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Old 10-29-2008, 10:08 AM   #17 (permalink)
Jim Allen
5.4L Econo Box
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Location: NW Ohio
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Plugger - '05 Ford F-150HD 4x4 XL
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Originally Posted by tasdrouille View Post
This is sounding more and more like a myth. Every fuel economy enthusiast I know of who overinflated have seen increased tire life and even wear. There are a lot of people overinflating and reporting successful results. Yet, we don't hear about those who overinflated and got excessive center wear. Maybe because that's just not happening.
tasdrouelle: Well, yours is not exactly a scientific observation, so I'll offer one that's of equal value scientifically: I've been in the car business professionally since 1970, that's nearly 40 years now, and I have seen tire wear, belt separation and suspension problems due to overinflation many times. And I've seen tires that blew out due to it. Seen them first hand. It's happening!

Tires are a lot more complex than they appear. If you want an brainful, read the SAE book, "Tire Forensic Investigation" by Thomas R. Giapponi. You'll see the multitude of ways tires can fail... in gruesome detail. Call it CSI for tire guys ( : < )!

Yes, people get away with overinflation. That's partly because most tires are over-engineered. Plus, if you have to go one way or the other, overinflation is better in all areas than underinflation. So if a guy goes from checking his tires pressure every three years (whether they need it or not) and generally wearing out tires due being underinflated, then "getting religion" and going to the opposite extreme is going to seem like a whiz-bang concept that yield great results. If you compare tread life of a properly inflated tire vs an overinflated tire, you'll see some more unhappy numbers.

The over inflation saving graces for this Ecomodder group are that, a) they generally drive small, light cars, and b) those who know about such things buy tires with a high durometer and a tread design that offers low rolling resistance. These factors all contribute to a lower wear potential than the average tire (lower performance too, but...). Also, without wishing to insult anyone, logic dictates that a guy who destroys his tires by hyperinflation is not all that likely to advertise it in an, "I'm a bonehead," kinda post.

Me, I'm more concerned with the braking and handling issues. A little experimentation via a skidpad and stopping tests will show the loss of performance that comes from overinflated tires. The threshold is different for every tire/car combo and there may be a point where fuel economy and performance meet. Based on my knowledge, I'm willing to bet that point comes well under the tire's maximum pressure at any given load.

My little practical test showed the fuel economy difference between overinflated and properly inflated was too small to measure on my truck. Metro's rolling resistance test hints at much the same thing on his little car. To me, that makes the risk avoidance part of this very easy. If I discovered there was a 3 mpg gain in overinflating my tires, I'd crunch the numbers, do a little risk vs reward assessment and maybe give it a try. But, alas, all I got at 60 psi was a molar-loosening ride and squirrelly handling.
Jim Allen
The Frugal Four Wheeler and Farmer

My ultimate goal is not necessarily the highest mpg but to make my trucks more efficient configured as I need them.

Old Reliable '86 Ford F-250HD 4x4, 6.9L diesel

Red '00 Honda Accord Coupe, 3.0L V6, automatic

The Plugger '05 Ford F-150HD 4x4, Regular Cab, 8-ft bed, 8,200# GVW, 5.4L V8, automatic, 4.10:1 ratios, 285/70R-17D tires

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