I upped the PSI to my tires from 29 to 35 and...

[Chris D.]

your not going to wear the chalk out more or less, your still contacting the road, just not as much..

try putting about 15K miles and hitting it with a depth guage..

over time tires relax at the belts due to over pressure, depending on the durametor of the rubber, the centers will wear more..

I fill my tires with nitrogen now because I got a full tank for free from a friend of mine,
so now my tire pressure stays the same unless I get something stuck in my tire..
4 weeks and my pressures stayed the same and we've some tempuature drops recentally with no adverse effects.

Bias ply is a slightly different thing, I'm talking radials.
My grandfather had a buick Century that I would align every 30K and he always ran 65psi (there was no telling him oterwize)

He was a hypermiler before there was even a name for it..

anyways, his tires wore in the centers because of this, the outter edges remained with minimal wear.. Michelin's are known for that tho..

for the uhaul record, I was there picking up a car dolly and the guy there just filled up the tires till they didn't look like they had any sag in em, I asked, no tire guage.. He goes nope, I do this all the time LOL

Penske FTW!

[diesel_john]

i have over 110,000 miles on the windstar's Michelin X's. And at max. sidewall press. plus 5. (40) The front ones are showing 1/32 more wear in the center. The back ones are also 1/32 less in the center, but less overall wear.
Time to rotate.

[trebuchet03]

Originally Posted by Chris D.

your not going to wear the chalk out more or less, your still contacting the road, just not as much..

try putting about 15K miles and hitting it with a depth guage..

Well, I can't do that... Because (as I've already said), I've put 20K miles on... And have measured tread depth... AND have not had uneven wear....

Originally Posted by Chris D.

over time tires relax at the belts due to over pressure, depending on the durametor of the rubber, the centers will wear more..

And why would the center relax and not the outers?

Originally Posted by Chris D.

I fill my tires with nitrogen now because I got a full tank for free from a friend of mine,
so now my tire pressure stays the same unless I get something stuck in my tire..
4 weeks and my pressures stayed the same and we've some tempuature drops recentally with no adverse effects.

N2 is a whole different can of worms.... N2, will diffuse faster through a substance compared to O2 (just take a peek at a periodic table).... But, considering air is 78% N2 and most industrial gas supplies will bring you to 90% N2.... Whatever - it's 12% more of a gas that's atomically smaller (and thus easier to flow through interstitials and vacancies)... N2 is nice as a source of dry gas - nothing more. No need for air drying and it's very convenient.

Originally Posted by Chris D.

Bias ply is a slightly different thing, I'm talking radials.

Bias ply is a very different thing.... Wearing out centers is a bias ply problem, that's something radial tires solved. But, given the ease into the market, the association of high pressure and ballooning persisted. Thus the myth of today...

[roflwaffle]

Originally Posted by bhazard

I only worked at the tire shop for a short time, but I did manage to see a LOT of nasty things wrong with tires. Ive seen tires worn in the middle. What else would cause it?

Depends on the tire. IME, the passenger car tires do not wear unevenly in a noticeable fashion at 10psi over the max sidewall. The tires on my light truck otoh have worn unevenly at 10psi over the sidewall. That being said, since the camber isn't adjustable from the factory, and my ball joints are so worn in the front I have negative camber, I run j-yard tires at $20/tire+rim and rotate/flip to get as much out of 'em that I can.

[Gone4]

Originally Posted by trebuchet03

I follow the "Always be content, but never satisfied" model

And 55psi isn't a big deal. Search Google for "Factor of Safety" - it's one of the few engineering terms that's to the point in what it is I've been having trouble finding the FoS for modern tires, but bias ply tires were designed with an FoS between 4 and 11 with optimal FoS at 7. That's 7 times what's rated on the side. And, no doubt, modern tires at least meet this criteria. I'm not worried

Plus, added benefit of less tendency to hydroplane (something important to me given my location).

How well do you trust the material suppliers? A lot of that factor of safety is involved because in consumer fields you engineer to mean life failures of materials and nominal strengths, depending. Going over the rating is fine, but not that far over.

[johnpr]

Originally Posted by diesel_john

The front ones are showing slightly more wear in the center. The back ones are even so time to rotate again. It appears that on this particular vehicle, the tires under heavy tractive and braking forces wear slightly more in the center, than the tires in back that just idle along.

Originally Posted by Frank Lee

I've worn the centers out due to high psi and they were radials.

here are two examples of center wear due to high pressure, and as diesel_john points out (like i said earlier) there is more affecting the wear than just pressure. it is very much on of those things where "results will vary by user".

there are many factors which people are overlooking, another one ill toss in is the specific tires, take for example, the cheap tires from wal-mart, they are radials and when installed on a minivan and inflated properly they still fail, its because that is to much weight (which results in higher cornering and braking forces) for the tires. and again, driving style can combat the i'll effects of an over inflated tire. there is a reason why tires have things like load ratings, and max tire pressures, they are only man made objects and have there limits.

just my .02 but this is an endless debate because there are good examples on both sides of the fence, take my trans am for example, the center on my rear tires always wear out quicker, and that is at the proper tire inflation, i refuse to run lower than that though because it is worse to be at too low of a pressure than a slightly higher pressure.

ok
[/rant]

[trebuchet03]

Originally Posted by GenKreton

How well do you trust the material suppliers? A lot of that factor of safety is involved because in consumer fields you engineer to mean life failures of materials and nominal strengths, depending. Going over the rating is fine, but not that far over.

yes, very valid (and I've thought about this).... I'm at 55psi on 44psi tires. That .25% over rating. Lets assume the FoS is 4 (which was the lower end for the tires of yore). .25/4 = .0625... So I'm 6.25% closer to failure by pressure. It's over, bu not really that far over

here are two examples of center wear due to high pressure, and as diesel_john points out (like i said earlier) there is more affecting the wear than just pressure. it is very much on of those things where "results will vary by user".

In both of those cases, the pressures weren't given :/ I think I've said it once already - always go with what you're comfortable with... Check for wear frequently :/ NHTSA/FMVSS has some good stuff on this subject such as hydroplaning speed

Hydroplaning speed = 10.35 x sqrt(inflation pressure) <-- there's more methodology here, just a cool little tidbit for relative comparison

[johnpr]

that hydroplaning speed equation is great, but doesnt tread pattern affect hydroplaning also?

[tasdrouille]

Cr did a test with 32 pairs of tires. Half the tires were filled with nitrogen and the other hafl with air. The tires were left sitting for a year. Average pressure loss after a whole year, air 3.2 psi, nitrogen 2.2 psi. Not worth it...

As for diesel_john's tires center wear, I wouldn't care about minimal center wear if my tires would make it to 110 000 miles.

[johnpr]

^^do you have a link to an article / test information?^^ i would be interested in seeing the conditions that the testing took place (keeping in mind that tires stored inside a building is not comparable to tires used daily) just a thought but still interested in seeing the research