Track Tac

Air pressure contemplation

H

hotelcalifornia

Member
I've really been wondering about this..since I've only used ht3s for example, that's the only tire I'm familiar with..I've had these questions about air pressure for a long time.

What I'm wondering is:

1. What is the standard air pressure for a fairly grippy 1/6 mile track?

2. What kind of pressure would someone use for an indoor track generally?

I'm just trying to figure out my philosophy about tire pressure, and what I should think about it. One thing I've been wondering for so long is if more inside prep is used to gain more grip, and lowering air also gives more grip, why wouldn't I raise air pressure and use more inside prep in order to get the same level of grip, but roll more freely?

Please help, ive been confused for a while
 
I've been into racing for over a decade but just wondering more into the technicalities. For instance what makes us just choose 5&6 in the beginning when maybe we could use 7&8...I understand the deeper parts about weight transfer and preps and setup, but I'm lacking on the intricacies of why we choose certain air pressures and how to optimize freeing up roll speed in combination with having optimal grip
 
hotelcalifornia said:
Like wouldn't I want to run as high of an air as possible? So why not just run more inside prep and higher air?
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1st ? of course you want to run as much as possible, 2nd ? more inside than current track condition will handle could not be over come by more air because you would be in the track to much because of less spring rate.
 
I just run what the faster, obviously experienced guys at the track say to run, avoiding all the chemistry and physics headaches. Havent been steered wrong yet. Im careful not to receive their input then question it.
 
I'm just saying for instance, if people generally started with 4 and 5 air and 2 ounces of prep was optimal, why couldn't I run 6 and 7 air and 4 ounces of prep? Of course there are lots of different preps too..some just add bite without softening the spring rate correct?
 
depends where we race and weather/temp conditions . on stickier tracks the pressures come up, sometimes to 7 or 8 and on tracks where we are selling our souls for bite sometimes 2 and 3 pounds. For 'fairly grippy' I would start at 4 and 5 and go from there.
For low HP motored karts (clones and Predators) I try to run as much air as I can get away with and wipe as much bite as i can get in the tires. Not softeners, BITE. For the bigger stuff my rule of thumb is to run as low as i can get without feeling the tire slowing the kart down on the straights.
 
hotelcalifornia said:
I'm just saying for instance, if people generally started with 4 and 5 air and 2 ounces of prep was optimal, why couldn't I run 6 and 7 air and 4 ounces of prep? Of course there are lots of different preps too..some just add bite without softening the spring rate correct?
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You certainly could . Provided the contact patch holds .
 
hotelcalifornia said:
I'm just saying for instance, if people generally started with 4 and 5 air and 2 ounces of prep was optimal, why couldn't I run 6 and 7 air and 4 ounces of prep? Of course there are lots of different preps too..some just add bite without softening the spring rate correct?
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Any and all internal prep will weaken spring rate, some more than others of course .
 
I wouldn't do it all with internal. You can add bite outside and go up on air -- we regularly do this on jr classes or on big momentum tracks where roll speed is everything.

Some internal is very aggressive at breaking down sidewalls, while others is not. If you're using an aggressive internal, more of it will lower the spring rate of the tire.
Increasing air pressure will always increase the spring rate of the tire. With Maxxis, 1 psi increases it very little. With Burris or similar floppy sidewall construction tires, it can make a significant difference.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
CarlsonMotorsports said:
I wouldn't do it all with internal. You can add bite outside and go up on air -- we regularly do this on jr classes or on big momentum tracks where roll speed is everything.

Some internal is very aggressive at breaking down sidewalls, while others is not. If you're using an aggressive internal, more of it will lower the spring rate of the tire.
Increasing air pressure will always increase the spring rate of the tire. With Maxxis, 1 psi increases it very little. With Burris or similar floppy sidewall construction tires, it can make a significant difference.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
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What kind of air do you generally try to run on average? Like an air that you keep set at that level, and add or remove grip in order to run the same air
 
Looks like nobody wants to say LOL. Some top Burris guys run 3.8 left 4.8 right or 4lbs L 5lbs. R. I run 7.75 in the right and 6.5 left 7 left rear.
but again on Burris. Wish I could help you with Maxxis. but your tire guy should tell you. i was waiting for this answer as well.
 
