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Old 04-30-2009, 11:02 PM   #1
thebarber
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screw more psi in the tires.

k, just was looking at my tires from last summer....was running 35psi most of the summer and into the fall (maybe 20,000kms (12000mi)) and there is noticeably more wear in the center of the tire than on the outside and inside shoulders.

ill be going back to 32psi
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Old 05-01-2009, 12:23 AM   #2
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its been 1 year and 25,000 miles on my yaris, i keep my tires at 34psi exact and i have no wear and tear damage like that =).....well u are dirving a hatch back, and sedan is mine so...idk
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Old 05-01-2009, 07:14 AM   #3
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There is a reason the factory recommends the pressure that they do for the factory tires. It's important for handling, safety, and tire wear to keep the tires inflated to the pressure that gives the tire a good "footprint," i.e., uniform contact with the road across the width of the tread.

Tom
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Old 05-01-2009, 07:19 AM   #4
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From my experience, an increase of 3 psi makes much difference; if any; to the dynamics of your tire. I bet if you took accurate measurements and compared the wear over the next 20k you would see the same type of wear.

It's doesn't really matter what you decide as long as keep it in the 30's. It's the idiots like one of my co-workers who was running at 22psi on his Yaris who need to have their heads examined before they get a blow out.
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Old 05-01-2009, 07:34 AM   #5
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WHY would anyone run 22 psi????
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Old 05-01-2009, 07:36 AM   #6
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i had originally done this for the extra mpg it was supposed to yeild, but w/ the wear in the middle, im setting them back down to 32psi

$200+ semi annually in tires isnt worth the 1mpg
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Old 05-01-2009, 08:13 AM   #7
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Old 05-01-2009, 08:37 AM   #8
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Originally Posted by YarisOwnersDad View Post
There is a reason the factory recommends the pressure that they do for the factory tires. It's important for handling, safety, and tire wear to keep the tires inflated to the pressure that gives the tire a good "footprint," i.e., uniform contact with the road across the width of the tread.

Tom
Yeah, it's all about balance. 32psi for the win.
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Old 05-03-2009, 02:21 AM   #9
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WTF are yo guys serious?

you actually think a few PSI is going to save you MPG that you will be able to calculate?
The foot print has not been changed until max highway speed when the tires stretch to their limits, The engine still burns the same amount of fuel, the car still weighs the same... you have done nothing but shred 50K off your tires by over inflating them on such a light car... Guess what if you save $20 in the last year with the higher air pressure it just cost you $400 for new tires

Stick with the factory recommended tire pressure, if you have to get a a set of them valve caps that tell you when the presure is low...
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Old 05-03-2009, 04:08 AM   #10
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On my Falkens, running the max rated on the tire wall compared to 32 psi really makes a HUGE difference in FE.
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Old 05-03-2009, 04:21 AM   #11
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Originally Posted by Kaotic Lazagna View Post
On my Falkens, running the max rated on the tire wall compared to 32 psi really makes a HUGE difference in FE.
I second that. I run on falkens like Kaotic but at 42-45 psi nitrogen in the tires. Better mpg on highway speeds than keeping tires at 32-35 psi nitrogen.

Now w/ 32 psi, the only improvement i see is better ride quality, no bump smacks on the road. And I've had these tires since 7k, I'm at 23k not much wear at all.

Just my two cents~
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Old 05-03-2009, 07:09 AM   #12
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i noticed a small increase in mpg, but its not worth the tires ill go thru running higher pressure....
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Old 05-03-2009, 07:31 AM   #13
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I don't remember anyone even mentioning the safety aspect of running air pressure too high. You are leaving less rubber in contact with the road when you over-inflate your tires, and this could cause BIG problems, like loss of control of the vehicle.

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Old 05-03-2009, 07:36 AM   #14
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Originally Posted by 07WYarisRS View Post
WTF are yo guys serious?

you actually think a few PSI is going to save you MPG that you will be able to calculate?
The foot print has not been changed until max highway speed when the tires stretch to their limits, The engine still burns the same amount of fuel, the car still weighs the same... you have done nothing but shred 50K off your tires by over inflating them on such a light car... Guess what if you save $20 in the last year with the higher air pressure it just cost you $400 for new tires

Stick with the factory recommended tire pressure, if you have to get a a set of them valve caps that tell you when the presure is low...
I agree with you, except for the point you made about the footprint not being changed until the tires have been run at highway speeds.

I grant you, the footprint will get smaller when the tires are warm, which causes the psi to go up by two or three pounds over cold pressure, but if the footprint is already reduced by over-inflation, then it will become even smaller at the higher temperatures.

At least that's my understanding. I don't claim to be a tire expert.

(But...






















































I DID stay at a Holiday Express last night.)

