Smithie

All: I'm upgrading an old 1986 Cannondale to some indexing 105 downtube shifters. Obviously, the mounts on these regular sized shifters will not go flush against C'dale's oversized downtube. Any suggestions for some kind of shim which won't be aesthetically abrasive to take up the gap?

GeoKrpan

There was a thread recently about a DT shifter boss that had come unglued on an aluminum bike.
There was a link in it to a frame builders supply that might be a source for you.

Recently, I saw a brand new Fuji aluminum bike with oversize downtube and DT shifters, at a big box sporting goods store. Evidently, what you need is still being made.

Homebrew01

You mean you have Shimano clamp-on shifters designed for a frame without braze-on bosses ? A shim is for the opposite situation, if the clamp was bigger than the downtube. Can you remove the shifters from the clamp and use the braze-on shift bosses ?
(sorry if I'm misunderstanding your situation)

Andrew R Stewart 

Shimano has made the chromed spacer/fitting washer, that sits against the tube and over the boss before any other shift lever parts are installed, in a curved back (to fit 28.6 tube) and a flat back. It is the flat back that Cannondale used when they still had DT levers. Of course this assumes that your frame has "braze on" bosses. Andy.

Smithie

Sorry for the lack of specifics. I have a set of Shimano 105 indexing shifters, model FD-1050. These are for braze on bosses, so no clamp. I can fit them on the bosses just fine, but, the contouring of the primary washer/plate of the shifters is for a smaller downtube (regular steel tube size), leaving a small gap when its is attached to the larger diameter tube. So, the shim would be something to make the tighter/smaller diameter contour of the primary plate/washer on the braze-on shifter work flush against the larger/wider diameter of the downtube. Maybe spacer would be a better term here than shim.

There are not flat back bosses either, the bosses are actually two nuts on a single bolt which goes through the frame through drilled holes.

I'm sure brut force would make these functional, but, I don't want to screw up the paint and crush either the primary plate/washer or the aluminum to do it.

Also, I was hoping for a hardware store type solution. I could probably hunt down a new primary plate for these shifters, but, it would likely be the same price as buying a new set of older braze on shifters in the correct size. Maybe I can just use a rubber washer to protect the two surfaces and if it is thick enough, it will take up the small gap? Just spit-balling here.

Smithie

Probably should've just done this in the first place. Here's a pic. It's kind of hard to see, as it's a hard angle to shoot with the camera, but, the black space between the shifter and the downtube is the gap. Its not huge, but, without something to fill that gap tightening these things down would damage something.

fietsbob

file on it till it fits, or ask your C'dale dealer for the part they use.

Puget Pounder

Easy solutions:

1. File washers until they are flat
2. Buy the flat washers somewhere; they are the same ones that come on bar end shifters
3. I might have some. Will have to check.

HillRider

Yep, put a sheet of moderately coarse sand paper on a flat surface and sand the back of the washers until they match the downtube. I've done this to adapt curved downtube washers to work on Kelly Take-Offs that require a flat back.

fietsbob

or wrap sandpaper around something the size of your frame tube,
grit side out. [or the frame's down tube itself]
and sand on those pieces you have, notably the ends, till it fits.

Jeff Wills

Exactly. They are Shimano part number 643 4300, seen here:
https://techdocs.shimano.com/media/te...9830628723.pdf
Any bike shop that's been around for a year or two should have them.