Apr 23, 2003 2:25 AM
|I have an older Trek with 105 STI (8-spd) shifters. Both shifters work fine going to larger cogs/rings, but experience problems going back to smaller cogs/rings. It's difficult to describe, but somehow the pawl is not dropping into place correctly. Moving the small lever to drop to a smaller cog catches nothing but "air", i.e. there is not the solid resistance just before the pawl jumps over to the next ratchet position. If I play around with the shifter, letting it flick back by the spring tension a few times, eventually the mechanism realigns and I can shift to the smaller cog. It is definitely hit and miss whether I can shift or not.
Could this be a cable tension problem, clean and regrease, or is the pawl & ratchet mechanism likely shot? It probably have about 12,000km on it.
In the event I need to replace it, what are my options in 8-speed shifters?
|re: STI problems||boyd2|
Apr 23, 2003 3:49 AM
|I went through the same problem a few weeks ago with a used 105 bike. The thing works exactly like you have desctibed. My problem was stiff old grease in the shifter hanging up that little paw that you describe. My solution was to:
1. Find a tech manual on-line.
2. Disassemble and remove the shifter/brake housing. Note that there is no need to take the shifter off of the handle bar. Be careful not to lose the torsional spring and bushing that are under the 105 cover.
3. Remove the covers, but do not try and dis-assmble the inner works there are hundreds of parts in there.
4. Blast the thing clean with White Lightening "Clean Streak". That stuff is a great degreaser.
5. Lube up with Tri-flo or other.
6. Put it back together and ride.
My LBS wanted $25 to do the job, and it was totally worth it. I just like to do everything myself. A good bike mechanic should be able to fix it. Note that it is not a good idea to ride the bike before you get this fixed. I broke a ultegra shifter with this problem a few years ago when the little paw got jammed.
|re: STI problems||ridingthegyro|
Apr 23, 2003 4:30 AM
|Shimano-europe.com has some drawings of STI's inner workings but you may need a Phd to figure them out. I had the same problem on a RX100 8-speed a while back. I lubed the STI shifters (without taking apart the inner workings) and the cables but still had the problem. I then replaced the rear derailler and now the shifters work fine--on the rear derailler, that is. I'm still trying to fine-tune the front derailler.|
|re: STI problems||InTheMiddle|
Apr 23, 2003 1:01 PM
|have a friend that had exactly the same problem on his ultegra 9sp setup... they looked a little more like a 1 piece deal that you don't want to take apart than my dura ace shifters were....
we flipped the bike upside down (VERY IMPORTANT) and used the aerosol Tri-Flow and blasted the stuff into the middle as far as we could.... .. flipped it back over worked the levers a bit.... and let it drain/dry out a little...
good as new....
|re: thanks for all the good tips (nm)||Trek_man|
Apr 23, 2003 10:59 PM