Tire Pressure?

[Smith1000]

When you buy new tires, do you use the tire pressure on the tire, or the tire pressure specified for the vehicle? I usually just use the pressure recommended for the vehicle, which is 32, per the door; however, I just bought some Yokahamas that say the max pressure is 51 psi. These are passenger tires. I have about 40 pounds in them currently.

[MagicRat]

For average vehicle loads, go by the pressure on the door sticker.

The pressure shown on the tire sidewall is the MAXIMUM pressure that tire can take. You only use this if you have the MAXIMUM allowable weight on the tire.

This is written on the tire... it may say something like "MAX LOAD 1800 LBS AT 51 PSI"
This means that you only use 51 psi when you know you are carrying the maximum load on that one tire.
As the load decreases, tire pressure should also be decreased to maintain proper ride, handling and wear characteristics.

So, GM has figured out that 32 psi will be provide good ride, handling and wear for your car, when it has an average load. If you load the heck out of the car, ie 5 people and lots of luggage, it makes sense to bump-up the pressure a bit, to, approx. 40 psi. But chances are you will never reach the max load as rated on the tire, so you will never need 51 psi in it.

[jadatis]

It is a little diferent with the maximum pressure.
I got hold of the formula the European car-and tire-manufacturers use to make the advice stikkers for cars.
First I made the mistake to, to use the maximum pressure.
But for normal car tires ( in America P-tires ) you have to use the reference -pressure of 35 psi or 240 kPa
At that pressure the tire can bare the maximum load when riding not faster then 160 km/h \ 99miles/h. and with a camber-angle of under 2 degrees ( tires placed like this on the axle |-| and not so /-\)
For Extra load / reinforced/XL tires it is 280kPa ( 2.8 bar) and for LT tires it is mostly 450kPa but is always on the tires side-wall in the form of "max load xxxx kg (LBS) at yyy kPa( or PSI)"( cold)" .
Then that is the reference pressure to calculate with.
I made spreadsheets for it and translated a few to Englisch to go worldwide with it.
http://cid-a526e0eee092e6dc.skydrive...0tyre-pressure
in this map the spreadsheet with examples.
Questions can be asked here or on my hotmail adres with username jadatis. Then give it a title that cant be confused with spam so I wont delete it.

[Ralph123]

The correct tire pressure is the pressure that will make your tires wear evenly. The pressure recommended on the car will give you the smoothest ride which is what the car manufactures wants you to experience. the max pressure on the tire is a number some lawyer for the tire manufacture came up with. The pressure that will make your tires wear evenly is usually somewhere in between max and car recommended but usually just above car recommened. The important thing is to keep an eye on your tread wear. If your tires begin to wear more on the edges your tires are under inflated. If your tires begin to wear more in the center your tires are over inflated. I don't know what car you have but from the recommended car pressure you stated I would start with 35psi.

I got my last tires in May of 2005 (Goodyear 80,000 mi touring tires) and they still look almost new. Don't know how many miles are on them, I'll have to check the receipt. When I go in for my free balance and rotation the store finds it hard to believe.

My car
recommended - 30psi
max - 35psi
I use 32-33psi

Also, get a good tire guage. Not one of those stick kind

[jadatis]

Just use my spreadsheet and you will get 6 advices.
the car-manufacturer gives mostly that for what I call in the spreadsheet,
normal use and vacation use up to maximum technical speed of car.
You must see this as a minimum advice for the speed and load they are given for.
But because the actual weight is mostly lower then the loads the advices are given for you dont have to gighen up that advice.

[imidazol97]

Originally Posted by Smith1000

When you buy new tires, do you use the tire pressure on the tire, or the tire pressure specified for the vehicle? I usually just use the pressure recommended for the vehicle, which is 32, per the door; however, I just bought some Yokahamas that say the max pressure is 51 psi. These are passenger tires. I have about 40 pounds in them currently.

Depending on the brand and type of tire, I'd add 3-4 pounds over the Buick recommended pressure. Adjust them up and down slightly and you'll see a difference in the driving and feel.

[Smith1000]

Wow. This is great information. Thanks for sharing the spreadsheet. I'll have to try entering the values for an '02 Park Avenue. I reviewed the example calculations and something that stood out is that the recommended pressures for the rear of the vehicle are about 3 pounds less. The front are 38 and the rear are 35--unless there is a load, the rear then has at least as much pressure, or higher pressure than the front. This makes sense because of the engine weight. I believe I will reduce the front to about 38 and the rear to 35 and see how it does.

[MagicRat]

Originally Posted by Smith1000

I believe I will reduce the front to about 38 and the rear to 35 and see how it does.

You are correct.... unless you have a couple of hundred lbs in the back seat and trunk, the rears should be slightly less than the front.

How much weight do you carry? Imo 38/35's fine for a heavily-laden car, but if its just the driver, it's a bit too much pressure and will cause slightly-uneven tire wear. Imo 32 psi is better for lighter loads, generally speaking.

[HotZ28]

Imo 32 psi is better for lighter loads, generally speaking.

I agree, and it will improve ride quality. Most tires are designed to adsorb road imperfections through the sidewall and that feature is somewhat diminished with a higher pressure.

[Smith1000]

I generally carry very little in the trunk and nothing in the back seat. I reduced the rear to 35. The front are at about 38 or 39. The ride is great. There is one stretch of the interstate that I drive everyday where the concrete seems to cause a slight side-to-side rocking motion in the rear (for a spell). Reducing the rear pressure seemed to help this situation. Also, it was aligned last week, which helped.