105 compatibility (is an RD-1055 8 speed compatible?)
 

OK, long story short... I am building up a bike for my wife, a mid-late 90's Trek 2100 (a step up from her 1200.) Both bikes have 7 speed cassettes and are 105, though the 2100 looks to be a newer version than the 1200 (the 1200 is '89-'90.) The 2100 has 7 speed down tube shifters and the 1200 has 8 speed brifters that someone has managed to work with the 7 speed. She hates the down tube. The chain stay spacing will accommodate an 8 speed rear (I tried the rear 8 speed wheel off of my bike and it drops right in). Can someone tell me if the RD-1055 is compatible with an 8 speed rear end? If so, I will swap shifters and put an 8 speed rear on the 2100. Otherwise I'll leave the brifters on the 1200 and find some 7 speed for the 2100 (less work but more $$). Make sense or too damn much work?

You're good. Any Shimano 8speed shifters (besides ol' dura Ace) will work with any Shimano indexed rear derailers, up until they recently ruined everything with new ratios on late-model 10speed groups.

so that derailer will work with an 8 speed cassette?

I'm sure a quick answer will be posted right behind this with the info you want. But the Shimano web site is really good for component specs and compatibility. And if you just want an inexpensive shifter upgrade from 7 speed downtube to 8 speed it's hard to beat bar end shifters.

I think it will. Worth a try.

I'm running 1055 STI's that are 8 speed shifters right now, on an old 7 speed freewheel. The RD should definitely work. As it is, i'm running an RD 1050 that was originally on a 6 speed freewheel, if that tells you anything. you should be fine with that combination.

The 1056 was designed to have more travel for 8-speed cassettes, but it's very possible that the 1055 will work. Try throwing an 8-speed wheel in your bike and using a shifter in friction mode to sweep across it.

bres dad, The only hiccup would be the travel to reach the low cog. I had to back out the low limiter screw completely for a STX 7S RD to work with a 8-10S freehub on my touring bike. Worth testing before replacing the RD.

Brad