Weird Grinding Noise

[BennyBoi]

My car is standard, hasnt been lowered and has 15" VTR alloys. Whenever i hav 3 or more passengers, whenever i go over a bump there is a dirty grinding noise. It sounds like one of the rear wheels is touching the bumper. I didnt know if this was very common, or it my suspension is too loose or somethin? It has grinded before a little with just two passengers, i thought the car would be made so this doesnt happen :S
Any ideas why its grinding so much?

Chars

[YM03]

depends what speed you go over these bumps, as all cars will bottom out, made more easier if you have people in car

[williamsvts]

15" vtr wheels????

no such thing is there?

[BennyBoi]

sorry, 15" vtr ALLOYS. Im sure u cuda worked that out with jus a lil bit of common sense :)
I dont normally go at stupid speeds, i do try 2 slow down for most bumps, and i know it wud happen in most cars, im just sayin that mine seems to do it with onli 2 passengers in the car and that dont seem right, like my suspension is too loose or something?

[YM03]

could be shagged dampers?

just noticed you have a 1.1, and you have vtr alloys on, due to them being wider than the standard bike size width, jack the car up, and see where it is rubbing