Dear Tom and Ray:
Last week my boyfriend and I went backpacking in Montana and woke up to more than a foot of fresh heavy snow. My 2005 FWD Pontiac Vibe got stuck in the parking lot, and we spun the front passenger tire a bit in the snow and gravel before we got it to move. We then proceeded to drive it three miles down an unplowed road covered with deep snow until we got to the main highway. The balance was thrown off for a bit due to packed snow in the tires, but we cleaned them out and the balance was fine, and drove home to Wyoming. But when we got home and drove on dry roads, I noticed a little shimmy in the car at slow speeds, and a day later, I blew out the same tire that we spun in the snow. Could the spinning and driving in the deep snow have caused the tire to become out of round? Also, the tire store tells me now I need new struts. Could the deep snow also have caused a bend or leakage in the struts? Thanks! — Leah
RAY: Spinning the tires in the snow had nothing to do with the struts, Leah. If your struts are old and worn out, it’s probably because they’ve been in there since 2005.
TOM: But you could have damaged the tire by spinning it in the snow.
RAY: Here’s what happens: Because of the way the diff erential works, if one wheel is spinning — like on ice or packed snow — the diff erential sends 100 percent of the engine’s power to THAT wheel.
TOM: And if a tire spins at speeds of 80, 90 or 100 mph, two things can happen: The tire can deform due to the centrifugal force, or it can heat up from the friction and its tread can separate.
RAY: Now, you’re probably saying: “But I never spun the tire that fast. The highest the speedometer ever went was 60 mph.”
TOM: But because the speedometer reads the speed of the axle, not the individual wheels, when only one wheel is spinning, it’s actually going twice as fast as the speedometer reads. In other words, if your speedometer said 60 mph, you had one wheel going 0 and the other going 120!
RAY: And that’s more than enough to deform or damage a tire. So I’m not surprised that one trip to Wyoming later that tire blew.
TOM: So, if you’re in that situation again, don’t just step down on the gas pedal and let the wheel spin at a high speed. Aside from the tire damage, you’ll also just dig yourself deeper into the snow in most cases.
RAY: Right. Better to accelerate moderately and try to rock the car back and forth as quickly as you can. And if that fails, you have to move on to Plan B. Usually that involves at least one of the following: a shovel, a bag of cat litter, some wooden boards to place under the tire, several very large people who can push, or a tow truck. .
• • •
Get more Click and Clack in their new book, “Ask Click and Clack: Answers from Car Talk.” Got a question about cars? Write to Click and Clack in care of this newspaper, or e-mail them by visiting the Car Talk Web site at www.cartalk.com.
(c) 2010 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.