What causes tires to develop a "thump?"

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I've had three sets of tires on my '99 Corolla now and all 3 have had one tire develop a thump. It'a always been in a different location on the vehicle so I don't what on the car (if anything) is causing this. It seems to take place right around the 30K-40K mark. The first set of tires were Goodyears, and the last 2 sets were Kumhos. Once the tire starts thumping, it stays until I replace the tires. What is this and what could be causing it? It's very annoying.
 
Do you keep the tires properly inflated? Also could be delamination. But Alignment would be the first place to look. Is car stored for extended periods?
 
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I have a tire with a permanent thump. It was sitting is a small puddle of hydraulic fluid which swelled the rubber at that location.
 
Flat spots caused by sitting in one position too long, many Chinese "el cheapo" tires seem to do it for no apparent reason other than poor mfg. quality.
Really bad shocks or struts can cause it as well-hard braking on bumpy roads causes bouncing & flat spots.
 
I go through this every morning with my TL no matter what tires are on it. The softer NT05s seem to be worse. If it sits for a few days, it's much worse. Only car I've owned that you can notice this.
 
If it were an alignment problem, wouldn't I also experience premature tire wear? I don't have this problem at all. In fact, I usually get more mileage than the tires are actually rated for. The last set of tires I had were replaced at 70K (they were 70K rated tires) and they still at least 5K worth of tread left on them. One tire blew, so I just installed a new set. It could be a lack of frequent enough rotations which I'm really bad about. Because I put so many miles on my car (2500-3000 a month) I sometimes go 13K-15K before I rotate them. As far as inflation pressure goes, I keep them at 35 psi. The recommended pressure on the door calls for 30, but I seem to get more tread life, less road noise, better fuel economy, and better handling keeping them at 5 psi over. The theory of sitting too long in one spot I don't think pertains to me because my car never sits that long without being driven, and the tires don't develop the thump until they've reached about the 30K-40K mileage mark.
 
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Originally Posted By: grampi
If it were an alignment problem, wouldn't I also experience premature tire wear? I don't have this problem at all.......


Not necessarily. Tire wear is caused mostly by cornering and if you don't do a lot of cornering, the tires will wear slowly.

Besides, "misalignment" is a matter of degree. "A little off the target value" just takes longer for the symptoms to arrive than "a lot off the target value".

Originally Posted By: grampi
...... In fact, I usually get more mileage than the tires are actually rated for. The last set of tires I had were replaced at 70K (they were 70K rated tires) and they still at least 5K worth of tread left on them. One tire blew, so I just installed a new set. It could be a lack of frequent enough rotations which I'm really bad about. Because I put so many miles on my car (2500-3000 a month) I sometimes go 13K-15K before I rotate them. .......


So we've just comfirmed some of my conjectures - little cornering, rotation.

The rotation issue is more a case preventative maintenance. If you have a misalignment condition, rotating the tires just postpones the issue.

You may ask: Why only one tire?

When you get irregular wear, the irregularity builds slowly and gains speed the more irregular it becomes. The other tires are also developing irregular wear, but there will always be one that is worse - and some folks tend to focus on the "one", and not notice the others.
 
I think when I get my next set of tires I'll be more dediticated to doing rotations at every oil change (which is every 6K miles for me). The thump always seems to appear after a rotation where it's been over 10K miles since the previous rotation. Since I'm not experiencing premature tire wear I can't see where it would be cost effective for me to spend the money for an alignment. This should keep the wear even enough to avoid the thump (in theory anyway).
 
Grampi,

I'm going to suggest you get an alignment with the new tires. The alignment is what is causing the irregular wear - which in turn is causing the "thump". I think you'll find that once you get the alignment, tire wear will be even better.

BTW, my experience says that the published alignment tolerances are too wide. Not the target value, but the allowable deviation from that value. I think it ought to be half of what is published.

Put another way, the alignment should be within the inner half of the spec.

After the alignment, THEN do the regular rotations. I think you'll find that even going 10K doesn't produce the "thump".
 
I just don't understand why a misalignment would cause only one tire to develop a thump. It seems like a misalignment would cause problems with more than one tire. And that one tire that develops the thump just gets worse and worse. In fact, it got so bad I had to replace it. It was vibrating so badly on the highway I couldn't stand it anymore. I plan to rotate the tires at every oil change to see if it alieviates the problem.
 
Originally Posted By: grampi
I just don't understand why a misalignment would cause only one tire to develop a thump. It seems like a misalignment would cause problems with more than one tire. And that one tire that develops the thump just gets worse and worse. In fact, it got so bad I had to replace it. It was vibrating so badly on the highway I couldn't stand it anymore. I plan to rotate the tires at every oil change to see if it alieviates the problem.


Camber is unique to a particular wheel position. While toe is generally the major contributor to irregular wear, camber can aggravate the situation.

Plus you need to be aware that once a tire starts to develop irregular wear, the severity rapidly increases. I'll bet that the other tire(s) also has irregular wear, but is largely un-noticeable.

Not to mention that roads are crowned, and motorists don't always turn left as often (or as sharply) as they turn right.

Lots of reasons why there should be differences!
 
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Before I moved out West I needed tires to make the 3000 mile trip from NY to WA. I bought a set of Firestone tires, something my father was against. They were the Indy 500 series, and the loudest tires I have ever owned, it sounded like they were thumping, and just loud in general. I took them back and complained about 1 week after buying them. The dealer said the tires were fine but re-balanced them which did nothing. The aligment was done at the time of the purchase and was checked again and was on the money. Tires were properly infalated. I was then handed the line that the Indy 500 Tires are just noisy tires. I had to get to WA fast, and have been living with these loud annoying tires, but they do handle well.

It is now about 2 years since I bought them, and can't wait to wear them out and get something other than Firestone tires.
 
Sometimes, out of round condition is due to weakening or stretching of the steel belts embedded in the rubber. Maybe due to rust or poor design/materials. Example: a friend of mine rotated his 5 perfectly good tires and didn't use the spare for 2 years. That car was a low mileage car. One day, he discovered he had a flat while still in his driveway, and brought out the spare. It was useless - it had developed a "hernia" or two on the tread and was obviously out of round and dangerous to use.
 
You have that right. The firestones that came with my corolla were by far the worst tires I have every had.

I have Yoko Avid T series now, it is much much quieter and softer
 
Firestone has good and bad tires like any manufacturer.. I think their bad ones are pretty bad however.

where as michelin's "bad" tires are merely mediocre
 
The guilty thumper got so bad I had to replace the tire. I just couldn't stand the vibration it caused anymore while running down the highway. Now everything's as smooth as glass so I'm guessing it was just the one tire. I guess I'll just have to do more frequent rotations to try to prevent this issue.
 
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