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What pressure do you run in 265/30/20 tires?

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Old 04-15-2024, 08:49 AM
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Originally Posted by Rcsac
Thank you for your time. First of all, can you tell is this interesting test adapts to what is best for the car or for the driver style? I will reply your message later today
Generally, the inflation pressures determined above will work fine for typical daily driving, spirited driving in mountains or canyons, and lighter track duty, but you can always check scraping if you are not sure. As you get progressively more into performance-oriented driving on curves you will be placing greater lateral force on the tires, so the pressures might evolve gradually along with your driving skills. I would not sorry too much about this right now; however, if you do participate in an HPDE I would follow inflation advice from the instructors. Track speeds, lateral forces on the tires, and harder than normal braking will cause the tires to heat up more. Instructors will know the track and be able to give you some general guidelines on pressure changes. Unless you are going to a very high speed track you probably won't have to make any significant changes. Just make sure you have your chalk, pressure gauge, and a way to add some air for the return trip home.
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Old 04-15-2024, 09:07 AM
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Originally Posted by Dan99
Generally, the inflation pressures determined above will work fine for typical daily driving, spirited driving in mountains or canyons, and lighter track duty, but you can always check scraping if you are not sure. As you get progressively more into performance-oriented driving on curves you will be placing greater lateral force on the tires, so the pressures might evolve gradually along with your driving skills. I would not sorry too much about this right now; however, if you do participate in an HPDE I would follow inflation advice from the instructors. Track speeds, lateral forces on the tires, and harder than normal braking will cause the tires to heat up more. Instructors will know the track and be able to give you some general guidelines on pressure changes. Unless you are going to a very high speed track you probably won't have to make any significant changes. Just make sure you have your chalk, pressure gauge, and a way to add some air for the return trip home.
Interesting.
About my situation, i still dont understand one thing but i think I m on my understanding way😀

I mean this, for my last photo, you said i need to take a air out a bit (1/2 psi) and repeat the test, goal is top of of the triangle, but what if you drove my car, i m sure you would go to top of the triangle or maybe below and you would not need to take air out. What that mean? For the same my car we can have 2 diffrent test result, which one is best for normlal driving and for best traction and even wear ?
How can i tell is my test test good enough for best results?
Sorry for bothering and thanks a lot for trying to teach me this. Its not urgent, if you can reply for few days is also great

Last edited by Rcsac; 04-15-2024 at 09:19 AM.
Old 04-15-2024, 11:44 AM
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Originally Posted by Rcsac
Interesting.
About my situation, i still dont understand one thing but i think I m on my understanding way😀

I mean this, for my last photo, you said i need to take a air out a bit (1/2 psi) and repeat the test, goal is top of of the triangle, but what if you drove my car, i m sure you would go to top of the triangle or maybe below and you would not need to take air out. What that mean? For the same my car we can have 2 diffrent test result, which one is best for normlal driving and for best traction and even wear ?
How can i tell is my test test good enough for best results?
Sorry for bothering and thanks a lot for trying to teach me this. Its not urgent, if you can reply for few days is also great
The goal is to get even downward pressure across the entire tread surface at all times so you get 1) maximum traction available from each tire, 2) even wear across the tread surface of each tire:

* If you and I both drive your car in a straight line we will need exactly the same amount of pressure to achieve these goals. That is because the only force on the tire is acceleration and braking, and each tire needs just enough air to overcome gravity. The amount of air needed is a function of the weight distribution of your car and the specific tire you are using. Get the pressure right, and you achieve both goals when you drive in a straight line.

* Conversely, if all we do is drive in a circle, each tire will also have lateral forces (in addition to gravity) that put more load on the edges of the tires closest to the outside of the curve. In that case, you need enough air to prevent the tread surface from rolling too much. If I drive the turn faster than you, I will need slightly more air to make sure the sidewall does not roll too far, keeping the tire as flat against the road as possible.

* Since all driving involves both straight roads and turns, you have to strike a balance between these two competing air pressure requirements. Tire wear will be a combination of driving straight and turning, so you are finding a compromise pressure that, in the end, will give you even tire wear. When you have even tire wear, you have maximum traction. The sidewall scraping test does a good job of finding the right pressure for your car, tires, and how you drive.

