Debunking the Tire PSI Debate: Ground vs. Lifted Weight Impact

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In summary, there is a heated debate over whether or not the pressure in a tire changes if it is on the ground attached to the car with the extra weight of the car added, or if it is suspended in the air by a car lift. Some people believe that the pressure will increase, while others believe that it will not change significantly. However, if you are worried about the increase in pressure, just simply measure the pressure in the tires after you lower the car to make sure it is not over the 39 psi.
  • #1
waca
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tire psi--heated debate

here is my question:

does the pressure (psi) in a tire change if it is on the ground attached to the car with the extra weight of the car added, or if it is suspended in the air by a car lift?

my roommates and i are having a heated debate on this topic and any advice/input would be appreciated
 
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  • #2


Yes. When there is a load on the tires, they will compress, and their pressure will go up.
 
  • #3


Yes it does - in fact you can use the tire pressure and the area of the contact patch to measure the weight of the car.
 
  • #4


thank you very much for your responses, do you know if the change would be significant enough to worry about?

for instance if i were to fill my tire up to 35 psi on a lift would the increased pressure of a 2k lb car spread over 4 tires pressing down on anyone (or all) of the tires be something to be concerned with?

note the manufacture recommends that the tire be filled to 35 but anything over 39 is considered dangerous
 
  • #5


Load/increased load is taken into account, which is why tire types should be matched to the vehicle type/vehicle use.
2 different tire types with the same psi spec can have very different load ratings due to differences in tire construction.
 
  • #6


waca said:
thank you very much for your responses, do you know if the change would be significant enough to worry about?

for instance if i were to fill my tire up to 35 psi on a lift would the increased pressure of a 2k lb car spread over 4 tires pressing down on anyone (or all) of the tires be something to be concerned with?

note the manufacture recommends that the tire be filled to 35 but anything over 39 is considered dangerous

Probably not enough to worry about. If you are worried however, just simply measure the pressure in the tires after you lower the car to make sure it is not over the 39 psi.

CS
 
  • #7


in fact you can use the tire pressure and the area of the contact patch to measure the weight of the car

Oddly, I don't think that actually works: A tire can be 35psi or 25psi and yet appear to have the about same surface contact area...I guess the stiffness of the tire masks what should be a valid approach??
 
  • #8


It's deceptive - remember the tire is spreading out in 2 directions, so a 20% increase in the length of the flat spot is a 50% increase in area.
For most vehicles at normal pressures the tire mechanical stiffness isn't a factor.
 
  • #9


again thank you for all your responses, i plan on doing a test on this in a local shop with an electronic gauge, if anyone is interested in the results i will post them here
 
  • #10


Let me know results..i suspect you will not have a gage accurate enuff to read any change.I never saw any and my gage is analog , has 1/2 lbs. resolution. what is purpose of your question?
 

What is tire psi and why is it important for heated debates?

Tire psi stands for tire pressure, which is a measure of the amount of air inside a tire. It is important for heated debates because it directly affects the handling, performance, and safety of a vehicle.

What is the recommended tire psi?

The recommended tire psi varies depending on the type of vehicle and the manufacturer's specifications. It is usually listed in the owner's manual or on a sticker inside the driver's side door jamb. It is important to follow the recommended psi for optimal vehicle performance.

What happens if the tire psi is too high or too low?

If the tire psi is too high, the tire will be more rigid and have less contact with the road, resulting in a rougher ride and potential damage to the tire. If the tire psi is too low, the tire will be more flexible and have more contact with the road, resulting in increased friction and potential overheating.

How often should tire psi be checked?

Tire psi should be checked at least once a month, as well as before long trips or when there are significant changes in temperature. It is also important to check the psi of the spare tire.

Can tire psi affect fuel efficiency?

Yes, tire psi can greatly affect fuel efficiency. Underinflated tires have more rolling resistance, which means the engine has to work harder and use more fuel to overcome it. Keeping tires at the proper psi can improve fuel efficiency and save money in the long run.

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