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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 03-25-11, 07:39 AM   #1
mmac
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Repairing Giant Cadex 980c Lugged Carbon

My girlfriend has a carbon frame she bought off ebay a couple years ago, and has put a lot of miles on. I've been upgrading it for my spring break project.

The BB shell was backwards (like swiss style) so I had to install an external cup BB.

There is a gap between the chainstay and her rear dropout, I was thinking about filling this in for a year or two until we can afford better bikes. My gf just started grad school, and I'll be graduating with my undergrad soon so I have to live frugally until then.

I was considering putting epoxy into the gap and clamping it down by running a tourniquet style clamp between the bridge, and the dropout with a wood dowel for a lever.

Would this work? Are there better options? Am I asking to be a single man by putting the GF on this bike?

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Old 03-25-11, 08:15 AM   #2
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First the bottom bracket shell isn't "backwards", it has very standard "English" threading so the right-side (drive side) cup is left hand threaded. Any type of bottom bracket; square taper, Octalink, ISIS and external cups. are readily available in that threading everywhere.

Second, that frame can be repaired but doing it correctly will be rather expensive. Craig Calfee's company does repair carbon frames and does it right but they aren't cheap. I would not attempt a home-made repair on that frame. For less money than a proper repair, you could probably locate a replacement frame.
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Old 03-25-11, 10:14 AM   #3
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It looks to me like the bond between the stay tube and the dropout has broken and the dropout is slipping in the stay. If I'm right you need to do more than just smear some epoxy into the crack. What you need to do is make up a tube clamping block for the stay tube to hold it really well but without crushing it. Then you need to set up something to pull the joint apart more than it is by a good half inch but to do it with some measure of control. So something like a jack or cable "come along" will be needed with some way to secure that stay with the clamped on block. Once it's apart by that much of a gap you'll want to scuff up the dropout stem and then slather on some good but thin epoxy and then turn things around and push the dropout's stem fully back into the tube. For this you'll need enough stuff to turn the pressure around and push it together under the same sort of control that you used to open it up.

I'm being deliberately vague in all this because I don't know what sort of tools or skills you have. And frankly if you can't figure out how to do all this in some manner that won't put the wrong sort of pressure on that tube then you should not even start on it. I know that if I were to try such a thing I'd make up a big flat board from a couple of layers of thick plywood glued together onto which I'd set up the saddle clamp block for the tube and then attach a long screw jack setup attached to the dropout that would allow me to first pull it further out under good control and then push it back in again slowly and with the same control while I keep spreading the epoxy on the stem of the dropout.

The epoxy I'd use for this repair would be a thin laminating resin to encourage the most glue possible to enter the small space between the dropout and tube.
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Old 03-25-11, 10:37 AM   #4
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First the bottom bracket shell isn't "backwards", it has very standard "English" threading so the right-side (drive side) cup is left hand threaded. Any type of bottom bracket; square taper, Octalink, ISIS and external cups. are readily available in that threading everywhere.
No, it was BACKWARDS. The fixed cup was on the wrong side and it would unscrew itself often during normal use. Two bike shops could only fix this by rethreading the BB and I didn't want them to. I probably could have installed other BB types, but the standard fixed cup was not an option, and I got the Cadence Crank and BB for 30 from my LBS.

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And frankly if you can't figure out how to do all this in some manner that won't put the wrong sort of pressure on that tube then you should not even start on it.
As is the bike still works, and I don't want to break anything. We don't have mountains (just hills) and I have seen a rear triangle break before, it brings the bike to a skidding stop.

That said, it would be really nice to fix this to prevent any accidents. (I like my girlfriends skin better when it's not spread out on the highway)
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Old 03-25-11, 11:42 AM   #5
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No, it was BACKWARDS. The fixed cup was on the wrong side and it would unscrew itself often during normal use. Two bike shops could only fix this by rethreading the BB and I didn't want them to. I probably could have installed other BB types, but the standard fixed cup was not an option, and I got the Cadence Crank and BB for 30 from my LBS.
Maybe that's why the bike was on E-bay.

So, if I understand you correctly the drive side cup was right-hand threaded and the non-drive side was left-hand threaded. They are English dimensioned threads right? I guess someone used the wrong tap on the wrong side. Actually both cups should have unthreaded with riding.

If that's the case, Lock-tite is your friend.
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Old 03-25-11, 12:36 PM   #6
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So the BB threads are wrecked, and the carbon bonded rear stays are falling off, thinking it'a an excuse for a nice new frame.
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Old 03-26-11, 10:58 AM   #7
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I perfer the turn up the volume and don't worry about it method. It works for cars...for awhile. I'd say call up Calfee and see if they can give you a rough idea on the price. You can get those threadless bottom brackets if all else fails for the bb issue.
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Old 03-26-11, 02:45 PM   #8
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You should unplug that loose joint entirely and clean both surfaces thoroughly.
that will make the bond work, dirt is always an enemy of joining stuff.

then some 2 part Epoxy can be mixed and put around the pieces ,
and as suggested
clamped in place until the Epoxy cures .
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Old 03-26-11, 02:58 PM   #9
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Calfee has a price list on line. But give Craig a call for a more accurate price if needed. The shop I work at has sent in 6 or 8 frames for repair and all looked great when retuned. Including the gold leaf replacement on a Livestrong bike. Much cheaper than replacing or hospital bills.
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Old 03-27-11, 01:04 AM   #10
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I had one of those, with those forks, but it was a CFR1.

Very nice frameset, if a bit noodly. Cracked the bond between the seat tube and seat cluster, but it was hanging in there till it was pinched.

IMO this isn't a tricky fix if you can work that gap open and closed by hand a few mm; just smother it in epoxy and work it in by flexing the stays, and keep re-applying epoxy until you're sure you've soaked the joint.

Keeping it closed could be as simple as looping a dozen stretched turns of thick fishing line between the brake mounting hole and the dropout.

I doubt you need to be super-careful and in the know to fix this; the vast majority of the load on this joint is compression, so it shouldn't take a whole lot to hold it in place.

And a threadless BB from Velo Orange. Sorted.

Oh, BTW, my CFR1 had a 135mm OLD. What about this one?

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Old 03-27-11, 06:34 PM   #11
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I appreciate advice on fixing the carbon, but I think I will stay with my current BB choice that works, and is installed in the bike -.-
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Old 03-27-11, 10:21 PM   #12
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Do you have to squeeze the stays much to clamp a 130mm hub?

This may be part of the cause...

If it's happier with a 135, it's a good move to stick an extra spacer on the left, and re-dish to have a stronger wheel.
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