tire air pressure (vehicle, German, sedans, fuel)

[sailordave]

I'm going to make this into a poll. Do you inflate your tires by the vehicle's label plate recommendation or by your own preference. If you go by your own preference, what pressure do you use, what type of vehicle you drive, and why do you use this pressure.

My car is a 2003 Malibu. I follow the recommendation which is 29 psi front and 26 psi rear. I tried to go 32 all the way around and though the suspension was firmer, it really "thump" hard when hitting the bumps on the horrible Louisiana roads. Went back to the recommended pressure. I had even tried 32 front and 29 rear. Though it was better, it still "thump" on the roads. We're looking forward to our parish remaking the road we live on. There are sections that are literally falling into the ditch. One day, maybe today, I'll take photos and post to show you I'm not exagerating.

Do you feel a difference in ride when your tire pressure has been changed?

[M3 Mitch]

My real answer is "it depends". The M3 calls for 36 in the front, 39 in the rear, just another spec that the "wizards of M" got right.

But on regular sedans, I typically add about 3 psi - roughly 10% to the manufacturer's recommendations, but typically do maintain the same differential, if any, front to rear.

It also depends on what I am up to. If I am planning an interstate jaunt, I may add another 3 psi to my usual 3 over.

For autocrossing, when I get the rare chance to do that, typically way over "street" pressure, but of course not over the tire mfg's recommended max.

[ranger17]

may also depend if you are running stock or close to stock wheels/tires, or have made a major change. I normally run manu's psi's for normal driving; and on the wife's where she did upgrade her "shoes", i follow what was recommended to us by the location we purchased them at. I'd hate to run the lower sidewall tires with too little of pressure

[filmsniffer]

I like to overinflate just a tad to increase fuel economy. I usually experiment with pressure until I find it to my liking. I use the manufacturer's recommended pressures as a base.

I've been looking into filling the tires with nitrogen.

[texdav]

It really depends on teh driver . My wife for instance ternds to brake late and not enough ;so they weight is shifted to the front outside edge of the tire . This causes it to wear on outside edge ;so I like a little more pressure in the tires.I tend to adjust according to wear really. Even different tires with sidewall construction makes a huge difference.With that and rotation tires can last alot longer.

[Mouser]

Because both my vehicles have custom wheels and tires
I set my own using the recommended psi as a guide

And being in the extreme heat I check them quite often
and rotate every 7000 miles


'04 Chevy K-2500 @ 70 psi



'04 Chrysler Sebring @ 36 psi

[Steve Bagu]

The old days of the biased tires is gone. Today we have the radial tires with less rubber on the ground.

The old standard 32 psi has also flew the coup.

Remember having caddys yrs ago that said 24 lbs was to be used that gave me a soft ride but wore the s*** out of the rubber. Changed to 32 psi and they wore evenly for many miles untill the need for new came along.

A factor has to be condidered is the cars weight and roads being driven upon. Different roads for different strokes might be the MO. Country with dirt/gravel will require a different footing then that of high speed fwy driving. Weather be it rain/snow/extreme heat are the main concerns.

Mfg plants design a product for general usage and like my old mechanic father would say "you have to tweek a little to the left or right to make it work".

Steve

[Zea mays]

Originally Posted by sailordave

My car is a 2003 Malibu. I follow the recommendation which is 29 psi front and 26 psi rear.

Those manufacturer recommendations are for the original equipment tires, an assumed weight load, front and rear camber angles, as well as a number of other things. Change the tires and the manufacturer's recommendations would change.

A simplification of the formula used is
⠀⠀⠀⠀⠀⠀Inflate2 = Inflate1 x (MaxInflate2/MaxInflate1) x (MaxLoad1/MaxLoad2)^1.25

For example, if the manufacturer's recommendation was 30 psi for original equipment tires whose max pressure was 44 psi, and they are replaced with tires whose max pressure is 47 psi, the manufacturer's suggested tire pressure should be increased by 47/44 or 1.068, that is from 30 psi to 30 x 1.068 or 32 psi.

In my case, my original equipment Michelin tires have a max pressure rating of 44 psi and a max load rating of 1400 lbs. An identical size Bridgestone has the same max pressure rating of 44 psi, but a max load rating of 1477 lbs. If I switched from the original equipment Michilans to the Bridgestones, I would adjust my original manufacturer's recommendation of 30 psi to
⠀⠀⠀⠀⠀⠀30 x (44/44) x (1400/1477)^1.25 or 30 x 0.936 or 28 psi

These formulas come from a German automotive handbook which I have, but perhaps similar tire pressure formulas could be found in English on the internet by Googling.

For the record, I inflate to 1 psi above the manufacture's recommendation for ordinary driving, and 2 psi above manufacture's rating for long distance interstate trips of 700 miles or more.

[deepcynic]

I start at the recommended and customize to the conditions, much like M3 Mitch.

When my GTI was new I played a lot with the pressure, finding just the right combo (front/rear) for the mountain roads I drive (and the particular tires). It is amazing what a couple of PSI will do for the handling dynamics. I tend to be a couple or 3 over the recommendations for most of my driving.

[Omaha Rocks]

I generally run right at 35 psi, all the way around, on my vehicles.

If I'm hauling or pulling something heavy with the truck, I'll run it's rear tires up to 40 psi.