hi could anyone help with the problem i have, the problem is that i bought a 2005 kona fire mountain from halfords it has 24 speed gears with a deore rear mech and a acera front mech but im unable to use all gears because the chain rubs on the front mech cage on some of the gears. I tried adjusting it myself with no luck so took it back to halfords for them to adjust but after adjusting they still confirm that all the gears can not be used without some rubbing, i find this very strange as i have a dawes mountain bike with 27 gear deore set up and not one gear rubs on the cage so would it be possible to put a deore nine speed front mech on and solve this problem.if there is any other suggestions i would be very greatfull
thanks col

The nine speed mech will cause more rubbing because it's narrower. Surley you can get it set up so that you can use the 'correct' combinations of gears rather than 'all' combinations.

The only way to garuntee no rub is use Sram grip shift on the front mech, gives you 3 clicks of adjustment for each front ring.
but you should'nt really run small front to small rear or large front to large rear those combinations rub on every bike i have had..