never over inflating my tires again

I honestly think it is not the over inflation that is causing the uneven wear on you tires. 38/40 psi is just not high enough for that to happen. I do however think either the tire, your car or your driving conditions, way you drive or the road you frequently drive on are the culprit. Just like your mileage may vary, your tire wear may vary for numerous reasons. You may save tires tread life and thus your money by adjusting your new tires down to the manufactures suggested pressure, or you may not. If you do buy a new set of tires and adjusting your new tires down to the manufactures suggested pressure, please report back to us the condition of the tires and mileage after 20 kmiles. Good luck.

 

I attached the wrong link. Here is the one I intended, showing 18 different Goodyear Assurance models:
Goodyear Tire Traction, Temperature, Treadwear Ratings

 

The tire pressures the OP quotes should be well within spec. I run around 40 PSI front, 38 back, on both of our Prius vehicles and have had absolutely no tire wear problems. Frankly, I dare say that they are doing better with slightly elevated pressure vs. 'door sticker'.

Granted, I am using Michelin Defenders...which have a very high treadwear rating...so that certainly plays into it somewhat.

 

Again, just a caution: just maybe, higher pressures contribute to premature wheel bearing and/or suspension failure? When a tire encounters a bump or dip, with lower pressure it's more capable of absorbing the shock. Higher pressures, it's transmits more shock to the wheel bearing, makes the suspension components work harder.

I think one or two pounds over is a good strategy, but am reluctant to push it further.

 

Premature bearing wear has been a theory around here for quite some time ( as you well aware I'm sure ). However, I'm not sure if it has ever been 'proven'?

 

Several other issues are popping up:

(1) Goodyear's Assurance All-Season page doesn't even show that particular size:
Assurance® All-Season Sizes & Specs | Goodyear Tires

Tirerack's page for that size also shows no Goodyear models. A different vendor I've never heard of did have an Assurance Armorgrip in that size, but that model name doesn't appear on Goodyear's own page.

(2) Another Goodyear Assurance All-Season page showing the tread, shows a different tread pattern:
Assurance® All-Season Tires | Goodyear Tires
The tire offered by that other seller above does appear to have a pattern similar to oil_burner's tire.

(3) Checking for any news about counterfeit tires, I am seeing warnings, though nothing yet for tires sold as Goodyears:
Counterfeit Tires Pose Consumer Risk - Consumer Reports News
Consumer Reports: Counterfeit Chinese Tires May Be Selling Under US Brand Names – CBS Pittsburgh
2.6 million counterfeit units in Australia: Fake Treads — 8 Ways to Spot Counterfeit Tyres
Fake Toyos: Time to be aware of counterfeit tires - Traction News

(4) Oil-burner's estimated tread life is quite short of the Goodyear treadwear ratings.

My (admittedly incomplete) understanding of tire construction suggests that the 'radial' element of modern tires doesn't prevent the ballooning that would lead to excess center tread wear. But the longitudinal 'steel belted' element should prevent this. Those steel belts simply should not stretch and expand enough to allow any meaningful rubber-like ballooning under at any pressure within or even near the sidewall max pressure rating. That is why I am wondering about counterfeits that might lack the belts, or have them made from some fiber more stretchy (and cheaper) than steel.

 

Yeah, I don't think I read about it, just a notion. It stands to reason though, if the tires have a goodly amount of sidewall flex at the suggested pressure, and then you raise the pressures, say to max sidewall pressure, the tires will not flex as much, and you will be transmitting more shocks to other components.

Just butt-meter: you can feel more shocks, everything's rattling more, when you air up the tires.

 

Great detective work!

 

Nor disproven. It is a hypothesis that seems to have a very reasonable basis, but no actual research or evidence either way brought up in this forum.

 

I've always heard when car manufacturers recommend tire pressures, it's a balancing act, considering all factors, with significant attention to ride comfort.

 

How about the tread pattern inconsistency?

For dry roads, I don't believe that has yet been established here.

For roads wet enough to be at risk of hydroplaning, that is demonstrably false.

 

That could still mean due to tires (different brands). But since you seem to be 100% convinced, so be it. That said, I totally agree with you that for a small potential saving on gas, you do not want to jeopardize the safety of the vehicle. Although as I understand it, under-inflated tires are more dangerous than over-inflated ones, so I keep my tires usually bit higher (2-3 psi) than plate indicated 36/35 within similar range as your "over-inflated" tires. Tire looses 2-3 psi of pressure easily by lower temperature or time alone. That's just my 2 cents.

 

Wow, your tires are 2.3" smaller in diameter than what should be on the vehicle, 22.7" vs 25"
The 25" tires would give much better mpg's.

 

This is a bit unusual as the stock size for a standard 2006 Prius (any non-touring model Gen 2) is 185/65/15. I'd go with the theory about just not remembering correctly.

 

I don't think its true for quality wheel bearings. Higher tire psi isn't that much different from the perspective of the design loads. If the bearings were so soft that tire pressure mattered, they wouldn't last very long.

Vibration can cause fretting or false brinelling in bearings that have only small oscillations, such as bicycle headsets. That happens mainly because lubrication is lost under the contact points, pushed away by the vibrations and small movements. Vibration is not a factor in bearings that spin all the way around like wheel bearings because the lubrication is continually being redistributed under the contact points.

Wheel bearing failure is mainly due to water and contaminants getting past the seals, and seems especially frequent for places that get a lot of road salt in the winter.

No, competition cars on street tires, such as for autocross, often run at higher pressures. This Tire Rack article suggests 40-45 psi front, 30-40 psi rear for a front engine/front wheel drive car:
https://m.tirerack.com/tires/tiretech/techpage.jsp?techid=58&

My Prius came to me with lightly used Avid Ascends that I used for the last 30K miles of life. I measured tread depths across the tire - inside, middle, and outside - and was always finding more wear on the edges. So I always ran higher pressures to try to even things out (40/38). The edges still wore faster than the center.

I accept that your experience with different tires and your rough roads are different than mine. No need to over generalize. It makes sense for everyone to adjust to their own experiences.

 

I tend to agree with this. I replaced the front bearings on our Prius v (wagon) last year with Timken bearings as part of a front suspension overhaul. The Timken bearings are very robust.

Suspension component torque specs? | Page 3 | PriusChat

Maybe a lesser quality brand could possibly be affected by tire pressure though...

 

My old set of Goodyear energy savers ran at 35psi wore the corners then blew the sidewalls on 2 tires by 12,000 miles.

I was told it’s not covered by warranty and appeared to be underinflation

The next set I ran at high pressure and the corners still wore but I got excellent tread life.


What I am saying is that every car and tire is different your premature center wear was like caused by something else out of your control

 

I saw a study a few years ago on tire pressures and fuel economy. There's a mpg difference between thirty five and say thirty eight or even forty psi. There's a very minimal difference between say forty and max sidewall of 44 psi.

I use to run mine at 44F 42R but I'd say over the last year or so I've been running mine at 40F and 38R.
My snow tires I run at 38 psi all around.

I've never seen the center wear like the pictures that the OP put up on any of my tires from over pressure. They're usually worn evenly across the tread.