Suntour XC Ltd / Shimano / SRAM Compatibility Issues...
 

Hi from the UK

Quick question, hope somebody can help? (sorry for the rather detailed background, thought it might help if you had all the info from the off).

BACKGROUND: I have a 1991 Kona Cinder Cone which I used as my only bike on and off road between 91 and about 2001 and then just off road since then. It has probably covered a few 000 miles by now, and various bits have been changed / upgraded aong the way such as wheels, brakes (to deore V), stem, saddle, tyres etc. When I had the new Campag Mirox MTB rims made up, the bike shop used a Deore LX Parallax Hub, and possibly a Shimano cassette (not that techie so not really sure - it is chrome/silver and has different shaped teeth - wedged / slightly hooked - on different cogs and has a Lock Ring with Hyperglide stamped on, so I'm guessing Shimano though could have used this lock ring on suntour cassette?). It has a Shimano HG chain, however, it retains the original Suntour XC Ltd RD & FD & Thumbies (indexed on right shifter for RD, friction on left).

After replacing RD cable and re-adjusting from start, i.e. H/L, B-Adjuster, Indexing, I still can't get it to run very smoothly - if I get it right going up the cog, it then doesn't shift properly coming down, and this seems to get more pronounced when I take it off the work stand and go for a ride. Checked chain - Fine. Sprocket teeth all seem OK. Cable - New. Whole mech degreased and re-lubed. Only thing I can find that doesn't seem right to my untrained eye is the side to side movement in the RD itself, i.e. when you hold the bottom of the cage it can be moved a reasonable amount from side to side, so when you look at the chainline from behind the lower run of the chain is not below the upper run. When turning cranks on workstand and experiencing metallic noise from chain/cassette, if you put slight pressure on cage, effectivly removing the free play, the noise disappears... So, me thinks the Suntour RD is shagged and needs replacing (please correct me if you think otherwise).

RIGHT, THE QUESTION: If I retain the same hub/cassette/chain/Thumbies, what are my options re RD's currently on the market? I've read a couple of relevant threads on here and general concensus is that indexing ratios etc are very similar on suntour and shimano RD's (not sure about SRAM), so assuming this is correct, what do you think (specific model please) would work best with my existing combo?

Thanks

Ok, you have a Shimano hub with a Shimano spaced cassette. These are very common and very good items. But, Suntour used a different cassette spacing. This means your derailleur is always going to moving a little too much/too little to get the gears exactly right when indexing. If you have friction, you should be set in that mode. Otherwise, I would suggest you buy some spacer rings for your new cassette, so that they will be spaced correctly for Suntour indexing. You could achieve this by butchering an old Suntour cogset or by buying them from Highpath Engineering.
http://www.highpath.net/
I'd call them :)

Thanks for the response. I suppose the question I should be asking myself is if I don't want to go to the trouble of butchering cassettes, and I need to get a new RD anyway, perhaps I should bite the bullet and change the XC Ltd thumbies.

I do have a pair of Deore XT thumbies in the parts bin which I could clean up and fit (or just the rear shifter), would that be the best way to go in so far as I can then just get a SRAM or Shimano RD?

Cheers

I'd recommend getting a Shimano derailleur to match your shifter. I don't know for sure what the pull ration of the Suntour models was, but it could be different enough to cause trouble. Deore models are pretty nice and very cheap. Btw, butchering cassettes is not too hard. You just change out all the spacers.

Thanks for the advice - I'm going to buy a Deore LX or XT RD to use with my XT Thumbies, only question now is wheather to stay with 7spd or change to 8spd???

In terms of space between spokes and dropout, is an 8spd cassette wider than a 7spd? Or are the sprockets / spacing narrower so pretty much the same thickness?

If I bought a current Deore RD, would it work with 7 / 8 spd cassettes ot are they designed purely for 9spd?

Cheers

What hubs are you running again? Some older Shimano hubs were 7 speed only; 7 speed cassettes are a bit narrower than 8 speed ones. You can run 7 speed cassettes on 8/9 hubs by using a 4.5mm spacer. I'm doing this. Shimano derailleurs don't care what speed they are, so you can use a "9 speed" one with 7 speeds at the back. I'm actually doing this too :)
How many speeds do your thumbies have? That determines how you proceed from here...

Hi, I'm running a Deore LX Parallax rear free hub, which I bought new when lacing up some Campy Mirox rims back in 94/95, and shimano 7spd cassette.

Checked the thumbies, and they're actually DX not XT, and apparently have an 8th click, though I can't find any evidence of this!

Ok, I would try and run either 7 or 8 speed cassette on your freehub (choose whichever one fits the freehub and matches your shifter) and I would replace the Suntour mech with a Shimano Deore or Deore LX. Change the chain at the same time.

Done and done :)

Cheers!!!:)

Your shifter will have 1 less click than the # cogs in your cassette.
IF they used a 7 speed Free Hub body, you need a new one for more than 7 cogs. If they used an 8/9 speed body, you'll just remove the 4.5MM spacer when putting on the new 8/9 speed cassette.
IF you go to 9 speed, you'll need a new 9 speed chain to clear the narrower cog spacing.