Well, I've been through 19 pages of this forum trying to find any posts that might relate to the problems I've been having with my Shimano 8-speed systems, with no matches yet. Finally figured I'd simply post my saga up here instead of waiting for the BF Search function to return.
I have two 8-speed equipped machines: One, an '83 Peugeot PSV-10 that I built up with an FSA RD-80 wheelset, Shimano 8-speed Ultegra/105 barcons, and a Shimano RX-100 8-speed RD; the other, a stock, 1999 Gary Fisher Tassajara with Shimano LX.
Neither bikes came with their respective cassettes, as the Fisher was missing the rear wheel, and the Peugeot, of course, is a custom build-up.
I recently purchased a used (600 miles max) 8-speed 12-21t HG cassette off of eBay to use on one of the two machines. I intended to use this cassette on the Gary Fisher, as I plan to use the Fisher as my basket bike/grocery beater.
So far, so good. The cassette arrived in the mail a few days ago. I mounted it, tightened it, and put the wheel in the dropouts. The gear cable was replaced, and the derailer adjusted accordingly.
I also replaced the chain with a slightly-used HG chain I had on hand, as the chain that was on the Fisher when I got it is shot to the extreme - at least five rollers in various places are gone, and at the very least, 6 more are cracked. The wear on the front chainrings are evident of this.
But I digress - back to where I was. I set the system up as I described above, and proceeded to adjust the cable tension accordingly.
To make a long story short, no amount of adjustment could get the derailer to shift up the cluster, and down, without the chain grinding (but not engaging) on one cog or another when either upshifting or downshifting. Sure, I could adjust it to get up the cluster fine, but that particular adjustment wouldn't allow it to shift down properly. I could also get it to downshift flawlessly, but not without problems getting it to shift up.
At this point, I determined the problem was probably one of the following:
#1: Shifters made for 8-speed IG cassette instead of HG cassette. As the front chainring on the bike states "for IG chain only," I figured that this could be a possibility. Then again, I have my second thoughts as to this, for HG and IG chains aren't vastly different, and I could see where an overstock of IG-labeled cranksets would be used on HG equipped bikes. Furthermore, I scoured Google and Sheldon's site for such a thing as an IG 8-speed cassette, and came up with nothing.
#2: Derailer is bent. I don't think it is, but from the way the chain faired on this bike, I wouldn't be surprised if the yahoo who owned this machine before me did manage to damage the derailer in some way or another.
Both fed up and curious with my findings, I inspected the 8-speed cassette to make sure it wasn't jerry-rigged out of various cassette parts (been there, done that - the first 8 speed cassette I bought had been cobbled by the LBS with some 7 speed cogs). This time, at least, I got myself an OK cassette - all cog codes match, and all the spacers check out at 3mm/ea.
Curious at these findings, I figured I'd mount the cassette on a bike that I know was made with new, or nearly-new 8-speed Hyperglide components - my Peugeot PSV-10 project. Equipped with brand new Ultegra/105 8-speed barcons with brand new cables and housing, a KMC 7/8-speed chain, and a used RX-100 derailer from the LBS. Nothing can go wrong this time, eh?
Well, you'd be wrong. The same damn problem presented itself on the Peugeot. As the RX-100 derailer was the only used part in the group, I pulled out a nearly-new Shimano 600 8-speed ("8s" stamped on pulley cage to boot) rear mech that I had, and mounted that in place of the RX-100.
Improvement? Yes, but marginal at that. After about 10 minutes tinkering with both the derailer and downtube adjuster barrels, double checking to see that all derailer adjustments were correct and that the cable was set correctly, AND that the cable was not binding anywhere - I was able to get the derailer to shift both up, and down the cluster - in the most marginal fashion.
Curious as to whether this poor excuse for HG shifting would hold up on the road, I took it for a test ride. Sure enough, it would actually shift through the cluster both up and down, but not without some nice gear grinding.
Incidentally, these grindings happen in similar locations as when I had the Fisher in it's (relatively) best shifting form - grinding on 5th to 6th (from the small cog) when going up, fourth to third when going down. Of course, if I tightened the adjuster barrel a quarter or half turn, this problem would go away...when upshifting. Similar result for downshifting if the barrel was loosened - but then upshifting would be a nightmare.
After testing both the Fisher and the Peugeot and experiencing these same problems, one would believe that the cassette is the part at fault, eh? Yet, further examination confirms what I said before about the cassette - never been fiddled with, and save for some grease on the cogs from these tests, looks virtually new.
I should mention that I also inspected the cables on both bikes, and am pleased to say that both are as smooth as butter.
Well, folks - I'm at my wits end. Anyone have any insights or help? Maybe an 8-speed cog known to be in working order (Hint, Hint )?
ANY help whatsoever would be greatly appreciated.
All the best,