Bicycle Mechanics - What front derailleur clamp size do I need

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kmart
02-13-08, 11:06 AM
I need to get a Shimano 105 or better 9-speed front derailleur that will fit my 28.6mm seat tube. I realize this is a common size, but if I get a 31.8mm clamp will that work too if I just tighten the bolts down a little more? Does the larger size require a shim?

redtires
02-13-08, 11:11 AM
Ahhhh!!!! Yes, you will need a shim!!! You will NOT be able to simply "tighten the bolts down more". You will only end up with a front derailleur that still won't fit and will most likely now have a stripped bolt. If your LBS doesn't have a shim, Universal Cycles has them, and I believe Loose Screws sells them as well.
atomship47
02-13-08, 11:30 AM
i bought a 28.6 problemsolver clamp adaptor for braze on rd's. i think it cost $11.

kmart
02-13-08, 11:30 AM
OK, just checking :) The reason I asked is because I saw an ebay listing for a front derailleur that claimed to fit a range of sizes between 28.6 and 31.4mm. I guess they meant that the derailleur would fit these sizes, but each individual size would require a corresponding clamp.
Retro Grouch
02-13-08, 11:35 AM
OK, just checking :) The reason I asked is because I saw an ebay listing for a front derailleur that claimed to fit a range of sizes between 28.6 and 31.4mm. I guess they meant that the derailleur would fit these sizes, but each individual size would require a corresponding clamp.

Probably it includes nylon shims to match smaller seat tubes to a larger clamp on the derailleur.