Just to be clear... what type of bike do you want to put these new cranks on?

this is the bike

So, the answer is a road bike.

What brand and model is this new crankset? What is the price?

If you don't have any specific issues with the 172s and 175s on your other bikes, I wouldn't advise going shorter on a road bike. I think you might miss the longer cranks on climbs.

I tried short cranks on the TT bike for a couple years (152s vs 172s on the road bike). No gain, no loss in TTs. Definitely different. Always felt odd (and weaker) on hills or any out of the saddle. Possibly it would have improved with adaptation.

Ultegra 6800 50/43..the whole groupset for $500

i dont want to go slower up hills but it seemed a good price for switching from 10 to 11 speed

6800 is good but you can get R8000 crank, shifters, brakes, front/rear derailleurs, chain and cassette for under $600 from a few places in the US, near $500 from Merlin.

https://www.merlincycles.com/...groupset-102895.html

My bad...R7000

Strange coincidence, I just bought the R7000 crankset in 165mm because it was cheaper than the 170mm option which matched what I already had on my road bike. The 172.5mm length was also cheaper. For me, going from 170mm to 165mm I thought meh, who gives. 5mm is half a centimetre. I'm in a very hilly area and run 165mm on my TT bike already. I'm sure it won't matter two hoots. And on the plus side I can raise my saddle half a centimetre as well, for a slightly more "pro" look, which is what really matters.

If you look on Wiggle as I say the 165mm and 172.5mm are both cheaper than the 170mm and 175mm options. But in compact 50/34 (which is what I wanted). And in black which is sexy AF.

I wanted to experiment with shorter length and did this exact change on my tri bike (172.5 to 165). been riding it since about march. i still have 172.5 on my road bike which i also ride regularly.

the change is noticeable for me, from a FEEL perspective. whether it's a performance benefit, i'm not able to tell quite yet. i feel less powerful in the shorter cranks, but my power and speed numbers/ratios haven't been noticeably worse or anything. i think it's just getting used to the different pedal stroke. i did a proper short little sprint on the 172.5s the other day and i felt much stronger than if i were on the 165s and, coincidentally, set a peak 10 sec power for the year (but i haven't done the same type of rippin' sprint on the tri bike lately so take that with a grain of salt of whether my sprint power is better with the 172.5). i could really notice the extra leverage when cranking out big watts. climbing out of the saddle feels this way too, but granted the cockpit/position differences of a road/tri bike contribute to that feeling as well for me, so not sure how much of it is ALL the crank length. climbing out of the saddle feels better on a road bike than tri bike, no matter what the crank length.

So this is to say that im still playing around with it. im trying to get used to the feel of the 165s, trusting that on the tri bike they help with aero, and perhaps help with having the run muscles be a little fresher. i sorta wish that i went with 170s, that way i wouldn't feel the difference as much, but in reading around i wanted to actually try cranks that were significantly shorter. going from 172.5 to 170 isn't much of a change, so they say. but I think i'm going to commit to it for the year, at least. sample size, and acclimation time, is not big enough yet to know for sure how much of an advantage it may be. if at all. i've been riding the 172.5s for 10 years so i feel like i need to give myself some more months to really get used to the new feel and see whether i want to stick with it.

I don't think the cranks or rings cared... at least mine didn't when I went 9 to 11.

If you hopped on a bike with 165s and everything was set up exactly like your 172.5s my guess is you wouldn't really notice it.

it's just stomping down on the cranks, don't over think it.

---

Brian Stover USAT LII
Accelerate3 Coaching
Insta

Agreed. Bought a gravel bike with 165s vs. 172.5s on my tri and two road bikes and don't really notice the difference at all.