How can I tell if I have a Short Cage or Medium Cage Rear Derailleur

Ben_.

I'm trying to work out if my OEM Shimano 105 (10 speed) rear derailliuer is the Short Cage Model (SS) or Medium/Long Cage (GS).

The tech docs list the different parts that go on each variant but not the measurements (or other identifying marks).
(I'm working on the assumption that I can measure the plate (or some other part) and determine which size derailliuer cage is fitted)

davesnothere

Do you have a triple on the front or a double. You'd generally only have long cage for a triple i believe

Ben_.

DavesNotHere wrote:

Do you have a triple on the front or a double. You'd generally only have long cage for a triple i believe

Double 46-36 - but it's a cross bike so it has lower gearing than a regular road bike.

I'd rather know for certain though than guess.

keef66

You can pretty much guess by comparing the shape of what you have with the pictures of the side plates in the exploded diagram in the tech docs.
Failing that I can measure the distance between the pulley centres on mine for you. Mine's the longer of the two because I have a triple.

keef66

Or you can take it off and look for a part number somewhere. Shimano are quite good at that. You just need to know where to look...

lesfirth

You should also be aware that all 105 long cage are the same. I recently altered one of my bikes to run 34 rear cog using a 105 long cage and fiddling with the b screw. Worked a treat. I tried to do the same on another bike.It just did not work.
Problem was that the first rear mech was a 5701 and second, that I thought was and looked the same ,was a 5700. I think 5701 is designed to go up to 32t rear cog and 5700 30t maximum.The numbers are on the wheel side of the inner plate.

davesnothere

Mine is - Shimano 105 RD-5800GS,11 speed

Distance from centre to centre on pulleys is approx 85mm. I just measured it

keezx

Short cage-Distance is app. 55 mm

Ben_.

Thanks