Hey all,

I have a trip to CO coming up in 6 days and my bike is broken. There is a small metal mating surface on the rear right dropout that has broken out and now the wheel skews and rubs on the frame.
I have fashioned a replacement and have tried Super Glue and a Loctite Epoxy that sets in about 6min, is ok to handle in 20 and cures fully in 24 hours. We neither will hold the piece in place. I used a chrome washer with a ton of dremel work and the frame is carbon fiber.

What type of glue/adhesive would you use?

I have been getting this bike ready for this trip for a bit. New wheel, seat, bars, stem, large chainring, chain, rear derailleur and cassette. I would hate to not be able to bring it with me. The idea of renting a bike sounds like a hassle and expensive. The bike manufacturer is sending me a new frame but it won't arrive for a few days and it will be really hard for me to get it taken apart and rebuilt, not to mention expensive, before I leave.

Help?

(It would be easier to help if I could post pics but I have to go on a posting binge to get above 10 posts apparently. )

Take it to a shop that works with cf fiberglass?

Having already altered the surfaces I suspect any repair is not going to be a quickie, or one that I would trust on a multy day tour without prior testing. No good info or photos prevent more speculation. Andy

Any Pictures?

This may be repairable, or it may be a sign that the frame has failed and is absolutely not safe to ride.

In general terms, if you wanted to fashion a replacement for missing carbon fiber, you'd want to use another fiber and epoxy. Chromed metal doesn't take to glue. You can use carbon fiber, glass fiber or even thin cotton cloth after degreasing all surfaces and fibers. The strength of the added piece will come from its fiber density.

If the manufacturer is sending you a new frame (assuming warranty and free) then what you have is probably broken badly and probably dangerously.

Colorado has mountains, you don't want a frame breaking or a wheel popping loose and jamming in the frame in the mountains.

Based on current info (no picture) conservative approach is don't ride the frame.

Six days is plenty of time to swap parts to a good frame. One day job.

Broken


New insert

Wait for the new frame, swap parts. It's less than a one day job. I'd even replace the cables too.
There is no way I'd take a bodged repair like that on a week long tour.

Advantage: steel..

Fabrication on the washer is impressive but riding it is not worth the risk.

The last ambulance ride I took cost $1119 and I only spent 36 hours in the hospital. No trip is worth even that.

Hell no, I wouldn't risk my life on that.

While you certainly could fill that spot in with something that will last under compression, you haven't fixed the problem of how much weaker that area is due to losing a huge chunk of what makes the structural connection between wheel and bike. You'd have to be nuts to ride that down a mountainside.

Note that the CF has not been compromised; it's still as intact as before. The part that fell off is metal insert that provides scuff protection for the CF. The repair washer replaces that function just like before. Any 2-part epoxy works for holding the pieces together. Since lateral-load is in compression from QR-skewer, it really doesn't matter what you use as long as it holds metal insert. Heck, even double-sided tape or bubble-gum will be fine.

Vertical loading from weight goes upward into structure same as before.

disagree...if you look at the first picture there is significant cracking in the carbon matrix at the front of the drop out. bike companies don't swap out frame for minor details. bike should not be ridden

+1
I'd ride it. The piece that fell off was only bonded on and thus only slightly structural. The skewer will keep everything in place. Just inspect frequently.

Aside from the OP thinking it was a metal insert, how do you know that it was?

And the OP has ridden this bike with other stuff substituted and the wheel came out - how do you know the wheel popping out at an angle didn't do damage to both dropouts?

Aside from the hanger, there should be some right/left symmetry, so if the left has some kind of inserts on both sides, then the right probably did too.

I'd probably use the skewer to clamp, and epoxy that washer into place, and try it out.

Probably not a life and death risk. So, if the wheel pops out, and rubs the chainstays???

The issue would be whether or not I'd be comfortable taking it on a multi-day trip. I'd probably prefer taking it a few days around the neighborhood, but part of the decision will depend on how isolated one will be, and how harmful a day or so of downtime could be.

Be aware that frame mods might affect any warranty coverage, if that is an issue.

The OP already tried super glue and epoxy and the washer fell out.

As mentioned above, chrome may be a slippery surface, and perhaps stainless would have been better. Make sure the surface of both pieces is roughened slightly.

I probably wouldn't choose superglue for an app like this, and if it failed, it needs to be 100% cleaned off of both surfaces.

One issue might be load application. It shouldn't take much to hold the washer in place with a compression load from the skewer.

However, a vertical load from the axle setting on the washer may be bad (or forward from the chain tension). So, it might be beneficial to undercut the washer slightly, and perhaps also build up the dropout slightly with epoxy, or even a fiber reinforced epoxy.

Obviously poor prep as it was originally epoxied on from factory. From photo of washer, it doesn't have sufficient epoxy behind it. You should see it oozing out at edges, a sign that all gaps and voids between washer and dropout has been filled.

I've done this repair on numerous frames, starting with aluminium frames back in '80s. On some frames, washer have pins that goes through dropout and are welded to washer on other side.

yep.

Looks more like paint chip. Crack is below centreline of axle anyway. Not much force there as most load is applied directly above axle.

How many miles have all of us ridden with insufficiently tight or completely loosened QR skewers?

You don't need much below axle-centreline. That extra amount below is really to allow QR to clamp on parallel surfaces.

There is all sorts of reasons that the repair didn't work, and most of them come down to what happens when you close the skewer. Epoxy does not have much compressive strength, so more of it is only going to help around the edges - anything between the locknut and skewer is just going to turn to powder if the metal isn't bedded against the underlying carbon.

And even if it is bonded properly, it needs to be entirely perpendicular to the lucknut, or the force of the skewer is going to squeeze it out sideways from the locknut pushing on one side more than the other.


I'm not surprised this didn't work - I'm surprised that the original metal part bonded to a carbon dropout lasted any time at all. If the OP insists on repairing this, make the washer out of fiberglass so it can flex with the underlying carbon in the dropout and so the resin matrix in the fiber provides a good bond to the matrix in the dropout.

But I still think having your hub pop out of dropout is more potential destruction than I'd trust on a bike that will be climbing and descending.

I will try with more Epoxy. I am also thinking that the epoxy I got, even though new, was somehow bad as the mix I made didn't harden more than 24 hours later. It was rubbery.

I prepped the metal with a little grinding and the carbon with some acetone and some brushing. I made the spacer a bit smaller to reduce the chance it will have a vertical pressure applied to it. The frame itself looks ok - no cracking that I can see but I will reinspect.

I hear the concerns and respect them. I did some checking and can't find a bike to rent in Denver atm. Well I did but they want $700.