Xtr crank dropped off…

M9000 crankset. I’m aware that it’s probably chewed the splines a touch.
Tried to refit in the wild and it popped off.

So I’ve probably got another try or two before the splines are badgered… I’m thinking a good clean down with carb cleaner. Then loctite to fit and cure…

The question is what grade? Or what am I missing ?

638 is what you’re after

you’ve still got the crank arm fixing bolt in there…?

https://www.thamecycles.co.uk/copy-of-shimano-fc6800-fixing-arm-bolt.html?srsltid=AfmBOop1cIO884vlGo1UIZxxnBpkkw2pc6ejmME9kWyKyn2C3a3cCtLpqU0

I stripped my xtr crank off two years ago.

Smacked back on in the rain and it came off 30 min later. Thought it was going to be a very tedious 20 mile scoot back to the car. Put in back on and it was fine all the way back.

Put it back very carefully when I got home on as it’s been fine since. New bolts, new tensioner end cap thing on the cranks.

Hope yours is fine too!

I had my XT crank arm drop off. I was advised to forget the pathetic plastic end cap (non)tensioner thing and get one of these alloy jobbies that you can tighten up properly.

Burgtec Shimano Crank Bolt

They’ve been fine ever since. The fact that companies like Burgtec provide aftermarket solutions to replace the crap originals probably tell you all you need to know about how often shimano crank arms fall off

+1 to alloy tensioner. Crank fell off but has been fine since the plastic one was swapped for an alloy one.

Shimano has plastic caps to stop you overloading the bearings. it’s by Design that they don’t go tight and that shouldn’t be what’s holding the crank on. That should be the pinch bolts (and the little safety clip with a pin that goes into the hole on the axle should stop the crank falling off before you’ve  felt it’s loose).

I sometimes very lightly tap the crank onto the axle with plastic mallet to ensure it’s fully seated before fitting the plastic nut. Tighten the pinch belts evenly a bit at at a time with a torque wrench. Check after a few rides. Think shimano is the only crank fitting system I’ve never had an issue with.

I can easily tighten tighten the plastic shimano preload cap up properly.

I can certainly tighten it up enough that the bearings don’t spin as freely. Then back off under a quarter of a turn and it’s done.

Every issue I have seen where a shimano crank has fallen off it shows all signs as being a result of incorrect process used to tighten them up. You need to pop the clip down and then tighten each pinch bolt a little. I tent to do a a quarter of a turn tops on each one until it’s at torque spec.

That burgtec cap isn’t solving any problem other than the shimano one looking like crap. Much the same can be said of a few other burgtec parts. Didn’t stop me buying them for da blings

My xt fell off recently. Found there was play in the bottom bracket so swapped that and all good now. Might be worth checking?

you can tighten up properly

0.7 – 1.5nm is the same whether it’s applied by a plastic nut or an alloy one.

As others are saying, with a preload it should be on the axle properly. The wee ‘marker’ nubbin drops it’s pin into the axle hole.
Then they cranks are held on by the pinch bolts super tight.

I believe the aftermarket alloy pre-tensioner bolts do serve a purpose. I think they help the axle maintain it’s shape and make it easier to achieve even tension on the pinch bolts. They do look a bit better but I just have the Hong Kong Fuey ones from eBay that cost about 3 quid.

KCNC preload bolt is better than Burgtec version as it uses the Shimano tool interface instead of a big Allen key, why make a rather low torque item to use one of your biggest Allen keys on, weird choice imho, the kCNC one also looks way better and stays that way as the shimano tool to tighten it is plastic, I bought a few coloured ones years ago and they’re still mint.

Once you fitted the cranks you can take the tension cap off, same with the headset tension cap. It’s only there to provide the correct preload on the bearings. If your cranks fall off it’s because the two pinch bolts weren’t tightened enough, which I understand because overtightening strips the threads which is where my contribution to the thread come in. On many Shimano cranks the bolts are too short and don’t bite on all the threads, so replace the pinch bolts with longer bolts and you can up the torque slightly.

Once you fitted the cranks you can take the tension cap off

Not IME, having once gone to do exactly that when taking cranks off. I do agree that you can take a stem top cap off when the stem bolts are tight, as I have also done that. 🙂

Yesterday my crank started to wobble, undone the bolts and tightened up the preload cap bolts tightened.

Lasted 5min and wobbleed again , thought I need new Hope BB bearings .As I am in France better find a bike shop and buy a Shimano BB.