But, as I said earlier, monitor tire wear over time to make sure you are actually getting even tire wear and make adjustments as needed.
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Old 04-15-2024, 01:11 PM
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Originally Posted by Dan99
The goal is to get even downward pressure across the entire tread surface at all times so you get 1) maximum traction available from each tire, 2) even wear across the tread surface of each tire:

* If you and I both drive your car in a straight line we will need exactly the same amount of pressure to achieve these goals. That is because the only force on the tire is acceleration and braking, and each tire needs just enough air to overcome gravity. The amount of air needed is a function of the weight distribution of your car and the specific tire you are using. Get the pressure right, and you achieve both goals when you drive in a straight line.

* Conversely, if all we do is drive in a circle, each tire will also have lateral forces (in addition to gravity) that put more load on the edges of the tires closest to the outside of the curve. In that case, you need enough air to prevent the tread surface from rolling too much. If I drive the turn faster than you, I will need slightly more air to make sure the sidewall does not roll too far, keeping the tire as flat against the road as possible.

* Since all driving involves both straight roads and turns, you have to strike a balance between these two competing air pressure requirements. Tire wear will be a combination of driving straight and turning, so you are finding a compromise pressure that, in the end, will give you even tire wear. When you have even tire wear, you have maximum traction. The sidewall scraping test does a good job of finding the right pressure for your car, tires, and how you drive.

But, as I said earlier, monitor tire wear over time to make sure you are actually getting even tire wear and make adjustments as needed.
The reason i didn't continue the test is that I wonder if what I drove was enough, so I took a short break until I hear from you.
The second reason is that my front left valve is defective, so the pressure gauge cannot read the pressure, so for testing i was used left turns only.
I can normally use gas station compresor on that valve. I didn't feel like going to the garage.
Although I didn't finish the test the next morning I measured the tire pressure(I had deflated the tire by 0.1 bar the day before) so this morning gauge showed me some strange readings, but maybe I shouldn't be surprised because it got quite cold during the night. Tomorrow morning I will return the pressure to 2.6/2.3 because 2.3/2.2 looks no so good. For few days i will repeat the test but now completely.
You sound like a professional who can teach in the classroom and on the field. Maybe you already said that and I didn't see it
Old 04-15-2024, 02:47 PM
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Originally Posted by Rcsac
The reason i didn't continue the test is that I wonder if what I drove was enough, so I took a short break until I hear from you.
The second reason is that my front left valve is defective, so the pressure gauge cannot read the pressure, so for testing i was used left turns only.
I can normally use gas station compresor on that valve. I didn't feel like going to the garage.
Although I didn't finish the test the next morning I measured the tire pressure(I had deflated the tire by 0.1 bar the day before) so this morning gauge showed me some strange readings, but maybe I shouldn't be surprised because it got quite cold during the night. Tomorrow morning I will return the pressure to 2.6/2.3 because 2.3/2.2 looks no so good. For few days i will repeat the test but now completely.
You sound like a professional who can teach in the classroom and on the field. Maybe you already said that and I didn't see it
I'm not a professional, just a sports car enthusiast for many decades. I've attended classes taught by many different professionals, and had numerous in-car instructors. I'm just passing on what I've picked up over the years and have first hand experience with. When you get into more advanced classes they dig deeper into the weeds. For example, you talk about the tire "contact patch" and how it is the only thing that controls where the car goes, as it's the only point of contact with the road. You learn that inflation, braking, accelerating and turning affect it, and step #1 is to get inflation correct because everything else is dependent on that.

Regarding driving for the scraping test, just drive corners as assertively as you feel comfortable. After all, that's how you will be using the car. You can drive as long or as short as you want, just as long as you drive long enough to scrape the chalk. You might want to go for a longer drive through curvy roads, then check the chalk when you are done. There are no hard and fast rules about this. Just go through some corners with some gusto and check the scraping. You can go through 1 or 100. Regardless, the tires will scrape and you can adjust the pressures accordingly whenever you are done driving.

