screw more psi in the tires.

[thebarber]

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

[Aothachos]

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

[YarisOwnersDad]

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

[voodoo22]

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.

[YarisOwnersDad]

WHY would anyone run 22 psi????

[thebarber]

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

[33OH]

OT: I like your new sig barber, those wheels are really clean. :thumbsup:

[1stToyota]

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. :smile:

[07WYarisRS]

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...

[Kaotic Lazagna]

On my Falkens, running the max rated on the tire wall compared to 32 psi really makes a HUGE difference in FE.

[Kioshi]

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~

[thebarber]

i noticed a small increase in mpg, but its not worth the tires ill go thru running higher pressure....

[YarisOwnersDad]

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.

Tom

[YarisOwnersDad]

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.) :bellyroll:

Tom

[nemelek]

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.

[thebarber]

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

[BailOut]

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.

[GeneW]

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.

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

[supmet]

@bailout

60 psi WILL increase tire wear and WILL decrease traction. end of story. I'm not arguing this one. Go find me one auto crosser who runs 60 psi on their yaris.

and again, the tunnel vision of hypermiling is coming into play. What about all the added stress on suspension, suspension mounts, engine mounts, transmission mounts, interior trim pieces, pretty much the entire car???

I suppose the 20 dollars a year(again) you are saving will pay for all of that??

If you want the all important MPG, and that's ALL you are worried about, listen to every word bailout says. If you are interested in the total cost of something, I suggest doing your own research.

[GeneW]

Brian is especially correct about hypermilers having different needs from tires than the usual consumer. A tire which is inflated to 60psi is probably not safe for use at speeds over, let's say, sixty miles an hour. To the hypermiler such speeds are beyond the pale, and hence for them a higher pressure is safer.

Gene

[BailOut]

Go find me one auto crosser who runs 60 psi on their yaris.
This is the fuel economy forum. For discussions on autocross please see the racing forum. If you can get any of the folks over there to test anything other than a butt dyno please let me know.

What about all the added stress on suspension, suspension mounts, engine mounts, transmission mounts, interior trim pieces, pretty much the entire car???
What about them? In over 6 million miles of road testing not one driver has ever reported early suspension component replacement or interior trim pieces jumping off or mounts/bushings failing. Those kinds of events are usually related to things like autocross.

I suppose the 20 dollars a year(again) you are saving will pay for all of that??
Please show your math as I cannot tell when your amount of $20 came from. Most Yaris drivers average 32 MPG. I average about 48. Over the 17k miles I drive each year that saves 177 gallons of fuel. At a price of $2.25 per gallon that saves me about $400 per year.



supmet, I'm not sure why you continue to hang out in the fuel economy forum as you don't seem to have much interest in it and you consistently deride the practices of those that do. You seem to thrive only on misinformation and alarmism and continue to do so in the face of mountains of data and practical examples that contradict you. Please feel free to frequent other parts of the forums that are more in line with your personality and personal desires.

[supmet]

This is the fuel economy forum. For discussions on autocross please see the racing forum. If you can get any of the folks over there to test anything other than a butt dyno please let me know.

You are the one the said you get better handling at 60 psi than 32. Don't back out now!


What about them? In over 6 million miles of road testing not one driver has ever reported early suspension component replacement or interior trim pieces jumping off or mounts/bushings failing. Those kinds of events are usually related to things like autocross.

Uhm, because hypermilers don't report ANYTHING but MPG? And most of the cars that you use for your "scientific data" haven't been on the road long enough to see the damage you are doing.

Its pretty much elementary physics. You aren't absorbing as much energy with the tires = more energy gets transferred into the suspension and chassis. To completely write this off is irresponsible.


Please show your math as I cannot tell when your amount of $20 came from. Most Yaris drivers average 32 MPG. I average about 48. Over the 17k miles I drive each year that saves 177 gallons of fuel. At a price of $2.25 per gallon that saves me about $400 per year.

You are the king of fuzzy math, and that's my biggest problem with you. Ok, you save 400 dollars a year over the average, but that includes EVERYTHING YOU DO, not just over inflating your tires. 20 dollars may be low, but I'm betting you'd still have to go years to cover the cost of a SINGLE engine mount.



supmet, I'm not sure why you continue to hang out in the fuel economy forum as you don't seem to have much interest in it and you consistently deride the practices of those that do. You seem to thrive only on misinformation and alarmism and continue to do so in the face of mountains of data and practical examples that contradict you. Please feel free to frequent other parts of the forums that are more in line with your personality and personal desires.

