Crank bolt coming loose

[frostbite]

Hi,
Ive got a set of truvativ stylo cranks, and the non drive side has been coming loose lately. Ive taken it to a shop, they put loctite on it and it doesnt really seemed to have helped. The 8mm allen key bolt is the culprit. I dont know the proper name for it.

If I really crank on it, it seems to stick for a while before coming loose. From what I've been told they need 35Nm of torque.. which is heaps. From memory this should be 35kg on the end of a 1 meter stick right? (year 12 physics education dimly shining through)

Is there anyway of fixing this without replacing the cranks? ie is it the actual bolt thats worn out, or is it a thread in the non drive side crank?

 

[Plow King]

Probably not the smartest thing to do.. But I had the same problem with my butterfelt howitzer cranks. I just got an 8mm allen key and tightened the bastard up as tight as it'd go, didnt come loose again. Just wouldn't want to be the person trying to get them off

 

[LJohn]

The thing that pisses me off is the caps for the self extracting systems on my raceface cranksets keep coming loose and disappearing. Damnit.

 

[warrior]

The thing that pisses me off is the caps for the self extracting systems on my raceface cranksets keep coming loose and disappearing. Damnit.

I had the same sort of problem with mine. I found that the bolt was tightening onto the spline rather then the crank arm. I fixed this by putting in a small spacer. I'm talking a bee's dick of a spacer, just to make the bolt tighten onto the crank arm not the spline. Have never come loose after doing this.

 

[thompo]

its the case with most truvy cranks, i can't wait till i ditch mine.

 

[tu plang]

If I really crank on it, it seems to stick for a while before coming loose. From what I've been told they need 35Nm of torque.. which is heaps. From memory this should be 35kg on the end of a 1 meter stick right? (year 12 physics education dimly shining through)

3.6kg x 9.8m/s^2 x 1m = ~35Nm

 

[mike-]

From memory this should be 35kg on the end of a 1 meter stick right? (year 12 physics education dimly shining through)

Force = Mass*Acceleration

35N = x*9.8ms^-2

x = 35/9.8

x = 3.6kg

EDIT:

^^ Beaten by Tu Plang.

 

[xc_machine]

did you leave the cranks with locktite on the threads for a period of time before riding it?

It needs to cure. If it's let to move, it will never cure hard. might be a tad obvious though.

 

[frostbite]

Cheers guys - I was thinking about this on the way home from work and realised I'd messed up the units. 3.5kg it is. Which means basically since my allen key is about 10cm long, I can crank away to my hearts content.

Also - I made sure not to even so much as touch the cranks for 24 hours after they put the loctite on. I will try just tightening the crap out of it, and see what happens then.

Otherwise it might be time to get some XTs. Thanks for the help.

 

[ajay]

Otherwise it might be time to get some XTs.

Good idea

 

[tu plang]

Good idea

Best idea yet.