100+ hypermiling / ecodriving tips & tactics

[MetroMPG]

Good idea - thanks. Added "Dress for success."

[PaleMelanesian]

Agreed. In the summer I take off my shoes and drive home barefoot.

[michael.long8]

original thread:

8) Check tire inflation regularly 
Make sure that your tire pressures are, at minimum, set to manufacturer specifications. The higher the pressure, the less rolling resistance.

Remember that pressure is affected by ambient temperature. As temperature drops, so does your tire pressure, so keep track as the seasons change.

my post:
I am aware that properly inflated tires do increase mileage over tires that are underinflated; however, as indicated above, higher pressure equates to lower rolling resistance, which leads to my question. Has anyone done a real-life study to see how much sooner their tires wear out because of overinflation? Also, does the tradeoff for premature wear offset any savings you might see at the gas pump? I have inflated my truck tires about 3 psi over the manufacturer's recommended psi, and now I'm showing a noticeable amount of premature tire wear in the center of the tread. Mind you, I'm only talking about a max psi of 35 psi versus a recommend psi of 32. My concern is that now I have increased my mileage by 1 mile per gallon by overinflating, and I've shortened the treadlife of my tire by approximately 5-10,000 miles, or more. That's by no means a science; it's just an estimate on both accounts.

Label me curious.

Thanks in advance.

[euromodder]

Originally Posted by michael.long8

Has anyone done a real-life study to see how much sooner their tires wear out because of overinflation?

They don't - or shouldn't - wear out faster.

I have inflated my truck tires about 3 psi over the manufacturer's recommended psi, and now I'm showing a noticeable amount of premature tire wear in the center of the tread.

Lower the pressure again.
You shouldn't get noticeably more wear down the center by increasing the pressure.

Mind you, I'm only talking about a max psi of 35 psi versus a recommend psi of 32.

What kind & make of tyres are they ?

Only 32psi being allowed in a road tyre on a truck is plainly ridiculous.
In Europe, vans and light trucks run tyres rated for 80psi once they go beyond regular passenger car tyres due to the required load index.

[hackish]

Originally Posted by michael.long8

original thread:

8) Check tire inflation regularly 
Make sure that your tire pressures are, at minimum, set to manufacturer specifications. The higher the pressure, the less rolling resistance.

Remember that pressure is affected by ambient temperature. As temperature drops, so does your tire pressure, so keep track as the seasons change.

my post:
I am aware that properly inflated tires do increase mileage over tires that are underinflated; however, as indicated above, higher pressure equates to lower rolling resistance, which leads to my question. Has anyone done a real-life study to see how much sooner their tires wear out because of overinflation?

Tire pressure is a balancing act. Overinflation does give you a lower rolling resistance as you've pointed out. However, overinflation also gives you a reduced contact patch. This means at speed you will not have as good a handling or braking - especially noticeable in poor conditions, rain, snow etc.



The above image should make it evident why your tires will wear faster. There are also a few other things to think about. As you drive (high speed especially) the tire friction turns into heat. Heat dissipation is one of the specifications that give you the tire speed rating. With this heat you have expansion. Now if you over-inflate then get them hot, it will at some point become a safety issue.

My old man worked at Michelin for 25+ years. I can give you a few snippets of insight from talking to him. First, the grade a manufacturers test the @#$@# out of their tires. So the maximum PSI they give accounts for a fully loaded vehicle at maximum speed and they multiply it by a design factor (Fudge factor if you will).

As a family we always got the employee tires (blems). When they were used up we had to return them and they'd cut them up and do all sorts of tests (like blow them up!) to make sure they fared well with the safety factor. Ongoing R&D and this gives you insight into why a Michelin costs more than a wang tire.

Tire manufacturers put a lot of R&D into rolling resistance. This actually sells tires. Carmakers have their vehicles tested with the OE supplied tires for fuel economy and EPA listings. Producing tires with lower rolling resistance helps these figures so carmakers will bias the tire choice for the best results.

With overinflation you get gains because there is less tire deflection as it rolls. If you have a lighter car that helps too, so take your junk out. Runflat tires tend to have slightly better rolling resistance because they have stiffer sidewalls - less deflection.