What mountains of data? I keep hearing about these 6 million miles of data, but I bet you don't have complete service records for any of the vehicles included in the data set.

And I like getting better gas mileage. That's why I post here. I just like to get the WHOLE story - not the tunnel vision story that hypermilers THRIVE on.

[voodoo22]

And I like getting better gas mileage. That's why I post here. I just like to get the WHOLE story - not the tunnel vision story that hypermilers THRIVE on.

Tunnel vision applies to people who tailgate, race to the next light and drive only with themselves in mind. Tunnel vision applies to the sheep who follow without questioning and crying that the sky is falling anytime someone claims the earth is not flat.

People whom you label hypermilers can only attain optimal performance by paying attention to their entire environment, maximizing their safety level while enhancing their mpg.

You can say what you want, but until you have experience on both sides of the fence you're simply making statements with nothing to back them up but you're opinion.

Fact is, Brian is right and you're wrong. You don't have to accept that, but hopefully your ignorance will not mislead others interested in facts proven by real world experience.

For people who want to learn and not buy into conjecture; check out posts by Brian and check out cleanmpg.

[07WYarisRS]

here's a thought... go talk to the guys at the tire shops, see what they say about tires that are over or under inflated... ask them if it affects the mileage of the tires..
I have no intrest in what the local kids are doing and what they think work.. I want facts... I have yet to have my tire suppliers tell me to double my air pressure to increase my mileage... why? because what I save in a year running on over inflated tires i'll spend on tires the following year when these are pooched.

tire pressure is very important...
how do i know?
I'm a mechanic (motorcycle) Sure most of my background is racing, bikes and offroad but tires are tires people.
The number one cause of tire damage on motorcycles is caused by incorrect tire pressure, cupping and tire deformation is most common.
I can't tell you how many times owners have come to me complaining of poor hadling or poor tire life...guess what...tire pressure is usually the cause or part of the cause.
then there is the traction issue, with a motocycle even 2-3 psi cam make a HUGE difference. Usually not as noticable at slow speed when the foot print/contact patch is the largest and tire temps are cooler. The same applies to Auto tires though

A tire at 60psi ..what is that at highway speeds when the air temps increase...its dangerous. if it were not for the steel belts in the tire holding it together it would likely explode when you hit a pot hole. Do you really think the tire remains the same shape at slow speeds as they do at highway speeds/

I enjoy the great fuel mileage, but come on... if it means that much to you go with a smaller set of 13" pie cutter tires like the geo/sprints had.

BTW a simple tire tread depth gauge will easily show you what over inflating tires does as far as uneven wear.. you can't always see it just standing there with you arms folded staring at the tire sayin nope no wear yet!
Most people never notice tire cupping or a shifting belt until they have a bald patch or the tire deforms and starts causing vibrations

FWIW I followed the mileage group on the Ford focus forums... I had an 03 with 155km... I JUST got my second set of tires last fall at 120,000km. I ran 35psi The hypermilers on the same sight running even 44-50psi were getting 60-80k km to a set.
figure that into the math... with the 1-2mpg less I may have got and what I saved using synthetics etc.. I bet it cost more buyin tires every 2 years for them.

[Rick]

Strange, when I took my Cobra through the Bondurant school of high performance driving they REQUIRED that my tires be inflated to sidewall max. Not negotiable.

I have the stock Goodyears that Toyota puts on the 15" steelies. My three-door hatch is a hopeless, hapless disgusting pig in the corners with 32 psi in the tires. The TRD rear sway bar helped some, but running 51 psi front and 50 psi rear makes it dry corner like it's on rails. That's only six psi higher than sidewall max. These tires are wearing evenly so far as well. I'm not saying that any old tire can accomplish that though.

Also, most of the pothole related tire failures I've seen were the result of the sidewall being pinched (crushed) between the road and the wheel. Higher tire pressures should make that harder to accomplish.

[supmet]

Fact is, Brian is right and you're wrong. You don't have to accept that, but hopefully your ignorance will not mislead others interested in facts proven by real world experience.

WHAT FACTS? No tire manufacturer will recommend double PSI. No car manufacturer will. There are at least 3 people in this thread alone that have seen increased tire wear with increased PSI.

www.tirerack.com

If a vehicle's tires are overinflated by 6 psi, they could be damaged more easily when encountering potholes or debris in the road, as well as experience irregular tread wear.

