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I have a boost frame (Orange Clockwork Evo 29) which I setup with a non-boost XT crank-set (M8000) The chain-line meant things were rather noisy so I put a second 2.5mm spacer in the bottom bracket and everything was great..... until Sunday, when the crank fell off. It didn't appear loose before but half way around Sherwood it popped off. I reattached at the trail side but could only do the plastic fixing cap up by hand and everything was loose again within a mile or so.
I think this is likely due to the reduced amount of crank shaft(?) for the non-drive side crank arm to tighten on to. Is there a better solution to moving the chain-line outwards involving a dished chain ring out there somewhere?
Did you do up the pinch bolts correctly?
Are you sure the noise was due to chainline? Maybe you just need a bit more B-screw?
Did you do up the pinch bolts correctly?
Definitely torqued up correctly initially. During he trail side fix I just got them as tight as possible with the multi-tool.
Are you sure the noise was due to chainline? Maybe you just need a bit more B-screw?
Possible. Maybe I'll have a play with that again.
What is your spacer set-up now? Are you able to remove a spacer from the opposite side of the BB that you added the second one?
Other than that, the offset is defined by the spider on the M8000 chainsets so you may have to live with the less-than-ideal chainline, or replace the cranks.
but could only do the plastic fixing cap up by hand and everything was loose again within a mile or so.
It's only supposed to be finger tight.
Definitely torqued up correctly initially. During he trail side fix I just got them as tight as possible with the multi-tool.
They're not particularly highly torqued, so something is amiss there.
If it's been loosening for a while then the splines may be worn which would cause it to keep falling off. In which case it's new cranks time as nothing else will solve it.
I imagine the splines are goosed now even if they weren't before. The plastic endcap should play no role in keeping the crank on, it's just there for preloading the bearings.
Did you manage to get the little plastic retaining clip at the head of the crank seated correctly? If you can't get that to close then yes, there isn't enough axle to secure the cranks.
If you remove the extra 2.5mm spacer, and the splines are damaged, you could try some loctite.
If it's the extra strong loctite, you will need to heat it up with a hot-air gun if you ever need to remove the cranks.
I think i was just sick in my mouth a little bit.
just chucking an extra spacer in one side wont help. The crank is not designed to be "adjustable width". its a fixed length. if its not seated into the splines properly it doesnt matter whether you torque it up or not, its not "on".
The spacers are to take up slack in different width BBs.(73mm or 83mm, either of which could have been over enthusiastically faced)
You can add a spacer in one side if you remove it from t'other, though that will offset your cranks in relation to the rest of you,
OR put the chaining on the other side of the crank spider (if it fits), ie, middle ring in the position of the outside ring, though i dont know if it will actually clear the arm
^^what he said.
you can get away with 0.5-1mm just about, but unless you're running a 68mm bb shell and have a spare spacer on the non drive side, and enough thread on the drive side BB cup, you're stuffed.
in all liklihod, you've knackered your non driveside crankarm.
if you do have a 68mm BB shel, and you stick all of your spacers on the drive side, you will have a non centred crank, so may need to either add pedal washers to the non driveside pedal, or adjust your left cleat to compensate. Not ideal though.
That frame is 73mm BB shell, you can't just add 2 spacers on the drive side, its turned the shell into 75.5mm, the arm won't clamp the splines correctly, a burgtec chainring will increase chain line as they dont have an offset like other brands or theres some cheap ones on ebay for m8000 that don't have offset. If you need a new left arm ask on here.
This may have been said, if you added a spacer to a 73 bb there will be 2.5 mm less spindle for the crank arm to attach to. This would make it fall off.
My ht frame is 73mm bb shell(no spacer required)or so I thought ! Couldn’t preload bearings with plastic end cap 🙁
Put one spacer on bb all good 🙂
The spacer on the drive side is there to allow the use of a BB mounted front derailleur.