Tiagra Rear Mech issues

[ElyDave]

V Old Tiagra rear mech, approx 13 yo.

Was in my spares box so decided to use it as a rebuild part on my Giant, originally it was 8 sp, now using with 10-sp 105 shifter.  It's shifting in response to clicks, but not consistently. I can get the cable tension about right to allow it to shift to low/big, or to small/high.  It wil not however move across the range and back again.  I seem to remember when last used it was getting a bit sloppy in shifting.  Are there any user replaceable parts in here that will rectify it, I can't see how to get at the main spring in the parallelogram for example, or is it just a case of easier to bin it and get a replacement?

[Brucey]

grab hold of the mech low down and try to wiggle it. Also try to see if there is a lot of play in the pulleys. If the spring is a diagonal type one and is weak, in theory you can replace it with another. In reality the spring can be a right b***er to change and if the mech is worn anywhere it won't be that long before it gives trouble anyway.  Given that 10s is a lot less tolerant of wear than 8 s or 9s , I'd suggest a new 10s mech (and new cables) is in order.

Before doing that, however, be 100% sure that the shifter is working properly, and that the cable is not frayed inside it and /or the mechansim is draggy in any way.

cheers

[Poacher]

Whatever you do, divvent bin it; plenty of us still run 8 speed or less! 

[ElyDave]

grab hold of the mech low down and try to wiggle it. Also try to see if there is a lot of play in the pulleys. If the spring is a diagonal type one and is weak, in theory you can replace it with another. In reality the spring can be a right b***er to change and if the mech is worn anywhere it won't be that long before it gives trouble anyway.  Given that 10s is a lot less tolerant of wear than 8 s or 9s , I'd suggest a new 10s mech (and new cables) is in order.

Before doing that, however, be 100% sure that the shifter is working properly, and that the cable is not frayed inside it and /or the mechansim is draggy in any way.

cheers

It's a rebuild of the bike I cannibalised for the cruzbike build
- shifter was working before the dismantling - did not transfer to the cruzbike as I used bar ends on that
- all new cables and outers, might try another new cable as it was a sod to get in and I could have kinked it in the process.
- it's actually an 8 speed mech now being used with a 10 sp shifter.

thanks, that gives me a plan

[ElyDave]

Replacing cable seems to have worked, adn it was much easier to fit this time round

Once I'd remembered that HIGH does not equal BIG when adjusting limit screws it all seemed to work much better and looks like it's indexing OK.

I may now need to go to Marseilles tomorrow for one day, will fit chain and play ASAP after that