I'm new to this so bear with me pls.
My chain "slips" sometimes when its down on the smaller side of the cassette and I'm putting some power into it. Doesn't matter which front ring I'm in and doesn't happen on the bigger rear cogs.
I tried adjusting the robber covered thumb screw but that didnt help (looked like it was moving the whole jockey wheel assy left and right)
What do I need to adjust to stop this slipping? It really throws me off when it happens.
Thanks.
Sounds like you need a new cassette and chain.
The [i][url= http://www.parktool.com/repair/readhowto.asp?id=64 ]barrel adjuster[/url][/i] only adjusts the position of the chain in every gear; so if it is mal-adjusted for one gear it shouldn't work for others.
I'd take it to a bike shop and ask them if the chain has stretched.
How old is the bike?
don't get a new cassette yet. get a new chain straight away. this should fix it, if it doesn't its new cassette time...
The 'Measuring Chain Wear' section of [url= http://sheldonbrown.com/chains.html ][b]this[/b][/url] page from sheldon browns site should tell you everything you need to know about chain wear.
flamejob - not strictly true - if the hanger is bent, then the mech can be out of line for some cogs only.
Most likely a worn chain (+ possibly cassette) though.
EDIT: Also check for stiff/bent links in the chain too.
Check the rear mech cable tension could be to tight or slack, depends on the mech. Check out park tools web site or Sheldon Browns site for gear adjustment advice.
thanks everyone - i'll look there
Oh and check the cable too - if it's dirty it can not move quite as much as it should when dropping down to the small cogs, as it sticks.
If its only the smallest two or three, check for a build up of gunk between the smaller gears on the cassette, & scrape it all out with a screwdriver. Mine was skipping because there was so much filth in there the chain wasn't sitting properly between the teeth of the smallest two gears.