Ok, I just tested all of this for the sake of argument. I had a HPA r32 that needed 130k worth of chassis repair. I ran 20 laps on the same track (high speed ring). With my very timid driving style, I averaged a 12.1.
Paid the 120k for chassis repair. Ran another 20 laps. Average lap time, 12.13.
Absolutely NO DIFFERENCE at all for me when the car needed 130k in repairs.
P.S. After all these laps, it tells me i need another 130k chassis maintenance where there were ZERO collisions or crashes. It's complete BS. Has anyone actually seen it change prices? I wonder why it stays at 130k for my car?
EDIT: More testing with an opel has given my theory even more evidence.
Ran one race, a few bumps, one spin out. Quit out in 30 seconds. Needed 24.5k in chassis repairs. Ran 2 more races finished one, quit the other. Ran into numerous walls at 130 mph. Finished one race where I was bumping the hell out of computer cars. Chassis repairs needed 24.5k. Looks like it is set in stone based on the cars value. Also, it probably has no effect on cars under 1000 miles on the odometer. Probably only useful when you buy used cars with 50k miles on them. Just IMO.
One last thing. My buick special happens to need exactly 362,500 in chassis repairs. So weird how we could accumulate the exact same damage!!! Oh wait, we didn't. It's a set number regardless of what you do.