High Tire Pressure Warning

[Toms007]

I, too, am no tire expert, but Vettehead Mikey is right on with his post. Tire manufacturers make the tires for a variety of cars. The weights of those cars can vary dramatically. Depending on the load rating, they can have two tires the same size that have different pressure ratings depending on the maximum load the tire can handle.

With my pickup, for instance when I run with it empty I run the GM recommended tire pressures. Once I load it down or when I pull a trailer I add air to help carry the added load...maybe clear up to the max pressure listed on the tire, maybe something less. If I leave the higher pressure in the tire once it is unloaded, the ride becomes very uncomfortable. The auto manufacturers have done all the engineering to find what is the best pressure for the cars at a normal operating condition. I believe that the owners manuals even try to discuss these differences.

As to your reference to the bike, the only thing I can say is I don't think that the bike manufacturers do quite the same engineering for bikes as they do for autos. But, for your information, I follow the same rules. On our bikes (Schwinn) I usually have the maximum recommended pressure for the tire on mine, 50 psi (I weigh around 215) on my wife's identical bike (except the frame size is smaller) I run about 40psi (she weighs considerably less than I ).

I hope that this explanation clears up some of your questions.

 

[Vettehead Mikey]

Well I was thinking similar to a bike tire....they build the tire to handle a certain amount of pressure and you adjust it (under the max) to your preference. If you have a heavy bike and/or your a heavy person, you might add more air to insure the ride isn't to smooshy (yes, smooshy is a technical term! ). If you are light you might want less air pressure to make sure the tire can absorb bumps. You never have the bike mfg tell you how much air to put in. Because the tire manufacturer doesn't know how much a car will weigh, they just build the tire to handle up to a certain weight.

That's kinda apples and oranges. The same bike might be ridden by a 50lb kid one day and a 200lb adult the next. That's a 400% variation in load. Obviously one set tire pressure would not be suitable for both, possibly neither.

A 400% load variation is not possible in a Corvette.

 

[Hib Halverson]

Government regulation requires tire makers specify the maximum load a tire can support and the inflation pressure necessary for the tire to sustain that load. That load may or may not be the twice the car's GVW per axle as determined by the manufacturer.

For example, if a tire can carry 1100 lbs and to do that needs to be inflated to 50 psi, theoretically, the car's GVW might be 4400 lbs.

But, let's say the car weighs 3600 lbs GVW and has 1800 lbs on the each axle or 900 lbs on each tire.

The car company decides that when loaded to GVW, and to have optimal handing and braking, 34-psi in each tire is necessary to support the load. It then specifies that 34-psi is the maximum tire pressure and prints that on the B-Pillar sticker.

Now...a different tire company might use the same tire on a different vehicle with a GVW of 4400 lbs and then may list 50-psi as the max rated pressure.

 

[Toms007]

Thank you Hib, for that helpful post. I learned something there.

 

[doingMach1]

It was informative hib...thanks for the info. But that all seems to reference using the tires that come with the car, which are the ones the manufacturer did their testing with. What happens when you get different tires? Like a low profile tire, or something. What do you do in that case?

I'm not being argumentative....I'm sincerely asking.

 

[Toms007]

I would follow the car manufacturers recommendation anyway.

 

[Hib Halverson]

It was informative hib...thanks for the info. But that all seems to reference using the tires that come with the car, which are the ones the manufacturer did their testing with. What happens when you get different tires? Like a low profile tire, or something. What do you do in that case?

I'm not being argumentative....I'm sincerely asking.

Great question.

As "Toms01" says, follow GM's recomendations as listed on the B-pillar sticker.

 

[the boss]

There is information in some tire catalog that say ''when changing tire size, take the oem spec and add 3 psi''. I have tried this over the years whit some good and bad result. This statement does not take consideration for the number of ply, the speed rating, the way the car is aligned, if it is an extra load tire, the temperature and obviously how it will driven. There is some charts that exist to tell you how much psi a tire of a specific size and numbers of ply need to hold a certain weight but they are hard to find mostly because these info are usually for truck and trailers issue. Hib is right about the oem spec, for two different brand whit similar structure, the pressure that need to be use is the oem spec. If you replace your tires whit the same size but whit a stronger or ligther structure you may have to adjust pressure but the difference will not be very big (2 to 4 psi approx), the starting point being the oem spec and measuring your tires whit a depth gage regularly is often the only way to know if your tires worn evenly. On tire sidewall, many manufacturer will put a max psi, read carefully, it is often a max pressure to set the tire on the wheel, not to drive the car.

 

[Vettehead Mikey]

It was informative hib...thanks for the info. But that all seems to reference using the tires that come with the car, which are the ones the manufacturer did their testing with. What happens when you get different tires? Like a low profile tire, or something. What do you do in that case?

I'm not being argumentative....I'm sincerely asking.

This would also mean that the diameter of the tire has changed considerably throwing the speedometer and odometer off. The car height and ground clearance would also be affected. Low profile tires also may have much stiffer sidewalls which will change handling and ride comfort.Tire pressure is just the tip of the iceberg.

 

[doingMach1]

This would also mean that the diameter of the tire has changed considerably throwing the speedometer and odometer off. The car height and ground clearance would also be affected. Low profile tires also may have much stiffer sidewalls which will change handling and ride comfort.Tire pressure is just the tip of the iceberg.

Not necessarily...it's common to buy larger diameter wheels, and compensate with a lower profile tire, and end up with the same overall diameter.

 

[Vettehead Mikey]

Not necessarily...it's common to buy larger diameter wheels, and compensate with a lower profile tire, and end up with the same overall diameter.

Obviously- but you made no mention of that in your post above, just going to a low profile tire. Changing wheel size adds another variable to the equation.

 

[doingMach1]

You're right...I wasn't clear. Either way, there is some wiggle room when it comes to air pressure, allowing for preference....with all the variables, it's never going to be an exact science.