But its all a conspiracy huh?? I'll bet you thebarber and supmet work for the big oil companies.

[b_hickman11]

I think Obama is behind it all.....

[ka0sx]

I think Obama is behind it all.....

lol

[thebarber]

Strange, when I took my Cobra through the Bondurant school of high performance driving they REQUIRED that my tires be inflated to sidewall max. Not negotiable.

i was under the impression you raise the pressure a bit so the sidewalls flex less under heavy cornering...im kinda surprised they put it at the max....but maybe the tires have a level of safety built into the "max pressure"?

[GeneW]

Tunnel vision applies to people who tailgate

...actually that's not true. A good tailgater drives at least two, maybe three cars beyond their victim. You have to have your empathy dailed up to ten to see where they might brake so that you can brake before they do.

If all you do is look at the bumper of the person ahead of you it's a matter of time before you feel it.

Gene

[GeneW]

Strange, when I took my Cobra through the Bondurant school of high performance driving they REQUIRED that my tires be inflated to sidewall max. Not negotiable.

Bet you had high heat rated tires too. It helps.


Also, most of the pothole related tire failures I've seen were the result of the sidewall being pinched (crushed) between the road and the wheel. Higher tire pressures should make that harder to accomplish.

If you're talking catastophic failures I could not say. If you're talking belts breaking, that's another topic. Don't know if higher pressures would help or not. I pays my money and takes my chances at factory pressure settings.

[TheUnGroomed]

...actually that's not true. A good tailgater drives at least two, maybe three cars beyond their victim. You have to have your empathy dailed up to ten to see where they might brake so that you can brake before they do

There are no good tailgaters!


I have very little experience with tire wear. I'm still on my original tires on my Yaris, and I had two sets on my old Elantra. When I first got the Elantra it had new Potenza G009s on it. I kept them at the pressure Hyundai recommended. After a few months the outer edges wore down quite a bit. My next set of tires were Falken ZE-512s. I played with the pressure until I found a comfortable psi, which was 40 psi. After 63,000 miles the treads had barely worn down at all.

I found the ride in the Yaris to be comfortable at about 42 psi on the stock Eagles. 9,000 miles in all is well.

I've been consulting this site for tips: http://www.carbibles.com/tire_bible_pg2.html Scroll down about 2/3 of the page.

Your results may vary!

[voodoo22]

WHAT FACTS? No tire manufacturer will recommend double PSI. No car manufacturer will. There are at least 3 people in this thread alone that have seen increased tire wear with increased PSI.

www.tirerack.com

If a vehicle's tires are overinflated by 6 psi, they could be damaged more easily when encountering potholes or debris in the road, as well as experience irregular tread wear.

But its all a conspiracy huh?? I'll bet you thebarber and supmet work for the big oil companies.

No, I don't think the big oil companies would hire you to represent them and I fail to see anywhere where I stated double psi or conspiracy. You don't seem too hung up on being accurate anyways, so your misquotes come as no surprise.

If you actually did research and tried things out you could find the truth out for yourself. Posting a link from a reseller proves nothing. Believe what you want. I know I believe the over $700 savings in gas costs alone, and improvement in MPG by 15% since I started to slowly test, confirm and then apply the knowledge and techniques appropriate to my driving conditions and car, shared by people such as bailout. I'm also looking forward to seeing how many thousands of km's past mtbf I can go on my tires which show very little wear after 30k of 44-60psi.

[voodoo22]

I've been consulting this site for tips: http://www.carbibles.com/tire_bible_pg2.html Scroll down about 2/3 of the page.

Your results may vary!

Thanks for posting that link, looks like an interesting read.

[1stToyota]

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.) :bellyroll:

Tom

You'll get an instant change in the footprint. Get a tape measure reading of what's hitting the pavement @ 32psi, then run it up to 60psi and see how the tire gets up on its tippy-toes. :thumbdown:

[1stToyota]

@bailout

60 psi WILL increase tire wear and WILL decrease traction. end of story. I'm not arguing this one. Go find me one auto crosser who runs 60 psi on their yaris.

and again, the tunnel vision of hypermiling is coming into play. What about all the added stress on suspension, suspension mounts, engine mounts, transmission mounts, interior trim pieces, pretty much the entire car???

I suppose the 20 dollars a year(again) you are saving will pay for all of that??

