Incorrect Information re: Tire Pressure in Efficiency Mods

[euromodder]

the increased pressure will increase the tire radius

The flat side on the grond will be lifted up, making the tyre stand a bit taller.

But I seriously doubt a few more psi will stretch the circumference (say 2m) of the tyre to any noticeable extent - which ultimately is what is in contact with the road, no matter at what psi.

1 revolution of the axle will always get you 2m further, i.e. 1 revolution of the tyre.

[trikkonceptz]

Originally Posted by Weather Spotter

What car what that with?

I also added your data to the wiki:
Increase tire pressure to max sidewall - EcoModder

It was a 2004 Pontiac Vibe, Automatic.

[PaleMelanesian]

I can only report that higher pressures greatly increase the rolling distance of my car. I don't know how much mpg improvement that gives, but it is a positive. Better rolling = longer glides with fewer and shorter pulses to maintain speed.

[user removed]

I think he meant decrease rolling resistance.

regards
Mech

[womprat]

Originally Posted by Old Mechanic

24,000 miles rotated once.

Contact patch size is reduced with higher pressures which places more weight per square inch on each square inch of contact patch.

Coefficient of friction is the single biggest factor in traction here. Reducing the size of the contact patch linearly increases the contact pressure by area, you end up with only a slight reduction in available grip.

Only, going above max sidewall may deform the tire, you start to lose traction.

With the occasional exception, running up to max sidewall pressure should not compromise the wear and performance of any decent tire. It should be designed not to lose it's contact patch shape at the rated sidewall pressure.

I have front wheel drive, the rear tires don't wear perceptably, but the front ones wear on the outside edge quite strongly (power steering, front wheel drive and macpherson strut suspension). Running my tyres at max sidewall of 41psi I can't get the tires to wear unevenly - the they are still wearing at the outside edges faster than the centre.

I can confirm that pumped up tires will most certainly loose traction much faster on rough, loose or soft surfaces. Had a scare or two

If your driving on sandy, muddy, gravelly surfaces you want to back of the pressure a bit.

[Shwa Kid]

Originally Posted by gasstingy

..The Ford Explorer fiasco was using Firestone tires that the tread peeled off of. Firestone tried to claim they were underinflated. Underinflation is a serious safety issue, but I don't agree that overinflation is a problem.

The original reccomended tire pressure for those explorers was actually only 24psi, when the replacement tires were installed in the recall (Goodyear Wrangler RTS), Ford issued a new door jamb sticker to accompany them which raised the reccomended tire pressure to 30-35psi (I can't remember for sure what the new pressure was).

Originally Posted by Frank Lee

F150 came with OEM Firestones- best dang tires it ever had. I hunted for exact replacements but there were none to be had

Some tires that come OEM on vehicles are only issued to the OEM as they are purchased specially. Typically if that is the case, you can find the same tires under a different name.

[Weather Spotter]

I updated the wiki to reflect the change in wording.

New wording:
Reduces rolling resistance which decreases the amount of power your car needs to move.

There are mixed anecdotal reports about improvements in other properties (steering response, wet traction, and tire wear). Some folks report improvements and some report degradations.

[ktaylor]

I have a question, what is the limit to inflating tires. My Nokian WR's have a max sidewall of 81 psi and are currently inflated 50/45 F/B. I don't feel too comfortable with going any higher but I keep reading in the forum "just bring it to max sidewall." Also, were do I buy a good pressure gauge? Like Home-depot, or Canadian Tire?

[euromodder]

Originally Posted by ktaylor

I have a question, what is the limit to inflating tires. My Nokian WR's have a max sidewall of 81 psi and are currently inflated 50/45 F/B. I don't feel too comfortable with going any higher

If the tyre manufacturer states they are good for 81 psi, it means they tested them up to (and even beyond) that pressure.

Are they dedicated truck or van tyres ?
Those have a higher psi-rating.

[CapriRacer]

Originally Posted by ktaylor

I have a question, what is the limit to inflating tires. My Nokian WR's have a max sidewall of 81 psi and are currently inflated 50/45 F/B. I don't feel too comfortable with going any higher but I keep reading in the forum "just bring it to max sidewall." Also, were do I buy a good pressure gauge? Like Home-depot, or Canadian Tire?

I think you've read the sidewall incorrectly. Look again, and I think you'll see it says 51 psi!