I replaced the chain on my tourer / commuter at the weekend.

What has gone wrong?

I am absolutely confident the new chain is the same length as the one it replaced (less the wear) as I placed them alongside each other.

And on the biggest cogs it looks like this

I have wound the b screw in as far as possible but can’t take out the slack. Derailleur still seems quite stiff and springy.

Thanks

In small-small the chain looks too long, but in big-big, it looks about the right length, that suggest to me that the rear mech doesn’t have enough capacity.

BUT

If it was working before and all you have done is fit a new chain then i’d double check the chain length

.

It’s possible it was like this before, but you never used this combination of gears (because you’re not supposed to).

If you were in the smallest chainring, what’s the biggest gear/smallest cassette sprocket you’d get to before you moved to the middle chainring?

You should never use the gear in the first picture anyway. The rear mech looks like it’s taken all the slack up that it’s design allows.

2nd pic looks fine.

I wouldn’t worry about it.

Is the main pivot stiff? Can you push the mech further back?

Anyway, I can’t see the new chain being happy on either the outer or middle chainrings, they look pretty worn out.

While we’re at it – have you fed the chain through the rear mech correctly?

Replacement chain looks a bit pre-loved

Thanks for the commnents. I think I will stick with Sweedishmetal’s advice.

Chain is brand new, first outing this morning, but I admit I hadn’t cleaned the residue of Putoline off the sproket and chainrings. Chainrings are probably due for replacement hopefully last one more chain!

@jaminb you have one link too many. In the small to small combination you have used up all the swing of the rear mech – the two jockey wheels are horizontal. In the big to big combination you have just enough swing to take out one link. The “b” screw only positions the top jockey wheel nearer or farther from the cassette cogs. It should be adjusted in the small front ring to big rear cog by back peddling until it rotates without fouling (usually heard as a rubbing or knocking sound). You bike looks like my old Dawes Galaxy – 531 ST frame.