Checking tire pressure

[O.J.Sakuma]

Ok, I get that. We need to park it and let it sit to get a good reading.

Does outside temperature make any difference? My car sits in my home garage. It could be 110 degrees in there like yesterday (Sunday) afternoon. And it'll hold 100 till probably past midnight.

If my car has been parked in my garage all day, when should I take a reading to be the most accurate?

[Go Goody]

When the tires are in the shade. And as cool as possible prior to driving.

[bugzsrt]

Just check them immediately after you start the car in the morning. Ambient temps wont make any difference.

[SF18C]

I know that this may sound unconventional to most and I will not try to persuade anyone to my way of thinking.

A few years ago (okay, it was more like 10) I was detailed as a Personal Security Detachment Driver. One of the training events for this was attendance to the Bill Scott School of Racing for advanced offensive driving techniques. There, we were taught about some of the mechanical aspects hard advanced driving. One of the things we were told to do, and did so several times throughout the training cycles, were to check the pressure of the tires while HOT. Tires heat up during use, hot air expands, expanding air increases the pressure; we all know this. As I was instructed, a tire at its upper limit cold will be “over” inflated after several hours of hard driving. An overinflated tire will react harder on impact and will loss grip when pushed hard. We would log these temps both hot and cold and after changing tires we would be able to correctly fill the cold tires to the correct PSI so they would not be over inflated after abusing them for a few hours! We changed tires 2 or 3 times a day…oh yeah brake pads were usually changed every night!

Now the reality is what is the difference between hot and cold temps on air pressure? Not really enough to effect modern tires used for everyday driving.

[NOTSURE]

Great post thankyou for this info...

Originally Posted by SF18C

I know that this may sound unconventional to most and I will not try to persuade anyone to my way of thinking.

A few years ago (okay, it was more like 10) I was detailed as a Personal Security Detachment Driver. One of the training events for this was attendance to the Bill Scott School of Racing for advanced offensive driving techniques. There, we were taught about some of the mechanical aspects hard advanced driving. One of the things we were told to do, and did so several times throughout the training cycles, were to check the pressure of the tires while HOT. Tires heat up during use, hot air expands, expanding air increases the pressure; we all know this. As I was instructed, a tire at its upper limit cold will be “over” inflated after several hours of hard driving. An overinflated tire will react harder on impact and will loss grip when pushed hard. We would log these temps both hot and cold and after changing tires we would be able to correctly fill the cold tires to the correct PSI so they would not be over inflated after abusing them for a few hours! We changed tires 2 or 3 times a day…oh yeah brake pads were usually changed every night!

Now the reality is what is the difference between hot and cold temps on air pressure? Not really enough to effect modern tires used for everyday driving.

[O.J.Sakuma]

One thing I always wondered. What about aftermarket wheels/tires?

Let's say I got the V6 Challenger with 17" wheels. I want to go 20" aftermarket. How would I know what psi it should be? Do I ask SRT guys since they got 20" wheels that are OEM?

[SF18C]

Originally Posted by O.J.Sakuma

One thing I always wondered. What about aftermarket wheels/tires?

Let's say I got the V6 Challenger with 17" wheels. I want to go 20" aftermarket. How would I know what psi it should be? Do I ask SRT guys since they got 20" wheels that are OEM?

If they are a different size and tire rating, consult the tire maker or the service center that put them on. If the tires are a direct replacement (size and speed rating), the tire pressure should be the same recommended pressure. But the simple answer is that the pressure you should use should create the same load carrying capacity as the vehicle manufacturer specified. Tires are primarily about carrying the load. The pressure shown on the tire is the MAXIMUM pressure the tire can safely hold. But you don't always need the maximum, and it's not a good idea to always have it filled to the maximum.