Running Below Recommended Tire PSI

[tompass]

Anyone running below 33PSI? If so, what has been your experience regarding the ride and handling?

 

[Gurkha]

Anyone running below 33PSI? If so, what has been your experience regarding the ride and handling?

Running at 31 psi on the stock 18" Dunlops. Not much difference to me really. At least not the type of driving I do. Maybe slightly less impact harshness that's about it.

 

[homeofstone]

Being in management with Goodyear years ago and going through their training I am anal about tires, just to warn you. I run 32 psi with the Bridgestone Turanza Serenity tire on the Genesis. I have a tire tread depth gauage and measure across the tread in several places and adjust the pressure to get the most even wear considering rotation from front to back etc. I found that 32 psi with the tries I have is best. Each tire design and brand will vary somewhat as to what the best psi will be for a car or truck. That is why you see the tire pressure stated as recommended.

 

[Mark_888]

Tire pressure is specified per car (not by tire), and required by the government to be posted on a label in the car (located in the door jamb). Now I do agree that it probably should vary somewhat by tire design, but that is not how the government regulations mandate it.

For my 2009 I initially ran 31 PSI because of the suspension issues. I had no particular problem with that. After I upgraded my suspension to 2010 specs, I went back to 33 PSI.

I recommend a digital tire pressure gauge be used to check your pressure. Even the relatively inexpensive digital ones are much more accurate than other kinds. If you are going to lower your tire pressure a few PSI, you don’t want to lower it inadvertently beyond that just because of an inaccurate gauge. The other issue is that in winter time, you will need to be diligent about checking your tire pressure since cold tire pressure is reduced by about 1 PSI for each 10 F of temperature below 70 F (basic law of chemistry regarding gases and pressure).

 

[Ernie3647]

Running at 31 psi on the stock 18" Dunlops. Not much difference to me really. At least not the type of driving I do. Maybe slightly less impact harshness that's about it.

Had my 18” tires set to 33 PSI as per specs. Took car in for routine service at my dealer. They have specific mechanics for Genesis and Equis cars I found out earlier. Spoke to the mechanic concerning recommended tire pressure. He told me they had received notice that the Genesis cars tire pressures were to be set to 31 PSI so that’s what he had set mine to. Decided to leave it and try it. Didn’t find much of a difference maybe a little better bad road composure no change in handling but I’m one of those rare people who actually like the ride of the car as is. Think I’ll keep it at 31 PSI.

 

[tompass]

Interesting responses. I am in SC for summer and am conscience of the high day temps so I know even though I set them at 33 PSI about 2 weeks ago in NJ, the pressure is likely higher now. I will check them cold tomorrow AM and I assume that when you report a PSI it is when tire has not been run for several hours.

 

[Gurkha]

II am in SC for summer and am conscience of the high day temps so I know even though I set them at 33 PSI about 2 weeks ago in NJ, the pressure is likely higher now. I will check them cold tomorrow AM and I assume that when you report a PSI it is when tire has not been run for several hours.

As Mark_888 mentioned, tire pressure will vary based on ambient air temperature.
So yes if you set it at 33psi in a colder climate it should read higher if you read it in a warmer climate, all else being equal of course.
When I measure using a digital gauge, it's always when the car has not been driven for many hours.
I've also read that the sunny side of a car can influence it a bit. Morning before driving off is best.

 

[tompass]

Gotcha.

 

[Mark_888]

Had my 18” tires set to 33 PSI as per specs. Took car in for routine service at my dealer. They have specific mechanics for Genesis and Equis cars I found out earlier. Spoke to the mechanic concerning recommended tire pressure. He told me they had received notice that the Genesis cars tire pressures were to be set to 31 PSI so that’s what he had set mine to. Decided to leave it and try it. Didn’t find much of a difference maybe a little better bad road composure no change in handling but I’m one of those rare people who actually like the ride of the car as is. Think I’ll keep it at 31 PSI.

"Notice"? Yeah, they received notice from the sales people to set tire pressure to 31 so customers would not complain about the ride. There is no official notice from Hyundai (unless someone cares to show us the TSB).

My suspicion is that a lot of demo cars are set low also, so that is one reason some people are a bit surprised about the ride when they drive home from the dealer in their new car.

 

[robthoke]

I don't notice any difference in the manner's of the car between 31psi and 33psi, so I keep my tires at 33. Car is kept garaged and usually when it's brought out it hits the highway. I am 2 miles from I-75. Tomorrow it goes to Lake City, Fl which is approx 56 miles from home.

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[X-racer]

I took delivery on my 2011 Genesis 4.6 a couple of weeks ago and was surprised to discover that my tire press was set at 38PSI on every tire from the dealer! I mentioned this to my neighbor who knew of someone else who bought a Genesis in a different state and his tires were also set at 38PSI. Not sure why they would do this other than to make sure customers make the fuel mileage numbers at the expense of the ride and early tire wear. Over inflated tires will begin to wear in the center of the tread. I dropped the pressure to 33PSI and noted an immediate improvement in ride quality. I'm not sure I would want to go below 33PSI though as under inflated tires will tend to show wear at the outside portion of the tread. Genesis tires are filled with nitrogen as opposed to air. Heat buildup has little effect on nitrogen so the tire holds a more constant pressure on long trips whereas an air filled tire would build up additional pressure because air molecules grow further apart when heat is applied thus increasing pressure. I don't think you can go wrong sticking with the recommended tire pressure called out on the data sticker located on the driver's door jam and servicing tires with nitrogen when needed.

 

[Mark_888]

I took delivery on my 2011 Genesis 4.6 a couple of weeks ago and was surprised to discover that my tire press was set at 38PSI on every tire from the dealer! I mentioned this to my neighbor who knew of someone else who bought a Genesis in a different state and his tires were also set at 38PSI. Not sure why they would do this other than to make sure customers make the fuel mileage numbers at the expense of the ride and early tire wear. Over inflated tires will begin to wear in the center of the tread. I dropped the pressure to 33PSI and noted an immediate improvement in ride quality. I'm not sure I would want to go below 33PSI though as under inflated tires will tend to show wear at the outside portion of the tread. Genesis tires are filled with nitrogen as opposed to air. Heat buildup has little effect on nitrogen so the tire holds a more constant pressure on long trips whereas an air filled tire would build up additional pressure because air molecules grow further apart when heat is applied thus increasing pressure. I don't think you can go wrong sticking with the recommended tire pressure called out on the data sticker located on the driver's door jam and servicing tires with nitrogen when needed.

Cars shipped from overseas are usually inflated to air pressure way over the recommended pressure. A lot of dealers are too lazy/cheap to set it correctly during dealer prep. Hyundai would have had to use 33 PSI during EPA fuel tests, because those are the published numbers on the driver’s door jamb.

The reason why nitrogen holds pressure in a tire better than air (in theory), is that nitrogen molecules are larger than oxygen, so it is harder for them to escape from the microscopic leaks in the tire (along the rim, etc). Another advantage is that because nitrogen (unlike oxygen) does not hold moisture; there is less chance of corrosion to parts like the TPM or degradation to the tire itself due to moisture.

All "ideal" gases expand at the same rate when heated. However, if there is any moisture in the air (in the O2 portion of the air) then air is no longer an ideal gas. So, because pure nitrogen is dry (does not hold moisture) the degree of expansion under heat is more predictable with 100% nitrogen (not because the nature or size of the molecules). But that degree of consistency is probably more important for race cars where precise tire pressure can be the difference between winning and crashing.