Trek Madone CF-BB liner/shell replacement?

[bikes4two]

Having recently acquired a used Madone 5.5 CF road bike, I'm on a voyage of discovery with technology I've not rubbed shoulders with before, hence this question:

1. After suffering a squeky BB for a while, a removal of said BB revealed that the metal liner/shell that sits inside the frame was cracked.
2. Armed with a suitable drift (1 & 1/8th AF socket) the offending piece came out without any difficult.
3. And now the questions!
> What is the proper term for this part (so I can search for a replacement)?
> Where might I find a replacement for said part?
> When replacing the liner/shell, do I just push fit it, or seal it in some way (there looked like traces of silicon sealant around the entry points - to keep out water?)?
> Is this breakage a common problem with this component? The material is a light alloy of some kind - are there more stronger options I'm wondering?
4. The BB is a standard English thread 68mm shell, square tapered sort (currently using a Shimano BB-UN55)
Many thanks for your input on this one.

[Brucey]

if that is the part I think it is, then it should be adhesively bonded into the CF structure, I think.

That part is the bottom bracket sleeve. It is probably designed for H-II bottom brackets, not ST ones; a UN55 will impose a huge tensile load on the sleeve which may be (along with some light disbonding) enough to cause it to fail when the BB unit is tightened fully.

Your frame may be scrap. On the other hand it might be repairable if the CF isn't damaged.

Trek usually warrant frames for life to the first owner. No good if you bought this used, unless it was from a chum and he bought it new.

A good machine shop would be able to make a replacement part for this. An engineering grade epoxy adhesive may secure it.

Sorry it is not better news.

cheers

[cycleruk]

Is that large slot where the front derailleur cable goes or something else?

[bikes4two]

Is that large slot where the front derailleur cable goes or something else?

Assuming you mean the large slot in the middle extending from the circular hole - no, that's the original crack which when the BB sleeve was in the frame appeared just as a hairline crack - it's only as wide as it is because I prized it apart a little to see what was going on before I removed it. All control cables for this frame are external cables.

[bikes4two]

Thanks for the input Brucey

if that is the part I think it is, then it should be adhesively bonded into the CF structure, I think.

Removing the BB sleeve was easy in that it 'drifted out' with only light hammering, so if there was any bonding it was not doing its job very well. I've had a good look at the BB area on the frame and the only surface area that could be bonded to is the bottom part of the frame (see pic). What would be a good bonding adhesive - any suggestions?

That part is the bottom bracket sleeve. It is probably designed for H-II bottom brackets, not ST ones; a UN55 will impose a huge tensile load on the sleeve which may be (along with some light disbonding) enough to cause it to fail when the BB unit is tightened fully.

Apologies for my lack of knowledge: H-II - that's Hollowtech 2 then? and what are 'ST' ones please? How does the compression force/tensile loading differ between the two types?

Your frame may be scrap. On the other hand it might be repairable if the CF isn't damaged.

A good machine shop would be able to make a replacement part for this. An engineering grade epoxy adhesive may secure it.

cheers

I've looked closely at the frame with a magnifying glass and I can't see any signs of hairline cracks or any other visible damage, so I'm hoping we're still good The BB sleeve length was such that the compressing forces from tightening the UN55 would have bourne directly on the sleeve rather than the CF shell.

Middleburn engineering are not far from me and the MD lives just down the road from me - that might turn out to be fortuitous?

[Brucey]

IIRC ST (square taper) cartridge BB units are tightened to about 60 or 70 Nm. This generates a clamping load on the cartridge of several tonnes and a corresponding tensile load in the BB sleeve.

A H-II BB fitting does not generate a similar stress in the centre part of the sleeve; all it does is compress the ends of the sleeve slightly when the cups are tightened.

I'd use a H-II BB and crankset in a frame like that.

If you can chat up the guys at Middleburn maybe they can help you out. If you want an -off-the-shelf fix then you could try;

a) machining down an eccentric BB insert (to make it concentric)

b) using a plain tube and a threadless BB of some kind.

Maybe there are other ways that might work too.

The adhesive you use will have to bond to the CF matrix and/or the fibre and/or the old adhesive (you won't get it all out without damaging the CF). I'd look to use a high strength epoxy resin; a filled grade if the new sleeve is a slack fit. But maybe there are better adhesives than this for this kind of application.

It is unlikely that there has been no collateral damage to the frame arising from this failure. However if trouble does develop in time, the worst that will be likely to happen is that you will descend gracelessly onto the top tube and/or your pedal will hit the road. Not fun, but not that likely to kill you, either.

Trek OCLV frames are, I think, (in the grand scheme of things) one of the better made mass-produced CF framesets. Imagine what the rubbish ones are like....

cheers

[Dave W]

Might be worth a chat?

http://www.cfrbikes.com/index.html

http://www.carboncyclerepairs.co.uk/about-cbs_11.html


And ...... any help? http://www.trekbikes.com/pdf/owners_man ... 062309.pdf

[bikes4two]

Thanks Dave, I've written to the first of the two repairers listed - fingers crossed!

As for the Madone PDF link - the frame in that document seems to be the later Madone and it doesn't list Shimano Square Taper BBs? On the other hand, the sleeve that I had, had left and right handed threads - what type of BB, other than the BB-UN55 used here, would fit such a sleeve?