Later, as your driving skills develop and you drive more aggressively, re-run the test and adjust pressures. Or, if you get a new set of tires, re-run the tests.
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Old 04-16-2024, 08:56 PM
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Originally Posted by Dan99
I'm not a professional, just a sports car enthusiast for many decades. I've attended classes taught by many different professionals, and had numerous in-car instructors. I'm just passing on what I've picked up over the years and have first hand experience with. When you get into more advanced classes they dig deeper into the weeds. For example, you talk about the tire "contact patch" and how it is the only thing that controls where the car goes, as it's the only point of contact with the road. You learn that inflation, braking, accelerating and turning affect it, and step #1 is to get inflation correct because everything else is dependent on that.

Regarding driving for the scraping test, just drive corners as assertively as you feel comfortable. After all, that's how you will be using the car. You can drive as long or as short as you want, just as long as you drive long enough to scrape the chalk. You might want to go for a longer drive through curvy roads, then check the chalk when you are done. There are no hard and fast rules about this. Just go through some corners with some gusto and check the scraping. You can go through 1 or 100. Regardless, the tires will scrape and you can adjust the pressures accordingly whenever you are done driving.


Later, as your driving skills develop and you drive more aggressively, re-run the test and adjust pressures. Or, if you get a new set of tires, re-run the tests.
So, the ideal settings you found (41/35) on the street and on the track.
What you mean when you say 1 or 100?
"Just go through some corners with some gusto and check the scraping. You can go through 1 or 100. Regardless, "
I'm not in Germany at the moment, I will definitely repeat the test and definitely drive longer around the curves than in the first test. The route was not short, but there weren't as many turns as i wanted
Old 04-17-2024, 05:58 AM
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Originally Posted by Rcsac
So, the ideal settings you found (41/35) on the street and on the track.
What you mean when you say 1 or 100?
"Just go through some corners with some gusto and check the scraping. You can go through 1 or 100. Regardless, "
I'm not in Germany at the moment, I will definitely repeat the test and definitely drive longer around the curves than in the first test. The route was not short, but there weren't as many turns as i wanted
Let's remember that this part of the tire pressure discussion started (in post #6 of this thread) when I said :
...We all use our cars differently, so I want to add some nuance to the advice above. As everyone else has said, start with the pressures in your manual for your specific combination of vehicle, wheel and tire size. That will work fine for most people. However, if you want to maximize handling, here are some links that discussed how to fine tune your tire pressures to maximize traction for the best handling in corners...
So, this discussion is aimed at getting the most traction from your tires in spirited/performance driving, but it translates very well to the street. These methods work on a track, but they also apply to going around any corner anywhere with some gusto, and they result in more traction and even tire wear on the street if done correctly. If you ever do end up on a track, some tracks place higher demands on tires and you will have to let air out as tire temperatures increase, so that your scraping remains correct; otherwise the tires will become over inflated as the heat increases significantly and you will lose traction. However, it is unlikely that this would ever happen on the street. Spirited driving in the mountains/canyons will probably never heat the tires as much as a track. So, please keep this in mind if you ever end up on a high speed track, or on any track in very hot weather. Keep an eye on your tires after each track session and adjust pressure if necessary. If you never go on a track, the pressures will work fine on the street.

My point about 41/35 was that all tires are not the same and that, if you want to get the most performance out of the tires that you have, the scraping test can help you figure out the most beneficial pressures for your combination of car, tires and wheels when you like to play in corners. 41/35 worked best with Michelin PS4S tires on my B9 RS5 Sportback, whereas 39/32 worked best on the same car with the oem Continential SportContact6 tires. So, if you want to get the most performance out of the tires that you have, you can't just assume that the pressures will remain the same from one tire to the next. That's why I said you should re-test when you get new tires, even the same brand and model tire, as manufacturers do change tire formulation from time to time.

Regarding 1 or 100, you asked how many times to run through corners. It does not matter as long as you get through a corner and apply sufficient lateral force to the tires. You could, for example, mark your tires and go for a long spirited drive in the country; or, you could just zip around a cloverleaf. The point is that you need to drive the car enough to exercise the tires in turns. That can be one turn or a hundred turns.
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Old 04-17-2024, 09:15 PM
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Originally Posted by Dan99
Let's remember that this part of the tire pressure discussion started (in post #6 of this thread) when I said :So, this discussion is aimed at getting the most traction from your tires in spirited/performance driving, but it translates very well to the street. These methods work on a track, but they also apply to going around any corner anywhere with some gusto, and they result in more traction and even tire wear on the street if done correctly. If you ever do end up on a track, some tracks place higher demands on tires and you will have to let air out as tire temperatures increase, so that your scraping remains correct; otherwise the tires will become over inflated as the heat increases significantly and you will lose traction. However, it is unlikely that this would ever happen on the street. Spirited driving in the mountains/canyons will probably never heat the tires as much as a track. So, please keep this in mind if you ever end up on a high speed track, or on any track in very hot weather. Keep an eye on your tires after each track session and adjust pressure if necessary. If you never go on a track, the pressures will work fine on the street.

