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Rapair Carbon Brake Bridge?

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Rapair Carbon Brake Bridge?

Old 02-07-24, 07:35 AM
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Rapair Carbon Brake Bridge?

I bought a cheapo rear wheel (105 hub, Mavic CXP 22 rim $25) for my wife to use on the trainer and the guy I bought it from had a bunch of other stuff listed for sale. One of the items was a Calfee frame with a broken brake bridge. I told him how I am on my second Calfee and love the brand due to it's rowing connection. He said that the guy he was going to sell it to backed out. He was asking $100 for it and was desperate to get rid of it because he is moving to LA in a week.I said I think I could fix it as I have experience repairing carbon fiber racing shells and oars and asked what he was going to do. He ended up just giving it to me! Even if I can't fix it, I can salvage the King headset for sure.

It measures ST 60cm CTC by TT 58.5 -which is exactly the same as both of my other Calfees. So I am not sure what is "Custom" about this one. I guess I will send the serial number to Calfee and ask.


Using a razor blade, I scraped away as much of the paint as I could on the brake bridge to try and see how bad and deep the crack is.



I stuck a screwdriver into the brake hole and gently pried. The crack is bad, at least in a rotational way. I couldn't feel any flex when I pressed on it directly towards the hole, or vertically from the top (or bottom) of the bridge, but that rotational torque crack is concerning.

My plan is to continue removing all the paint on the bridge (time for the Dremel) then gently pry the crack open and inject as much resin into the crack as I can. Then I'll clamp it down and let it set overnight. Finally, I will wrap the bridge in carbon and proceed as if I was repairing a teeny little oar. I think I will put a carbon strip along the top and bottom of the bridge, then wrap both sides of the bridge with a second layer or carbon. Does this seem adequate? I have ordered Predator Cycling's repair kit.

My question for you all is: do you think this will be enough to make the bike safe? Not super worried about cosmetics, just want something safe to ride.

Then I will build it up with stuff I have laying around. It will be a total Franken-build.

I will also sand and touch up all the war wounds on the frame. Probably just with primer black. The paint is pretty rough with lots of chips, some quite large. However, the color is very nice. I wonder what happened to this frame? It was obviously very well loved (look at all the chain slap damage).

Then? Maybe give it to a buddy. Or keep it for visiting friends.
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Old 02-07-24, 11:28 AM
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You could run it as a fixed gear? Sorry I'm not more helpful about the carbon fibre repair, don't really know anything about that
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Old 02-07-24, 01:46 PM
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I would concentrate on the fundamental part of the repair being carbon strand running in a corkscrew along the bridge from the seat stays (and starting on the stay, not just at the interface). Run the right side from the top at the seatstay to the bottom at the bridge, going far enough to be covered by the left. Wrap the left as a mirror image to the right. Do this so you can view the wrap like it was a spring being stretched by the twisting action of the brake.

I would probably fill the inside first with resin filled with micro-balloons. (I have the WEST System epoxy stuff being a one-time boatbuilder and racer. Very, very useful! West Marine has been my source forever. Maybe Tap Plastics.) Perhaps fill with the balloons and put the excess I mixed up in the freezer. After the insides set, putty knife the frozen resin/balloons on a smooth layer over the gouged and split bridge, then do the CF wrap immediately. Finish with a tight wrap of thin CF or fiberglass, both for looks and to keep everything pulled tight. I'd do that last wrap from seatstay to seatstay, probably going right over the holes and finishing by wrapping the still dry and clean CF to the seatstay sand taping it there with masking tape (likewise, starting with the CF taped to the starting seatstay.

With care, you can do a repair that will look different that the rest of the frame but will look good and like it belongs. And it will be strong. Doing the wraps with one end anchored as dry CF taped to the stay, keeping the CF tight as you wind it over the balloons and enough fresh resin to soak through nicely will leave you with a minimalist repair that is completely integral to the hardened resin/micro balloons under and the bridge in between. Keep the wrap tight and minimize and or remove the resin. Glass on epoxy resin will float up and be quite uneven (as well as less strong) if it is allowed to.

Another trick - have on hand strips cut from inner tubes. When you finish and have cleaned up, return and do the same wrap, only with the rubber strips. Resin will bleed out alarmingly. But when you remove it, if you did a nice initial wrap, the end result can look professional. Oh, and tape off or otherwise protect everything around and below your work! Tape neatly up to the edge of paint removed. So you can wet the CF past the tape edge. When the CF is 3/4 set, trim the tape edges with a trim knife and new blade. (Not deep! Don't cut your frame!

I did basically this repair (minus the resin/balloons except to fill a couple of hard to wrap corners) to steel frame that had be hit by a car breaking both chainstays about halfway just behind the bridge. Turned a flexible sport Peugeot to the stiffest BB'd Peugeot ever made!
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Old 02-08-24, 07:00 AM
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I was considering using microballoons* to sort of fill in the ridge on the front and rear of the bridge to make it a rounder shape so I could compression wrap the bridge more uniformly. I figured that the crack itself is not a place to use filler, but rather to try and get as much adhesion as possible.

Anyway, I am now leaning towards having Toby at Hot Tubes handle this.

*Being a rowing coach, I am quite familiar with West System!
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Old 02-11-24, 05:12 PM
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This is an easy fix. Don't overanalyze it. You can just sand the area down to bare material and use carbon tow to tie everything back together. Mask off the bare circular areas and go right over it with your wrap. After you sand things down you can remove the material on top of the tape and expose the bare surfaces again.
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Old 02-12-24, 07:22 AM
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Done:


Toby is the Man. Not only does it look good and is very strong, he was super fast too. I dropped this off Friday and it was ready Sunday.
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Old 02-12-24, 06:04 PM
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Looks kind of rough but should do the job.
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