Optimum tire pressure

[veesix]

There should be an optimum tire pressure for:
mileage
handling
comfort.
Are they the same? My 2010 v6 says to inflate at 33 psi. Is that optimum for all of these things? Do the rest of you use 33?

I recently discovered that my tires were inflated a good bit higher than the 33. I had not checked them since buying the car in January, so warmer days may have accounted for some of the increase. After I lowered the pressure, the ride improved a lot and, surprisingly, the mileage improved as well. I am still concerned that the factory number may be too low (or high) for some situations.

 

[charlesleiss]

I use 32psi all around.

 

[veesix]

I should have added these to the list:

safety
wear

What pressure is best and why?

 

[Disaster]

There should be an optimum tire pressure for:

mileage
handling
comfort
safety
wear
noise

Are they the same? My 2010 v6 says to inflate at 33 psi. Is that optimum for all of these things? Do the rest of you use 33?

I recently discovered that my tires were inflated a good bit higher than the 33. I had not checked them since buying the car in January, so warmer days may have accounted for some of the increase. After I lowered the pressure, the ride improved a lot and, surprisingly, the mileage improved as well. I am still concerned that the factory number may be too low (or high) for some situations.

There are multiple answers. Here are the factors you listed and the effect.

1. mileage: Higher pressure yields better mileage as the tires deform less and heat up less...there is less friction loss. Hypermilers will inflate their tires to the maximum allowed and high efficiency tires are made that are designed to run at higher pressures.
2. handling: It depends. Handling is generally best when kept in the proper range designed by the tire manufacturer. Slightly lower pressures, but within range can yield better tire contact...therefore improved traction, however, depending on the design, the lower pressure might cause more sidewall rollover during cornering.
3. comfort: Tires are one of the springs in the system and going softer softens the ride.
4. safety: Tire pressure too low can cause overheating and rollover and generally poor handling. At lower pressures you are more likely to pinch the sidewall against the rim when hitting severe bumps...which can sever the tire. Tire pressure too high can cause poor tire patch contact, lower traction and higher risk of blow outs from severe impact.
5. wear: Lower pressure generally causes more wear, from heat, and additional tire contact, but higher pressure can cause excessive wear at the center of the tire.
6. noise: Lower pressure generally causes more noise, though too high a pressure can cause tread to deform such that it causes more noise...at least initially, till it wears off.

As far as you getting better fuel economy on lower pressure that is not likely the factor. More likely your fuel mileage improved as the weather got warmer and the engine spent less time dumping fuel during the warm up stage.

Always measure tire pressures cold...before driving.

For your safety and best performance run the tires within specifications.

Run them at the high end of the specification to get better mileage and longer tread life.

Run them at the low end of the specification to get better traction and a softer ride.

 

[flyboy2]

There should be an optimum tire pressure for:
mileage
handling
comfort.
Are they the same? My 2010 v6 says to inflate at 33 psi. Is that optimum for all of these things? Do the rest of you use 33?

I recently discovered that my tires were inflated a good bit higher than the 33. I had not checked them since buying the car in January, so warmer days may have accounted for some of the increase. After I lowered the pressure, the ride improved a lot and, surprisingly, the mileage improved as well. I am still concerned that the factory number may be too low (or high) for some situations.

I worry about that factory number too and have spend many a sleepless nights. Why do they mess with us?!!

 

[BacktoHyundaibychoice]

There should be an optimum tire pressure for:
mileage
handling
comfort.
Are they the same? My 2010 v6 says to inflate at 33 psi. Is that optimum for all of these things? Do the rest of you use 33?

I recently discovered that my tires were inflated a good bit higher than the 33. I had not checked them since buying the car in January, so warmer days may have accounted for some of the increase. After I lowered the pressure, the ride improved a lot and, surprisingly, the mileage improved as well. I am still concerned that the factory number may be too low (or high) for some situations.

I know that opinions are as plentiful as members here, but is there a reason why you don't trust Hyundai when they say 33 PSI is best for normal loads? Isn't 33 PSI what they consider optimal for the parts and functions they've assembled?

 

[BacktoHyundaibychoice]

And if you want to read what others are doing, let "search" be your friend:

http://genesisowners.com/hyundai-genesis-forum/showthread.php?t=3033&highlight=tire+pressure

 

[veesix]

Backto: Thanks for the link. It looks like people are using a wide range of pressures. As for not trusting Hyundai, that isn't the issue. I listed 5 items that might have optimal pressures. If the optimum points are all the same and are all 33, then there is nothing to worry about. Hyundai didn't say how they determined the 33. If it was for ride and not wear, there might be a reason to use a different pressure.

Disaster: Do you happen to know the optimum pressures for the six conditions? My mileage was measured on six trips of 230 miles each. I doubt that warm-up matters for those long trips. When I reduced the pressure to under 35, my mileage increased by 5 mpg.

 

[Sayantsi]

Optimal tire pressures change depending on what you want. The numbers Hyundai provide are for a set tire size under its best mixed-use conditions. You need to decide what is most important to you, and then go with the optimal pressure for that. On a car like the Genesis, I would go for comfort and handling over anything else - probably 32-33 psi cold, which will hit 35-38 psi hot.

When you run higher pressures, you are essentially hardening the tire and reducing the contact patch, so less roll resistance and shock absorption. You'd do this for higher mpg at the expense of comfort and handling. When you run lower pressures, you're increasing the contact patch, so increased grip for cornering and more shock absorption comfort are available.

