Hi,

I upgraded my SLX BB last year when it died after 2 solid years. I stuck an XTR one in there because it wasn’t much more thinking it would wear better. After 4 months riding no more than once to twice a week on south downs it has developed a really bad cracking noise which after today is now 3 solid crunches per rotation, is this normal? Anyone else experienced this? Could it be something else? Or am I just unlucky?

Over with the questions

My first XTR BB lasted over two years – riding it 6 or 7 times a week.

I have another which is now 3 years old, but ridden as regularly.

They’re not any better than SLX/XT in my experience but shouldn’t be any worse. What are the cranks? I’d suspect overtightening personally- pretty much everyone overtightens their cranks. But I’d want to have a look inside and see if the bearings are full of dirt or water, or if they’re just squashed.

My first one failed within 6 months of light use. Sent it to Merlin, whom I bought it from, and Shimano did a warranty replacement. Worth checking out!

I am a bit gutted, part of the problem is that when I took off the cranks (deore) and tried to fit the new BB I found out the thread were knackered so had to take it to a bike shop, the mechanic told me that it was difficult to get the new one to take and I may not get another one in there because of thread stripping so I fear if I take it out it could be new frame time

remove cranks and give the outside of the BB and the cranks a good clean. Could just be grit caught in there.

As for SLX/XT v XTR I am sure they are the same. Only a couple of £ difference at Rose who charge a much more realistic price than UK stores and I am sure that is down to the lower volume sales and the black cups.

If it has failed I would also look at installation as being the cause over any problem with the BB.

Thanks Andy, I have mused over it being the pedals, but the crunching is so loud now I cant believe pedal bearings would make that sound

Strip the whole lot out, clean and liberally grease everything. Basically any surface that touches another surface then put it all back together with more grease.

Should I risk removing the BB given that the threads were in really poor shape last time I looked at them?

I think you’ve answered your own question, it’s definitely a problem due to installation when it was fitted. When the mechanic said it was hard to fit I would imagine it’s been tight going in so it’s therefore squeezed in and so tight on the cranks sort of crushing the bearings. If the frame is worth it I’d get it taken to a decent bike shop who can sort the BB threads out properly and then you should be fine. If the frames well past it get a new one and see if you can get a warranty replacement for your old XTR BB and fit that to your new frame.

A good bike shop will chase the threads out and face the BB if need be,

Betd can put a new thread in the frame for you if it goosed. Premature bb failure is almost always caused by installation issues.

What Jeffus said!

if you think its the bb mate id take it out no point worrying about the frame that can always be repaired if needs be and no point leaving a a suspect bb in the frame if its that loud what ever happens its probably going to cost you somewhere along the line to get it sorted

I don’t really agree with hadge’s explanation unless it’s ended up installed out of line. tight threads won’t directly affect the bearings.

First thing you need to do is strip and clean it all; BB, cranks, pedals. Then go from there.