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I'm still waiting for turkeydance's - and your - definition of it.
Upping the pressure a bit improves handling by decreasing sidewall flex and the resulting tread lift on the inside of the tire under cornering, making the tires more responsive and lets the tread do more and better work.
But there is a point at which you are overinflating the tires for the load and will ride mostly on the center of the tread wearing out your tires faster in the center. And of course it rides harsher as there is little sidewall flex to cushion the ride.
The max pressure on the sidewall of the tire is for the max load that tire will be carrying, which tends to be about 1300-1600lbs per tire for typical passenger car tires, or 5000+ lbs per 4 tires. If your car and it's passengers/cargo don't weigh 5000+lbs then don't inflate to max. Light truck tires run higher pressures, especially when you get to load range E tires like I have on my tow rig, which are designed to be run at 60+psi to carry the loads that the truck is designed to carry.
The tires which originally came on my car were Michelins, with a maximum PSI of 51. Later I replaced them with a different brand, which had a maximum of 44 PSI. And there is another common maximum tire pressure for this size tire, 35 PSI, though I've never had a set of tires with that spec.
It seems unreasonable that the same inflation level would be appropriate for all three types of tires. After years of experimentation I've settled on inflating to about 85% of the maximum PSI for the optimum balance of handling, fuel economy, and tread wear. This works well whether I'm running Pirellis in the summer or Blizzaks in the winter.
Location: Removing a snake out of the neighbor's washing machine
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Quote:
Originally Posted by J Baustian
The tires which originally came on my car were Michelins, with a maximum PSI of 51. Later I replaced them with a different brand, which had a maximum of 44 PSI. And there is another common maximum tire pressure for this size tire, 35 PSI, though I've never had a set of tires with that spec.
It seems unreasonable that the same inflation level would be appropriate for all three types of tires. After years of experimentation I've settled on inflating to about 85% of the maximum PSI for the optimum balance of handling, fuel economy, and tread wear. This works well whether I'm running Pirellis in the summer or Blizzaks in the winter.
Both the tires Max Cold pressure and the recommended cold pressure for my 1981 Buick Century = 35psi. Of course, that was a long time ago! lol
85% of 44psi = 37psi. A little high and quite rough for my particular car.
I usually look at the specs on both the car and the tires and then feel things out. Usually going to the max on the tire if the ride and handling is decent, better MPG.
Location: The Circle City. Sometimes NE of Bagdad.
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Quote:
Originally Posted by dkf747
If we are not loading our cars to the maximum load-carrying capacity very often, then putting a few extra pounds in the tire doesn't hurt anything, right?
Again, you're preaching to someone who already understands all of this. I never set my tire pressures anywhere near the Max. Cold pressure listed on tires.
In the vast majority of modern(post 1990s) vehicles, the vehicle manufacturer recommended tire pressures are well below the Max. Cold pressure stamped on the tires. On some light trucks, the vehicle decal pressures do = max cold psi on the tires, particularly for the load axle(the rear), but that is the exception.
Listen the whole point of my thread was to indicate that everyone, including those we trust and pay to service our cars, no longer goes by the car manufacturer recommended pressures, but inflates to what the tire max says. Which. Is. WRONG.
to a point we agree. however, with most cars i own, vintage compacts/pony cars and full size, they tend to not be sensitive to tire pressures, unless they are below 28-30psi. even then i can feel the difference between 32 and 35 psi, but then i am sensitive to what my cars are doing.
also remember that the pressures that the automakers recommend are a compromise between best handling/ride/fuel economy/tire wear. up the pressures, and ride quality goes down, but fuel economy goes up. tire wear depends on how close the rim wirth is to the design rim width of the tires. for instance the design rim width for a 225/60-15 tire is 7 inches. put that same tire on a 6 inch wide rim, and you need to lower tire pressures to get the best wear. put that tire on an 8 inch wide rim, and you have to raise the pressures. what you are trying to accomplish is having the tread be flat on the ground for best overall performance.
Location: Removing a snake out of the neighbor's washing machine
3,095 posts, read 2,040,736 times
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Quote:
Originally Posted by rbohm
to a point we agree. however, with most cars i own, vintage compacts/pony cars and full size, they tend to not be sensitive to tire pressures, unless they are below 28-30psi. even then i can feel the difference between 32 and 35 psi, but then i am sensitive to what my cars are doing.
also remember that the pressures that the automakers recommend are a compromise between best handling/ride/fuel economy/tire wear. up the pressures, and ride quality goes down, but fuel economy goes up. tire wear depends on how close the rim wirth is to the design rim width of the tires. for instance the design rim width for a 225/60-15 tire is 7 inches. put that same tire on a 6 inch wide rim, and you need to lower tire pressures to get the best wear. put that tire on an 8 inch wide rim, and you have to raise the pressures. what you are trying to accomplish is having the tread be flat on the ground for best overall performance.
That is true: Wider wheels and tires, especially lower profiles, generally require higher PSI for even road contact across treads. Something to consider if one is plus-sizing from, say, 65-series narrow tires to 55- or lower series profiles and bigger wheels. The suspension might be tuned stiffer, for taller, softer tires, and could yield a rougher ride with wider wheels and low profile tires.
Is it a better way to manage pressure change from cold to hot and limit the exposure of the TPMS sensors to moisture in modern vehicles. Yes.
If it's worth the cost or not is up to you but, it is not a scam.
Neither really.
Gas constant of nitrogen is 9 J/Kg K higher than air.
However the molar mass of Nitrogen gas is 28g, and air is 28.9g.
pV =nRT
p = Pressure
V = Volume
n = number of moles
R = gas constant
T = Temperature in Kelvins
Presuming both tires are the same volume, and at stp.
Pressure is proportional to the number of moles (particles) of the substance and its gas constant.
Thus the gain of 9J/Kg K is offset by the increased numbers of particles needed for a given volume and temperature. In fact the 9 J/Kg K nitrogen gains is against 287 J/Kg K so nitrogen only gains approx 4% versus air in heat absorption, but air loses 4% on quantity needed.
Next to moisture, what happens to water vapor on air compression?
Ever wonder why the drain plug on a compressor squirts water?
The amount of water vapor in compressed air is negligible, certainly less worrisome than a TPMS sensor sitting on a shelf at your tire store. That's a red herring (although you need some insight to realize it).
So yes it's a scam, though I'm not even sure the suppliers know it's a scam.
Please note that most shops that use expensive air tools have a dryer/filter on the outlet of the compressor.
Nobody wants water/oil/particulates being fed to their air tools!
If they service tires, they have a very good air dryer. Moisture in a tubeless tire can cause wheel corrosion, which can, over time, lead to wheel failure. In the "I'll sue!" society of today, no shop can afford that possibility.
Dry air, or dry nitrogen? Which is best? Damifino. I do know I will not pay to have my tires inflated with dry nitrogen when dry air is readily available, free.
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