Tire Pressure

saturn
sl

#1

Some tire people say to use the cold inflation pressure on the tire, car manufactures say use the pressure on the car decals, independents, and old guys say use a little of both. What is the best pressure to use for wear and traction?


#2

There is no “cold inflation pressure” marked on the tire!
Marked on the tire is a maximum possible inflation pressure. It means if you go above that pressure, the tire might fail.
Use the pressure on the car decal.


#3

Use the car decal tire pressure as recommended by the car manufacturer. Old (and young) guys may choose to adjust from there, based on a variety of reasons, but for the vast majority of applicatons, the decal should be the start and end point. Pressure max on the tire is exactly that. Does not necessarily relate to the tire pressure that the vehicle manufacturer thinks is best/tested/engineered for the car.


#4

If you can’t find the pressure on the decal on the door jam, it’s also in your owners’ manual.

And yes, it should be checked “cold”, meaning not right off the highway.


#5

There are three issues involved.

  1. Maximum pressure: The tyres have a maximum pressure that they can be safely handle. You want to use. In this case you seem to be suggesting you want to use it at the max listed on the tyre, so as far as the tyres go, that should be fine.

  2. Ride comfort: You seem to accept the harsher ride and since you are the only judge of that, then that should also be OK.

  3. Safety: This is the one that I can’t offer a yes or no answer. While all the authorities (see below) agree that the pressure listed in the owner’s manual is the recommended proper pressure by all authorities, it must be acknowledged that there likely is some amount of flexibility.

Car manufacturers are concerned with many things. They want people to be happy with their cars and that means they want the car to give good mileage and the want the car to ride comfortably.

I have yet to see anyone who has access to real test track facilities and actual test results on modern cars and tyres, offer objective data to support the idea that pressures higher than that recommended by the manufacturer are as safe as the recommended pressure.

My opinion is that a few psi over the recommended value is not likely to compromise safety by any material amount. I would also suggest that there is a point where higher pressure will reduce safety enough to make a difference.

If mileage is more important than safety, go ahead and keep upping that PSI. Other wise, I would suggest reading the following and going along with the professionals. If it really was safe to go higher, then I don’t think all the authorities are going out of their way to tell us to use what the car manufacturer recommends.

http://www.tiresafety.com/
This is sponsored by a tyre manufacturer Bridgstone - Firestone and instructs the reader to check the owner’s manual for the correct tyre pressure.

Here is another from the Goodyear site.

Tire Inflation
Proper tire inflation is a key ingredient in driving safety and long tire life. It is wise to check your tire’s inflation at least once a month with an accurate tire pressure gauge. Continuous loss of inflation pressure is an indication of a possible tire/wheel assembly problem; consult your tire professional immediately if you encounter this situation. Be sure to check the pressure while the tires are cold, and have not been used recently. If you drive even a mile this will cause your tire pressure to increase and give you an inaccurate reading.

Check Your Air Pressure
Keep your tires properly inflated and you could improve gas mileage by more than $1.50 every time you fill your tank. The recommended tire pressure for your vehicle is located on a sticker inside your driver-side door or noted in your owner’s manual.
You might also try the US Department of transportation.
http://www.nhtsa.gov/cars/problems/E...intenances.htm
They say:
You can find the correct tire pressure for your tow vehicle in the owner?s manual or on the tire information placard.


#6

On every vehicle sold in the US - and I understand this is a worldwide practice as well - there is a sticker ? commonly called the tire placard - that lists the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box ? but sometimes it is located in the trunk or on the fuel filler door.

BTW, it doesn’t matter who makes the tire or what pressure is listed on the tire’s sidewall, if the tire size is the same as the placard, then the pressure listed on placard is also appropriate.

If you are using a tire size that is different than what is listed on the placard, then the pressure has to be recalculated. The calculation is not difficult, but it requires tire load tables which are not allowed to be published in the Internet because of copyright laws. However, I have a copy and would be glad to do the calculation, but the starting point is the vehicle placard: Tire size and inflation pressure. I will also need to know the new tire size.


#7

You overlooked the word “maximum” printed on the tire. There is a difference between maximum and recommended.


#8

Exactly!

If your doctor told you that he did not want to see your blood pressure rise above…let’s say…140/90, that does not mean that this blood pressure is desirable. Rather, it is the upper limit of what might be considered safe.

In a similar fashion, you don’t want to be running your tires at their maximum pressure.
Inflating them to perhaps 3 lbs over the recommended pressure listed on the door jamb is okay, in the interests of better gas mileage, improved handling, and somewhat longer tread life, but the maximum pressure listed on a tire sidewall would result in an extremely rough ride, skittish handling on wet surfaces, probable long-term damage to ball joints and other components, and an increased risk of punctures.

Simply follow the car manufacturer’s advice, and if you are so inclined, add 2 or 3 lbs to those numbers.


#9

Thanks to everyone who responded to my tire pressure question.(Actually my brand of tires does have a stamping (35 P.S.I. Max Pressure At Standard Load), I assumed the pressure is a cold pressure. Over the years, I have had independent garagemen set my tire pressure at 35PSI claiming this better protects against tire failure, the placard calls for 30PSI front and 26PSI rear, at this pressure the car seem soft and inclined to wallow, also less good MPGs. The dealer, after the FORD SUV tire failure and roll-over issue, started to set the rear at 30PSI(quietly, I check my own pressures and questioned the dealer who reluctantly told me it was to help safeguard against rear tire failure). As my cars age, tires become much more important in the handling characteristics of the cars, and the tire pressure issue continues to make me uneasy. Based on the responses, I’m going to keep all tires at 30PSI. Thanks again from an old motorist who would like to see the 29 Model A return along with its high pressure tires.


#10

Solutions to math problems are copyright protected? I’m calling bogus on that one.


#11

“Simply follow the car manufacturer’s advice, and if you are so inclined, add 2 or 3 lbs to those numbers.”

You can’t do both. Simple as that.

Max pressure in the Alaska and max pressure in Arizona. Same or different? Discuss.