So THAT'S why there's a wobble

[Darris]

Originally Posted By: CapriRacer
Originally Posted By: Darris
The tire looks indented and shaved down in the middle - I thought that was usually from over inflation?? Although the outer blocks aren't exactly in good shape either... I wouldn't think 36psi is nearly enough of a deviation to account for that kind of wear though.

The Insignia was a very weak tire near the bottom of Bridgestone's line up and supplied as the factory fit on the base Corolla for a number of years. I would not judge any tire manufacturer based on a product for such an application.


I hope Darris won't think I am picking on him ....

And I would also caution making an assessment of inflation pressure based on wear. As a tire designer, I could alter the wear by changing the shape of the belts - and sometimes we would deliberately change it to improve rolling resistance, knowing that we were hurting wear. In other words, do NOT assume that center wear is caused just be inflation pressure.


No, not taken personlly at all. I'll buy that form you as factual information.

But at the same time its kind of worrisome that you can't take for granted the observations which have been taught to lay people for years in car magazines and tire dealer websites (such as center wear=overinflation, shoulder wear=underinflation, random wear spots=alignment and so on.) I just assumed that engineers across the industry would agree to use models which resulted in wear symptoms presenting in ways consumers could become accustomed to identifying.

 

[supton]

Originally Posted By: Astro14
Originally Posted By: CapriRacer


And I would also caution making an assessment of inflation pressure based on wear. As a tire designer, I could alter the wear by changing the shape of the belts - and sometimes we would deliberately change it to improve rolling resistance, knowing that we were hurting wear. In other words, do NOT assume that center wear is caused just be inflation pressure.


Capriracer, you are a great resource for the forum, I learn something from your posts often, but this one really surprised me....I had no idea that this was true!

As an example, with 50,000 miles on them, my Conti Extreme DWS in 235/45R17 are worn to the bars in the center, but still at 5-6/32 on the edge. I had run them at factory specified pressures (34 -38, depending on anticipated load) their entire life. I had assumed it was simply Volvo specifying too high of a pressure...now, I see that the issue is more complex...


I used to run 40psi in several sets on my Jetta, wore nice and even. This past set though gave indication of premature wear so I dialed it back a bit. I was confused as it the same size tire--granted, I've had several different kinds. Interesting, never realized it could be yet another design parameter.

 

[CapriRacer]

Originally Posted By: Astro14
Capriracer, you are a great resource for the forum, I learn something from your posts often, but this one really surprised me....I had no idea that this was true!.....


Thank you for your kind words. It's why I do this

Originally Posted By: Astro14
......As an example, with 50,000 miles on them, my Conti Extreme DWS in 235/45R17 are worn to the bars in the center, but still at 5-6/32 on the edge. I had run them at factory specified pressures (34 -38, depending on anticipated load) their entire life. I had assumed it was simply Volvo specifying too high of a pressure...now, I see that the issue is more complex...


Originally Posted By: Darris
No, not taken personlly at all. I'll buy that from you as factual information.

But at the same time its kind of worrisome that you can't take for granted the observations which have been taught to lay people for years in car magazines and tire dealer websites (such as center wear=overinflation, shoulder wear=underinflation, random wear spots=alignment and so on.) I just assumed that engineers across the industry would agree to use models which resulted in wear symptoms presenting in ways consumers could become accustomed to identifying.


I put both of these quotes together, because they are related.

Treadwear on bias tires is more sensitive to inflation pressure than for belted tires. (which would include radials). Much of what people see regarding the affect inflation pressure has on wear is from that bias tire era. It isn't that what is said isn't true, it's just that the effect isn't as strong as it used to be.

2nd thought: Steer tires tend to wear in the shoulders (for obvious reasons), and drive tires tend to wear in the centers. In RWD cars (and trucks), you can see the difference, but on FWD's the fronts do both, so what you get is about the ratio of steering to driving - and usually they are about the same, so even wear.

I think the affect inflation pressure has on treadwear evenness is about the same as the affect steering/driving has on even wear. So what one gets is more a matter of which is dominating. One can get pretty much any combination, so it will be quite confusing for the average person to figure out.

And on a side note: In the sphere of consumer knowledge, things change very slowly. It can take a long time for an "Old Wife's Tale" to become a quaint, but unused bit of folklore.

Tires are no exception - and in some respects are part of the problem. People only occasionally pay much attention to them.

I'll give you an example. Last week I gave a deposition, and one of the lawyers pointed out that General Motors says in its owners manual that bias tires and radial tires should not be mixed on the same vehicle. Good advice, but it has been 35 years since GM offered a vehicle with bias tires on it - and for practical purposes, you can not find bias tires in the proper size, so why continue to have this recommendation?

And what about AWD cars? Some vehicles are very sensitive to rolling tire diameter, but the owners manual didn't reflect this until quite a few years AFTER this became apparent. Even today, it is hard to find the passage in the owners manual - and the average guy doesn't even know that it is there.

I could go on and on.

 

[Mr_Joe]

My sister had a 'whobble' a few months ago, just after a shop took off Winter tires in MI. She asked a guy to look, he didn't see anything. Within 2 days of the wheel changes the wheel came off while driving. She was going about 30 at the time, damage was modest.

The shop owned up, still a few issues with proper repair.

 

[ARB1977]

My Bridgestone Revos 2's are starting to cup. There are times you feel it and times you don't. I still have 6/32's left with 50K on them. Starting to get loud on the freeway.

 

[Nick1994]

I got Goodyears on order from Walmart. Can't beat $49 per tire for a name brand. We'll see how they do