good downshift, bad upshift

[Tollers]

A friend came out a few weeks back for our sunny sunday ride to the coast. He was bringing his mountain bike which i know hadn't been maintained at all, so i suggested i give it the once over before we went out.

I'd never seen a drier chain in my whole life. I couldn't even get a smudge of grease onto my hands, but anyway.....his gears were also pretty badly adjusted so i started tinkering.

After a few minutes playing, i was able to get the shifting perfect at the rear mech, but only on the dowshift (pulling the cable as the gears move from small to large). On the upshift (releasing tension), it would never quite align and would skip. The poor guy (actually, he's called Guy), had to cope with that for 25 miles.

I reckon the problem is that the cable must be sticking, so have offered to do the job for him. Think i'm right? Anyone have any other thoughts?

Tollers

p.s chain, casette and chainrings are fine.

 

[rusky]

Yup, cable or the pivot points on the rear mech

 

[MacB]

Agreed, new cable and remove, clean and grease the rear mech, you can even take apart the jockey wheels and grease them, as I discovered. When putting back on it's also worth checking the upper/lower limits are set correctly.

 

[BigTone0777]

I would definately go with new cable and a clean and relube of the mech.

Oh. I would also make sure the "loop" of outer cable from the chain stay to the mech is long enough and not too tight a loop as this can also cause drag on the cable.

 

[Tollers]

Cheers all. I suspected as much. It could just be the mech needing lube as you all suggest. Given that the chain was so dry, then i could believe the derailleur is crying out for some TLC.

Great minds think alike. Thanks for the advice.

 

[Globalti]

Lubing the derailleur never seems to make any difference for me; I think it's because the tolerances are so tight and the pivots so well made.

Changing the gear cable will transform the shifting though. I change my outer at the rear derailleur every six months.

 

[the_mikey]

I had a problem with a MTB last week, the bike has never travelled more than 20 miles in it's life, and has been languishing in the garage unused, until last week, but the rear mech wouldn't shift properly. Disassembled the shimano GS100 rear shifter, applied some grease worked the levers until everything was good and greasy, tightened the securing bolts and tested, shifting perfectly. The owner was happy, and rode it half a mile around the village and back into the garage where it's not been moved from since...

 

[rusky]

I found that if the shifter was pushed hard on to the brake lever, it caused the internals to bind!