help with tire air pressure

[greenasgrass]

i just got a firebird with 245/50 16" tires. the recommended tire inflation on the door is given only for the 215/55 tire. does anyone know the recommended inflation for the 245/50 16" tires?

thankss !!

[Jack]

Look on the tire itself, it will have the required pressure there. Different tires have different requirements, go with what is on the tire you have.

[V6Bob]

"Look on the tire itself, it will have the required pressure there"

Don't use that pressure. The pressure on the side of the tire is just the absolute maximum pressure the tire can take. Use it and you'll be way overinflated.

Get the tire pressure for a V8, which uses those tires. Maybe run 1-2 lbs lower in the front, because the V6 is lighter.

[TheBlackSwordsMan]

I always run 30-32 hope that helps.

[Jack]

<blockquote>quote:</font><hr>Originally posted by V6Bob:
"Look on the tire itself, it will have the required pressure there"

Don't use that pressure. The pressure on the side of the tire is just the absolute maximum pressure the tire can take. Use it and you'll be way overinflated.

Get the tire pressure for a V8, which uses those tires. Maybe run 1-2 lbs lower in the front, because the V6 is lighter.<hr></blockquote>

For the most part I agree with Bob on this, for stock tire sizes and types this is accurate. Changes in the stock size can bring on different requirements. Plus sizing requires higher inflation and different tires sizes also have different requirements. I was curious about the sidewall info. and paid a little online visit to BF Goodrich and Goodyear, both have listed on their website to follow the vehicle manufacturers pressure requirements. I wonder if this has anything to do with the massive lawsuits caused by Firestone and Ford?

On my Silverado I have some Eagle RH's which have on the sidewall 50 psi max cold, at 30 psi they are obviously low. The tire info on the placard on the door states 30 to 32 psi, the stock Tiger Paws had 32 on the sidewall. I hate confusing info. so I e-mailed Goodyear to see what psi they recommend me running the Eagles on my truck at. I know it is a truck and not a car but the same principle holds true. Also the truck has different size tires on it now.

Thanks for the heads up V6Bob I will report back with the reply from Goodyear on this to see how well they cover their tracks from a legal standpoint.

:D

[Jack]

<blockquote>quote:</font><hr>Originally posted by V6Bob:
[QB
The pressure on the side of the tire is just the absolute maximum pressure the tire can take. Use it and you'll be way overinflated.

Get the tire pressure for a V8, which uses those tires. Maybe run 1-2 lbs lower in the front, because the V6 is lighter.[/QB]<hr></blockquote>

From Goodyear..."Operating air pressure is determined by the vehicle manufacturer.

If you're using the same size tire that came as original equipment on your
vehicle, the proper air pressure is indicated on the door placard or owners
manual of your vehicle.

The air pressure indicated on the sidewall of each tire is the inflation
pressure required to carry the maximum allowable load for that tire.

Vehicle manufacturers have invested considerable time and testing to
establish an air pressure that will provide a smooth comfortable ride in
addition to an even treadwear pattern."

Not a bad answer from Goodyear, naturally they did not answer my question so I rephrased to them more specifically this time. It seems from this that your tire will not be overinflated at the sidewall pressure depending on the load in general. In our cars it will probably be overinflated at the sidewall pressure marking.

Thanks Bob, I learned something today.
[img]smile.gif[/img]

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Jack:
For the most part I agree with Bob on this, for stock tire sizes and types this is accurate. Changes in the stock size can bring on different requirements. Plus sizing requires higher inflation and different tires sizes also have different requirements.<hr></blockquote>

Jack, good questions, good research.

I think V6Bob's point was that the V8 cars come with tires this size (your new size) from the factory, so that would be a great starting point.

On any car/truck I have, I always run a minimum of 32. The pressure I like best on the current Camaro is 35. I had run 35 on a '78 T/A about 10 years ago with some aftermarket tires, and the centers would wear faster than the edges, so that was too much pressure for those tires and that car.

You can watch the tire wear, and if you get more on the edges, use more psi, and if more in the center, use less psi. Kind of a pain to have to wait for the tires to wear before you can tell though...

If you are wearing evenly, then you are most likely getting the best contact patch most of the time, which would be the main goal.
(besides not popping a tire or letting the sidewalls roll under...)

Then if you find a good base setting, and are really into cornering, you can try tweaking the pressures a little, even varying them from front to rear a little. The autocross guys will either chalk the sidewalls and see how far up the chalk rubs off, or feel the tire and see if the middle or the edges are hotter, and adjust accordingly.