Bicycle Mechanics - swapping crank arms

i have 175mm bontrager sport triple crank arms. I want to switch to 170mm since i'm a spinner not a masher. also, longer crank arms tend to bother my knees.

i'm having a heck of a time finding just replacement crank arms. personally, i'm not into the proprietary components that trek and specialized use. i'd like to go with another, lighter make/model.

i've been searching the forums for links to on-line parts stores. i really can't find what i'm looking for. hell, even the bontrager website doesn't list info on their atb components. i can't find anything on the "sport" model specs. also, i can't find info on my bb on the trek site. i guess the crankset includes the bb and rings so they are all bontrager "sports."

a few questions;

anyone know where i can get the specs on my bontrager sport crankset?

anyone know what other brands are compatible?

anyone know where i can buy them?....i've found just the arms on ebay but i don't thing they're compatible.

What bottom bracket do you have? Once you figure that out you can match the crank arms to it. Loads of manufacturer options; Truvative, Bontrager, Shimano, FSA, etc.

It is likely you will have to get a new bottom bracket to match whatever new cranks you choose so you can pick any make and model you want.

As you have noticed 170mm MTB cranks aren't that common but they are available.

How many "speeds" (i.e. cogs in your rear cassette) does your bike have? That will also have a bearing on what model cranks to consider although a 7/8-speed spaced crank will work with a 9-speed chain.

If you're hoping to find a crankset without rings, that's unlikely.

i'm looking for just the crank arms. i didn't remove the bb to see the make, but the spindles are a square taper. i'm guessing its a bontrager bb. trek doesn't list the bb specs on their website and i haven't gotten a return email from them yet. i have an 8-speed cassette. rear derailer is an x-7. i don't know the make of the cassette.