Carbon Drop Out Touch Ups
08-15-18, 09:00 PM
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Carbon Drop Out Touch Ups
Is it possible to add material to a carbon drop out?
08-15-18, 09:04 PM
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sure, it's all laminated with epoxy.
08-16-18, 08:17 AM
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If it was my bike, and the repair wasn't structural, I might try it. And I'd no doubt spend 40 hours on the internet doing research.
08-16-18, 09:16 AM
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I don’t have any experience in material patching.
Heres the full story:
there was a chip on the right drop out axle contact face. So I sanded the left one to match the depth of the chip so that the rim can sit centered. However that leaves dead space behind the axle on the left drop out which the wheel is free to slide back into and go off center again
the easy solution is to patch that dead space in the left drop out, the complete solution is to patch the chip on the right as well as restore the original material on the left
Heres the full story:
there was a chip on the right drop out axle contact face. So I sanded the left one to match the depth of the chip so that the rim can sit centered. However that leaves dead space behind the axle on the left drop out which the wheel is free to slide back into and go off center again
the easy solution is to patch that dead space in the left drop out, the complete solution is to patch the chip on the right as well as restore the original material on the left
08-16-18, 09:26 AM
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So are you describing an actual problem, the wheel slips within the drop out when riding? Or are you trying to avoid a problem that isn't yet happening? A well secured wheel doesn't need the axle to contact a drop out slot's inner face to stay put. Witness the many millions of bikes with horizontal drop out slots and that their wheels only move about when the QR (axle nuts) are not properly tightened. Andy.
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08-16-18, 09:31 AM
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The problem is happening. When I’m on the bike and do a sprint, afterwards I’ll find that the wheel has slipped back into the space and is rubbing again.
Maybe my KCNC skewer is too flimsy
Maybe my KCNC skewer is too flimsy
Last edited by Reeses; 08-16-18 at 09:34 AM.
08-16-18, 10:10 AM
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I admit that I'm no fan of non metallic interfacing with bike components, carbon drop outs might not accept the level of QR tightening that a good enclosed in cap cam design can produce. The QR's that use a plastic cam bearing surface are well known for their lesser clamping forces. QR's with steel serrated end caps (and axles with same) can hold onto the drop out better then smooth faced or AL parts will.
But to answer the OP. Adding a "drop" of epoxy on the drop out slot's inner surface to nudge the axle just so isn't hard to do and is reversible if ever needed. Using a couple of pieces of masking tape on either drop out face will hold the curing epoxy in place, like two dams on either side of the slot. A med cut 3/8" round file does a quick job of the final shaping of the epoxy and the needed fit for the axle end. Andy
But to answer the OP. Adding a "drop" of epoxy on the drop out slot's inner surface to nudge the axle just so isn't hard to do and is reversible if ever needed. Using a couple of pieces of masking tape on either drop out face will hold the curing epoxy in place, like two dams on either side of the slot. A med cut 3/8" round file does a quick job of the final shaping of the epoxy and the needed fit for the axle end. Andy
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AndrewRStewart
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08-16-18, 02:02 PM
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Let me know if I’m understanding this. So I can use masking tape and make like a U shape on the drop out. Then apply epoxy so that it covers the area I need new material, wait to dry. Then sand it down as needed, and it’ll hold the wheel without buckling?
08-16-18, 02:10 PM
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No. He means just make a wall of tape on either side to seal it and then pour a bit in to fill the deepest portion of the dropout.. Overfill a bit and then use a round file/rasp to finesse the shape.
Make sure you thoroughly degrease the area though.
Make sure you thoroughly degrease the area though.
08-16-18, 02:17 PM
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Last edited by Reeses; 08-16-18 at 03:40 PM.
08-16-18, 06:03 PM
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No, use structural epoxy. You're gluing to an epoxy matrix, not polyester.
Something like 3M DP 420 would be ideal.
Something like 3M DP 420 would be ideal.
Last edited by Canaboo; 08-16-18 at 06:13 PM. Reason: additional info
08-16-18, 10:00 PM
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i took off my pastic kcnc skewer today and replaced with an alu one and the wheel holds much better.
now debating if it's worth the effort for the repair but if the wheel keeps slipping I will attempt it.
Another question is how good is the epoxy repair vs an actual carbon repair?
now debating if it's worth the effort for the repair but if the wheel keeps slipping I will attempt it.
Another question is how good is the epoxy repair vs an actual carbon repair?
Last edited by Reeses; 08-17-18 at 01:23 AM.
08-17-18, 06:51 AM
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A proper repair will have an edge in strength and durability but likely not to a measurable degree unless the strength of the dropout has already been compromised.
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