i have released chain removed plastic cover and aluminum guide shaped bit like a horse shoe. removed 16 and put on 17 but aluminium does not quite line up again its touching rollers on chain do i need to file out center of aluminum to clear. thanks for any help .i think i just found the answer on the forum search. its the case saver and it does have to be filed a bit .i am fitting it because it is used only on the road and 20inch tyres .i have been told it will be better geared for road use.it has been offroad once and that was a 8hr endurance race through woods and stubble fields last weekend. *** still sore .next time going to use the outty max,much more comfortable

 

The aluminum piece shaped like a horseshoe must be ground down for a 17 to fit.

 

thanks.job done much improved on the road.