Rear Deraileurs

Hi people,

First of all, thanks for a great site, thought I was the only one that liked older mtb's.

The bike that I am riding is a home brew, it was built by a bloke that used to work in a bike shop (I bought it when he was working in the bike shop). For all intents an purposes it looks like a mid to late 90's Marin/Saracen. It has a CrMo frame with Shemano hubs, STX RC chainwheel/crank set and V brakes and twist grip gear change, I know that they are not everyones cup of tea but I quite like them.

Now for a couple of questions. It looks like my rear deraileur, Shimano Alvio RD-MC18, has come to the end of it's life, by that I mean it is very reluctant to go into 8th gear, I have made sure that everything is adjusted properly. When I pet it into 8th you can see the deraileur move but it wont shift into 8th, now if I give the deraileur a light helping hand it shifts into gear. With that all said I think that the springs a little tired and I would like to change the derailer for a better one.
Can I put any 8 speed Shimano deraileur on or does it have to be a direct replacement or can this be rebuilt.

Many Thanks

Markendo

Provided the new mech has sufficient capacity to accommodate the number of teeth in the largest cog in the cassette, then any "top normal" 8 speed Shimano derailleur will work.

I'd be inclined to try a new cable and adjust it all up from scratch before buying a new mech.

Yes, try the cable first, these gum up way before rear mechs die.

To add further to the mech question, all shimano mechs from about 1986 onwards work with 6,7,8,9spd indexed shifters and cassettes unless designed for 10spd.

Thanks for the replies.

I eliminated the cable by removing the cable and pushed the mech into 7th and then let it go and it still wouldn't drop into 8th without a little help. I suspect that the rear mech was what he had to hand at the time of building and was second hand when it was fitted.

@legrandefromage. Thanks for the info on Shimano mechs, just the kind of thing I was looking for.

Markendo

And some 10 speed mechs, especially the road range, also work, but there lies a.murky world of ifs, buts and maybes, so best to avoid that route.

Is it worth checking the adjustment if the limit screw on your mech?

Chopper

Checked the limit adjustment, the whole mech does feel a sloppy at the pivot points of the parallelogram (I hope you understand what I mean as I'm not sure what the proper name is) part of the mech. Thanks for the input though.

Markendo

Have a look in the for sale section http://www.retrobike.co.uk/forum/viewforum.php?f=2. You'll find something 8 speed in no time for a fair price!

I know just what you mean chum. If that's the case it does sound like its time is up. Follow LGF s advice and get yourself another.