If you want the all important MPG, and that's ALL you are worried about, listen to every word bailout says. If you are interested in the total cost of something, I suggest doing your own research.

True. 60psi is all about getting best mpg by going with extreme measures, has nothing to do with keeping wear, handling, braking, mpg and comfort levels all at normal and safe levels.

[SpaceShot]

Just an observation:

The TPWS in the Yaris seems to trigger somewhere down around 25 psi, and there doesn't seem to be any upper limit. (purely a limit warning system and not an active monitoring)

Thus for myself, I am more concerned about letting them get too low, than running a few psi high.

[1stToyota]

I think I'd rather be warned after losing 6 or 7 lbs vs losing 36 or 37 lbs (running 32psi instead of 60psi)

[SailDesign]

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

You're obviuosly not "enjoying" the corners enough. :smile:
I keep mine at 36 cold to increase sidewall stiffness (for cornering), and decrease wind movement.
If you corner harder, the outer edges will wear the same as the centre.
Each to his or her own, however. I set my car the way I like it, and fully hope everyone else does the same (i.e. how THEY like it, not how their friends tell them it should be)

[aclark246]

Each to his or her own, however. I set my car the way I like it, and fully hope everyone else does the same (i.e. how THEY like it, not how their friends tell them it should be)

+1
Spoken like a true Rhode Islander!

I doubt that any of the belligerents here will ever agree on this issue, or more importantly convince the other side. I recognize that both sides only want what is best for us fellow yaris drivers and want to share their info and educated opinions on the topic. But at the point where it shifts from a positive sharing of information and opinions to a negative, mudslinging argument (from whichever side it may be...) I second the solution of "to each his own." :respekt:

On a side note, I personally keep my OEM tires at or around 44 psi. As weird as it is, I prefer the comfort of 44 as opposed to 32, and that is why I keep it there. I have not noticed any uneven or untimely wear on my tires, although as someone mentioned previously, I am not measuring the wear scientifically. I have noticed a significant change/decrease in fuel economy the times my tires have been around 32psi, so I also second Bailout. (And that is my contribution to forming any kind of unscientific consensus.)

[Kaotic Lazagna]

Seems like the police is on the side of having the tire wall max rating rather than the door jamb rating.

http://cardealerforums.com/alt-autos-toyota/t157249-maximum-tire-pressure-police-perspective.html

A good read.

[Kaotic Lazagna]

For those who are lazy to click on the link (:laugh:)

Maximum Tire pressure (a police perspective)

We've talked here before about max cold tire inflation pressure.
Here's a fascinating article from Officer.com . Some police
officers drive with maximum air pressure in their tires as shown
on the tire sidewall, not the door sill or the owner's manual.

Here's a link to the article for some great photographs:

http://www.officer.com/article/artic...on=19&id=27281

and here's the text in case the page is deleted in the future:

Driving Under Pressure

Proper Tire Pressure Could Save Your Life

Posted: Wednesday, December 21, 2005

SGT. DAVE STORTON
EVOC Contributor

Officer.com

How many officers check the tire pressure on their patrol car
on a regular basis? We all seem to be great at checking that
the lights and siren work, because the time to find out they
don't work is not when you get a Code 3 call. Likewise, the
time to find out your tire pressure is too low is not when you
are in a pursuit and trying to take a corner at high speed.

What is proper pressure?

The proper tire pressure for the Police Crown Victoria is 44 psi.
If you look on the sidewall of the tire, you will see that it
lists 44 psi max pressure. Regardless of what vehicle you have,
use the maximum pressure listed on the sidewall. Higher pressure
results in better performance, decreased tire wear, and it
lessens your chance of hydroplaning at a given speed. This number
on the sidewall lists the maximum amount of pressure you should
ever put in the tire under normal driving conditions. Pursuits
and Code 3 responses are not normal driving conditions. Many
agencies maintain tire pressure at 35 psi since this is what
is listed in the owner's manual and on the door placard. The
reason the owner's manual lists 35 psi is because we get the
same manual as the civilian version of the Crown Victoria. The
police version, however, is fully loaded with communications
equipment, a cage, and your gear. You are not looking for a soft
and cushy ride, you want performance.

