daoswald

My road bike has a Shimano 105 "GS" medium cage rear derailleur from the 5600 series. The maximum cassette size for the 5600 series is 27t. However, I've been riding for about a year with an 11-28t rear cassette. The shifting is ok but has never been great. I'm wondering if I could swap over to the 5701GS rear derailleur which has a 30t max for the rear cassette. Would this swap require changing the shifter also?

The motivation for wanting to do this is that currently I have to tighten the b-screw almost all the way down to accommodate that 28t cassette, and this has made shifting at the small end of the cassette less reliable. It seems like swapping over to a derailleur that is designed for up to 30T would help improve shifting throughout the range when using an 11-28 cassette (and who knows, maybe at some point I'll get a 30t sprocket in back).

alcjphil

I am surprised that your 5600 GS derailleur has trouble with a 28 tooth large cog. A one tooth deviation from Shimano's stated capacity should not make a huge difference in shifting performance. What sort of crank setup do you have? That said, a 5701GS rear derailleur would work with your shifters. Another possible solution would be a "9 speed" Shimano mountain bike derailleur. That is what I have on my touring bike. It give me the option to be able to use a much larger cassette than the 11-28 I currently have

BlazingPedals

I could probably look it up if I weren't so lazy, but does Shimano make a 5703 derailleur anymore?

MikeWMass

No, but they are available on EBay

Maelochs

Derailleurs aren't that picky. Some newer ones, designed for 10- or 11-speed, might balk at a 6-7-8-speed chain ... but otherwise, they just swing as far as the cable is pulled. Up to 9-speed (as far as i recall) you can swap MTB and road rear derailleurs and road shifters will work fine. And up to 5800, I think you can mix and match anything road. The derailleur doesn't know ho many ratchet-stops the shifter has, just how far the cable is pulled.