Gear Problem

[Plax]

I've just changed the gear cables on my bike. I'm having difficulty with the indexing now.
It is a 8 speed cassette. I can get it going 8-7-6-5-4-3-2, it refuses to go to the lowest gear. No amount of faffing with the barrel adjustor works. If I tighten / loosen it after a certain point then it goes to pot. It'll go 8-6-5-4-3-2 (so it'll jump past 7), 8-7-6-5-3-2 (so it'll jump past 4) or it will go 8-7-6-5-4-3 and refuse to go to 2 or 1.
Any ideas? I don't know if my clipless moment really has damaged the rear mech (no visable damage), which is why I have wasted hours of my life on the effing gears again. If it makes any difference - I can't choose the 1 on my gears, the lever refuses to budge past 2 which made me think perhaps the cable was too taught, but I've loosened it loads to no avail.

Please help it's driving me mad. I've read all the usual suspects (Haynes manual, Sheridan, Alex's bike tutorial etc).

 

[Tynan]

is this a High Low stop problem? there's a couple of screws that physically limit the range of the change to stop it falling off the ends, or perhaps in your case onto the last gear?

I wouldn't offer should a basico idea but you don't mention it

 

[02GF74]

the position of the rear mech as you know is determined by the inner cable length. this as you also seem to know is adjusted using barrel adjusters - depending on your shifter and mech, there should be one at the shifter and and one on the mech itself (talking shimano here).

also there are two small screws in the mech that adjust its range of movement - this is to stop the chain caoming off the biggest sprocket (and into your spokes - not recommended) or off the smallest sprocket.

Undoing the screw for the high gear (small sprocket) will move the mech further from the spokes so should allow you to engage the smallest sprocket as long as the cable is adjusted - i.e. no tension.

 

[Plax]

I have had a fiddle with the H and L screws (I thought they just stopped the chain getting thrown off rather than affecting the indexing as such).

I take it that if it won't go into 1 (the lowest gear / biggest sized sprocket). That if it is the H & L screws, then it it the L screw that is the culprit?
Maybe I should fiddle with that a bit more with the odd half turns. Just to clarify I'm doing it correctly;
Should I leave everything else as is - i.e. not undo the cable adjustor etc. Just move the screw half turns (whilst in the highest gear at the front mech i.e. 3rd / biggest sprocket at the front)?

 

[fossyant]

Make sure the mech is shifting properly mid range - i.e. 2-7 OK then adjust the high low screws if it won't change into them..

Put the bike in a middle sprocket, and just check your top jockey wheel is directly in line with the spocket - you'll have to crough down if you don't have a work stand. Then start adjusting half a turn until the middle sprockets change smoothly.

 

[gbb]

Go to youtube and search 'rear derailleur adjustment' i think.
It's good because although i know the principles, i dont practice it enough to remember the sequence when i actually do it. With the video clip...it's simple.

I'd put in a link to the clip, but work restrictions on youtube make that impossible

 

[ianrauk]

Here you go,

View: http://uk.youtube.com/watch?v=SkzvfCaIbyQ&feature=related

 

[HLaB]

Youtube is blocked at work but here's another site that might be a help

 

[Plax]

Just thought I'd say I have finally managed to get the gears working properly. Thanks for everyones help. I basically loosened the cable again, tweaked the L screw and started again. Hey presto. Think I must have had the cable too tight to begin with. At least I don't need to replace the rear mech - I bent it back into place after a clipless moment and thought maybe it was damaged which is why I couldn't get the indexing right.
I've just changed the front brake blocks too, so hopefully I'll remember not to pull them has hard as I have been tomorrow or I'll be having a flying moment to add to the clipless one!