Kim Kardashian -- I Banged Up My Bentley

8/17/2010 7:15 AM PDT
Kim Kardashian had a super-expensive boo boo on the front of her ultra-expensive convertible Bentley yesterday ... and TMZ has learned it's all because she hit a speed bump too damn fast.

Yesterday, Kim rolled up to the Madison clothing store in Beverly Hills with some serious scrapes on the front of her ride ... and warned the valet parker, "It's gonna make a noise when you drive."

Sources close to Kim tell us it happened when Kim "hit a speed bump too hard" ... which screwed up a custom Platinum Motorsports kit she had installed on the front of the car.

We're told Kim is "pissed" at the damage -- which could cost around $25,000 to repair.