few newbie questions

Hey all, first post and I've got a few questions im searching for answers to. First problem is when I'm driving at low speeds I notice a bumping from either the right rear or front end, it synchs with my speed so I figured it was a tire problem. After rotating front/rear left and right the bumping is still there. Any ideas? I didn't figure it was a rotor/brake problem because you can't hear any grinding and when you step on the brakes it doesn't get any stronger. Second Q is mainly for interior looks, the seats are lookin kinda ratty so I was leaning toward some seat covers. I like the look of these matrix seat covers:

http://www.andysautosport.com/products.php?id=Ch00Cavali&make=Chevrolet&mcat=Seats&scat=Seat%20Covers

but I'm not feelin the flames :( anyone know of any sites? 2002 coupe cavy btw. Thanks for any help.