QDear Tom and Ray:
Please respond ASAP! A late-'90s special-edition Porsche was driven down a ramp. At the end of the ramp are two speed bumps, two feet apart. The first bump is made of concrete and the second one is hard rubber. Neither is more than 2.5 inches high at the center. The owner of the car is claiming that the valet parkers drove his Porsche too fast over the speed bumps, causing $10,000 in damage to his engine. He claims the bottom of the Porsche hit the bumps, causing the oil pan to separate or loosen from the engine, which led to an oil leak. Please tell me if this is possible, and if the cost of repair is reasonable. -- Hadi
ATOM: Oh, you're in deep doo-doo, Hadi. Yes, it is possible to drive a Porsche down a garage ramp at 60 mph and then scrape the oil pan on a couple of speed bumps. But I bet it was fun, wasn't it?
RAY: Actually, it can happen at a lot less than 60 mph. The Porsche has such low ground clearance that the problem may have been the angle of descent, and the fact that there were two speed bumps.
TOM: Actually, if you drove it over the bumps at a reasonable speed -- say, less than 5 mph -- and damage was still done, then I'd say it's not your fault. Then it would be the fault of the manufacturer, who made a car that can't be driven in normal public facilities. Or it would be the fault of the guy who bought it, who should've warned you that it can't be driven over bumps.
RAY: And is it a reasonable price for the repairs? Well, let's see. An oil pan for a normal car costs about $400. So . . . $10,000 for a Porsche sounds about right!
TOM: Actually, my guess is that the guy is claiming that he drove away with the oil leaking and then ran out of oil, croaking the whole engine.
RAY: Now, we should add that while it's possible that the engine was ruined by the method you describe, it's by no means the only explanation. It's certainly possible that the owner of the car is a sleazeball, and scraped up the bottom of the car himself in a drunken stupor, or by showing off to one of his ex-wives, only to try to blame it on you guys. Or that no one's at fault, and the pan failed over time, and he's just looking for someone to blame.
TOM: But if you know that you, or one of your guys, drove it too fast, felt an impact and heard a thunk or a metallic scraping sound when you hit the speed bumps, then you guys probably toasted it.
RAY: So call your insurance company, Hadi. They're better equipped to investigate the alleged accident and determine whether you guys are responsible or not. Of course, they'll cancel your policy after that, but we're talking about 10 grand here, so I don't think you have much choice but to let them fight it out with the guy. Good luck.
Dear Tom and Ray:
My roommate and I have been arguing about tire traction. I said that a racing slick (or just a bald tire) has more traction in a dry environment, and is able to stop a vehicle faster on a dry road. He said that a tire with tread has more traction and is able to stop a vehicle faster. We are on the verge of war: I've taken his dipstick hostage, and he's got my hubcaps. Please help end this war and bring peace (and my hubcaps) back to this house. -- Matt
RAY: He needs to return your hubcaps with a humble apology, Matt. You're right.
TOM: On a dry road, a racing slick will give you more traction. Why? Because there's more rubber surface area actually in contact with the road. That's why drag racers, who need as much traction as they can get, as quickly as possible, use "slicks," or tires with no tread.
RAY: But remember, as soon as a half-ounce of rain comes out of the sky, you'll be in the ditch with your slicks. The problem with slicks is that when there's water on the road, the tire rolls up on top of it, and the water has nowhere to go. And when the tire's on top of the water, none of its rubber is touching the ground! That's called hydroplaning, and it severely limits your ability to turn or stop.
TOM: The purpose of the grooves in treaded tires is to provide pathways for the water to escape. That way, while the rest of the rubber is maintaining full contact with the road, the grooves are channeling the water out back, behind the tire. And onto the windshield of the poor schnook driving behind you!
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(c)2005 by Tom and Ray Magliozzi
and Doug Berman