Clydesdales/Athenas (200+ lb / 91+ kg) - Crank Arm Length?

I need a new crank arm on my mtb. There are 175mm length arms on it now, but I have a pretty short inseam(29"). Should I replace the arms with 170's? I know it's not much difference, but I don't know what should be considered in making the decision. Since I have to replace them, just wanted to know. BTW - I stripped out the pedal hole on my right crank arm. Gee, I know I'm a clyde, but you'd think they'd make those things a little stronger! Just kidding. I imagine someone had crossthreaded the cheapo pedals and the threads just gave it up since I've bought the bike.

It's kind of like a piston rod on an engine, a shorter crank arm is better for spinning, but a touch less leverage. It will be easier on the knees, though. I actually prefer a 170 over a 175.I need a new crank arm on my mtb. There are 175mm length arms on it now, but I have a pretty short inseam(29"). Should I replace the arms with 170's? I know it's not much difference, but I don't know what should be considered in making the decision. Since I have to replace them, just wanted to know. BTW - I stripped out the pedal hole on my right crank arm. Gee, I know I'm a clyde, but you'd think they'd make those things a little stronger! Just kidding. I imagine someone had crossthreaded the cheapo pedals and the threads just gave it up since I've bought the bike.

If you are having problem with the current crank than you might consider replacing it.
I'm about 5.9 and around 30" inseam and I use 175mm crank arm for my commuting bike and 172.5 on my road bike. I did try my wife's bike 170mm crank before and i could not tell the difference.

Wait til you have 48 year old knees. ;)

If you are having problem with the current crank than you might consider replacing it.
I'm about 5.9 and around 30" inseam and I use 175mm crank arm for my commuting bike and 172.5 on my road bike. I did try my wife's bike 170mm crank before and i could not tell the difference.

Wait til you have 48 year old knees. ;)
I was wondering what will happen by then, I still have about 12 years to go but this can be a concern. As people get older, do they need a shorter crank length ?

I use 170mm cranks on my mountain bikes and 165's on the road. My first mountain bike had 175's on it and I had it for ten years before I got a road bike. After getting used to the road bike with shorter cranks, my knees would feel tired pretty quickly whenever I took the mountain bike out. I think I would probably like 165's on the mountain bikes too, but I don't know where I would find any.

Well, if it will be easier on my knees, that's all I need to know! I have one bad knee and one VERY bad knee! I'm virtually the same size as netbug, 5'9" with a 29 / 30" inseam. I'll call the lbs tomorrow and make sure they look for 170's to replace the old crank arms.
Thanks all!

For your inseam, go to the 170's.
It WILL change your pedaling dynamic to some degree. You'll spin lower gears a little faster. In my case, a LOT faster, with MUCH better stamina.
See the thread I started about the exact subject.
Note- My conditions are probably somewhat different than you, but the idea is the same.
Read the first couple posts and then skip to the end to save time.

http://www.bikeforums.net/showthread.php?t=361045