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My ht2 crank has fallen off (xt M8000 I think) splines are clearly shot.
What is it that wears? Is it the crank or spindle - really what I'm asking is, can I just replace the nds crank and solve the issue or should I accept the inevitable and get a new crank set?
Mine went through a spate of doing that, it was very annoying. I tried a new l/h arm which worked for a while but ended up replacing the lot after that too started to fail.
Touch wood the replacement's been sound for a good 2/3 years since fitting.
Splines can die, although I've gotten away with swapping the plastic crank bearing preloader for a metal one and putting Loctite on the bolts.
In honesty the crank was second hand, not 100% convinced it wasn't borked when I got it as its creaked from day 1 - though admittedly I didn't realise it was the crank until recently, mainly as I ran out of other things to try.
I tried an Alu end plug thing but it didn't solve the creaking, nor the fally offyness
but ended up replacing the lot after that too started to fail.
I guess I should explain to Mrs brain why the XTR cranks I bought by accident "on one click" aren't going back then...
So STW what wine and dinner for XTR...
In my experience once a crank has been ridden when not properly tight then it will likely never be the same. They should last a very long time otherwise
The alloy splines on the crank arm do wear if the pinch bolts aren't done up correctly. Once its worn enough to fall off or slip then the crank arm is pretty much dead.
I've done it myself, you can get away with a new NDS crank arm as the crank spindle is steel and a bit tougher than the crank arm itself, but most of the time the solution is a new crankset.
They should last a very long time otherwise
Yeah I've a closing on 20 year old set of XT triple cranks going strong on my commuter at the moment that have probably been on 7 bikes by now.
I'm pretty certain it's not an install (by me) issue - could be I got it wrong on this one but I've done plenty over the years with no problems. A quick Google turned up a disproportionately high number of reports from folks with m?000 series cranks so not sure if it was an issue with those particular model years or just confirmation bias.
Oddly the m9020 sat in the garage has a self extractor etc and no pinch bolts.
Seems little point spending £60/70 on a new arm if it has any significantly increased chance of doing it again.
So ... I've had a couple of problems with the latest 8100 series cranks. I've been using ht2 cranks for years (over a decade for sure) and never had any issues. However, I've found that the pinch bolts on my latest two sets of cranks have "self loosened", resulting in one crank falling off and me catching the other one on a ride as it showed a little play of play. That's how I found the bolts had loosened. I thought I'd just check they were tight and they were properly loose. I nipped them up, removed the crank when I got home and found that the little pin that pokes out of the plate between the bolts was very bent. Replaced the pin with a spare and put the cranks together OK.
I am not a person to under torque a bolt and this was a real surprise. Lesson for me is that checking the tightness of the pinch bolts now has to be part of my maintenance routine.
Very weird.
Overtightening can cause problems too of course.
I've had three sets of ht2 cranks do similar things. Only one of them so bad I stopped using it (after trying a second left arm).
It's quite disconcerting when the arm falls off isn't it? Rivalled only by bending the gear shift into a horseshoe on a motorbike I think 🤣
Pinch bolts are still tight and the pin is straight - if anything is say the pin is a bit short but no signs of damage or anything, it just doesn't look long enough to engage properly.
That said the spindle looks short in the bb, given its a pf41/bb92 its not even as if there are spacers to get wrong. Not that I've ever spaced a 73mm bb for 68. No siree Bob, nothing to see here.
It’s quite disconcerting when the arm falls off isn’t it?
Fortunately the first occasion I was on a twisty slightly pumpy section of single track, it made for a crap bit that I normally enjoy but nothing too painful. Oh and a one legged pedal back to the car.
Last night (i commuted on the wrong bike to see if I'd fixed it) was just pulling onto a roundabout which was less fun but fortunately completely expected by that point. Oh and a 4mi walk home in cleats.
It is definitely worth keeping an eye on the torque of those pinch bolts.
I also don't think they like being taken on and off a great deal.
The splines definitely don't last forever, especially if you are a) heavy b) on a "hardcore" hardtail and c) ride clumsily.
I have snapped 3 sets of cranks so I suspect I'm a, b and c.
But they are cheap...