[Brucey]

...As for the Madone PDF link - the frame in that document seems to be the later Madone and it doesn't list Shimano Square Taper BBs? On the other hand, the sleeve that I had, had left and right handed threads - what type of BB, other than the BB-UN55 used here, would fit such a sleeve?

pretty much any BSC threaded BB will fit but not all will load the BB sleeve in the same way.

Hence as stated previously I'd use a H-II BB in this kind of frame.

The later madone appears to use a BB30 (or similar) type BB unit where the bearings are fitted to an unthreaded sleeve.

cheers

[Valbrona]

I would do two things:-

1/ Measure up the internal diameter of what remains of the BB shell and see if a Push Fit 30 (PF30) bottom bracket will fit. PF30 cups are pressed into bare carbon fibre bottom bracket shells, like what remains on your frame. For a BB shell to take PF30 cups or adapters it needs to be 46mm ID and 68-73mm wide. See here: http://wheelsmfg.com/products/bottom-br ... train.html PF30 cups/adapters could also be glued in with epoxy ... but glued in forever, which might not be a bad idea.

2/ If the only option is to fit a replacement threaded metal sleeve, like the one you have removed, then measure the OD of the aluminium sleeve and contact Ceeway. You might find that you can simply glue in either a steel or aluminium bottom bracket shell, like what would be used in a welded steel or aluminium frame. Obviously a steel BB shell like those in lugged frames would be no good.

[Brucey]

some info about the changes in Trek's frames here;

http://www.chainreaction.com/oclvhistory.htm

and here

http://www.chainreaction.com/madone_08_review.htm

cheers

[Dave W]

" In late 1997/early 1998 they phased in a new, much improved bottom bracket shell. The original shell wasn't bad, but because the internal aluminum sleeve ended flush with the carbon fiber surrounding it, it was possible to put a compressive load on the carbon when installing a bottom bracket, which, in some cases, caused a disbond between the aluminum shell and the surrounding carbon. This didn't happen often, but we did see some frames that had to go back for replacement (under warranty) of the bottom bracket shell.

The new bottom bracket shell (still in use today) has the aluminum internal sleeve going all the way out past the end of the carbon part of the frame and over the edge, so that there's no possible way to make contact or compressively load the frame when installing a bottom bracket. It's also a bit beefier overall in the carbon part of the fitting, which has virtually eliminated the issue of an under-shifted chain chewing a hole through the chainstay (although that wasn't an issue anyway as long as the adhesive stainless steel chainstay plate was in place). The beefier design is something some people find a noticeable improvement in climbing & sprinting."

Sounds like it?

[Brucey]

IIRC 2008 onwards the Madone 5.5 has an unthreaded BB shell and the model only started in, what, 2006 or something? So your bike is roughly between five and seven years old.

But anyway I think the original BB on that bike would have been an H-II -esque one, (e.g. a shimano one or a SRAM GXP) i.e. cups that screw in and tighten against the end of the BB sleeve without applying a load to the sleeve centre.

I wouldn't have automatically suggested that a UN55 would have bust the BB sleeve (as it appears to have done) but having seen what has happened it does kind of make sense that the tension load in the sleeve has contributed to the failure. That sleeve is pretty thin and has big holes in it. Once the sleeve cracked, the BB would have loosened. Retightening it would then have helped one end of the sleeve to come disbonded (if it wasn't already...), and once that happens the other end is bound to follow suit.

cheers

[The Mechanic]

I would do two things:-

1/ Measure up the internal diameter of what remains of the BB shell and see if a Push Fit 30 (PF30) bottom bracket will fit. PF30 cups are pressed into bare carbon fibre bottom bracket shells, like what remains on your frame. For a BB shell to take PF30 cups or adapters it needs to be 46mm ID and 68-73mm wide. See here: http://wheelsmfg.com/products/bottom-br ... train.html PF30 cups/adapters could also be glued in with epoxy ... but glued in forever, which might not be a bad idea.

2/ If the only option is to fit a replacement threaded metal sleeve, like the one you have removed, then measure the OD of the aluminium sleeve and contact Ceeway. You might find that you can simply glue in either a steel or aluminium bottom bracket shell, like what would be used in a welded steel or aluminium frame. Obviously a steel BB shell like those in lugged frames would be no good.

Are you sure this is true. I have a BB30 on my Felt and the BB has an alu sleeve that the bearings are pushed into. This is BB30 rather than PF30 to that might be the difference.

[Brucey]

in 2008 it seems that Trek started to use the direct fit bearing system, and (amazingly) it seems they went for it big time, fitting the bearings straight into the carbon structure; the first time anyone had mass-marketed a system like this. These BB shells are 90mm wide IIRC (to reduce the bearing load presumably) and won't accept any other BB bearing system without modification. [You wouldn't easily confuse one of these with an earlier type BB shell, or have an ST BB unit fitted to it].

Trouble with these direct fitting bearings is not uncommon, it seems. Some folk don't have a problem ever, but others do. Trek had to quickly introduce oversized bearings to fit to those frames where they have worked loose. These can in turn work loose, so then I presume, the frame is jiggered.

cheers