hotelcalifornia said:
What kind of air do you generally try to run on average? Like an air that you keep set at that level, and add or remove grip in order to run the same air
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There's not a one-size-fits-all answer to that question. A lot depends on the class, size of track, amount of grip, and more.
Let's throw a particular scenario out there:
Adult heavy class running @ 1/5 mi. big momentum track on Maxxis only.
Normal starting air on Maxxis would be 5# left and 6# rights, but with the bigger track and roll speed being the main objective, I'd put more bite in the tires (again primarily externally) and go up on air at least 1 psi all around. I also tend to run the LR psi the same as the right sides on our own program as I feel that the higher LR psi helps the car gain roll speed on big tracks where the car is sitting on the LR so long. Keep in mind that it carries the bulk of the scale weight.)
Keep going up on air until you lose enough side bite that you can't go any higher. I rarely see pressures above 7 or 8 psi right sides. Not saying that you can't go higher, just that our program works best with pressures no higher than that. (With soft sidewall Burris, we've been higher, but with Maxxis I'd say no.) To get enough bite back in Maxxis to run higher pressure than that, you end up with a heavy tire, which is counter=productive to increasing roll speed.
Now, as the track bites up, and you still don't lack sidebite, keep going up on air and back off of the external bite prep. When the track bites up hard, then either go to a different internal (less harsh), or a different cure time or tougher scuffed set. Then continue up on air as you can.
Now, with all that said, be careful on simply going up on air and adding bite. This tends to work alright on lighter weight & slower classes like Jr1, but you'll see your tires fall off with a lot of heavier weight and faster classes.
Again, there is no one answer for every scenario -- we're talking generalizations here.
I realize that it's not always as simple as that.
Experience - experience - experience. That's the best answer.

Hope that helps.
 
CarlsonMotorsports said:
There's not a one-size-fits-all answer to that question. A lot depends on the class, size of track, amount of grip, and more.
Let's throw a particular scenario out there:
Adult heavy class running @ 1/5 mi. big momentum track on Maxxis only.
Normal starting air on Maxxis would be 5# left and 6# rights, but with the bigger track and roll speed being the main objective, I'd put more bite in the tires (again primarily externally) and go up on air at least 1 psi all around. I also tend to run the LR psi the same as the right sides on our own program as I feel that the higher LR psi helps the car gain roll speed on big tracks where the car is sitting on the LR so long. Keep in mind that it carries the bulk of the scale weight.)
Keep going up on air until you lose enough side bite that you can't go any higher. I rarely see pressures above 7 or 8 psi right sides. Not saying that you can't go higher, just that our program works best with pressures no higher than that. (With soft sidewall Burris, we've been higher, but with Maxxis I'd say no.) To get enough bite back in Maxxis to run higher pressure than that, you end up with a heavy tire, which is counter=productive to increasing roll speed.
Now, as the track bites up, and you still don't lack sidebite, keep going up on air and back off of the external bite prep. When the track bites up hard, then either go to a different internal (less harsh), or a different cure time or tougher scuffed set. Then continue up on air as you can.
Now, with all that said, be careful on simply going up on air and adding bite. This tends to work alright on lighter weight & slower classes like Jr1, but you'll see your tires fall off with a lot of heavier weight and faster classes.
Again, there is no one answer for every scenario -- we're talking generalizations here.
I realize that it's not always as simple as that.
Experience - experience - experience. That's the best answer.

Hope that helps.
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That helps big time. I appreciate it man. I'm not even racing but still trying to put things together like this and I appreciate the info
 
When I tested much higher air many years ago we were as high as 9-10 PSI on Maxxis or similar tires. Generally still running correct amount of inside prep for the track conditions. What I found was that they work great for a few laps, but almost always fell off after 5-8 laps

More inside prep would only compound this issue for a few reasons. Tires with higher air tend to gain heat faster, which internal doesn't always make tires gain heat faster, but generally more inside will make them come in a little faster. Generally inside helps to stabilize temps and keep the tires more consistent. Problem is, more inside could potentially drive the tires to be "too hot." to be effective for the conditions. Which only drives temps up higher with the air, and possibly pressure gains as well.

Brian has said a lot of the same things as well in his post above, most of this is all generalizations.
This is a reply to your similar question in another post, which goes along with what Brian and I have said as well.
SoCo Tire Treatments said:
The Pros run what air pressure at the that specific time to get the best lap times possible. Air is track dependent with how much grip is available . Less grip in track less air, and vice versa.
As for internal, more internal plus higher air, isnt the same as the correct internal with the correct air. What i mean is you cant overcome too soft a sidewall by adding air. Now with the added air, you have changed the contact patch in relation to the track, you are going to build heat at a different rate, and you also change the "compression" of your spring/tire. Now if you already have tires with too much internal, you can use higher air and maybe get away with it for a lap or 2.
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