Front mech question?

sideshow-bob

Hi,
I'm in the process of 'revitalising' my '99 kona cindercone.
Up till today she was still running the original bb/crankset (sq taper stx rc).
I am fitting a raceface crankset complete with a raceface isis bb, all this
has fitted ok.
The old top ring was a 42 tooth, the new one is a 44 tooth, i have retained
the 8-speed rear cassette/derailleur setup.
The problem i'm having is i cannot get the front mech to work properley.
I've raised it a bit, so that it clears the top ring, but just cannot stop it rubbing
the chain on top ring & bottom ring (it's either one or the other!).
I'm wondering whether the raceface crankset is slightly wider due to it
being designed for a 9-speed setup, therefore the front mech just won't shift
the chain enough.
My question is... Is there any difference in front mech's between 8 & 9 speed?

supersonic

9 speed front mechs are fractionally narrower, as are 9 speed chainsets (both chainring width and total width)

Have you adjusted the limit stops?

supersonic

Sheldon Brown has a great article on this. This quote sums it though:

"Front derailer adjustment is not an exact science. It requires a good eye and a bit of patience to get it right"

sideshow-bob

supersonic wrote:

9 speed front mechs are fractionally narrower, as are 9 speed chainsets (both chainring width and total width)

Have you adjusted the limit stops?

Ok, thanks mate.
I'll have another bash at it tomorrow, off to the pub soon..lol!

supersonic

Doing it while pissed helps enormously!

;-)