Crankarm Length

[ridemoreoften]

I currently ride a CIII that was custom fitted with a 172.5 campy crank (53x39). Bought a new bike with a 175 crank arm. Although I haven't rec'd the bike yet my buddies think I made a hugh (2.5mm) mistake and absolutely need a 172.5 to match my custom fitted ride. I'll ride the bike and decide, but in the interim to me it doesn't seem to be a big deal. I don't have much experience in this department and was wondering what you folks think. Also,
I'm 6' tall with a 30-32 inseam.

[keelybepesto]

I am 6'-2", my inseam is about 35 inches and I ride 172.5mm arms. I am not a spinner and these arms give a little more leverage. 175's are very long for your inseam and will be very difficult to spin. They might be kind of awkward to use. I would use 170's if I preferred to spin. Don't let big numbers (macho) influence your choice. I raced with a guy who could spin like mad, 5'-6" or so, and used 170's. He could have been faster with 167.5's. It is physics my friend!

[ridemoreoften]

Thanks for the info. This is kind of new territory for me.

[benb]

I'm 6'1", I ride 175s.

I tried 172.5s for a season as an experiment (partially as a result of making a similar mistake.)

I've also used 170s on a fixie for quite some time.

With the 170s I clearly felt less powerful in almost any situation.

172.5 I felt no difference on the flats but I was subtly worse climbing.

I had been ring 175s for a long time before trying the 172.5 cranks though.

I think you are probably fine either way... but it might be worth trying the 175s.. at 6' you are probably big enough to use the 175s... Zinn would have you using even longer cranks, it's mostly who fit you.

Just adjust the seat accordingly.

[thwart]

Don't know about "huge mistake". I'm only about 5-10 1/2 (pubic bone height 85 cm) and most of my bikes have 172.5 mm cranks.

However my favorite climbing bike just happens to have 175 cranks... a coincidence, maybe? So many other factors, obviously, although I've eliminated gearing, total bike weight and wheel/rim weight as the reason for this preference. I've always wanted to switch things around with the crank to find out. Maybe this spring...

[benb]

Same gears + longer cranks = lower effective gearing. You have a longer lever arm and gain extra mechanical advantage. The problem is when the crank is so long it causes excessive knee bend.

In any case no way it's a "huge mistake". Give it a try. Huge mistake to me is injury.. 2.5mm difference is unlikely to cause an injury.

[keelybepesto]

If you have access to different sizes, try them all. Also, consider your primary riding style and terrain.

[jimcav]

you just have to allow the adaption to happen.

kops is one place to be, you can also be ahead or behind within reason and you will be fine--you just can't jump positions dramatically.

adjust saddle ht especially and fore aft to maintain a similar position as you are currently using. your ankle movement will absorb a lot of that 2.5mm difference unless you are at a real extreme of your saddle height range.

my bikes have 175 or 172.5 and no issues. years ago i rode 170 and had no issues--because i set my postion correctly relative to the BB and cranks.

take it slow in changes and your body won't perceive them as such

[WadePatton]

I ride 170, 175 and 180 cranks on the fixie, gearie, SS-atb. 34" inseam. Some sources suggest I should be on 180 roadie and 190 atb. Gonna try. I like leverage 'cause I don't care for gears. :cool:

And I've never "noticed" a difference--the bike have other much larger differences than crank length. ;)

[Ken Robb]

I'm 6'1. I can tell the difference when riding 170 vs. 175 but not 172.5 vs. either. I mean c'mon that's about 1/10th of an inch isn't it?

[keelybepesto]

My point is primarily about spinning on the road on a road bike. It is a very efficient style with little wear and tear on the rider. I would like to see a video of someone riding 70 to 90 prpm with 180mm or 190mm arms! Steam locomotives begin self-destructing the moment they begin to move. It is physics my friends.

