Do I need new tires?

tires
vibration

#1

Any help with this problem/decision would be greatly appreciated. Over the last couple of months I have noticed that at highway speeds I will experience a strong vibration that sounds like it is coming up from the wheels and can be felt in the steering wheel. The liquid in a bottle of water in the cup-holder will visibly shake.



The weird thing is, the vibration is not constant. I might get on the highway and drive for 15 minutes without noticing anything unusual. Then, for no apparent reason, the vibration will begin - softly at first and building in intensity. It might last for a few minutes or 15 minutes and then will disappear. During an hour long drive on the highway, it might happen once or 3 or 4 times. If I drop my speed to 50 or below, it usually goes away and will return as soon as I get up past 60 again. If I increase speed beyond 60, the vibration will increase in speed too.



I brought my car in for a tuneup recently and told the mechanic about what I had been experiencing. Everything on the car was checked out and I was told that anything that might cause the vibration looked fine.



The wheels were rotated and balanced too, which actually made the problem worse. I brought the car back and he rotated them back to the way they used to be. Since then I have been on the highway for two separate, hour long drives. The first time I noticed nothing wrong for the entire drive. The second time, I noticed some slight vibration at times, but nothing intense.



My mechanic has suggested that one of the tires may have a problem with the steel belts - slipping or warping or such. Could this or something else with the tires be to blame? If it is the tires, is it dangerous to drive on them?



Since my car has all wheel drive, I’d have to replace all 4 tires and I’d prefer to avoid that if possible. I’d think the tire treads could offer another 10k miles for me at least.



I have a 1999 Subaru Forester with 117k miles. My tires are Bridgestone Turanza’s with about 60,000 miles out of their rated 80k lifespan.



Thanks,

Ken


#2

Yes, I believe you do. The 80,000 miles is not a lifespan; it is a rating, merely a means to compare that tire with others. Tires are used in so many different circumstances, weather, driving habits, etc., that it is not practical to assume that any wear rating will be valid as an indicator of actual mileage. Sixty thousand miles on your tires is very good, but you are due, probably past due for a new set. The condition you describe could be very dangerous at highway speeds. Get the new tires.


#3

If there is a problem with the steel belts, the problem would be constant. It would get worse over time and be more noticeable at highway speed. It would not come and go. Rotating and balancing the tires would not improve it. Eventually, you would see a warp in the tread pattern or a bubble forming on the sidewall of the tire. That is dangerous and the tire would need to be replaced.

With 60k on the tires, how close are you to the wear strips on the tread? These are bars of rubber that run across the face of the tire. (when the tread gets low they start thumping) The tires may just be nearing the end of their lifespan.


#4

[i] My mechanic has suggested that one of the tires may have a problem with the steel belts - slipping or warping or such. Could this or something else with the tires be to blame? If it is the tires, is it dangerous to drive on them?

Since my car has all wheel drive, I’d have to replace all 4 tires and I’d prefer to avoid that if possible. I’d think the tire treads could offer another 10k miles for me at least.
[/i]

Yes, it could be an internal problem with one or more of the tyres. The fact that it changes when you rotate the tyres is a good indication of it being tyre related and not a suspension problem, although it may be both.

My guess is that it may be related to the AWD. Are all four tyres the same Tuaranza’s? Do they all have the exact same tread wear? If they vary, even a little in tread wear then I would suggest a new set of tyres now. That problem you are having could well be the transmission complaining about a difference in size on the tyres and could be damaged by continuing to use slightly different size tyres. If they have worn differently then they are now different sizes.

The extra cost of tyres is just one of the cost of having AWD.


#5

Thanks everyone, it sounds like the concensus is that I need new tires. The tires were examined by my mechanic and he pronouced them visibly ok. I have always rotated them regularly and yes, they are the exact same tires. If there was an AWD issue, wouldn’t it occur constantly, or at least more frequently?


#6

You didn’t say exactly which Turanza tire model you have, but many (like EL42) Turanzas come with a 5 yr replacement warranty down to end of treadlife. Take the car to the dealer and have him test drive and evaluate under the conditions you describe. If they agree that a tire is an issue, you should get pro-rated credit for the remaining treadlife. Since Subaru has standards about the tire tread must be relatively uniform across all four tires, you should get credit for all four tires that have to be replaced.

Unfortunately it may take more than one visit to see the problem. Based on the way the Subaru AWD works, I don’t think that the issue would necessarily be constant if it were an AWD issue.


#7

Be careful here!

The consensus is that you need to replace the tires, but there is disagreement as to whether they are the source of the problem - and I’m voting for “They are not”.

As was previously stated, a wheel end vibration would be there all the time - and wouldn’t come and go without apparent reason. So don’t be surprised if changing the tires doesn’t fix the problem.


#8

I’ll measure the tread depth and check the exact model tire after I get out of work today. If the tires aren’t 5 years old yet, they are close to it.

If the tires aern’t the source of the problem and my current mechanic can’t find anything else wrong with the car… I guess the only other option is to bring it to a different mechanic (perhaps a Subaru dealer) for a 2nd opinion. The trouble is, as has been pointed out, the vibration comes and goes, so it is going to be difficult for anynoe else to even experience the problem, let alone diagnose it.

Thanks again to everyone offering their suggestions and trying to help!

Ken


#9

The tires are Protenza LST’s and they have about half an inch of tread depth remaining. Wear and depth appears even on all four tires, which is consistent with my mechanic saying that he couldn’t find anything visibly wrong.

What I am left scratching my head over is that this problem only occurs at highway speeds and even then, it comes and goes.

At this point, do I replace the tires or bring the car in for a 2nd opinion for a problem that is hard to replicate?