What air pressure for tires?

[DJ in WA]

I probably should have figured this out about 30 years ago, but am hearing different things now.

Was airing up snow tires yesterday. On the side they say maximum pressure 44 psi.

So what is optimum?

And if it's cold when you air them up, pressure will go up when hot. In the summer, I suppose you give less air because they'll heat up on the road?

I know they'll wear wrong when under/over inflated. I figure more air might be good because you'll lose some. Also better mileage with more air.

What are the risks of airing up to the maximum? More likely to blow a tire?

[tamsam]

I always check mine after driving at hi-way speed for 15 to 20 minutes so they are up to temp. Sam

[Bearfootfarm]

There are no risks to running max pressure as long as the vehicle isn't overloaded

[Ross]

The vehicle's owner's manual should spec air pressures, not the tires.

[Countrybumpkin]

I agree with Ross-use the max pressure stated in the car itself, and not the tires. I used to fill my truck tires to thier max, instead of what it said on the drivers door, and the tires were too inflated, and wore the tread off in the center, where it was riding high. Never again!

[tyusclan]

Originally Posted by Ross

The vehicle's owner's manual should spec air pressures, not the tires.

Bingo.

You can also find it on the label on the driver's door.

[Reptyle]

Originally Posted by tamsam

I always check mine after driving at hi-way speed for 15 to 20 minutes so they are up to temp. Sam

Tire pressure should be checked when the tire is "cold."

"Be sure to properly check all four tires "cold" once a month and before a long trip."

http://www.michelinman.com/tire-care/tire-saving-tips/air-pressure-tips/?Wt.mc_id=Paid%20Search;Google;{KeyWord}&WT.srch=1 &gclid=CKaTpL3kw6UCFYde7AodYji7PQ

[backwoodsman7]

Originally Posted by DJ in WA

So what is optimum?

As it was explained to me by a tire guy many years ago: A tire is designed to run with a certain "contact patch" on the road, which you get when the tire is at max. pressure and carrying its max. rated load. When the load is less than that, adjust the pressure accordingly to keep the same contact patch; i.e., if the tire is carrying 2/3 its rated load, use 2/3 its max. pressure. For a passenger car, just use whatever is in the manual or on the door sticker. For a truck, when it's loaded heavy, make sure to use enough pressure so the tire isn't squashed and flexing more than it's designed to.

In the summer, I suppose you give less air because they'll heat up on the road?

No, you'll notice the max. pressure on the tire and recommendations by the vehicle manufacturer are always when the tire is COLD. Whatever COLD means for the season you're in is when you want to check & adjust the pressure.

What are the risks of airing up to the maximum? More likely to blow a tire?

No, but you'll have less tread on the road, which reduces traction. Bad idea, especially on snow, or wet roads.

[Beeman]

Originally Posted by DJ in WA

I probably should have figured this out about 30 years ago, but am hearing different things now.

Was airing up snow tires yesterday. On the side they say maximum pressure 44 psi.

So what is optimum?

And if it's cold when you air them up, pressure will go up when hot. In the summer, I suppose you give less air because they'll heat up on the road?

I know they'll wear wrong when under/over inflated. I figure more air might be good because you'll lose some. Also better mileage with more air.

What are the risks of airing up to the maximum? More likely to blow a tire?

What are these tires on? Tire pressure on the sidewall is maximum pressure but doesn't take into acct. what application. Vehicles have a tire pressure and size label, the sticker can be on the drivers door, passengers door, in the glove box, on the trunk lid, etc. It varies by manufacturer but should give you the proper tire size and pressure for the vehicle and will give you differences loaded and unloaded.

First get a good gauge. No reason for more air and you shouldn't lose any, if you do something is wrong.

[DJ in WA]

These are snow tires on a 93 toyota camry. Though I was also airing up my daughters 93 honda civic which tires said max pressure 51 psi.

Anyway, I did as suggested and found the sticker in the camry glove box and read the owners manual (which real men ignore).

Sticker says at max load (900 lbs) or 5 passengers, 29 psi front and rear. For 4 passengers or less, 26 psi front and rear. We rarely have more than 2 people.

