[Closed] Hollowtech II crank arms keep going slack.

BB is spaced wrong, cranks arent sitting onto the axle properly.

Had this with some 5/6 year old XTs recently. The splines were worn and they wouldn't stay tight, I ditched them for some new ones.

BB is spaced wrong, cranks arent sitting onto the axle properly.

I've used all three 'spacers' so I cant see this being the problem. The crank bolt tightens up fine, I'm just scared of overtightening it as I know then can break. It's one of the plastic ones....maybe a new alu one from eBay might help?

Sounds like you need a torque wrench and some threadlok.

[i]The crank bolt tightens up fine[/i]

isn't that just a pre-load thing - shouldn;t be more than finger tight anyway?

As above - they've been run loose and the splines on the nds crank arm are damaged.

but try the threadlock and torque wrench thing too.

If you have a 73mm bottom bracket shell and have used all three spacers you will have the problem you describe!

If you have a 68mm shell then I have no idea.

I've had this on XT cranks and Alfine cranks, all with the correctly spaced BB, torqued bolts, etc.
I put it down to my MASSIVE power.

've used all three 'spacers' so I cant see this being the problem. The crank bolt tightens up fine, I'm just scared of overtightening it as I know then can break. It's one of the plastic ones....maybe a new alu one from eBay might help?

You will trash the BB bearings if you go down that route.

Look at the torque setting on the pre-load bolt - it's tiny. Any more and you will wreck the bearings fast.

Check your frames BB shell width and check it needs all 3 spacers.

UPDATE:

4 days since I tightened up everything and after 50ish miles it's loose again 🙁

Stripped everything down today, primarily to 'de-grease' everything and try a dry fit approach. On closer inspection the splines inside the non drive crank arm were showing signs of wear. Has anyone else had this issue?

I guess I have a couple of options:

1. Buy a new non drive crank arm.
2. Upgrade to XT or XTR.

I've always been of the opinion that SLX and XT were the same with the main difference being in the chain rings and decals?

Any opinions?

Get the spacers right.

Have you remeasured the bb shell width?

Jambo: it's a 68mm shell, so according to Shimano I'm using the correct amount of spaces. I tried taking one spacer out and I then can't tighten up the cranks properly I.e. even when the crank bolt is tight there's loads of play.

Just checked on CRC when I bought them....June 2011! They're still technically within the Shimano warranty. Think I'll give that a go and see what happens....they can only say no!

you probbers damaged the splines riding them loose...nae warranty pal.

I remembered halfway round Cwmcarn that I forgot to do up my Saint cranks after a new BB. Oops... Did them up and carried on riding. A few weeks later could feel some play so cranked them right up to the point I thought the threads were going to strip. Anyway, so far so good. Those threads can take more torque than I imagined. Wang'em right up and see what happens. Nothing to lose.

Like cynic-al says, once the splines have worn then it's game over. Happened to me with a set of Hone cranks. Time to go shopping.

Take it to your LBS and ask them nicely to have a look for you.

Support your Local Bike Shops before they are gone forever.

Tom KP

May I recommend Marshalls in WGC, The Bike Shed or Saddles & Paddles in Exeter, Booles in Fishponds Bristol and Hot Pursuit in Newton Abbot. All friendly, knowledgeable and helpful shops who won't automatically try to sell you a new one.

Take it to your LBS and ask them nicely to have a look for you.

Support your Local Bike Shops before they are gone forever.

Diagnosing over the phone/internet is hard enough...

If the splines are worn then they will keep loosening. I got the Al end cap because I found the plastic ones damage easily xthread etc.