Felt a bit of play in my old BB (shimano deore I think) so bought a replacement MT800 as I figured it was quite old and had probably gone.
when I removed it, the bearings felt a bit dry, but there was no grittyness taht I’m familiar with, but fitted the new one anyway.

Fitted the cranks, nipped them up, all seemed OK.

one ride in and there’s the same knocking. Cranks are tight, preload was doen as I always do, tighten to pull the crank in enough, tighten the inner pinch bolt, back the preload adjuster off a bit, then finish tightening the pinch bolts to the right torque. That way the crank doesn’t shear off the top of the plastic preload adjuster when you nip it up.

Now, the crank is an old SLX M660, so it may be feasible that the axle has worn, though I’ve never come across that before. I’ll get the verniers on it later, but wondered, anyone else had this? is there a fix? tighter BB tolerance (like using enduro 24mmID bearings etc? or is it time to chuck them in the bin….:-(

Potentially, although I’ve not heard of tightening them up like that. Just nip the preload cap up, then do the pinch bolts equally and opposite, i.e. thread each one in, then either 1/4 turn on each one until they feel tight, or set your torque wrench to 1/4 the stated torque, then half, then 3/4, then the full amount so that it clamps evenly between them without distorting the clamp, the same way you should do stems and bars.

My money would be on the clamp being distorted by the uneven tightening and it’s now relaxed a bit.

I’ve never had a problem with breaking the plastic caps?

Is it definitely the BB? I had a knocking under load, replaced BB and it was still there. Tried greasing all sorts and it was still there. Finally narrowed it down to a worn pedal bushing.

Cranks are tight, preload was doen as I always do, tighten to pull the crank in enough, tighten the inner pinch bolt, back the preload adjuster off a bit, then finish tightening the pinch bolts to the right torque. That way the crank doesn’t shear off the top of the plastic preload adjuster when you nip it up.

Never had or heard of that issue before. Axle through, slight nip of preload, tighten pinch bolts, ignore until you next have the cranks off. I’ve never even had to bother with a torque wrench on them either with everything from XC to DH bikes

I’ve had a bike with HTII cranks and there was quite a deep bit of wear where the plastic bearing spacer sits on the axle, basically the axle was scrap. Over preloading the BB won’t help if the axle is worn as it will just wear the bearings as the play is radial not axial.

I had a few crank arms falling off, using the OP’s technique stopped it. The both bolts clamp the arm to the shaft rather than the shoulder on the preload screw.

As above. Definitely the crank, not the pedal or a loose chainring?

M

coppice

Member
I had a few crank arms falling off, using the OP’s technique stopped it. The both bolts clamp the arm to the shaft rather than the shoulder on the preload screw

That just sounds like something was wrong in the first place. HTII cranks should stay put for a long time, but if you’re be ridden them to the point of falling off then the spline likely ended up damaged, which just leads to more issues, possibly resulting in bodging how you install them

That just sounds like something was wrong in the first place. HTII cranks should stay put for a long time, but if you’re be ridden them to the point of falling off then the spline likely ended up damaged, which just leads to more issues, possibly resulting in bodging how you install them

Well its saved me buying 2x new sets of cranks. They still work and the bearings are still correctly preloaded so whats the issue? Yes the splines may be a little worn, possibly from not pulling the arm off square but there no rock or play between the shaft and the arm.

it’s the crank, wobble detected in the arms, transferring to the opposite arm, so def not one crankarm, pedal etc.

I’ve used that tightening technique since the first editions of HT2, before they came with that spacer that’s supposed to stop overtightening, and has the pin that anchors the crank into the hole in the axle.
the reason that wa sincluded in the design was that people don’t read instructions, did the preload up tight, tightened the pinch bolts up, th outer bolt tightened down on the shoulder of the preload cap and over a short space of time, tended to shear off, meaning only one bolt was effectively holding the crank on. a lot of the time the crank arm would wiggle off the axle and eventually fall off, often damaging the splines in the process.

Using a torque wrench properly, i.e. tighten one, tighten the other, repeat until both are at the right torque, mean that both pinch bolts are evenly tight.

I think it’s a really old crank, came to me second hand, and may have been ran in a seized BB for a while.

it’s an unusual one for sure.

Look like new cranks time, then.

There was a PSA jusy the pother day for some Raceface Ones which would fit your BB. I think they were £60.

Appreciate it’s unlikely, but are you sure you have enough spacers in the BB?

If that was the case, the wobble could be axial play, or mild radial play from a failure to preload the bearings, where the crank has grounded on the splines before exerting sufficient pressure.

Dunno, I’ve never cracked one, or heard of it. Tightened up correctly I’ve never had one come loose, and my longest running HT2 crank was the original XT one that I left fitted to a bike I sold a couple of years ago, I think they were on their 5th bike at that point!

It’s not like the old tapered BB’s where the bolts were needed to keep the cranks on the taper, it’s not even really pre-load, it’s stopping the bearings inner race wanting to slide out of the outer under load.

It’s not like the old tapered BB’s where the bolts were needed to keep the cranks on the taper, it’s not even really pre-load, it’s stopping the bearings inner race wanting to slide out of the outer under load

yeah, it’s a weird one really, hence the post. I’ll have a proper look later on and report back.

ppreciate it’s unlikely, but are you sure you have enough spacers in the BB

yeah, it’s an old fisher superfly carbon that it’s in, so I have the right amount of spacers and the metal sheild spacer fitted. when you slide the crank on there’s enough gap between the end of the axle and the end of the crank to provide preload.

I checked this morning that it wasn’t the BB shell that had come unbonded, thankfully the movement is at the axle.

I’ve had an axle on a Hollowtech ‘wear out’.

I first spotted some play in the cranks, so fitted a new bottom bracket. There was still play in the cranks. I removed the cranks to check I’d fitted everything correctly and discovered a pitted and worn section (almost like it had corroded) on the axle at the drive end, which aligned with the plastic bearing sleeve. I ended up getting a new crank. I never got to the bottom of what caused it, although I suspect a seized bearing may have been involved.

Think I may have an answer, though will see how it goes.
The preload cap has about a 3mm shoulder on it. The spare ones I have, have about 1-2mm shoulder.
It’s just too much, so I think is tightening up onto the axle just enough to stop it preloading properly.
Fitted one of the Spares and a thin axle spacer for good measure and I think it’s sorted it.
I’ll get out on a ride on Friday and see what develops.
🙂

Have you tried another pair of pedals & removing/cleaning the chainring & bolts? If rule them out before splashing out on new cranks.

It was definitely movement in the axle. You could see it at the opposite side of the BB if you rocked one side.

Hopefully I’ve sorted it.

I broke a XT spindle once. Just riding along I was.

Still got the pictures somewhere.

So, after a couple of rides, there was still a little play in the axle. Not a huge amount, but enough to notice if I thought about it.

Stripped it down this evening and too the verniers to it.

Internal dia of the BB, 23.9mm
External dia of the bearing load areas of the axle, 23.7 and 23.8mm.
All of the, what I assume to be nickel plating, has gone.
It’s not going to be structurally much of a problem, but it’ll bug me, and I’d think it’ll uneavenly load BB bearings and lead to premature BB death.

So, the scout for replacement cranks is on…:-/

I had the exact same problem as you a few years ago. Thought it was new bb time but after taking the cranks out noticed the nds bearing had seized in the bb and I could see the wear on the axle wear the bearing would be. That was a set of XTR cranks in the bin* 🙁

*on a shelf in the garage