Front Derailleur Shim?

wombar Posts: 119
edited September 2011 in Workshop
Hi All,

I bought a front mech from CRC which said it fitted 28.6/31.8 diameters. Turns out it only fits 28.6 with a shim which I had assumed was included.

Anyway, I'm now trying to source a shim, and I'm really struggling. Anyone know where you can get a 28.6 shim for a 31.8 clamp? I've found a few products which look like they might work, but I don't fancy shelling out £18 for a little bit of metal.

Thanks in advance...


  • sungod
    sungod Posts: 16,889
    if crc advertised it as fiiting both, then i'd give them a call and ask about it

    maybe the shim *should* have been included, but went astray

    otherwise, if they advertised it as fitting 31.8, they should allow you to return it for a refund so that you can get one that does the job
    my bike - faster than god's and twice as shiny
  • wombar
    wombar Posts: 119
    They adverise it with "Band Diameter: 28.6***/31.8/34.9mm" and it would appear those little stars mean that you're going to have to find an adapter somewhere. Of course it would be nice if they said something about it.

    The actual mech is a 31.8, and my bike is a 28.6. It's just irritating because I thought I had everything I needed to get the bike build coming along.

    Ah well, I'll give them a call in the morning, but I expect them to say that I'm out of luck.


    I was sitting there scouring the net for a cheap option (sorry, but £18 for one of these is just ridiculous). Anyway, to cut a long story short, I've bodged a shim and it has cost me precisely £0 :)

    I'd looked around and some people were saying to use inner tubes, etc. However, I wanted something metal as I don't want to worry about whatever I put on there perishing over time. Once it's on, I don't want to worry about it.

    So, I've just cut an inch or so off the bottom of my road bike seat post. It's 31.8, and fits absolutely perfectly.


    I've filed down the edges so it doesn't scratch the frame. Jobs a goodun :)
  • sungod
    sungod Posts: 16,889
    oops, yes i had the dimensions the wrong way around

    looks like you've found a good solution!
    my bike - faster than god's and twice as shiny
  • I have one of these somewhere I think, which was this one:

    You might find a local source for them, rather than the US one here.
    Open One+ BMC TE29 Seven 622SL On One Scandal Cervelo RS
  • wombar
    wombar Posts: 119
    Yeah, I've seen those (or something very like them) at SJS. If they'd been ~£5, I probably would have ordered one, but they were around £18 which is ridiculous. I can buy a seat post for that and make like 30 of my DIY shims.

    A lot of the other shims I'd found were for converting down from a 34.9 which isn't any good to me. In the future, I'm going to buy a braze on derailleur and just buy a bracket.

    The method I've used is perfect, I think I just need to resize it a little so it'll look a bit tidier once it's installed on the bike. It's just lucky my road bike takes a 31.8 seatpost and my new bike is a 28.6 :)