By on March 28, 2012


Mark in Upper Kentucky writes:


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 [email protected] . Spare no details and ask for a speedy resolution if you’re in a hurry.

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16 Comments on “Piston Slap: The Cupped Tire Quandary...”

  • avatar

    That is a common Focus issue, one I personally have had. Ford has very broad alignment specs, so when doing an alignment if it is in these broad specs most mechanics will leave it alone. However, the best alignment (for handling and wear) is to set the alignment as close to zero as possible and still be in the specs, ie, toward the zero end of the specs.

  • avatar

    That is a common Focus issue, one I personally have had. Ford has very broad alignment specs, so when doing an alignment if it is in these broad specs most mechanics will leave it alone. However, the best alignment (for handling and wear) is to set the alignment as close to zero as possible and still be in the specs.

  • avatar

    I’d blame the suspension components first especially since you are indicating just one rear tire. Looks to me that the strut has failed badly, allowing the tire to kick up and down rapidly when driving. The inner edge of the tire gets it because the suspension causes the top of the tire to rotate inwards a bit when the wheel moves upward. Sometimes you see cars on the highway and the tire is moving up and down rapidly. You’d wonder why they don’t hear it, but then again there are fools out there that think a strut is factory fine with 100K on it. This car has almost certainly has a strut with zero damping left in it. At the mileage posted, I’d say the damping medium has simply leaked out. Do the right thing. Either just disclose the defect or replace the strut and put a good used tire on it. I’d venture to be that you will lose less money fixing it than trying to explain it away to a wary buyer…

    • 0 avatar

      Cupped tires are usually a shock or strut failure; the tire starts to “hop” because of the loss of damping from the bad shock/strut and the damaged tire causes the problem to compound.

      Alignment problems tend to show as wear to the inner or outer edge of the tire (front or rear tires).

      I would suggest that it would be more cost effective to replace the bad shock or strut than to sell the vehicle with a known defect; potential buyers usually discount the vehicle value more than the cost of the repair, assuming that if they can see an obvious defect there are probably other hidden defects.

      Easy, cheap fix. Good luck.

  • avatar

    He didn’t say how many miles were on the Focus, but it sounds like some suspension settling has moved things out of alignment a bit. You could also have a blown strut, or a broken spring as well. The Escort before the Focus was notorious for breaking rear springs, as in, all of them broke without fail. This would cause strange tire wear, and really odd handing issues.

    I’m thinking a blown strut is causing the tire to bounce up and down as you’re going down the road. On most FWD cars this is hardly noticeable.

    Sell the car as is and say it needs new rear struts, but I’d replace all of them if it were up to me.

  • avatar

    Last Sunday on my way home from Mom’s, driving up I-5, I noted a similar issue, but this time, in a mid 90’s era Camry.

    The whole front end was bounding up and down, almost like a pogo stick, though I didn’t notice the front tires bobbing up and down so much as the ENTIRE front was bouncing up and down way more than normal.

    The gal driving it was going along at around 70, totally unaware probably of the problem at hand.

    I’ve seen another Camry, similar vintage but way more clapped out who’s back struts/shocks were just as bad as it went over any dip, the back end would rebound very obviously and the whole car looked like it’d seen better days to begin with.

    I’d say, bad strut here but perhaps not both of them in the rear.

  • avatar
    DC Bruce

    Certainly a bad strut. I’ve had this exact problem on other cars I’ve owned. If you’re trading it in, the dealer buys the car “as-is” and his appraiser will notice the tire wear and draw the appropriate conclusion. If you’re selling it your self, I would either disclose the problem or fix it and replace (or shave, if possible) the cupped tire.

  • avatar

    Swap the tires from side to side (rotating in the opposite direction). Noise will be less. Sell the car as is. Done.

  • avatar

    I would guess the tire in the picture has never been rotated. Some vehicles tend to cup a tire even when in spec. Rotation does wonders.

  • avatar

    Going to echo the fact that it is likely a blown shock/strut. I had a car with adjustable damping on the suspension and mistakenly had one side ni the rear set stiff and the other side set soft, it produced cupping on the “soft” side. readjusting them to identical settings fixed the problem.

    FWIW it’s really crappy to sell a car without disclosing known problems, and if you let the buyer get it inspected they’ll find out anyway.

  • avatar

    Not sure this relates, but my 94 LHS would cup a front tire in a New Yerker minute (see what I did there?) if you inflated it even a pound above the manufacturer recommended 32 psi.

  • avatar

    Thanks for reminding me again that I need to put new struts on my Subie. Now if I could only find some money for the task… hmmm… banks have money, don’t they? I should ask them very nicely while wearing my finest ski mask and carrying that subtle touch that tells someone you need business – a firearm ;)

  • avatar

    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.

  • avatar

    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.

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