Myths about pressure

Let^�s put to rest some common misconceptions. The tires will
not balloon out creating a peak in the center portion of the
tread when tire pressure is above 35 psi. There is a steel belt
that prevents this from happening. Also, you are not
overstressing the tire with higher pressure, and the tire will
not be forced off the rim with higher pressure. The picture
above is Bobby Ore of Bobby Ore Motorsports driving a Ford Ranger
on two wheels. The tires on the left side have 100 psi in them,
and they happen to be tires and rims from a 1999 Crown Victoria!
This is a dramatic example of how pressure holds the tire in
shape, and how much stress a tire can handle.

Performance

If you were able to watch a tire as it travels across the
ground at high speed, you would see that it deflects to one
side during cornering. The faster you are going through a corner,
the more tire deflection you get. As the tire deflects over onto
the sidewall, you get less traction and more of a tendency to
understeer or oversteer. This could spell disaster when
negotiating a corner at high speed during a pursuit or a Code 3
run. Higher pressure keeps the tire from deflecting onto the
sidewall as much, which keeps more of the treaded portion on
the road.

A good demonstration for EVOC instructors is to have students
drive a high-speed course in a vehicle with 32 to 35 psi. Then
have them run the same course with 44 to 50 psi in the tires.
The student will experience a marked difference in performance.
Having officers experience this difference in vehicle
performance is much more effective than just telling them to
check their tire pressure.

Hydroplaning

When a tire rolls across a road covered with water, the tire
tread channels water away so the rubber remains in contact with
the road. The factors that affect hydroplaning are speed, and
water depth. Conventional wisdom says that vehicles will hydroplane
in as little as 1/16th of an inch of water. Not so coincidentally,
legal tread depth is 1/16th of an inch.

Tire manufactures and the Association of Law Enforcement Emergency
Response Trainers International (ALERT) have shown that tires have
more of a tendency to hydroplane when pressure is low. This
happens because the tire footprint (the portion of the tire
actually in contact with the road) is larger. For those of you
who water ski, think of which is easier to get up on: a fat ski
or a skinny ski. More tire surface in contact with the water
makes it easier to hydroplane, just as it is easier to water ski
on a fat ski. Also, a soft tire can be pushed in more by the
pressure of the water on the center portion of the tread. This
results in less rubber in contact with the road.

Tire wear

Much better tire wear results from maintaining proper pressure.
Tires with lower pressure will wear off the outside of the tread
faster from the deflection of the tire during cornering, and the
tires will heat up more from increased road friction. This is one
of the factors that caused the failure of a certain brand of
tires on Ford Explorers some years ago. In 1999 the San Jose
Police Department realized a significant cost savings by
increasing the pressure in the training fleet to 50 psi. They
soon followed up by increasing the pressure in the patrol fleet
to 44 psi. For liability reasons, most agencies are reluctant to
exceed the maximum pressure listed on the tire for actual patrol
vehicles, but they reap the cost saving when going to 50 psi on
training vehicles.

Next time you inspect your vehicle, make sure you check your
tire pressure since your ability to performance drive is
significantly affected by it. You are not driving to the store
to get a loaf of bread! You may be called upon to chase a
dangerous criminal or respond to assist another officer in
trouble. You don't wonder whether or not your gun is loaded
before you hit the street; don't wonder whether your tire
pressure is correct once the pursuit starts. Check your tires
routinely, just as you do with all other critical equipment.
--
Sgt. Dave Storton is the Director of the San Jose Police
Academy, and he holds a Master's Degree in Adult Education.
He is the lead instructor for the Emergency Vehicle Operations
Course (EVOC) at the San Jose Police Academy, and is a lead
instructor for the local regional academy. He teaches EVOC
instructor courses, advanced EVOC instructor courses, off road
EVOC, counter-terrorist / dignitary protection driving, and
motion picture stunt driving. Dave has trained over 3,500
drivers.

Photo courtesy of Bobby Ore Motorsports

[Rick]

Overall it seems that those who actually run with high tire pressures on their Yaris note that it works rather well while some who have no actual experience in the matter (haven't even tried it) are convinced it is wrong/false/dangerous/blahblahblah.

How can we expect to enhance our technical knowledge it we poison every thread that begins to challenge our existing understanding? Isn't just laying out facts and observations without including our "unconfirmed beliefs" and then letting the readers piece it together a more productive way?

Who is going to come back here to "talk tech" when all they'll get for their trouble is a ration of shit??

[33OH]

I ran 45+ PSI in my tires for gas mileage reasons.

I personally believe it led to less grip, which led to this:

Bottom line, I run 32 PSI now.