Weird shifting problem with 105 5500(?)

[adamr]

My brother in law asked me to help fix up an old Trek with 9 speed 105 gears. I have done everything I can think of, but can't work out the problem with shifting.

The bottom 7 cogs shift fine, but when I step slowly through the gears I can't shift into the eighth and ninth (the smallest 2). The lever feels like it is at a limit.

BUT, when I shift up very quickly, so that the derailleur is left behind and has to catch up, it will shift past the apparent limit and go into 8 an 9.

In short, when in 7, I can't shift to 8 or 9. When in 6 or lower, I can quickly shift past 7 into 8 or 9.

Thoughts?

[Duck!]

5500 shifters are getting a bit long in the tooth. It could, hopefully, be that the grease in the ratchets is simply solidifying and gumming up the small parts, preventing them working smoothly. Liberally spray some light lubricant (this is the only situation I'd suggest WD40 or similar on a bike) and work the shifter mechanism back & forward to loosen up the workings. If it's only cheesy grease, they will come back to life after a few minutes.

The other thing to check is a small screw at the top of the release paddle (the shift lever behind the brake lever); at the top of that lever when viewed from behind, there should be a screw with - I think - an 8mm head, that fits into an actuation tang in the shifter mechanism. In uncommon cases that screw can fall out, which will prevent the release shift (to a harder gear) from working properly. You can still shift, but need some hand acrobatics to hold the brake lever/main shifter against swinging inward while pressing the release trigger.

Given that the trouble with the release shift is only at a certain point in the range, and not in all positions, I suspect it's more cheesy grease & unlikely to be a lost screw.

[jackthelad]

have you installed a new shifter cable first, after lightly lubricating with WD 40 or silicon spray? , i'd say cable would be stiff and possibly breaking in the shifter, best $20 upgrade you can do to fixup bike