Bike shop mechanic loosened everything off checked play in bearings. Fix was new preload cap ,old one had striped threads and straight into bin . Still ok today after about 120 Kms on road/tracks.

Years ago a LBS forgot to put the safety clip back in on a service, and my crank fell off halfway down the London to Brighton off road. Something that encouraged me to learn about own maintenance.

This is what you need in case the preload cap comes off…..I always have one in my on bike kit, and a couple in the tool box

https://www.sjscycles.co.uk/chainsets/shimano-105-fc5600-security-plate-1ge-9805/

the stem top cap is an interesting one. I agree with the theory of removing it after the pinch bolts are set, but in practice, in heavy use, the top cap is still in play..

On my DH bike I’d swapped the default cap for a oneup lite tool that I had spare from a trail bike. loosened all 3 sets of bolts, tightened the preload appropriately, tightened them all back up to the specced torque. All was fine for a run or 2, then there was knocking at the front end, head set it loose. Repeat the process, and the same thing happens. So I drive the star flanged nut out, replace with a new one and use my mates top cap (which is surprisingly tight on his dh bike), retighten everything, give the top cap back, and again after 2 runs its a little knocky. Did the same with a different mates top cap, which is also really tight on his bike (neither of the other bikes had any binding in the headset). Get the same results

End up nipping to a local shop and buying a standard top cap, set it once, tighten everything up the same as before and not a single knock for the rest of the 8 day trip.

Lesson learned – the top cap does make some small amount of difference to the overall systme in heavy use, and the oneup system (being plastic) is I guess not rigid enough to give the same affect. Oneup works fine on my trail bike, so I’ve got to assume its some combination of heavier loads (I’m a 90kg rider, we were riding double-black dh trails) that go beyond what the pinch bolts can withstand. Given how tight all the top caps I borrowed were, this seems like something thats not specific to my bike.

This is what you need in case the preload cap comes off

That will do the square root of naff all to hold your crank on if the pinch bolts aren’t done up properly. Aiui the main function of that plate is to show that you’ve got the crank far enough onto the axle.

Had a problem where the crank on MrsPs bike fell off on holiday – I went back along the trail and found the (alloy) preload cap about 20m back, but I was still concerned about another failure so put cable ties round each crank arm and looped another one between them through the axle. That way if anything fell off we should at least have had all the bits.It stayed like that for about another 10 months.

I’ve said it before on here, but Saint cranks come with an alloy tension bolt rather than the plastic one. It maybe just cos a gold cap looks cool, but maybe they know that it makes it a bit more secure for DH stuff….

Aiui the main function of that plate is to show that you’ve got the crank far enough onto the axle.

I’m pretty sure it’s there to stop your crank arm falling off, the give away is in the name security or safety plate. The pin clicks down into a hole in the bb axle, and if the crank arm tries to work off, the pin just grips tighter in the hole. No matter how tight i torqued the bolts, the crank arm would not stay on with out the preload jobbie and no safety plate

This what park tools say, and that’s good enough for me….

For Shimano® Hollowtech® II, inspect for a “stop plate” inside the left arm slot. Use a thin screwdriver or integrated hook on the BBT-10.2 to lift this plate upward. The stop plate acts as a safety redundancy to prevent left arm removal.

https://www.parktool.com/en-us/blog/repair-help/crank-removal-and-installation-two-piece-compression-slotted

I’ve said it before on here, but Saint cranks come with an alloy tension bolt rather than the plastic one. It maybe just cos a gold cap looks cool, but maybe they know that it makes it a bit more secure for DH stuff….

but Zee comes with plastic

Shimano manuals say

“• The two left crank arm mounting bolts should be tightened alternately and incrementally rather than each bolt being fully tightened all at once. Use a torque wrench to check that the final tightening torques are within the range of 12 – 14 N·m. Furthermore, after riding approximately 100 km (60 miles), use a torque wrench to re-check the tightening torques.
It is also important to periodically check the tightening torques.
If the tightening torques are too low or if the mounting bolts are not tightened alternately in stages, the left crank arm may come off during the ride causing the rider to lose control and fall.”

I found the q factor to be short on the xtr M9000. I had to get a m9020 I think which was slightly longer.

I had a chain guide that was fixed by the drive side bb. I had to remove that. Then the plastic locking pin fitted into the hole on the non drive side crank arm.

How much spline is sticking out? How many spacers on the bb do you have?

Im thinking of ditching my xtr cranks, far too fiddly and the chainrings are far too expensive these days.