I run a BB5 on the rear(160) and a BB7 (180) on the front. If you are going to upgrade , buy the new Deore Hydro disks , great upgrade for little money. Some claim performance in line with XT-XTR and better than SLX. Shimano is great at trickle down technology. BB7 is better on the front IMO with a larger rotor but only with compressionless housings and teflon inners. By the time you do that you are into Deore. JMO.