Bicycle Mechanics - Crank torque question

I have an SR Custom triple crankset (square spindle) and I haven't been able to find exact torque specifications for the cranks. Barnett's Manual (http://www.bbinstitute.com/DX%20Demo%20Chap%2020.pdf) says "In absence of manufacturer’s recommendations, torque to 350 inch-lbs" and I tried that. But afterward, it wouldn't shift to the smallest chainring any more. It [i]almost/i] shifted, but not quite. Apparently the chainrings are now slightly closer to the frame than they used to be. So I pulled the crank again and re-torqued it to 300 inch-lbs, plus adjusting the lower limit screw on the front derailleur a bit. Now it shifts correctly and the crank seems tight enough.

Did I do the right thing? Should I have left the crank torqued to 350 inch-lbs and just loosened the FD limit screw more? Also, the non-drive side crank is still torqued at 350 inch-lbs. Should I leave it alone or reduce it to match the drive-side crank?

Yes, you should have just tweaked the lower limit screw the first time. Removing and replacing square taper cranks repeatedly isn't a real good idea but can be done without harm if you torque them once per installation.

I'll bet the reduction from 350 to 300 inch-pounds isn't what solved your problem but the limit screw adjustment did.

Personal opinion would be to torque to spec and adjust the FD. The FD adjustments are easy; having a crank arm come loose would suck, to put it in simple terms.

I recently went through this with a square taper crank on my road bike. I had pulled the crank to try and find the source of a creaking noise (never did fix it) and retorqued to the middle of the manufacturers spec, as opposed to the lower end that I was using. I had to adjust my FD to be able to get into the little ring and to keep it from shifting off the big ring.

Yes, you should have just tweaked the lower limit screw the first time. Removing and replacing square taper cranks repeatedly isn't a real good idea but can be done without harm if you torque them once per installation.

I'll bet the reduction from 350 to 300 inch-pounds isn't what solved your problem but the limit screw adjustment did.

Actually, it was both; I adjusted the FD first and it worked OK while stationary, but on a test-ride it hesitated and didn't shift smoothly. After re-torquing the crank it shifted quickly and smoothly again.

Personal opinion would be to torque to spec and adjust the FD. The FD adjustments are easy; having a crank arm come loose would suck, to put it in simple terms.

I recently went through this with a square taper crank on my road bike. I had pulled the crank to try and find the source of a creaking noise (never did fix it) and retorqued to the middle of the manufacturers spec, as opposed to the lower end that I was using. I had to adjust my FD to be able to get into the little ring and to keep it from shifting off the big ring.

So should I go ahead and torque it a bit more, back up to 350 inch-pounds, and adjust the FD again if necessary?

YES! Definitely do NOT use crankarm-bolt torque as an "adjustment". Use other things that are adjustable to fine-tune the bike, like FD limit-screws and cable-tension. You just have to search "loose crankarm" on here to see how common the problem of loosening crankarms is. A buggered crankarm may not be that big a deal, but certainly is more frustrating than shifting problems, especially if it falls off miles away from home.

YES! Definitely do NOT use crankarm-bolt torque as an "adjustment". Use other things that are adjustable to fine-tune the bike, like FD limit-screws and cable-tension. You just have to search "loose crankarm" on here to see how common the problem of loosening crankarms is. A buggered crankarm may not be that big a deal, but certainly is more frustrating than shifting problems, especially if it falls off miles away from home.

OK, I'll put it back to 350 inch-lbs. That particular value seems rather arbitrary to me, since it wasn't a specific recommendation for my particular cranks, but a generic "if you can't get it elsewhere, use this" value. However, since I've already had it up to 350 once, I can see how it might get loose if I tried to use a lower torque now.

+1 Danno. You're doing the right thing. Torque it up.

We have several of us vintage bike & component knuckleheads here in B'ham if you ever want any help. :)

FWIW, Shimano recommends approximately the same torque value for it's square taper cranksets. I've used 360 in-lbs (30 ft-lbs) on all of the square taper cranks I've installed without issues.