Tire thudding after replacing all 4

Just visited my grandparents in Hawaii. My grandma has a 2002 Toyota Camry LE, ~41K miles. They bought new tires for it in Jan of 2006 - 4 new Michelin tires from Costco. Costco’s tire center installed em. Ever since, they’ve been hearing this sort of thudding sound as the tire rotates. It’s loud enough to hear, and you can feel it in the steering wheel at certain speeds. In particular, it’s loudest/most noticeable when the car is nearest about 30mph and again around 60mph. Not “AS” noticeable at other speeds, but still present.

Quick history:

The first time it was noticed, was coming from the rear right tire and was just sound. In April of 2009, they took it to a mechanic to check it out. Mechanic found nothing, said it’s probably just a tire problem and to rotate the tires. They took it to Costco to have them rotated. The sound persisted, but then moved to the left front tire (where it is now). Btw, the right rear tire was moved to the left front. In Aug 2009, they took it back to Costco, where they checked it. They took off the 2 front tires, tested for leaks, inspected the outside and inside, found no defects, deformities or leaks. They put the tires back on, sound/feel persists.

Suggestions/help please anyone?

My first thought was an out-of-round tire, but that’s pretty rare for Michelin. I’m not sure how competent Costco is. I mean the price is right, but…

Call around to local tire stores. Most will do a free tire inspection. Find a reputable one and go from there.

Good luck and POST BACK!

If the sound moved from the back to the front with the tire, it’s pretty conclusive that it’s got to be the tire or rim. I’d have them rebalance the tire, and if that doesn’t help, ask them to do a warranty replacement or at least temporarily put another tire on and see if the thudding goes away.

We also suspected some surface flaw for the tire. I don’t have first hand experience with Costco’s tire folks. My g’rents have had Costco do the tires on their other car and that seemed ok. My buddy just had them replace the tires on his car as well…so far so good for him. But I know what you’re sayin. Having a free inspection done is an excellent idea - gonna call my g’rents tonight and tell em to go ahead with that and see what they say. THANKS for the suggestion! I’ll report any findings as soon as I hear something!

Interesting - didn’t think about the rim too much. We’ll have to check the warranty replacement - they did buy the tires in 06. But it’ll be worth looking into. I’ll have em do the inspection per karl_sieger’s suggestion, and then if that doesn’t produce anything, see if we can use your suggestions for diagnosing. THANK YOU for the suggestions. Will let you know what we discover!