How do Trek downtube shifters mount on carbon tubes?
02-11-21, 07:28 PM
#1
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How do Trek downtube shifters mount on carbon tubes?
So I have this Trek 2100 carbon frame with these downtube shifter mounts. The left mount is just a bit loose. It looks like it mounts with a screw which likely runs through to the other side. But I am not sure. I can't see in there well. How do these mounts...umm....mount and how can I make it secure?
02-11-21, 07:35 PM
#2
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Usually the base is epoxied and the mount is riveted to that. Might need to see a dealer on that, some with have the tools to fix it.
02-11-21, 09:50 PM
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That's an old one. I always thought they were just bonded on.
02-11-21, 10:18 PM
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So I have this Trek 2100 carbon frame with these downtube shifter mounts. The left mount is just a bit loose. It looks like it mounts with a screw which likely runs through to the other side. But I am not sure. I can't see in there well. How do these mounts...umm....mount and how can I make it secure?
02-11-21, 10:36 PM
#5
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It is probably bonded/glued to the tubes. Maybe a rivet is in there as well. There is a member on the forums who worked for Trek back in the day but I can't remember name maybe JohnDThompson but I could be wrong (Sorry John if I am wrong or if you don't know).
You might consider reaching out to trek or finding an older Trek dealer they might know.
You might consider reaching out to trek or finding an older Trek dealer they might know.
02-12-21, 07:40 AM
#6
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That's true. Could be a rivet. It's loose and yet not coming off so it must be something other than glue.
02-12-21, 08:10 AM
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I can’t speak for a 2100, but Cannondale used a threaded rod to pinch the 2 shifter bosses together against the downtube.
I believe the 2100 is epoxied, but it may also have a threaded rod for more support. What I don’t know is how the bosses come apart.
If the concern is keeping the boss from being loose, I would guess an epoxy could be used; but I wouldn’t want to guess which one to use.
John
I believe the 2100 is epoxied, but it may also have a threaded rod for more support. What I don’t know is how the bosses come apart.
If the concern is keeping the boss from being loose, I would guess an epoxy could be used; but I wouldn’t want to guess which one to use.
John
02-12-21, 08:30 AM
#8
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Yes, the Cannondale does use a threaded rod. I'm considering that as a repair for this one. Of course that may involve using a nut on the outer ends of the shifters. Even if I switch to brake/shift levers I'd still have to secure those cable mounts.
02-12-21, 09:14 AM
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So did the Trek- built Kleins from the late 1990's. There was a thin threaded rod that passed through the bosses and the downtube along with double sided tape to hold the bosses in place. The rod had a screwdriver slot accessible at the bottom of the threaded shifter mounting hole. These rods tended to vibrate loose and/or strip the threads which allow the bosses to fall off. Trek sold repair kits for a while.
02-12-21, 09:26 AM
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Yes, there is a rod that passes through the tube to the boss on the other side. The curved bases are epoxied to the tube to prevent any wiggling of the boss in use.
02-12-21, 10:20 AM
#11
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Thank you. If I can’t get this out I’ll have to drill it out.
02-13-21, 01:39 PM
#12
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So I drilled it out. I don't think that any kind of adhesive, epoxy would be strong enough to hold this on. JB Weld? I dunno. I'll need a skinny threaded rod to run through there and 2 nuts on the end...which would prohibit me from using downtube shifters but I could put on the cable mounts for the brake/shift levers. And I am going to lightly sand and clear coat the carbon tubes because of the flaking.
02-13-21, 10:57 PM
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I have no idea if threaded rod of that small diameter is available, but if not, you could make "treaded rod" out of an appropriate diameter bolt by cutting off the head and dressing the threads on that end.
02-13-21, 11:56 PM
#14
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So I drilled it out. I don't think that any kind of adhesive, epoxy would be strong enough to hold this on. JB Weld? I dunno. I'll need a skinny threaded rod to run through there and 2 nuts on the end...which would prohibit me from using downtube shifters but I could put on the cable mounts for the brake/shift levers. And I am going to lightly sand and clear coat the carbon tubes because of the flaking.
Cut the rod to a length that will allow it to go through the tube and into the bottom 3 to 5 threads on each boss. Thread the rod into one of the bosses. Set the bosses in place and clamp them (check the fit dry then the final assembly would use epoxy to hold the bosses). Then screw the rod into the second boss. Make sure the rod is evenly spaced to give the same number of available threads in both bosses. You may need to increase clamp pressure to squeeze the tube to flex it so the rod will fit into second boss. You may also need to shim under the boss depending on how close to an even number of threads fit between the bosses.
After the epoxy is set, you should still be able to install the downtube shifters although you might need to shorten the bolts holding the shifters in place.
