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I can't get my SLX cranks to stay tight.
They're fairly old cranks, but there's no sign of damage to the axle, the splines or the pinch-bolt area of the crank. The BB's fine. They just won't stay tight. I've tried doing the pinch bolts up to the correct torque, threadlocking them and now have a new set of bolts done up b*stard tight. It's still coming loose.
Can cranks wear out? Surely the pinch bolt would still hold them tight?
I've got a fairly low BB, get a lot of pedal strikes and have knocked cranks loose before (and just destroyed a pedal on a rock) so there's definitely potential for crank damage. Could I just be whacking them so many times that they're constantly coming loose? (I've just started riding again after 6 months off the bike. My pedal timing is definitely out. But I'm not hitting them [I]that[/I] much.)
The spline in the crank gets baggy once they've been run loose for more than a few minutes, so it'll never work properly again.
You can bodge it with certain threadlocks/bearing fitting compounds on the spline to stop it moving, but, at best, it'll only help for a few weeks/months while you decide which new crank to buy.
Best is to buy a new LH crank arm. (The steel spline on the shaft *shouldn't* be damaged unless you've really done a number on it)
Or a new chainset. Depending on how much it costs/how much you want shiny new stuff.
Is your BB spacing right?
Yeah^^^if you've put too many spacers in (increasing beyond 73mm) you'll not have enough engagement, so it'll keep coming loose. And then you'll end up with the baggy spline and a knackered crank.
Yeah, I've triple checked the spacing. There's nothing wrong with the set up.
How does the crank getting 'baggy' prevent the pinch bolt from keeping things tight? (Not questioning your diagnosis, just curious.)
very common problem with Hollowtech cranks - you need to replace.
Yeah, I've triple checked the spacing. There's nothing wrong with the set up.
How does the crank getting 'baggy' prevent the pinch bolt from keeping things tight? (Not questioning your diagnosis, just curious.)
Edit: It's not a problem I've encountered with multiple sets of hollowtech cranks before. Is it really that common?
they just wear out - I commute on mine so we are talking 10000+ miles before they fail
My XT's came loose after I installed them. Stripped, cleaned and reassembled with a wee dab of loctite on the crank arm bolts and no slipping since.
They only get baggy if you've ridden them while loose which wears the splines which makes them more loose which wears the splines...
Loctite on the pinch bolts may help.
My 105s did the same a couple of times.
The last time was during a biblical downpour with no cover about a year ago. I snapped and went the full Basil Fawlty on them with a brick found in a hedge. Haven't budged since, though swapping them out may prove tricky.
One of these from ebay sorted our problem out, it was still working fine when the scrotes stole the bike
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I had this on a pair of SLX cranks about 7 years ago. Agree with the "baggy" (although thats not what i would have called it) splines. Managed to get a replacement non-drive side and never had the issues again. But thats when that crank was still in production.
try some PTFE tape on the axle before installing the crank arm. this has kept many old crank arms secure for me...
Cheers guys.
The PTFE tape sounds like it might be worth a punt.
Not really what i would call it either. Just couldn't think of anything else that summed it up.Agree with the "baggy" (although thats not what i would have called it) splines.
Not sure how using a aluminium preload cap will help, unless you are just tightening everything up until it creaks, instead of doing it properly.