[Closed] what crank arm length

why?

Shorter cranks are nicer to spin with, I'd recommend 175 or 172.5 for you, but you could probably get away with 170s fine. Wouldn't go for 165s.

Totally oblivious to it tbh. 175s and 170s spread across various bikes, I've only got the vaguest idea which is which, certainly can't tell when I'm riding. Oh, I'm 5 foot 10.

GW might be along in a minute to scathe at me 😉

running 175's on the mtb and road bikes, seems to work for me, but i am 6' and have slightly long legs. Whether you'll notice the change in length seems to depend on how much you ride, how you ride, etc etc.

"considering 165 or 170 on 2*10 Xtr on the new 29er..."
Why not 172.5, 175, 177.5 or 180mm?
Especially when you are 6ft tall (and for a 29er?) what is it that is making you consider the shorter lengths?

34" inside leg, running 175mm on FS, XC HT's, jump(ish) HT, though mostly because thats what I had or what I bought
170mm on the rigid commuter/other bike. Swapped them from another bike that I wanted the rings from. Original 175mm crank rings were rivetted. Slightly easier feeling* spinning on the 170mm's seem to make sense to me on it. Slightly lacking feeling* 'grunting' uphill though. Not that it does anything like the 'grunting' uphill that the MTBs do8
165mm I've tried on my brothers 7" FS. Nice easy* spinning, but not much grunt, though you can't put a lot into climbing on that thing, too cramped/short post
I like the idea of 180mm maybe for realy trying to push down leant over in corners, but I guess I wouldn't notice much difference over 175mm's, AFAIK I'd have to fork out for XT/XTR and may well make spinning smoothly slightly harder

*Quite how much is percieved I couldn't say

NW. CBA scathing 😆 plus I was on 175s today (BMX)

dunno why anyone under 6ft would want longer than 170s on an mtb tho. (except for mibbie SS) 😕

James - coz they are too rare 😉

It has far more to do with your leg length than your height. But most bikes come with 175mm cranks regardless, which are longer than optimal, but it's hardly a big issue.

Shorter cranks are easier to spin with though, I'm 5ft11 near enough with a 33" inside leg (which is quite long for my height) yet I prefer to use 170's. I can spin them easier, I can use a smaller chainring without running out of gears so readily, and I barely notice the lack of leverage on a short steep climb say. Also, I used to have knee problems years ago, switching to shorter cranks and Crank Bros pedals from Shimano, both helped save my knees and I've not had a problem since.

"James - coz they are too rare"
They are, but there are available on XTR (177.5 on last gen. XTR), which he's wanting

I still wouldn't! XTR arms bend (try finding a replacement 177.5 arm)

One of the reasons is to alleviate pedal strike on tech climbs..

GW - Member

dunno why anyone under 6ft would want longer than 170s on an mtb tho

Bought them without really thinking about it if I'm honest... But luckily, I can't tell any difference. Phew!

the_lecht_rocks - Member

One of the reasons is to alleviate pedal strike on tech climbs..

Gw.. depends on which bike and Nicolai have low bb heights as std...

no it doesn't and not particularly

I used to think it was really important - hence why I have 172.5 on all of my road bikes (including the winter one, but excluding the tandem which has 175), rather than the more standard 170. However I'm less convinced now that it makes any real difference - you get used to what you have (and most people would barely notice the difference between 170 and 175 even then). Which leaves the only major reason for choosing a crank length being a practical one - 170 and 175 are far more widely available with 175 just a whisker ahead for MTB cranks. Choose one of those - at 6' 175 would normally be the recommendation (I run 175 on my MTB at 5'9").

The rock strike thing is spurious - we're talking about 5mm difference here, which is less than half the resolution people normally use to measure BB height.

I have 150 and 127 cranks on my unis - it's surprising how normal they feel in the application.

Can people really tell the difference? Even on identical bikes but with differing crank lengths a slight change in ankle position and all of that 2.5 mm difference is lost/gained, surely?

I'll be the first to concede I'm no pro though.....

gw - why are you arguing with me ? do you own a nicolai ?

my old 26" AM suffered inane pedal strike. my VF2 never did.

the new AC29er didn't on the extended demo, and that's how i'd like to keep it....hence the OP.......

sorry, just never seen a Nicolai with a particularly low BB as standard..
how low was yours? and what travel was it?

helius AM - 173mm of rear wheel travel on 200x57 shock [translated to 160mm rear travel on 200x51].

horrendous on any tech climb...

new AC29er however feels loke a different animal on all climbs - grip aplenty and no real strike issues... i'd like to insure against strike by reducing crank arm length. i live in Norther Scotland [lots of rock]....

Can people really tell the difference?

If I've been riding my bike with 170 cranks exclusively for a while then when I ride the bike with 165 cranks I can really feel the difference. If I go the other way I don't notice it. I've also had 175 cranks and they were fine off road but my knees didn't like them for riding on the road.