Problem with a Shimano RSX long cage 7 speed rear mech.

[Cyclopathic]

I've had the above knocking around for a while. It's seemingly in near perfect condition and looks like it's brand new despite them not being made for about 15 years. I've been dying to put it on something and have tried twice without success.

In both cases when peddling under pressure I get what I would describe as chain slippage. It feels the same as the slippage one gets with a worn chain or worn rear cassette. The first bike I tried to use it on was a mountaqin bike I built up with a Saracen frame and it looked like the nuts. I was very happy until the test ride. I tried adjusting everything and winding the b screw in and out. I changed the chain and cassette together and seperately and the problem remained until I swapped the mech for an acera. After that there were no problems at all and the bike was sweet.

The second bike I tried to use it on was a Birdy folding bike. I was hugely confident it would work as it was almost identical to the one I was removing. That too was an old Shimano rsx long cage. The only very slight difference being the jockey wheel cage was a tiny bit different. Not much and you had to look for it.

Confidebt of sucsess I took it for a test ride and the same again. Again I tried different new chain and different new cassette but again the problem was only solved when I changed the rear mech. This time for a reconditioned Sora 7 speed.

I am at a loss as to what could be wrong with this mech? There seems to be no sense to it and no reason why it should produce chain slippage. I don't think it has ever seen service on a bike as it is so pristine so as I say, I'm lost.

The only thing I've noticed is that the spring on the jockey wheel arm is just a tiny bit stronger than on the one of the other rsx but I put this down to it's not being used.

If anybody can think of what the sweaty hell could be wrong with it I'd be very interested to know.

 

[RecordAceFromNew]

In both cases when peddling under pressure I get what I would describe as chain slippage.

Those mechs are built like tanks aren't they? It is curious - a rear mech shouldn't do much when the sprockets are being driven. Sounds like it is overly affected by frame flex or such like. The top and bottom jockey wheels haven't been swapped, have they? The top one should have loads more lateral play.

 

[Cyclopathic]

Those mechs are built like tanks aren't they? It is curious - a rear mech shouldn't do much when the sprockets are being driven. Sounds like it is overly affected by frame flex or such like. The top and bottom jockey wheels haven't been swapped, have they? The top one should have loads more lateral play.

I'll check that out and perhaps change the wheels anyway. It has got me baffled I tell you because like you say at the point where slippage is happening there isn't really any involvement from the mech. I am determined to get it working and on something because it's a really nice looking bit of kit and in bike terms getting on for vintage.

Good idea about the wheels though. They look brand new and I assumed that was because the mech had hardly been used but it could be that they were replaced and done wrong. I'll update when I've tried it but that may not be for a bit. Depends what comes along that needs a mech.

 

[beeblemaster]

I had problems with mine and I couldn't get it right, but then I noticed that there was quite a bit of play in the mechanism due to the pins in the linkage being worn (I compared to my Tiagra and 1998 Acera mechs), effectively causing the jockeys to misalign. I was going to replace with Tiagra, but replaced with a brand new Alivio mech, not as pretty, but supposedly Tiagra equivalent reliability and dirt cheap for £16-£18 - it's perfect.