Crank Length Question

[Chuck Hammer]

Could I get some info on this question.... would I notice a large differance between 172.5 and 175 length, I have been using a 172.5 on my bikes? Because I may be able to get a great deal on a 175.

Thanks Guys

[oldpotatoe]

Could I get some info on this question.... would I notice a large differance between 172.5 and 175 length, I have been using a 172.5 on my bikes? Because I may be able to get a great deal on a 175.

Thanks Guys

Put 3 people in a room and ask about crank lengths and get 4 opinions.
I had a customer who had a 170 on one side and 172.5 on another(not on purpose) and didn't know it. I think it's a very small deal, 2.5mm in length.

I think if you did a blind test, you couldn't pick which was which.

[Charles M]

I disagree completely.

I think you'd get 5 opinions (only in the case that I were one of the 3 people).



Crank length is all about "feel" and comfort.

Crank length is all about fit.

Crank length is all about leverage and power.

Crank length is all about cadence and spin.

Crank length is about stiffness and power transfer.



Other peoples comments on Crank length is about as meaningfull as their opinion of which saddle someone else will find works best.

[Chuck Hammer]

The real question should be... I have 2 other bikes with 172.5 cranks. I am putting parts together for another bike build. Should I keep them all the same 172.5 or can I put a 175 on the next bike and never notice it?

[rockdude]

I notice when I am on a difference size crank but I don't have enough time doing it to see if it really bothers me or matters.

[tele]

I was riding one bike with 170 and another with 172.5 and didn't notice a thing. Imho its in your mind because it is such a small change.

[Ralph]

I notice crank arm differences. Once I get a bike set up for length I am using, I find changing to a longer length more complicated than it seems it should be. For me, there is more to it than adjusting seat up or down a couple MM to get it right. Others don't seem to notice much.

[Likes2ridefar]

I ride 170, 172.5 and 175 and can't tell a difference after a few minutes of pedaling.

[jischr]

I went from 170 to 175 on my road bike and never noticed, but then I wasn't looking to notice. LIke you, I got a good deal on a used triple and I was going to use it. I still spin rather than smash but I don't race so being able to 'spin up' is not important. I did notice a difference when I went from a 50 chain ring to a 53 so I'm not totally insensitive regardless of what my wife says. :)

FWIW I just measured my old mountain bike because it 'feels' smaller than my road bike while on the trainer. It's a 175 also, perception counts. Buy the 175 and run it for a couple hundred miles. If you don't like it sell it.

[Ken Robb]

I'm with Old Potatoe. I have had cranks of 170, 172.5, 175, and 180. My PBH is 89cm.
All worked well except the 180. At first I was amazed how they let me mash up hills in bigger gears than I'd usually use. Then I noticed some twinges in my knees. I don't know if it was because of increased flexion caused by longer cranks or because the longer cranks made me feel so strong I just over-did the mashing. :) I went to 175s and all was back to normal--weak climber. :rolleyes:

Through all of this I found that I could detect a 5mm. difference but not 2.5mm
but I can happily ride 170 to 175 cranks.

[luv2bike]

Hi,
Tried a 177.5mm FSA on a bike for a while ("normal" for me is 175mm).
I agree with previous posters who have said that you don't really notice a difference if you jump from one bike with one size to another with a different size. However, I definitely noticed a difference on long climbs. I tried the 177.5 'cause I thought I was a masher and wanted a little more leverage. However, the longer crank slowed down my cadence enough that I got rid of it.
I think your body is able to generate a finite amount of power (depending on your fitness etc) for an extended period. If you have a longer crank you are turning less rpm (and more force per revolution) at that same power. If that works for you...great, if not you stick with the crank that "feels" like it puts you in your comfort zone for cadence.
Does that make any sense?

[Ti Designs]

I think you'd get 5 opinions (only in the case that I were one of the 3 people).

6 - Crank lenght is about 6-1/2" give or take about an inch.

[Dlevy05]

I just swapped my 7800 175mm cranks for the same in 172.5, and I definitely notice a difference, especially when climbing (now it is harder). On the flip side, I've noticed much less strain on the knees. (As was mentioned before by Kenn Robb)

[cincicycles]

I think it's about your bio-mechanics. If you are prone to knee inflammation or hip flexor issues, one could make a solid case that crank arm length matters. One thing I noticed a few years back was I switched from regular rings to RotorQ rings on one of my bikes. It took out the dead spot at the top of the rotation. I know not directly related to crank length, but bio-mechanically, my knees felt better on the first ride than they had in a while. That being said, bike fit, flexibility and set up including length will impact power transfer, cadence and "feel." Have fun, play around and see what works best.

[Fixed]

t.t.er
or sprinter on the track ?
cheers

[Bob Loblaw]

A agree with everyone here, it's a matter of personal preference more than biomechanics.

I do think you should stick to one length across all your bikes though, to keep the fit similar. Zero facts to back that up, just a personal opinion that seems common-sensical and has worked well for me.

BL

[salem]

As I see it:
1) Some people are more sensitive to variation than others. That can be a good thing and/or and bad thing.
2) I see a lot of people out on the road for whom crank length is the very least of their fit problems. Many of them still appear to enjoy themselves.

For better and worse, I fall into the sensitive group.