[mr__j5]

Seems strange that its a problem with the largest sprocket, since that hasn't changed has it ?

If it was fine before it should still be fine, assuming that you put all the spacers in the correct places.

I'd expect possible problems on 12 sprocket either due to old chain or rear mech being too short to handle the 16 tooth range from 12-28.

[Johnny Brown]

I had the problem before I changed the cassette, but not when I got the bike. I figured it was an adjustment issue.

The spacer thing seems a big deal but when I've searched the Campag 9-speed has all the same?

[mr__j5]

I don't know my Campag stuff that well, but I am sure that the 10 speed cassette isn't evenly spaced.

[punkpunk]

9 speed is evenly spaced, or should be.

[SA Chris]

ratios? You only need one.

[Johnny Brown]

Bloody hipsters...

[Nibile]

I used to ride a lot when I was a teenager, and having 43/53 in front and five sprockets from 13 to 21 made me feel like a king of the road.
It's amazing how bikes changed, every time I see a modern bike I almost want to start riding again. Almost.
Then I remember how hard it used to be.