ridethecliche

I'm thinking of moving from a 172.5 double to a 175 compact double.

I know that shorter cranks allow for higher cadence and faster instantaneous acceleration.

I was wondering if getting longer compact cranks would offset this differential, especially if I moved my saddle down 2.5 mm and forward about 1mm.

Thanks!

Creakyknees

"Compact cranks" refer to gearing, not crank length, so that's irrelevant.

If you go from 172.5 to 175, lower your saddle 2.5mm. _Maybe_ slide it forward 2mm or so but I doubt you'll notice the difference.

Same with cadence and acceleration - any difference you notice is probably in your imagination.

sstorkel

+ 1000

I've ridden with both 172.5 and 175mm cranks. In a blind test, I know I wouldn't be able to tell the difference between them...

jcbenten

I rode 175s for years and switched to 172.5 when I bought a bike at the beginning of the year. My knees are thanking me but I am still adjusting to going up hill. I am a grinder and the cadence feel is a bit different.

The differences are subtle but I am able to feel them.

ridethecliche

Can't you move your saddle forward a little to counteract the knee position issue?

operator

Nothing you do will allow you to pedal a smaller circle. 172.5 to 175. That's a tough call because the difference is minor. But it might be minor enough to make a difference.

No amount of saddle/seatpost position shortens crank length. All that does is cause more fit problems. Please don't **** with fit because you wanted to save a couple bucks. It really is idiotic.

ridethecliche

Yeah, I'm talking to the person who fit me to see if it's a good idea to do this or not. My inseam is pretty long at 88 cm (about 34.65 inches). My bike just came with 172.5 cranks so I've never known any different. I rode with 170 for a bit, but I didn't actually go on long hard rides with them so I can't speak of their working or not working.

I'm not going to swing for them unless I get the okay from the coach.

As an additional question, does your cadence rise while climbing in the same gear combos when going to shorter cranks?

Edit: I'm also not selling my regular crankset, so I'll just swap back if anything feels really terrible.

gregf83 

No. Unless you increase your power output. If your cadence increased and the gear ratio remained the same you would be going faster and require more power. The force you apply to the pedals will need to increase proportionately with the shorter pedals but you will be applying the force for a shorter period of time as the crank rotates.

ridethecliche

I found this link which is interesting.

https://www.nettally.com/palmk/crankset.html

BarracksSi

It told me that, with a 33" inseam, my crank length should be 180 mm..

ridethecliche

I know, it said 190 for me. Hilarious isn't it?

My inseam is 34.65 inches. I think I'll be okay with 175s methinks. Just waiting on the word from le coach.

ridethecliche

I really wish there was an easy way of knowing what the direct results of changing crank arm length are. I know cdr has done some messing around with that, but I'm not sure how it goes around between people.