My point about 41/35 was that all tires are not the same and that, if you want to get the most performance out of the tires that you have, the scraping test can help you figure out the most beneficial pressures for your combination of car, tires and wheels when you like to play in corners. 41/35 worked best with Michelin PS4S tires on my B9 RS5 Sportback, whereas 39/32 worked best on the same car with the oem Continential SportContact6 tires. So, if you want to get the most performance out of the tires that you have, you can't just assume that the pressures will remain the same from one tire to the next. That's why I said you should re-test when you get new tires, even the same brand and model tire, as manufacturers do change tire formulation from time to time.

Regarding 1 or 100, you asked how many times to run through corners. It does not matter as long as you get through a corner and apply sufficient lateral force to the tires. You could, for example, mark your tires and go for a long spirited drive in the country; or, you could just zip around a cloverleaf. The point is that you need to drive the car enough to exercise the tires in turns. That can be one turn or a hundred turns.
Thats great if we can use the same pressure for the road as well. If you maybe understand me wrong i didnt mean ro copy your 41/35 to my car, just mentioned your pressure. This pressure difrrnece between 2 diffrent tires(I assume the same dimensions) on the same car are interesting.
I will continue to play with this definitely

Old 04-17-2024, 11:44 PM
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Originally Posted by Dan99
Let's remember that this part of the tire pressure discussion started (in post #6 of this thread) when I said :So, this discussion is aimed at getting the most traction from your tires in spirited/performance driving, but it translates very well to the street. These methods work on a track, but they also apply to going around any corner anywhere with some gusto, and they result in more traction and even tire wear on the street if done correctly. If you ever do end up on a track, some tracks place higher demands on tires and you will have to let air out as tire temperatures increase, so that your scraping remains correct; otherwise the tires will become over inflated as the heat increases significantly and you will lose traction. However, it is unlikely that this would ever happen on the street. Spirited driving in the mountains/canyons will probably never heat the tires as much as a track. So, please keep this in mind if you ever end up on a high speed track, or on any track in very hot weather. Keep an eye on your tires after each track session and adjust pressure if necessary. If you never go on a track, the pressures will work fine on the street.

My point about 41/35 was that all tires are not the same and that, if you want to get the most performance out of the tires that you have, the scraping test can help you figure out the most beneficial pressures for your combination of car, tires and wheels when you like to play in corners. 41/35 worked best with Michelin PS4S tires on my B9 RS5 Sportback, whereas 39/32 worked best on the same car with the oem Continential SportContact6 tires. So, if you want to get the most performance out of the tires that you have, you can't just assume that the pressures will remain the same from one tire to the next. That's why I said you should re-test when you get new tires, even the same brand and model tire, as manufacturers do change tire formulation from time to time.

Regarding 1 or 100, you asked how many times to run through corners. It does not matter as long as you get through a corner and apply sufficient lateral force to the tires. You could, for example, mark your tires and go for a long spirited drive in the country; or, you could just zip around a cloverleaf. The point is that you need to drive the car enough to exercise the tires in turns. That can be one turn or a hundred turns.
Last year I wanted to go in a Bmw driving school, an excellent school, but they didn't have the option to drive my own car, and that's not what I wanted so i didnt go rhen
Old 04-18-2024, 05:12 AM
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Originally Posted by Rcsac
Last year I wanted to go in a Bmw driving school, an excellent school, but they didn't have the option to drive my own car, and that's not what I wanted so i didnt go rhen
Many/most HPDEs are conducted with your own car. Just shop around.

As I mentioned earlier, tire technology really digs far into the weeds as you go up the performance ladder. This video is track-specific, but it gives you some idea of how complex this topic can be. Scroll down to watch a free lesson:

https://academy.yourdatadriven.com/p...ter-your-tyres


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