screw more psi in the tires.

[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]

Originally Posted by BailOut

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.

Originally Posted by BailOut

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.

[BailOut]

Originally Posted by supmet

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.

Originally Posted by supmet

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.

Originally Posted by supmet

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]

Originally Posted by BailOut

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!

Originally Posted by BailOut

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.

Originally Posted by BailOut

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.

Originally Posted by BailOut

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]

Originally Posted by supmet

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.

[supmet]

Originally Posted by voodoo22

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.

[voodoo22]

Originally Posted by supmet

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.

[GeneW]

Originally Posted by voodoo22

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

[TheUnGroomed]

Originally Posted by GeneW

...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!

[1stToyota]

Originally Posted by 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.

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.