Tony1

I drove my old 2002 bmw 330cic, from Ny to Miami and then back to NY and didn't get 1 chip.. the first 1 hour trip i took In my IS350 I got a chip... You do the math..

ff_

Interesting, so after the rock is thrown upwards by either a car's tire or the air that a car's displacing, it immediately accelerates, on its own, towards any car behind at a rate equal to the speed of the trailing car? That's a pretty neat trick. Rocks are much smarter than I had previously given them credit for.

4TehNguyen

iTrader: (1)

life didnt roll the dice in your favor then, its all luck

ff_

I had a 2002 330i and 2003 330i, neither of which had any troubles with rock chips. Lived in MN at the time too, where wintertime results in highways being literally coated in salt and rocks.

Part of the problem, too, is aerodynamics. The more aerodynamic a car is, the more likely that it's going to be struck with small debris, like small rocks, etc.

Tony1

I'm just curious as to where you're getting this information that all cars have
brittle paint as the IS350 does, can you link me the url? (I asked you for a link
in another thread but you didn't reply)

al503

I don't have a link, Tony, but my bud who has a tinting and clear bra shop says that there really isn't a manufacturer out there who's paint is better than the others. "They all suck" is what he says and he loves it because he has more cars that need the bras than he can work on.

FWIW, out of the 2 g35's I've had and my g/f's TSX, the IS held up better than all of them before I got the clear bra put on. The paint of the g35's were a joke compared to the IS.

ff_

al503

just reiterating that people seem to have different experiences as evidenced by this thread, no?

I apologize for not being clearer above.

Mike_TX

Yes, those rocks DO "immediately accelerate". The tire that throws up the rock is spinning at a rate equal to 50mph in my example, so the rock is accelerated from 0mph to (roughly) 50mph by the centrifugal force of the tire. Ever seen the ball thrower at a batting cage, or a tennis ball server? Do you think the rock (or baseball or tennis ball) is just somehow suspended in mid-air?

Then, it is coming at you at 50mph and you are coming at it at 50mph. 50 + 50 = 100mph. We're talking round numbers here, ff, so I could be off a few mph one way or the other. But all in all, it's basic physics.

So maybe that rock is smarter than *you* ...

ff_

Mike_TX, stand along side the highway during a rainstorm sometime. Take note of what happens to the spray created by water being thrown from the tires as a car speeds past you.

al503

The spray will tend to follow the car but I think much of that has to do with the aerodynamics of the car and the vacuum created at the rear. That may affect the spray but probably won't affect a little rock/pebble due to density, etc.

ff_

My point is that the water, rocks, whatever, will not be thrown rearwards, and not at a speed equal to the speed of the car in front, and and certainly not at a speed equal to the car in back. The debris is thrown upwards, and the car in back runs into it.

Mike_TX

I suppose we haven't all done the in-depth research into rock trajectories that you have, ff, but I can tell you with extreme authority that I have watched as rocks and other debris have shot back from cars and trucks ahead of me. They were NOT hanging in the air and I just happened to run into them. I could see them skipping along the road coming at me.

I agree that not all debris will be catapulted backwards in the same fashion, but it is fact that an object picked up by a spinning tire will often be sent rearwards like a shot out of a cannon. The rock may momentarily be trapped by contact between the road and tire, perhaps squeezed into the tread of the tire for a split second, then hurled free when the road and tire part company. Some will go up, some will go straight, some will go off at an angle.

And rocks and road spray aren't going to behave the same. While spray will in fact extend well behind a moving truck or car (I have ridden motorcycles for many years and can attest to that), water droplets don't have the inertia that solid objects like rocks do. And while I agree some rocks will fly off in all directions - like water spray - some will rocket back to cars behind. The ones that go harmlessly off ot the side I'm not worried about, since they aren't going to bother my paint anyway. The "hangers" and the one that are propelled backwards are the ones I care about.

But to make you happy, even at 50mph a rock is going to have a high probability of dinging your paint.

dscodogg69

Well to try to get away from a physics lesson for a minute... Has anyone noticed if certain colors are being affected more or less by rock chips? I have an 06' GS that's Blue Onyx with 14,500 or so miles and no rock chips. But tomorrow I'm most likely going to trade it on an 06' Crystal White IS 250 AWD. Am I going to have to put a clear bra on it?

ff_

Watch that same rock from a stationary perspective (alongside the road) and your extremely authoritative opinion on what's actually happening... will be changed drastically.