Crank Length

[Pinoy Rider]

Hey everyone. I've done some searches here and did not find the answers I was looking for. My hardtail runs a 170mm crank set. The new FS runs a 175. I'm 5'6 with a pants inseam of 28 inches. I like how my hardtail spins and I'm definitely not a masher. Should I go ahead and run 170's on my FS too? Thoughts would be appreciated!!! Thanks,

[phuncadelic]

[QUOTE=Pinoy Rider] hardtail ......crank ...inseam ... 28 inches...masher....[QUOTE]
crank length..... must hold back comments

[Pinoy Rider]

Yeah, okay it reads pretty funny!!! :)

[saxman]

I had the opposite problem. I'm 5'6", too, but with a 32 inch inseam. My Klein hardtail had 175mm cranks. When I first got my Trek Fuel 70 squishy, it had 170mm cranks. The shorter cranks felt really uncomfortable to me, so I switched them out for 175mm cranks.

I'd go with whichever crank size feels more comfortable to you. With a 28 inch inseam, the 170s may feel more comfortable...which, incidentally, I have a set of 170mm Truvativ Firex ISIS cranks that are practically brand new (that is, if your rig takes the ISIS splined BB), that I would be happy to part with at a reasonable price.

[DaveG]

Hey everyone. I've done some searches here and did not find the answers I was looking for. My hardtail runs a 170mm crank set. The new FS runs a 175. I'm 5'6 with a pants inseam of 28 inches. I like how my hardtail spins and I'm definitely not a masher. Should I go ahead and run 170's on my FS too? Thoughts would be appreciated!!! Thanks,

Personally I tried some 170 cranks for a few months and couldn't tell the difference. If the bike already has 175's try it for awhile before switching though. You might find that the 175's are good.

Dave

[bunky]

Thoughts from Sheldon Brown.

http://www.sheldonbrown.com/cranks.html

And from Zinn:

http://www.velonews.com/tech/report/articles/5257.0.html

The general formula is 21.6% of inseam. (Or as close as you can get to that based on the fact that the industry only churns out so many production lengths (165, 170, 175)--why they make three separate lengths 5 whole mm apart seems a waste, but hey . . . I'm not S corp.)

I am 5' 5.5" and had been running 175s without any thought to crank length. I had troubles because my knee would come up pretty high, and it just seemed like when I was really spinning that the inertia was throwing everything out of whack.

Based on the formula, I went to 165mm and have not looked back.

[bacalhau]

Thoughts from Sheldon Brown.

http://www.sheldonbrown.com/cranks.html

And from Zinn:

http://www.velonews.com/tech/report/articles/5257.0.html

The general formula is 21.6% of inseam. (Or as close as you can get to that based on the fact that the industry only churns out so many production lengths (165, 170, 175)--why they make three separate lengths 5 whole mm apart seems a waste, but hey . . . I'm not S corp.)

I am 5' 5.5" and had been running 175s without any thought to crank length. I had troubles because my knee would come up pretty high, and it just seemed like when I was really spinning that the inertia was throwing everything out of whack.

Based on the formula, I went to 165mm and have not looked back.


There was an article at Bicycling magazine a while ago, that talked about this, and among other issues, of how much it relates to knee injurees, and overall pedaling efficiency.
Aside all that I did also realize that w/ 175's on. I was hitting a lot of rocks around rock gardens and the ground itself in some turns.
It does not seem a lot, but once I switched to 167.5, I noticed the difference, not only with clearance but also with overall feeling riding the bike.
If you confortable as you are, great. If not, take a look on those websites and research some more. Road bikers seem to pay much more atention to it, and for a good reason.

[DaveG]

Thoughts from Sheldon Brown.

http://www.sheldonbrown.com/cranks.html

And from Zinn:

http://www.velonews.com/tech/report/articles/5257.0.html

The general formula is 21.6% of inseam. (Or as close as you can get to that based on the fact that the industry only churns out so many production lengths (165, 170, 175)--why they make three separate lengths 5 whole mm apart seems a waste, but hey . . . I'm not S corp.)

I am 5' 5.5" and had been running 175s without any thought to crank length. I had troubles because my knee would come up pretty high, and it just seemed like when I was really spinning that the inertia was throwing everything out of whack.

Based on the formula, I went to 165mm and have not looked back.

Using that I get 172.8; perhaps that's why a 170 doesn't feel that different from a 175 to me :)

Dave

[Pinoy Rider]

All great info gentlemen. Thanks. I guess the biggest reason why I'm asking is because high have two bikes that I want to ride for different types of rides. I do feel a noticeable difference between I peddle between my two bikes. I'm leaning toward the 170s to keep both bikes similar. I do have isis cranks but I think I'm going to save up a little and go with a totally new bb system with the new shorter crankset. Thanks for the info again

[saxman]

Using that I get 172.8; perhaps that's why a 170 doesn't feel that different from a 175 to me :)

Dave

I end up with 175.5, which is probably why the 175s feel so comfortable to me and the 170s drove me nuts.

[bunky]

Yeah, my ideal is 153.6. Good luck finding something close to that in a production crank!!!

[DaveG]

Yeah, my ideal is 153.6. Good luck finding something close to that in a production crank!!!


I think crank length is the least of your worries... :)

[bunky]

I think crank length is the least of your worries... :)

Why . . . .Thank you!!! :D

[DaveG]

Why . . . .Thank you!!! :D


That probably didn't come accross quite the way I wanted it to :eek:

[Pinoy Rider]

I just ordered a 170 length crank tonight. I did the calculations and ended up a little over 165. 2.5-5 mm for mountain biking as some literature suggest, so 170 it is. Thanks for pointing me in the right direction. For those of you looking for a set of XT Hollowtech II cranks, speedgoat are closing them out for 180.00 down from 270. 165, 170, and 175s. Thanks again.

[Pinoy Rider]

Update, today was my first day with my shorter cranks on my FS bike. The biggest thing I noticed was my turnover/cadence was a lot quicker. I was able to clear the same hills and obstacles however my legs felt not as spent(if that makes sense). My lungs still sucked but thats a different story. :) Thanks again for help in making a decision. Overall, very satisfied with the change in crank length.