Bottom bracket bearing wear
indeterminate
Posts: 63 Member
My winter bike has chewed through 3 sets of BB bearings in 1 year, latterly a set of relatively expensive stainless steel ones from Hope Tech (6 months). Is this normal?
I saw online that over-tightening the left arm can lead to pressure on the inner race, causing early failure, so I was very careful to follow the online guide when installing the latest set. Can anyone with similar experience, or just more knowledge, suggest what pit falls I might be falling into or what I might do to get more life out of my bottom bracket?
Thanks in advance.
I saw online that over-tightening the left arm can lead to pressure on the inner race, causing early failure, so I was very careful to follow the online guide when installing the latest set. Can anyone with similar experience, or just more knowledge, suggest what pit falls I might be falling into or what I might do to get more life out of my bottom bracket?
Thanks in advance.
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Replies
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What kind of bearings do you have? I assume that they are cartridge. Overtightening any bearing will dramatically shorten it's life, especially cartridge bearings which typically are smaller than open bearings. You should get many years out of them.0
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What kind of bearings do you have?
I would be devastated if my bike was chewing bearings that fast! Who's fitting them - are you/they doing it right?0 -
Thanks for the responses.
The bracket is a Shimano Hollowtech II. I started with the cheap and cheerful Tiagra that came with the bike and lasted about 4 months before it started clicking. I could have probably sent it back at that stage, but I had a spare Ultegra lying around from a different bike, so rather than lose the bike for a few weeks, I thought I would just replace it myself. They're very easy to change, just screw on the outer shell (I tighten with a torque wrench), grease and feed through the axle, and then attach the left crank and tighten.
The Ultegra only lasted about 3 months too (again only clicking rather than seized, but enough to do my head in during the course of a ride). I may have over-tightened that one, which is why I paid very close attention when fitting the stainless steel bearing. I figured that being made out of SS, it should ensure the weather a bit better than the cheaper ones, and it did at 6 months, but I still think they should last longer than that.
When fitting the SS bearing, I viewed and followed the instruction video listed on the Hope web site. Its not very specific about how tightly to attach the left crank, but it didnt look like brain surgery. It has run smoothly for around 5 months, when it started clicking. I took off the bearing cover, cleaned and re-greased, after which the clicking stopped for around 3 weeks. Now its back though.
As I have been doing the work myself, I was wondering if anyone with more experience might be able to advise some common mistakes that might lead to bearings wearing too quickly, or any good guides on fitting that might offer a different and reliable view to the ones that I have read/watched up to now.0 -
Last ultegra bb I had lasted over two years, call it 20,000km, winter summer you name it, beginning with me being 28 stone... I'd be slightly worried that the actual bb is tapped out of alignment or had been cross threaded. Just for good measure, I had a hope bb, (the non stainless one) albeit in the mtb, which lasted over 3 years, with every other ride ending in the bike getting hosed down. It gave up a fortnight ago...0
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Hmm...yes, I had started to wonder myself if the bb shell was off straight. I'll have a good look at the threads before replacing this set and see if I can find something straight enough to test the shell is straight inside. One more go and then I might need to look into a replacement frame.0
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it's difficult to actually check the straightness or otherwise of a BB at home - it really is something that's the domain of a good LBS - one thing that also crossed my mind, which is especially pronounced on the external bearing BB cup things is the "facing" of the frames BB - even the thickness of the paint applied can just "tweak" the alignment of the bearings enough to make things wear.
Even if the BB isn't quite straight, or it's mis-threaded, again a decent LBS should be able to come up with some form of repair that doesn't necessarily mean junking the frame - I've one frame that came to me with a completely munged bb - some gorilla had completely cross threaded the cups and when I removed them the threading from the BB came out with the cup. Fortunately this was in the era of steel, and I had the frame sleeved and re-cut (not all that cheap, but it WAS a Colnago frame in Columbus SLX, and purchased for buttons, as the seller thought it was completely knackered, a "wall hanger" basically)
As to the "side preload" on the bearings, well - there's a reason that the official shimano tool of fitting the nylon preload nut is just a knurled plastic disk and not something with a decent grip, handle or spanner-surface on it - and that is the recommended tightening torque is phenomenally low - 0.7-1.5N-m (6-13 inch-lb's) - that's pretty much just finger tight.0 -
Just to round out this thread, TBY was on the right track with the cross-threading. A disappointing amount of thread shavings were present when I removed the cup, both from the shell and the cup. It could have been me, or it might have been the original build, as it destroyed its original BB in no time.
It is steel, so I guess it could be tapped and given a reprieve, but it was only cheap and has already been repaired once at the rear hanger. I dont want to keep throwing money at an increasingly stressed frame, so it's probably time for a new frame.0 -
It gives me absolutely no satisfaction whatsoever to be correct mate... always hate to hear about a frame going bad.
If it is a steel frame, it's not actually that hard a job to fix it - either with a helicoil insert, a welded in sleeve, or (and this is a very dirty fix!) by getting someone in an engineering shop to run a little braze (or at a push, some tig weld...) around the BB to build up the metal enough to run a tap through it and rethread... Cheap enough if you know the right people
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Ouch! Sorry to hear about the cross-thread; it could've come out of the factory like that for all your know?!
As TBY has indicated, the addition of some 'new metal' and a re-tap will sort it!0
