Let's talk tire pressure

[zeng]

Originally Posted By: Linctex
My 265/70R-17's say max 44 psi on the sidewall, that's where I run them. I don't care what the door tag says.

I'd 38 all round where sticker says 29.
A cool 30% overpressure.
It's agile with harsher but acceptable ride.

 

[SteveSRT8]

In the old daze with bias ply tires at the track we overinflated them. I have run 60 psi at autocross in 32 psi tires that were way off todays materials.

But for modern track times just a couple psi over in the SRT. It works well.

Inflation pressure is wildly platform specific. No blanket recommendations are correct for all cars...

 

[Linctex]

Originally Posted By: zeng

I'd 38 all round where sticker says 29.
A cool 30% overpressure.


That is quite a bit over.

Are yours regular 1- or 2-ply sidewall passenger car tires?

 

[zeng]

Couldn't quite follow your questions .... pardon me.
It's Goodyear Duraplus 175/75R13 steel belted, if it's appropriate answers.

 

[SwampSurvivor]

Radials won't wear the centers when run at a higher pressure as bad (if at all) like a bias ply would.

 

[4WD]

I run OEM pressure on cars, truck, SUV ...too many bad roads for me to consider higher pressure ...

 

[CapriRacer]

As has been pointed out, I have a web page on the subject: Barry's Tire Tech - Load Tables

One of the things you should get out of that page is that the maximum tire pressure is relatively arbitrary and referencing that for usage pressure is not a good idea.

Some background for reference: In Aug of 2000, there was a massive recall of Firestone tires. At the time, it was pointed out that many vehicle manufacturers were not doing a good job of sizing their tires - that some vehicles needed either more inflation pressure or a larger tire. As a result every vehicle manufacturer made changes to the way they did tire size/inflation pressure - and this was completed by the 2008 model year. So some time between the 2001 model year and the 2008 model year, there was a change.

Prior to that, I was of the opinion that tire pressures should be run 3 to 5 psi HIGHER than the vehicle tire placard. I no longer hold that position.

As has also been pointed out, tire wear is not STRONGLY related to inflation pressure. There are other factors that play a larger role.

SO ....... I recommend people follow the vehicle tire placard for pressure if they are using the tire size listed there. If they are not using that size, then it has to be recalculated using the placard as a starting point.

This applies to summer tires, all season tires, and winter tires.

There is no great harm done by anticipating the drop in inflation pressure during the winter months and using up to 5 psi more than the placard. In other words, set your pressures up to 5 psi more while the weather is still warm, and you be good to 50 degrees colder than that - then adjust when it gets warm again.

 

[barryh]

Reference my earlier post, before I reduced my pressures 5% below the book values I did some research looking at load tables.

I was puzzled by the tables. Not yours CapriRacer because my size wasn't shown but you got me looking for the correct one for my tires.

What I found was that the manufactures recommended pressures seemed to provide for a loading weight some way above the gross vehicle weight of the car. So much so that the pressures the manufacturer recommended for a lightly loaded car with max of 3 persons and little luggage would still support the gross vehicle weight and then some according to the load tables.

I may be in the minority in running lower than book pressures for comfort reasons but according to the load tables I'm still inflating the tires more than enough to support the weight.

 

[4WD]

Folks did that once a year before TPM came along and started waking them up to air up a bit ...

 

[CapriRacer]

Originally Posted By: barryh
...... What I found was that the manufactures recommended pressures seemed to provide for a loading weight some way above the gross vehicle weight of the car. So much so that the pressures the manufacturer recommended for a lightly loaded car with max of 3 persons and little luggage would still support the gross vehicle weight and then some according to the load tables. ......


First, those aren't recommended pressures. They are MAXIMUMS.

And, yes, good engineering says that the rated load on the tires SHOULD be more than what the vehicle weighs. Otherwise the tires are overloaded.

Originally Posted By: barryh
...... I may be in the minority in running lower than book pressures for comfort reasons but according to the load tables I'm still inflating the tires more than enough to support the weight.


Be very careful here. Not only are the vehicles tested at the inflation pressures listed on the placard, but as a general rule, they aren't tested at other pressure and there may be some quirks in the vehicle handling at lower pressures (and I know of at least one vehicle like that!)

 

[NStuart]

Originally Posted By: Miller88
Radials won't wear the centers when run at a higher pressure as bad (if at all) like a bias ply would.


I would have to disagree, I stare at tire condition a lot more than most people in my day to day micro management of a few semi trucks. I see drastic differences is center of tread and outside wear when tire psi range from 70 to 110 psi . In general all the turning that my short haul trucks do ( even with 5k lbs sitting on each tire) on a fully inflated tire @120 psi hot you can see about 5/32 in more tread left on the outside grooves than the center . our tires don't last but about 80k miles where your average guy gets 300k miles on a set .I sometimes lower the psi at the end of tire life to use more outside tread lol

 

[CapriRacer]

Originally Posted By: NStuart
Originally Posted By: Miller88
Radials won't wear the centers when run at a higher pressure as bad (if at all) like a bias ply would.


I would have to disagree, I stare at tire condition a lot more than most people in my day to day micro management of a few semi trucks. I see drastic differences is center of tread and outside wear when tire psi range from 70 to 110 psi . In general all the turning that my short haul trucks do ( even with 5k lbs sitting on each tire) on a fully inflated tire @120 psi hot you can see about 5/32 in more tread left on the outside grooves than the center . our tires don't last but about 80k miles where your average guy gets 300k miles on a set .I sometimes lower the psi at the end of tire life to use more outside tread lol


My experience is that drive tires tend to wear in the center, and steer tires tend to wear in the shoulders - and that wear phenomenon is at an order of magnitude more than inflation pressure.

 

[Bear]

Based on several articles I read over the years I inflate 10% over door spec, so 3-4 psi more than sticker. Never had issues with abnormal wear due to inflation issues in the many cars, trucks or vans I've owned.

 

[Kestas]

I had a set of Michelin touring tires that ran 60K / 11 yrs, until they wore out. I ran them 7 psi over. At the end of their life they showed mild center wear.

 

[CR94]

I've generally run about that much over sticker. Some radial tires have gone over 100K miles that way, but none have ever worn out in the center first.