I don’t think I’d have guessed only putting 26 psi in them. I’ve had people telling me they look low at 30 psi.

As for checking them cold, how cold? I checked the summer tires that are out in the barn at 30 psi at 20 degrees. Brought them into the garage for a half hour at 60 degrees and read 33 psi. So I guess I’d lose 3 psi or so when going from the garage to driving in 20 degrees or less (was 10 below on Wednesday).

[HermitJohn]

I wouldnt go under 32psi for any passenger vehicle with radial tires. Lower suggested pressures are to give something more akin to the luxo-barge type ride. Ecoboxes rarely suggest anything under 28psi. Low pressures wont make them ride any better and will hurt fuel mileage. Probably wouldnt go over 35psi unless you have vehicle at max load, then put in max it says on sidewall. Pickups, it depends on load. My F250 with load range E tires, I run around 45psi empty. If I fully load it, I can go upto 80psi. Empty its bouncy enough at 45psi with the super stiff springs, dont want to ever experience 80psi empty.

[Ross]

I guess I'm not a real man, manuals and instructions are pretty much the only thing I read these days. Maps too I may not as for directions but that's because I read the map and know where I am or at least within a road or two!

[DJ in WA]

Ross, you lead a boring life. I find it's much more exciting after the accident to see how I should have been doing it!

Anyway, I've absorbed the input and I think I'll keep them around 35 psi. And read the pressure at around the temp they'll be running in as Backwoodsman suggested, not in the garage. I read that the psi goes up or down 1 point for each 10 degrees of change in weather.

Ultimately I suppose tire wear is a good indicator and the summer tires are worn down evenly and I believe have averaged 35 psi over the years.

Thanks.

[Allen W]

I would keep them around 35 psi, too low and a small leak will leave you with an unsafe tire to drive on.

[farminghandyman]

for car type or small pickups, 28 to 32 is average, If your carrying a heavy load one can up the rear tires some, to carry the load,

on trucks one needs to use the manual (may be on the door sticker or in the glove box on newer trucks), and adjust from there.

larger trucks more pressure,

under inflation is much harder on the tire than over inflation.

[WisJim]

There has been a lot of research in recent years about tire pressure, fuel economy, tire wear, traction and safety and how they all inter-relate. My recollection of the results is that higher than recommended pressure within the maximum limits on the tire sidewall, is better than lower than recommended pressure for all things, including economy, wear, and traction. I run 40psi in my car and more in the pickup with no problems, no unusual wear, for many years.

[DJ in WA]

I called the tire shop I got them at and they said they send these tires out the door at 35 psi. Apparently alot of people ignoring the sticker in the car.

[mightybooboo]

Originally Posted by WisJim

There has been a lot of research in recent years about tire pressure, fuel economy, tire wear, traction and safety and how they all inter-relate. My recollection of the results is that higher than recommended pressure within the maximum limits on the tire sidewall, is better than lower than recommended pressure for all things, including economy, wear, and traction. I run 40psi in my car and more in the pickup with no problems, no unusual wear, for many years.

Just about where Im at on my vehicles too.I once had a Jaguar XJ-6L and the tire pressure was something like 24!Big sidewall bulge even. But it had the softest ride and really held the road,crazy huh?

[travis91]

i have a ford ranger(little 4cyl) with P rated tires on it and i keep them at 35

[Beeman]

Originally Posted by DJ in WA

I called the tire shop I got them at and they said they send these tires out the door at 35 psi. Apparently alot of people ignoring the sticker in the car.

Most tire shops are the most ignorant about tire pressures and wheel torque. They surely are not going to take the time to walk to the car and check the pressure tag, not vey manly. Most are part of the don't read the manual club. I don't let tire shops do anything more then put the tire on the rim and balance it, they usually struggle with the balancing part. I remove and install my own and bring them to them and set the air pressure when I put them on. I just worked on a Jeep thet had new tires put on recently. I replaced 7 lug nuts and had to chase the threads on those studs.