Originally Posted by grolby
You misunderstood my question. I was asking if using the alternate cable routing would help. As it is, I've gotten it working, but it's a bit marginal in my two highest gears. I have it set up so that the highest index setting is "empty" - that is, I'm using the high-gear limit stop on the derailer to stop it from trying to move off the smallest cog. Perhaps I should try it the other way around? On the other hand, if using the alternate cable routing will do the trick, I see no reason not to try it.
Yes, I did misunderstand your question.
But, oy vey, you guys are making this so much more difficult than it needs to be. There is no need for ShiftMates or alternate routing. What exactly is the setup you are having problems with? If you are using any current Shimano RD with the non-DuraAce 8spd barcons it should work perfectly. If you are having problems with just the two top highest gears (the two smallest cogs, right?) then that is more than likely an initial cable pull setting problem combined with a tweak or two on the cable tension.
Here's the routine:
Disconnect the cable from the RD. Eyeball the alignment (from behind the bike) of the high gear (smallest cog) and the jockey wheel. Adjust the "H" limit screw if they are not lined up. Now, simultaneously turn the crank arm with your right hand and, with your left hand, manually push the RD so that the chain climbs up a cog or two. Release the RD and the chain should jump back down to the high gear smoothly. If it's not smooth, or jumps off the cog towards the dropout, then your limit is not set correctly. Adjust as necessary. Now adjust the low ("L") limit. With the cable still unattached, crank the drivetrain and manually push the RD in as far as it will go. It should move the chain up to the biggest cog (= low gear) and no further. If the chain goes past the big cog and jumps off the cassette towards the spokes, then your "L" limit screw is too far out. Adjust the "L" limit screw until the chain moves onto the low gear, but not beyond it. As with the "H" limit, when you have the "L" limit set correctly you should be able to eyeball it from directly behind the bike - while still pushing the RD all the way in - and see that the biggest cog and the jockey wheel are lined up exactly. Once you get the limit screws set correctly, re-attach the cable (make sure the barcon is set for the highest gear - if it's on the end of drop bars then the lever should be pointing straight down, or close to it). Before you tighten the holding bolt for the cable, turn the barrel adjuster on the RD in all the way. This would be full clockwise if you are looking at it from the back of the bike. This way, once you lock down the cable you can increase tension on the cable by turning the barrel adjuster counterclockwise. If you have any other cable tension adjusters, such a downtube barrel adjuster, adjust it to minimum (just like you did to the one on the RD) for the same reason. Now, pull the slack out of the cable with a pair of pliers or a cable stretcher (i.e. "4th hand") if you have one and tighten the locking bolt. Crank the drivetrain and shift the barcon to the next gear (which should be "6th" in a 7spd system). The chain should move up to the next cog. If it does not, turn the barrel adjuster to increase the tension in the cable. If you have to turn the barrel adjuster much more than a full turn, then you did not pull enough slack out of the cable before you locked it down. Go back and fix this or your barrel adjusters may not be able to gain enough cable tension on their own. Keep shifting back and forth between 7th and 6th gears and adjust the cable tension until you get a good and consistent shift between the two. Often once you get these two set properly the rest of the shifts will index properly. If there is some problem in any of the other gears indexing then carefully add more cable tension in small increments (i.e. a quarter turn at a time). Just a little fine adjustment should do the trick.
Your 8spd barcon with your 7spd cassette should now be working fine. The only thing that you should need to do to it in the future is add a little more tension to the cable after some time on it. It will stretch out a very small amount and a quarter or half turn on the barrel adjuster should make it perfect again.
While it's possible to set limits with the cable attached, it's much better, and easier, to set them with the cable out of the picture. Also, by doing it this way you know, for sure, that they are set properly and there is no shifter or cable tension issue to cloud the proceedure.
Rear derailleurs are very straightforward and simple to adjust. Unfortunately, front derailleurs - triples in particular - are not. The best thing about barcons is that they usually don't offer indexing for the front derailleur. This is a blessing, for sure. Best luck with the fine adjustments.