Piston Slap: The Cupped Tire Quandary
Mark in Upper Kentucky writes:
Sajeev,
Here’s a tire question for you to chew on: I just bought a new Mustang V6 (w/ the performance package), so I’ll soon put my ’07 Focus ST on the block. The car is in good shape mechanically and cosmetically, but I’ve got a bit of a tire issue. The Goodyear Eagle GT on the left rear has about 30k miles on it and is making a racket.
Close examination of the inside row of tread blocks revealed moderate tread cupping, so that’s the culprit behind the noise. I’d rather not put a new tire on a car I’ll sell in the next few weeks. Is tread cupping a safety issue? If it’s not a safety issue, is there any backwoods remedy I could try to limit the noise? The Eagle GTs are not directional, so I was thinking I might be able to swap the two rears. Any ideas?
Sajeev answers:
Tread cupping is a pretty minor problem; I have it on my Mark VIII. Between my job, my new home and every other rolling clusterbomb in the Mehta garage, the slight mis-alignment and slightly ruined summer tires are far from a problem…mostly since the car is still quiet on the highway. Then again, Magnaflow’s finest and Kooks Headers make road noise go away rather quickly with enough throttle application.
Here’s the part where I stop complaining about my cupped tires and answer your question.
You’re selling the car, so don’t bother doing anything. Swapping tires probably puts the road noise up front, so you might not see any change. This is truer on non-droning, hatchback-free, vehicles. Backwoods remedy? Go to a shop that builds/services race cars and ask them to borrow their tire tread shaving machine. Hey, I’ve seen dumber things!
Unlike Panther Love, my advice is conditional: if you sell it privately on Craigslist, openly disclose the problem and let the buyer see you are a trustworthy individual. If you trade it in for quick cash, who cares? You are dumping it (choosing time over money) and it becomes a problem for dealer’s scruples. Or lack thereof, but that’s a whole ‘nother problem.
Send your queries to sajeev@thetruthaboutcars.com . Spare no details and ask for a speedy resolution if you’re in a hurry.
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Check tire pressures, then check springs and struts. If your'e selling it private market could make it way way easier to sell with it fxed vs disclosing it, especially in the age of google on every phone "Oh I see it probably needs new struts, that'll take $200 off the price, right??" you get the picture.
In my experience, cupping has been due to bad alignment and/or steering/suspension components with too much play. The cupped tire isn't a safety issue itself, but a worn-out or damaged suspension component could be. I've shaved the high points on a cupped tire using a palm sander and coarse sandpaper. It worked well. The noise was greatly reduced. That one was due to misalignment resulting from an impact that bent an inner tie-rod end.