245/45/18s, correct air pressure is....
08-10-2008, 01:19 PM
#5
Re: Autocross - I used to run 38 rear, 36 front when tires are heated up.
did you have different tire pressure because the front became hotter and/or just to give it a little less understeer?
08-10-2008, 03:05 PM
#6
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On Track: 47 psi hot all around ...
It's <b>very</b> track dependent, but to get there I had to start with
...........Left .. Right
Front ... 36 .... 40
Rear .... 40 .... 43<ul><li><a href="https://forums.audiworld.com/racing/msgs/28103.phtml">Track Tire Pressures</a></li></ul>
...........Left .. Right
Front ... 36 .... 40
Rear .... 40 .... 43<ul><li><a href="https://forums.audiworld.com/racing/msgs/28103.phtml">Track Tire Pressures</a></li></ul>
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08-10-2008, 03:08 PM
#8
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No one can give you a correct answer (only approximations) because every tire is different
Therefore, look it up on the website of the tire-manufacturer.
Continental, Goodyear and Dunlop etc. have sites where you can input your specific car-model and tire-model and it will tell you the correct pressure.
Factors like axle-load of the vehicle, the load-index (and other properties) of the tire etc. determine the pressure.
This answer may sound lame but it is the only correct one. What others have in their tires is useless info for you if you don't have the exact same car model (axle-load) and tire-model as the person giving the advice. etc. etc.
People are trying to be helpfull and that's great but they often don't realize that they are not able to give you a correct answer. They can only give you an approximation.
It is important that the shape of the tire is according to the manufacturers specs.
That is why the correct pressure is so important.
The shape of the walls and the running-surface and so on defines the handling-, braking-, steering- and water-flow-off characteristics to name a few.
Ps. tire-pressure should only be measured when they are really cold. Like the next morning after cooling down the whole night.
If you need to fill them up while they are warm, add 2,5 psi to the "cold"-pressure value for your tire/car combo.
If the tires are hot (driven hard or very warm weather), add 4 psi.
Ps. i've made quite a study of this subject. I was surpised how many factors come in to play.
A tire that is pumped-up to high will have a somewhat convex shaped contact-surface. The tire will wear faster and braking-distance is less.
When the pressure is a bit too low, the tire gets hotter, steering is less responsive, fuel-economy is impacted slightly (less that most people think) and so on.
Honestly, ask you tire-manufacturer !
(via website or otherwise)
It may be an idea of generating a FAQ on audipages with the most common car en engine-models (because of the different axle-loads) en tire-models and sizes.
Continental, Goodyear and Dunlop etc. have sites where you can input your specific car-model and tire-model and it will tell you the correct pressure.
Factors like axle-load of the vehicle, the load-index (and other properties) of the tire etc. determine the pressure.
This answer may sound lame but it is the only correct one. What others have in their tires is useless info for you if you don't have the exact same car model (axle-load) and tire-model as the person giving the advice. etc. etc.
People are trying to be helpfull and that's great but they often don't realize that they are not able to give you a correct answer. They can only give you an approximation.
It is important that the shape of the tire is according to the manufacturers specs.
That is why the correct pressure is so important.
The shape of the walls and the running-surface and so on defines the handling-, braking-, steering- and water-flow-off characteristics to name a few.
Ps. tire-pressure should only be measured when they are really cold. Like the next morning after cooling down the whole night.
If you need to fill them up while they are warm, add 2,5 psi to the "cold"-pressure value for your tire/car combo.
If the tires are hot (driven hard or very warm weather), add 4 psi.
Ps. i've made quite a study of this subject. I was surpised how many factors come in to play.
A tire that is pumped-up to high will have a somewhat convex shaped contact-surface. The tire will wear faster and braking-distance is less.
When the pressure is a bit too low, the tire gets hotter, steering is less responsive, fuel-economy is impacted slightly (less that most people think) and so on.
Honestly, ask you tire-manufacturer !
(via website or otherwise)
It may be an idea of generating a FAQ on audipages with the most common car en engine-models (because of the different axle-loads) en tire-models and sizes.
08-11-2008, 12:46 AM
#10
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Wouldn't a wider tire w/stiffer sidewall need _less_ air pressure? i.e. spare takes 60...
Tire air pressure has to do with the weight of the load and the surface area of the tire. A heavier car needs a bigger tire, or more air pressure to support the load. I would think ugrading to a wider tire shouldn't require more pressure than the stock tire...especially if the profile is lower and the sidewalls are stiffer. I aim for the best handling and responsive steering, but while keeping the car's ride comfortable for every day driving. A friend of mine upgraded his A4 to 225/40 18's -- It handles great now...but I don't like riding in it cuz it rides too hard...it sort of reminds me of riding in an old Z28. I think he has the pressure cranked up too high. Just my 30-32 cents. ;-)