rdtompki

I recently added a brass washer between my SRAM RD and the hanger to increase spring tension. I have an unusual setup (Campy Shifters, SRAM RD) on a tandem and the spring tension wasn't quite sufficient to return the RD against the H-stop. This fix worked well, but I'd like to find a source of thinner shims, let's say .5mm, since the brass washer is a bit thicker than needed. Any suggestions?

HillRider

Most auto supply and better hardware stores sell brass shim stock and 0.5 mm is 0.02". You could buy a small piece and cut out a suitable size circle. RD bolts are 10 mm so a 13/32' drill would give the proper hole.

Also, thin washers are sold to refine the spacing on hubs and a rear axle is also 10 mm so a bike shop might have suitably thin washers already pre-made. I've seen them in 1.0 mm thickness but thinner ones may be available.

FBinNY 

I don't get what you're trying to do. If your talking of the pantograph spring not returning crisply to high gear, I can't see how moving the RD outboard by 1mm or less would make a meaningful difference in the tension of a spring with a 35mm working range.

1mm farther out would translate to a less than 3% increase in tension in all positions.

If you need more tension, your best bet is to try to figure out why, and check that the cables are running free enough.

rdtompki

The cable and housing are new, but I might consider replacing. One of the contributors is probably the geometry of the chainstay cable stop and SRAM RD. I would prefer a relatively big loop, but the cable stop is relatively close the the RD and that in combination with the stop on the SRAM RD doesn't provide much flexibility, literally or figuratively. I might be able to find a cable housing that is lower friction/more flexible (current is Jagwire), particularly for this last loop and see what happens.

I don't have a sound technical explanation as to why the shim works or why I was having difficulty in the first place. It's possible my unusual setup makes things a bit more sensitive. I'll also note that I wasn't having a problem with a 12t and 13t as the two smallest cogs, but going to 11t and 13t, the chain would occasionally snag the 13t when I was in the 11t; the greater difference in radius contributed to this. As it happens I'll be going back to the 12/13 setup; with my largest chainring being an effective 60t I don't really need the 11t cog.

reptilezs

we stock 1mm rear hub spacers from wheels mfg. i use them on frames that have thin hangers. ti or steel frames mostly