OT: Advice sought - pesky ISIS crank bolts keep coming loose

[Jason Thorpe]

In the spirit of Scott's post about bike projects...

I've pretty much finished building my CX bike (still dialing in the fit), but am having an annoying problem with the cranks. The cranks are used Bontrager Race CX that I picked up on eBay. They're older (marked with "9 Speed"), but look like they have hardly any miles on them at all -- no scuffs or markings on the arms / spider, and the rings look barely used. They're ISIS, and attached to a brand new Stronglight Twister ISIS BB.

I'm not using self-extractors, just garden-variety ISIS crank bolts. The problem: two 25-ish mile road test rides, two times the drive-side bolt has come loose (although the second time at least the crank didn't start to wobble - I specifically checked it when I got back).

The cranks are pressed up against the shoulder on the BB properly, and the bolts are torqued down pretty tight (though I can't remember exactly what I torqued them to at the moment, but lacking a manual for these cranks, I used the spec for a TruVativ GXP crank as a ballpark guide).

Wondering what I should do ... would using self-extractors help to mitigate this problem, or should I just use Loctite on the bolts (and would blue Loctite be strong enough)?

-- thorpej

[Nathan Davis]

I assume the cranks are not wallowed out at all? If not, you could actually try a little grease on the threads (if you haven't already), this might allow to you apply a little extra torque to keep things tight. Worst case, a little blue locktight would probably help. Do you have a torque wrench to ensure the bolts are getting torqued properly?

-- Nathan

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[Peter Chang]

Le 11 mars 2011 10:46, Jason Thorpe <tho...@me.com> a écrit :
> The cranks are pressed up against the shoulder on the BB properly, and the bolts are torqued down pretty tight (though I can't remember exactly what I torqued them to at the moment, but lacking a manual for these cranks, I used the spec for a TruVativ GXP crank as a ballpark guide).

you might want to check for the BB manual too. i recall being
surprised that the torque spec for ISIS bits was so high (ie, i think
~30ft/lb is relatively 'standard' but the one on the Id is ~45 which
is a pretty big relative jump).

\p

[Jason Thorpe]

Yah, the BB30 on my CAAD9 is ~37 ft/lb (middle of the specified range). Unfortunately, no spec given for the crank bolts in the Stronglight BB manual (just for the BB assembly itself in the frame). Maybe it's documented in the ISIS drive spec...

>
> \p

>
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-- thorpej