 

[Mark_888]

The tire inflation PSI that people prefer usually varies, in a similar way that there are different preferences for tires. Everyone has different priorities. Some people think a good tire is one that has excellent tread life, while others favor tires that provide excellent handling/breaking. All other things being equal, these will usually be different tires.

Likewise, a slightly higher tire inflation PSI may provide better tread life and better MPG, but make the ride harsher. It is up to you to decide which pressure to use, but I would not deviate from the manufacturer recommendations (33 PSI in the case of the Genesis) by more than 2 PSI either way, and I suspect the recommend pressure is already on the high side to achieve better fuel economy.

As noted elsewhere, tires are often seriously overinflated at the auto assembly plant (especially for foreign cars that have to be shipped to the US) and are supposed to be lowered to 33 PSI during dealer prep.

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[Mark_888]

Hyundai didn't say how they determined the 33. If it was for ride and not wear, there might be a reason to use a different pressure.

My guess is it was chosen by Hyundai to be slightly on the high side for better fuel economy.

 

[DavidNJ]

The best tire pressure will vary by load in the car, ambient temperature, tire model, shock absorber wear, etc.

While too much pressure can sharpen steering and increase mileage, it can also cause premature tire where.

The right setting ends up setting the spring rate and damping of the tire to work best with the suspension settings on the car.

I don't have a Genesis yet, but to find out you should make adjustments in 2 to 4 psi increments and run it for a few hundred miles. It should be pretty obvious.

For contact patch the racers have lots of tricks. Old school is taking tire temperatures across the thread. In testing, some data acquisition systems use IR sensors to measure it dynamically.

Another new technique is to put very shallow (1/32" or so) groove laterally across the tread. The wear pattern shows if the tire is properly inflated. The tools is available as a drill attachment.
http://www.ovalresearch.com/tirescribe.htm

 

[HeavyG]

I've noticed in most of the cars and trucks that I've owned that the placarded tire pressures are usually a few PSI lower than the max tire pressure listed on the tire itself.

I don't know if it's just the car companies generally being conservative or the lawyers mandating it.

 

[Mark_888]

I've noticed in most of the cars and trucks that I've owned that the placarded tire pressures are usually a few PSI lower than the max tire pressure listed on the tire itself.

I don't know if it's just the car companies generally being conservative or the lawyers mandating it.

Are you kidding me? Max tire pressure is just that, maximum. You should not be using max tire pressure. Do you drive your car at max speed or max RPM? Do you have the max load in your car (passenger and cargo weight)?

Usually the recommended tire pressure by the auto manufacturer includes factors such as the suspension of the car and other considerations that the tire manufacturer does not know about, and is usually more than a "few" PSI lower than "max" in my experience (especially for premium tires).

 

[Sayantsi]

Yeah, don't use maximum unless you're towing, and then be wary, right?

Also, keep in mind, tire psi is just one part of ride, handling, and mpg. The other is the tire you choose. We all get OEM, and these aret typically chosen for low price and passable mpg and comfort, but when you buy your first set of tires, you need to think about what you want out of the car and what tire will work to that end.

Want good mpg? Get a hard compound, high mileage tire with low roll resistance. Be wary though, these tires have terrible grip and ride quality.

Want performance? Get a softer-silicate compound with aggressive tread, but these tires are softer and will not last as long. These are usually called performance or Summer tires. (20k mi life is typical)

Want decent life and decent handling and comfort, look for touring and GT tires. These offer a longer life, but not as long as some, and decent traction, but not as good as performance tires. These can be summer or all seasons, and are probably the best option since you don't want a tire tread to last too long - tires will also heat cycle to death and dry rot over time.

Summer tires are the best for traction but can have short lives and become less effective below 40°. Winter tires are best below 40°. All seasons are a compromise - less effective in all conditions, but you don't need two sets of tires.

Personally, mpg is the last concern I have when buying a tire, I value traction and comfort first, then decent life span.

 

[Sal Collaziano]

There is a TIRE forum.
Please...
Post topics in the right spot...

 

[Disaster]

Here is an article from TireRack.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1

"Disadvantages of Underinflation

An underinflated tire can't maintain its shape and becomes flatter than intended while in contact with the road. If a vehicle's tires are underinflated by only 6 psi it could weaken the tire's internal structure and eventually lead to tire failure. Lower inflation pressures will allow more deflection as the tire rolls. This will build up more internal heat, increase rolling resistance (causing a reduction in fuel economy of up to 5%) and reduce the tire's tread life by as much as 25% while increasing the probability of irregular treadwear. Drivers would also find a noteworthy loss of steering precision and cornering stability. While 6 psi doesn't seem excessively low, it typically represents about 20% of a passenger car tire's recommended pressure.

Disadvantages of Overinflation

An overinflated tire is stiff and unyielding and the size of its footprint in contact with the road is reduced. If a vehicle's tires are overinflated by 6 psi, they could be damaged more easily when encountering potholes or debris in the road, as well as experience irregular tread wear. Higher inflated tires cannot isolate road irregularities as well causing the vehicle to ride harsher and transmit more noise into its interior. However, higher inflation pressures reduce rolling resistance slightly and typically provide a slight improvement in steering response and cornering stability. This is why participants who use street tires in autocrosses, track events and road races run higher than normal inflation pressures."

 

[veesix]

For contact patch the racers have lots of tricks. Old school is taking tire temperatures across the thread. In testing, some data acquisition systems use IR sensors to measure it dynamically.

The temperature idea is a good one. The infrared devices used by HVAC techs might work well. If the temperature is even, the inflation is at least not causing too much bending outwards of the center tread. It might even be possible to run a few different pressures and look at the sidewall temperatures, as an indication of the amount of flexing the sidewall is taking.