Correct Tire Pressure
10-11-2004, 03:36 PM
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Correct Tire Pressure
I have a 1999 Audi A6 with 205/55R16 tires. Trying to determine the correct tire pressure.
I have looked everywhere on this car for the sticker with that information; it just seems to be missing completely. It's usually on either the passenger or driver door or door pillar, but not on my Audi.
Would anyone have a car like mine with the same tires who can tell me what the pressure should be.
Thanks, krs
I have looked everywhere on this car for the sticker with that information; it just seems to be missing completely. It's usually on either the passenger or driver door or door pillar, but not on my Audi.
Would anyone have a car like mine with the same tires who can tell me what the pressure should be.
Thanks, krs
10-11-2004, 04:27 PM
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Did someone say tire pressure?
Road & Track has had several articles on the subject lately. The second, given your handle, might come in handy.
Technical Correspondence -- September 2004
Proper Pressures
Edited by Tom Wilson
32, The Magic Number
I'm looking for information concerning manufacturer's recommended tire pressures. My local national brand tire store says they just put 35 psi in all the tires of passenger cars, and don't think much of the recommended numbers. My car uses 32 front and 26 rear, and I believe 35 at both ends would enhance the inherent understeer. I have to adjust when I get home, and usually bump both ends up 2 psi. How do I know what is best?
Paul Nied
Vero Beach, Florida
Tire wear and the seat of your pants are the best inflation guides. It is likely 35 psi all around will reduce understeer, and you may find your car's dry-weather handling better with those pressures. Wet-pavement handling may not be as good because the car would have even more neutral handling in the wet with 35 psi all around.
Understand that high inflation pressures often feel great due to more rapid steering response, but ultimate grip is often not enhanced (it will fall off at some point). Tire wear is uneven at high pressures too.
All tire pressure recommendations are inherently general because it is impossible for the engineers to know your precise conditions, driving style and comfort quotient, so expect to fiddle with pressures until they feel right to you. Of course, you must remain within the maximum pressure specified on the tire's sidewall.
We've researched this question many times, and a surprising number of tire shops use 32 psi all around because they find it the best compromise of handling, tire wear and ride harshness, and it saves them from looking up the numbers. We've had the same advice from major tire manufacturers too.
------------------------------------------
Cold Enough for Your Tires?
Once a month I check our cars' tires. At last check, the pressure was down on all four tires on both cars. I thought that was awfully odd, until I realized it was an unusually cold day. And then I realized I didn't really understand tire pressure.
If I fill up the tires to the correct pressure in a 70-degree heated garage, would this also be the correct pressure when I take the car outside to 20 degrees? How can there be just one correct tire pressure? Why wouldn't the correct tire pressure vary with the ambient temperature?
Fred Parmenter
Medfield, Massachusetts
An excellent point, Fred. As John Rastetter at The Tire Rack explained to us, tire pressures should be set for the ambient temperature, and if adjustments are needed, the rule of thumb is 1 psi for every 10 degrees Fahrenheit.
So, if checking pressures in a 70-degree garage when the outside temperature is 20 degrees, over-inflate in the garage by 5 psi so the tires will be at their correct pressure in the 20-degree ambient air.
The same condition affects tire pressure settings in many real-world situations. For example, the afternoon is often 20 degrees warmer than morning and the sunny side of the car will have higher tire pressures than the shady side. To reduce such variables, the industry advice is to set tire pressures early, in the cool of morning before the sun has become a factor or the car is driven.
In other words, you want the tires stabilized at the coolest time of day. Then set the tire pressures as recommended.
Subsequently, should high temperatures cause higher tire pressures in the afternoon or while running across the desert, The Tire Rack says to disregard the higher pressures. Do not bleed air pressure off. The auto and tire industries have settled on cold pressures as the most accurate, and pressure advice is given with that condition in mind, and accounting for the pressure rise as the tire heats while in use or due to afternoon heating.
In fact, low tire pressures are easily the greater danger in tire life and blowout risk, much more so than higher pressures. As Rastetter put it, "I'd rather you are 5 psi high than 1 psi low."
Technical Correspondence -- September 2004
Proper Pressures
Edited by Tom Wilson
32, The Magic Number
I'm looking for information concerning manufacturer's recommended tire pressures. My local national brand tire store says they just put 35 psi in all the tires of passenger cars, and don't think much of the recommended numbers. My car uses 32 front and 26 rear, and I believe 35 at both ends would enhance the inherent understeer. I have to adjust when I get home, and usually bump both ends up 2 psi. How do I know what is best?
Paul Nied
Vero Beach, Florida
Tire wear and the seat of your pants are the best inflation guides. It is likely 35 psi all around will reduce understeer, and you may find your car's dry-weather handling better with those pressures. Wet-pavement handling may not be as good because the car would have even more neutral handling in the wet with 35 psi all around.
Understand that high inflation pressures often feel great due to more rapid steering response, but ultimate grip is often not enhanced (it will fall off at some point). Tire wear is uneven at high pressures too.
All tire pressure recommendations are inherently general because it is impossible for the engineers to know your precise conditions, driving style and comfort quotient, so expect to fiddle with pressures until they feel right to you. Of course, you must remain within the maximum pressure specified on the tire's sidewall.
We've researched this question many times, and a surprising number of tire shops use 32 psi all around because they find it the best compromise of handling, tire wear and ride harshness, and it saves them from looking up the numbers. We've had the same advice from major tire manufacturers too.
------------------------------------------
Cold Enough for Your Tires?
Once a month I check our cars' tires. At last check, the pressure was down on all four tires on both cars. I thought that was awfully odd, until I realized it was an unusually cold day. And then I realized I didn't really understand tire pressure.
If I fill up the tires to the correct pressure in a 70-degree heated garage, would this also be the correct pressure when I take the car outside to 20 degrees? How can there be just one correct tire pressure? Why wouldn't the correct tire pressure vary with the ambient temperature?
Fred Parmenter
Medfield, Massachusetts
An excellent point, Fred. As John Rastetter at The Tire Rack explained to us, tire pressures should be set for the ambient temperature, and if adjustments are needed, the rule of thumb is 1 psi for every 10 degrees Fahrenheit.
So, if checking pressures in a 70-degree garage when the outside temperature is 20 degrees, over-inflate in the garage by 5 psi so the tires will be at their correct pressure in the 20-degree ambient air.
The same condition affects tire pressure settings in many real-world situations. For example, the afternoon is often 20 degrees warmer than morning and the sunny side of the car will have higher tire pressures than the shady side. To reduce such variables, the industry advice is to set tire pressures early, in the cool of morning before the sun has become a factor or the car is driven.
In other words, you want the tires stabilized at the coolest time of day. Then set the tire pressures as recommended.
Subsequently, should high temperatures cause higher tire pressures in the afternoon or while running across the desert, The Tire Rack says to disregard the higher pressures. Do not bleed air pressure off. The auto and tire industries have settled on cold pressures as the most accurate, and pressure advice is given with that condition in mind, and accounting for the pressure rise as the tire heats while in use or due to afternoon heating.
In fact, low tire pressures are easily the greater danger in tire life and blowout risk, much more so than higher pressures. As Rastetter put it, "I'd rather you are 5 psi high than 1 psi low."
