172.5 vs175

[Starvin' Marvin]

Hi all

 

Probably a dumb question. What difference does the 2.5mm make?

[goya-goya]

Well the smaller the radius.. The smaller the pedal circle and the smaller the leverage...

 

Also the more ground clearance...

However the main reason should be because of the length of your thigh bone.

 

If i remember correctly (please do some research on this and dont take my word as absolute-my memory is not as good as it was):

Small frame-172.5

Medium frame175

Etc

 

However i ride 170 on my medium MTB

[andydude]

Hi all Probably a dumb question. What difference does the 2.5mm make?

 

Are you talking about your crank arm length? If no, ask the missus. If no, see goya-goya's response.

 

If you are really interested, research the topic on the interweb. There's many studies and conflicting advice, because there's no consensus. We've become accustomed to the standard 175mm and everything is measured from there, instead of starting from scratch. I've come upon a website before which according to their formula, I should ride 190mm cranks with my length of 188cm. Can't remember the address, though.

[Christie]

Somebody posted a link long ago to research done with different crank lengths, starting from 140mm up to 220mm. If I remember correctly, it made very little difference to the power output of the test batch of riders. The bodies of the riders in the test was able to adapt to a very wide range of crank lengths. Imo if your knees/feet/ancles are not hurting, ride what you have got in terms of crank length. Don't expect to do anything better on a different length of crank.

[Oltremo]

I have ridden both, and experienced no difference. I am 1.9 tall and ride a 58cm.

[Mornest]

I have also ridden both and experienced no difference at all.

[DR ◣◢]

To a very small extent it will help with a better fit on the bike. Only really if hips, ankles, knees and back is taking strain.

 

Theoretically a longer crank will make more power but in practise i have never seen or felt a difference. Used 170mm and now on 175mm on all my bikes.

[Christie]

Longer crank only makes more power if you turn it at the same cadence (in the same gear ratio). I've ridden 170, 172.5 and 175, i find that my cadence goes up slightly with a shorter crank.

['Dale]

Apparently, better leverage (shorter radius) to accelerate for short bursts of speed with the 172.

E.g. Good for roadies in a criterium.

 

I ride 175. My ideal fit is 172.5.

 

New crank arms is priced at 9 000 moola (Cannondale Hollowgram)!

:-(

Edited August 19, 2012 by ' Dale

[JA-Q001]

Like the last 2 said, it depends more on your riding style. Grind more = longer, spin more = shorter. Easy.

[Eugene]

You won't notice the 2.5mm difference. As the guys above have said, I rode both and couldn't feel the difference.

[RacerX]

It makes a big difference. I started racing (road) more than 20 years ago with 172.5 and quickly moved up to 175 and then a few years later to 180. I ride 180 on all my bikes now (MTB & road). I have a 94cm inseam which is long, but not uncommon. Once I learned to spin the longer crank I was more comfortable on the bike and my climbing improved. I can comfortably spin the 180s at 120+ rpm all day long if I need to. Oh, and for what it's worth, about two years ago I did a bike fit with Jeroen Swart which confirmed the 180mm crank length.

[davidlangebaan]

My Ergofit setup recommended 172.5 on my road bike and 175 on my mtb. As a rough guide i am 181cm. Can't remember the exact reason for the diff, but I think Renay said my knees would take more strain with 175 on the road.

[Jeepdude]

really splitting hairs between 175 - 172.5...

i see Lance now rides 172.5 on his TT bike for Triathlons and Crowie current Kona champ rides 170 and he is no midget

[Nic M]

175 will give you more power but less efficiency. Speaking from triathlon experience, a shorter crank will help keep your hip open and will help save a little for the run.

[SwissVan]

175's will give you pedal strike induced heart stoppage quicker than 172.5's