Vacuum Cleaners Discussions

Today I took my Bissell deep cleaner (the commercial grade "BigGreen" Rug Doctor killer) to my parents house to do some carpet cleaning as a favor. I get there, use their Dyson DC14 to vacuum everything first, then went about carpet cleaning. Throughout the process, I noticed clumps of cat hair and carpet fibers trailing behind the Bissell on the forward passes. This led me to believe that the huge brushbar on the Bissell big green was picking up stuff the Dyson was leaving behind. Since the Dyson is seven years old at this point, do you think that it is in dire need of a brush roll replacement, belt replacement, or both? In the case of having the belt replaced along with the brushroll, I'm assuming that my parents would have to take it to a repair center since they do not have the special tools for taking the clutch apart and slipping the belt in and out. How much would such a replacement job with parts and labor generally run for? Thanks, Keith