[SimonC]

I've owned bikes that I presumed to have 172.5mm, which upon checking (after an extended period of riding) actually had 170mm or 175mm. I wouldn't sweat it, give it a try and see

[R2D2]

I am 6'-2", my inseam is about 35 inches and I ride 172.5mm arms. I am not a spinner and these arms give a little more leverage. 175's are very long for your inseam and will be very difficult to spin. They might be kind of awkward to use. I would use 170's if I preferred to spin. Don't let big numbers (macho) influence your choice. I raced with a guy who could spin like mad, 5'-6" or so, and used 170's. He could have been faster with 167.5's. It is physics my friend!

No big deal to spin 175's. I keep 90 to 100 all day long.
Lance never had a problem and he rode 175's.

[soulspinner]

Don't know about "huge mistake". I'm only about 5-10 1/2 (pubic bone height 85 cm) and most of my bikes have 172.5 mm cranks.

However my favorite climbing bike just happens to have 175 cranks... a coincidence, maybe? So many other factors, obviously, although I've eliminated gearing, total bike weight and wheel/rim weight as the reason for this preference. I've always wanted to switch things around with the crank to find out. Maybe this spring...


I have an 85 pbh and am 5-10 and1/4. I feel best on my bike with 170s(old school spinner) but Im no faster. Style is key here...if ya cant produce power with raw strength, do it with rpm...

[chrisroph]

give em a try. you might like them.

i've got 172.5 on the road bikes and cross bike, 175 on the tt bike and mtn bike, 170's on the winter fixie (just installed in lieu of 172.5), 172.5 on the summer fixie, and 165's and 170's on the trackbikes.

not a big deal at all to switch around.

[J.Greene]

not a big deal at all to switch around.

I can't tell a functional difference between 170's and 172.5's. I'm not tall so I ride 170's like everyone says I should, but does not seem to matter.

JG

[Fixed]

you just have to allow the adaption to happen.

kops is one place to be, you can also be ahead or behind within reason and you will be fine--you just can't jump positions dramatically.

adjust saddle ht especially and fore aft to maintain a similar position as you are currently using. your ankle movement will absorb a lot of that 2.5mm difference unless you are at a real extreme of your saddle height range.

my bikes have 175 or 172.5 and no issues. years ago i rode 170 and had no issues--because i set my postion correctly relative to the BB and cranks.

take it slow in changes and your body won't perceive them as such
bro what he said .. but I sprint better on a shorter crank don't know why or care just do imho
cheers

[Waldo]

I'm 6'1" with an 89cm inseam and weigh 160lbs. I ride 190s. I'm not a masher. Love 'em.

[kgreene10]

I'm 6'1" with a 92cm inseam and my Advanced Serotta fitter put me on 172.5 cranks, primarily because I have tight hamstrings. No problems so far.

I did ride a friend's similar geometry IndyFab with 175s for a day and I thought I might have felt some extra power. Of course, it's really hard to know from just one ride.

[tv_vt]

I'm 6'2" - have used 175, 177.5, and 180s. I also wear size 48 shoes. I prefer the 177.5 cranks, but the others are ok, too. There is not as big a difference as folks make it out to be. Don't obsess over this - either length is fine for you.

TV

[WadePatton]

obsession: (thank God these are abstracts)
http://www.ncbi.nlm.nih.gov/pubmed/11417428?dopt=Abstract

http://www.ncbi.nlm.nih.gov/pubmed/10828327?dopt=Abstract

heeeeeeeere it is: (where I got the idea to try 180's and 190's-atb)

http://www.polaris.net/palmk/crref.html

obsession: winter is good for that. :bike:

[Ken Robb]

I'm 6'1" with a 92cm inseam and my Advanced Serotta fitter put me on 172.5 cranks, primarily because I have tight hamstrings. No problems so far.

I did ride a friend's similar geometry IndyFab with 175s for a day and I thought I might have felt some extra power. Of course, it's really hard to know from just one ride.

I'm 6'1 with 80cm PBH and if I considered how tight my hamstrings are I'd be on 120mm cranks. :banana:

[Satellite]

I originally bought 175 cranks with my new Moots; I never felt like I could get any power out of them; it also messed up my knee to spindle drop. I always used 172.5 and went back to them and my average speed increased 2mph, I know it sounds crazy but this is what happened. I would have believed it if someone else told me this story but I don't make it a habit of lying to myself :no: