cranks just like lower doesn't mean faster.

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24 Hour World TT Champs-American record holder
Fat Bike Worlds - Race Director
Insta: chris.s.apex

Not really.

I'm 6' and ride 150 mm for tt. 170 road...where hip angle isn't as critical.

My tt fit was also done professionally, by Trent nix. Retired now, but was also one if the best.

Look at the reasoning behind different crank lengths and decide what suits you best.

There are studies showing very little difference in power output at rider-selected cadence between crank lengths until something crazy like 120mm or 200mm.

Shorter cranks are preferred on TT bikes as you can raise the saddle and lower the height of the knee at the top of the stroke, allowing a lower and more aggressive position and reducing the maximum hip angle.

Longer cranks, while not explicitly necessary on road bikes are usually preferred for their increased leverage on steep climbs and bursts of acceleration. At least that's what they say.

That said, the difference between 170 and 165 is insignificant on a road bike, I'd go with whatever is on sale.

+1 for Balser.

I'm 6' 2.5" and ride 155 on Tri, 165 on fatbike, 170 on Road. I believe i asked Balser and he even said the varied lengths are good variation for the training stimulus on the different bikes.

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Blog: https://davidkoppeltriathlon.blogspot.com/
Coaching: https://dkendurance.com/

My younger son is 5' 11.5" and prefers 155mm cranks.

I want the trained muscles to do their thing and not ask them to stretch just that little bit further 20,000x during an event leading to something unexpected happening. //

SO that would mean you ride with the nose of the saddle relationship to the BB in the same positions too? So unfortunately you would be giving up a ton of speed and or power in either one or both of the different riding styles. If your TT bike is set up right, then it is in front of the BB, sometimes up to 5cm, your road bike will be well behind it, thus using way different muscles even if the cranks are all the same...So kind of defeating the purpose of what you think you are trying to achieve..

I am 6’2 and glad I went to 160mm. Don’t think I’ll ever go back.