Derailer Pulley Play - Shimano

woodgab said:

I'm troubleshooting a skipping, late to upshift, surprise upshift on hill, condition after having replaced cassette and chain (SRAM 970 & PC89R) on a 105 set up. I went through BOTH the adjustment proceedures (High, Low, B-screw and finally Barrel adj) on Shimano and the Park tool site, but am still having the problem, seemingly no matter where the internal wire tension (barrel screw) is set. So, I'm thinkin' guide pulley. It squeaked badly before I R&R'd back there. Lubing quieted it down, but I noticed the guide (top) pulley had much more lateral bearing play than the bottom one.

Question is should both pulleys have about the same play? My theory, please don't laugh, is that the guide pulley may not be aiming the chain as well because it slants toward the cogs I'm shifting from as the derailer goes on the move. If this sounds logical, it isn't a t-shoot item I've seen much of for poor shifting.

TIA,
Chris

Top pulley is built to have some play in it.
Have you checked the chain line and hanger alignment?

[b]" late to upshift, surprise upshift on hill,"[/b]

This is usually a sign of friction in the cables. Eventually flame-flexing and wiggling lets the cable move fully and the shifts... later than you want.

Also top pulley should have about 1mm of lateral play or so. This is to center the chain under the cog regardless of the actual derailleur's position.

Check the radial rotation of the derailleur as well. There's an adjustment screw at the back that pushes the pivot-spring off the hanger. Lossen this screw all the way and it'll allow the pulley to ride as close to the cogs as possible for quicker shifting.

Lateral play is closer to two milimeters full range. I bought an ultegra pulley from an LBS ($4 on phone, get there: "Only have the Ultegra, that'll be $15"😉. Anyway, I did the whole proceedure one more time starting with very little initial cable tension and letting there be just enough slack that the barrel adjuster needs about a full turn to grab the next cog inside. So far, so good. I had it out for an easy ride and it didn't surprise me. I think I'll put the new pulley on, in any event. I lubed the cables and cleaned misc when doing the cass/chain, so I don't think that was it this time.

The lateral play has to be there. It helps the hyperglide to work properly. A long time ago I replaced my Shimano pulleys with some aluminum ones, and the thing shifted like [censored].