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Old 05-03-2009, 07:41 AM   #15
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I do things by the book. I keep the air pressure and oil viscosity at what Toyota recommends. Rotating the tires last week for the 2nd time at 10,000 miles there was no un-even ware on the tires. Hopefully I can get 50,000 miles from these tires. Due to potential liability issues if I was running way over inflated I wouldn’t admit to it on a public forum.
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Old 05-03-2009, 08:08 AM   #16
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lol, liability?

well, i dont think its THAT dangerous running high psi..i went from my stock 175 wide tires to 185 tires at 35psi.....i dont think if i got into an accident they'd site 35psi as the cause, lol
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Old 05-03-2009, 11:51 AM   #17
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This is one of those charged topics that seems to repeat every six months or so, and though I endure lots of negative feedback every time I feel it is important to separate fact from fiction and fantasy from reality. Before I begin it is wise to understand 3 things:

1) Tire companies are one of the worst places to get information about their products. The same holds true of any other manufacturer of consumable goods. While they have to do enough to meet minimum safety standards and product longevity everything is secondary to their primary goal of selling you more of said product through repeated need.

2) Automobile manufacturer's tests for tire pressure are aimed primarily and almost wholly at passenger comfort rather than accident avoidance, product longevity or fuel efficiency.

3) Much of what is considered "common knowledge" concerning tires and tire performance is based on older tire formats and manufacturing principles, and has been negated by newer materials and newer processes.

With those 3 things in mind the rest of what I am about to say makes more sense. It is not just me speaking here, either, but the collective experience of over 6 million miles of road testing by hypermilers and/or hybrid owners.

- The OP's experience with just a few extra PSI causing center tire wear does not ring true as steel belted radials (today's manufacturing standard) do not change shape much at differing pressures, especially with minuscule changes like 3 PSI. His issue is likely caused by his driving style or a manufacturing defect.

- Most folks seem to have difficulty understanding how higher pressures increase traction but it truly is a simple concept. Even at 60 PSI (which I run year round) the contact patch is still large. It is indeed decreased a few percentage points from the original contact patch but not by much overall, and what I gain is greatly increased sidewall stiffness. I commute a twisting, winding mountain road and at the stock pressure of 32 PSI I experience an effect I call "tire side roll", where the sidewall of the outside tire buckles and causes general instability. This is not fun in a hairpin turn at 8,000 feet. At higher pressure I rail the corners without issue, even at higher speeds. It is also worth noting that I live and commute in an area that sees 400 inches of precipitation and hosts 13 ski areas. While not everyone commutes mountain roads every day your car experiences the exact same forces during accident avoidance maneuvering, which is the best safety technique for our small car.

- Tire longevity has increased for every one of us that run much higher pressures. This also makes sense as tires have less rolling resistance at higher pressure. This comes back to the contact patch being slightly smaller. If the tire is fricting on the road slightly less each rotation then it is also wearing down more slowly. I am now at 25k miles on my second set of tires on my Yaris (Yokohama Avid TRZ) and they show no signs of excessive nor uneven wear.

- The MPG gain with higher pressure scales with your driving technique. Someone that normally only gets 32 MPG will not see large gains with higher pressures (though there still will be gains) but for a hypermiler it is an integral part of the advanced techniques. Engine off coasting, pulse & glide, DFCO etc. all greatly benefit with higher maintained speed and longer coasting distances, so much so that I can tell when I have low pressure in a tire just from the loss in my coasting distances and speeds.
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Old 05-03-2009, 02:16 PM   #18
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1) Tire companies are one of the worst places to get information about their products. The same holds true of any other manufacturer of consumable goods. While they have to do enough to meet minimum safety standards and product longevity everything is secondary to their primary goal of selling you more of said product through repeated need.
The manufacturer and seller must make a good sufficient enough to meet customer demand but no more so. To do so is irrational.

Tires, being a consumer good, are subject to all sorts of consumer and safety regulations. There is also the Tort aspect. It's a jungle out there in Courtrooms.

It's always wiser to give yourself lots of wiggle room with specifications. Safety margins, variations in supply and processes, and so on. This allows you as a defendant to stack the odds in your favor with Juries. So no, you will not reveal to the customer the outer limits of performance, not in a nation where people can spill hot drinks on themselves and win judgments in Court.

I work in manufacturing, but not for the consumer market. Our customers are large entities which expect good specification and will train their staff about safety. However I have made consumer goods and know the hazards of such work.

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2) Automobile manufacturer's tests for tire pressure are aimed primarily and almost wholly at passenger comfort rather than accident avoidance, product longevity or fuel efficiency.
This makes sense - most consumers will judge a tire based upon its handling and "feel" than on the more pragmatic virtues that Brian discusses. Since the name of the game is market competition you have to adapt to the market or perish to competition.

As someone who drives on some of the worst roads in North America I never ever will go above the rated inflation pressures. Some of us drive on better roads or have other values than not having blowouts after passing through a gigantic pothole.

Gene

Last edited by GeneW; 05-03-2009 at 02:35 PM.
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