Fitted new cassette and chain BUT........

voodootrek

I have a trek 3900, I recently changed the cassette ( with the help of some friends) because the other one had lost a couple of teeth, the new one didn't run too well with the old chain so I bought a new chain and we fitted it. Everytime I put some serious weight onto the pedal the cassette/chain slips, I presume its the chain, before fitting the chain we counted out the links on the previous one so it was the same length, the previous one had stretched quite a bit. I'm thinking of taking another link out of the chain to see if it helps. I've looked at the chain to the cassette, wound it backwards and everything seems to be working fine, looked on youtube and I've had no help there so here I am. Can anyone help me please?

here is what I bought BTW

http://www.chainreactioncycles.com/Models.aspx?ModelID=68154
http://www.chainreactioncycles.com/Models.aspx?ModelID=21295

I thought they were compatible but now I'm not too sure

Chunkers1980

Should work fine. Sure it's not slipping on the front? Or not the freehub?

Chain length has got little to do with it.

voodootrek

Thanks for the reply Chunkers, certain its the back but I've no idea why, thought it could be the jockey wheels but they look in decent nick. The funny think is that when I first changed the cassette and ran it with the old chain nothing slipped although it did a bit of grinding which is why I bought the chain.

Chunkers1980

What cogs does it happen on. Test every one using the middle front ring

cooldad

How did you join the chain - using the pin or a missing link? If a pin, could be a stiff link.
Chain length does need to be right - around big/big missing out the mech plus a full link. Counting the old chain is not the way to do it.
Jockey wheels will not make a difference - but presumably you have re indexed the mech properly?

voodootrek

joined the chain with one of those quick release power links, I'll check the links for tightness.

It seems to slip in all gears, I've tried them all out and I've had a slip from 3-8th gear, its difficult getting enough pressure on first or second as they're so light.

cooldad

And you have reindexed?

voodootrek

TBH you've lost me on that, one of my mates who has a lot more experience than me, I've only been riding for 12 months, has taken a look, adjusted a couple of things and reckons its fine. Don't suppose you could stick a link on to show me what to do please? thanks for your help BTW.
If I can't sort it by tomorrow evening I'll have to get it in the shop which is a pain in the arse as I need it to get to work nowadays.

cooldad

Read 'Read this first' in my sig. All of it is useful, but you need to look at indexing the rear mech.

voodootrek

ok will do, thanks.

YeehaaMcgee

^^If "YES", then it could still be the chainrings that are worn.