Here is an interesting tidbit too. Overinflation helps your city fuel economy more. At higher speeds tires have a better rolling resistance. Centripedal force pushes the tread out and there is far less deflection at speed.

I would never advise overinflating a 32psi tire to 80. That's more than double the intended operating pressure! One person doing this saying well my tires didn't blow up does not compare with tens of millions of driving km tested by teams of engineers. While you can get away with some overpressure that's downright unsafe. Have a look at the lawsuit against firestone for the exploding tires. Overinflate them and go 150kph for an extended period of time and they blew up.

[euromodder]

Originally Posted by hackish

However, overinflation also gives you a reduced contact patch. This means at speed you will not have as good a handling or braking - especially noticeable in poor conditions, rain, snow etc.

The first thing to do is define "overinflation".
Is it inflation over
1) the car manufacturer's pressure recommendations;
or
2) the tyre manufacturer's rated pressure.


1) is usually safe to do as car manufacturers often recommend pressures that are low to too low.

My own car will wear down the shoulders when "correctly" inflated, and it'll wallow on its tyres.
Volvo increased the recommended pressure from 33.4psi early on, to 36.3 on their later, near-identical models.
One of the many areas of this car range where they were blatantly wrong.
On my car , the telltale signs of underinflation only went away at 43.5psi - and beyond.


2) Puts you in the safety margin that the tyre manufacturer built into the tyre.
I won't go there, though I do run my tyres at the max. rated pressure (51psi).

Now if you over-inflate then get them hot, it will at some point become a safety issue.

Tyres blow due to too low pressure, not from higher pressure.
There's tons of people on here running well over the rated pressure - how come their tyres don't blow out ?

Increased pressure reduces deformation, which generates the heat and RR.

My old man worked at Michelin for 25+ years.

Good tyres .
(well, mostly, as their Energy E3 a/b were dogs)

I always seem to return to Michelin after trying something else.
Looks like they're working for me.

I would never advise overinflating a 32psi tire to 80.

Nobody does.
If my post came across as such, it's not what I meant by it.

On a European van or light truck, depending on weight, manufacturers wuill often fit tyres that are rated for 80 psi .

32psi on a light truck tyre seems ridiculous - unless it's an off-road tyre.
Motorcycle typically run 36psi !
I find it mind boggling that at these low pressures, even a meagre 3psi more would lead to noticeable center wear.

[Intrigued]

Hey, I was also in the automotive industry for several years, and I think you all are over-analyzing the issue here. If Michael is having wear at the center of the tires at 35/32 psi then the VERY first thing I would be looking at is the width of the tire vs. the rim. My dollar says that those tires are TOO WIDE FOR THE RIMS, making them bulge out some in the middle of the tread. Now, I know there are other factors to be included in all this, but that is the FIRST thing I'd look at...

[Fat Charlie]

You've got to love blind spots. I'll bet that's it. Is everything here OE, Michael?

[michael.long8]

@ Euromodder. I forget the name brand on the tires, but to be an offbrand, they've performed like champs. The actual max psi for the tire is 35 psi because it is a 4-ply tire for a Nissan Frontier (midsize) pickup. I wouldn't be concerned near as much with a little higher psi if it were a better brand of tires like a Michelin or BFGoodrich AT. From what I know about tires, over and under-inflation, alignments, etc., I figure it's a hard sell to dramatically over-inflate and see a payoff when I'm buying a $500-$600 set of tires a year earlier.

[michael.long8]

@hackish. I'm with you. I think if I can come up with the kind of money it takes to purchase a set of Michelins, or BFG ATs, that will be the route I go. I worked in tires for about two years and Michelins have the highest quality of any tire I have installed for a customer. Goodyears and Firestone's scare me because the sidewalls and carcas are paper thin. I'm with you on the psi being a balancing act. If so many people are over-inflating, I'm curious if anyone has taken the additional tire wear into consideration. It seems to me that over-inflating might have minimal gains, if any, when compared to purchasing a new set of tires. I'll never run more psi than the tire is recommended for either, that's just asking for trouble...especially on the highway. Thanks for the feedback.