Recently I’ve felt play in my crank arm. After taking the cranks off, I discovered the internal ISIS BB FSA Crankset was only hand tight!!
I got out my Parktool book and tighten the BB accordingly.
However, the BB doesn’t turn smooth and light as it did before. It’s now tighter and takes effort to spin without the crank arms on.
I tightened each side to 360 IN/PD as directed in the book. After discovering it too tight, I naturally backed off the threads and loosened the BB for a smooth spin. The only problem now is that it’s not torqued to the right specifications.
Is 360 IN/PD too tight?
It looks like 360 in*lb is well within the torque spec range given on the FSA website for their bottom brackets. Are you measuring the torque correctly?
I believe so. Pretty confident in my mechanical skills. Worked on cars for years. Used my automobile torque wrench which translates 360 / IN/PDS to 60 Foot Pounds.
Unless the wrench is out of tune? Doubt it though. I have a good feel for the 60 pounds of torque. It’s tight, but not THAT tight.
Regardless, I loosened it and it spins much smoother. It’s still on tight, but not 360. Maybe 180?
The tightening fixed my crank arm play though!
Ummm…those are not equivalent. 360 inlbs converts to 30 footlbs.
360 / IN/PDS to 60 Foot Pounds
LOL…I can only imagine what you’re thinking! That’s funny.
I’m not sure why I wrote 60, but God as my witness, 30 pounds was the amount torqued.
ISIS BB’s are made to fit varrying shell widths, so when they’re in a 68mm shell they’re more compressed and not as smooth. It’s not a problem, just the nature of that beast. Running it at too low of torque will cause it to re-loosen and could damage the threads if it ridden too loose for too long.
Bring it back up to spec and it’ll be fine, just harder to turn w/out cranks on.
If you didn’t have a torque wrench, how would you do this adjustment? You’d get it tight enough to eliminate the play, but not so tight that it binds; this would be the correct torque. In general, the spec should get you to the right place, or close. What you have found though is that for your specific sample, in this particular case, the correct torque and what it says on paper don’t agree. There is an expression in engineering: “In theory, there is no difference between theory and practice, but in practice there is.”
or rather, “the difference between theory and practice is greater in practice than in theory”.