Lowerer air pressure

[DavidCorsaro]

What did you use to level the scales?

[X25]

Originally Posted by DavidCorsaro

What did you use to level the scales?

You are supposed to just put them on level ground, and level the car itself for even weight distribution if you have the means (coilovers), and if you so care. He seems to be merely lowering the car onto the scale sensors from the lift.

[Kendall421]

Originally Posted by DavidCorsaro

What did you use to level the scales?

Very good question...you obviously know something about using racing scales if you knew to ask that! I like that! Actually, this floor was poured and laser leveled. I had the shop built during the peak of my racing career and knew I wanted a perfectly level floor for working on race chassis and doing setup work. There is no taper or fall for water run off in my shop...floor is flat to well within 1/16 inch. I used to scale my late model in this exact same spot and have long leveled the scales many times just to confirm they are level. If one scale is higher than any other by even 1/8th inch in the horizontal plane, the readings will all be questionable.

[Kendall421]

Originally Posted by X25

You are supposed to just put them on level ground, and level the car itself for even weight distribution if you have the means (coilovers), and if you so care. He seems to be merely lowering the car onto the scale sensors from the lift.

This is true. He was just asking how I knew the ground was level. If the ground is not level, you have to level the scales so they are on the same horizontal plane. Typically this is done with shims of metal stock being placed under the pads. Ideally on a street car, you would level the car left to right. The Camaro has about a half inch of rake (nose lower than tail) which is good for handling. When I raced late model, we typically ran a half inch of rake and 1/2 to 3/4 inch tilt (right side higher than left side) depending on the track we were running.

[trashmanssd]

[AKA-22]

sub

[Gstick]

Originally Posted by Kendall421

Good afternoon all! Finally had a few minutes to put something together here. This is rather lengthy...so if you care to read it...have a warm cup of coffee! LOL

First off...where do I believe you should run your 1LE tires? I run my "static" air pressure at 38psi front and 37psi rear. Yes, I run them different and I keep up with making sure they are at the pressure I want. How do I come up with these pressures?

First and foremost, I am NOT telling you that you should do as I do! Please don't take this as telling you what YOU should do, you do what you want, it is YOUR car and your tires. I am just sharing what I do and why I do it...but I am going to put some science, physics, and technology behind my reasoning.

Couple points to start with:
1. Volume and pressure are inverse. Bike tire takes 60psi, car tires takes 30 "something" psi...the HUGE right rear tire on a Sprint car takes 4 psi! What? That HUGE ass tire only takes 4 PSI? That's right...while a tiny bike tire takes 60 just to hold up a bike! Volume equals less pressure required...they are inverse.
2. Street tires are stiff side wall radial tires, side walls don't fold up (wrinkle) with less pressure the way a bias ply does...so when air pressure is not right (high or low), the side walls put more or less pressure on the outside edges of the tire contact patch and thus the center of the tire results in more or less pressure...in the opposite direction of the side walls. The center of the tire will run flat across at proper pressure, be concave at too low of pressure, and convex at too high of pressure.
3. Tire contact patch is the surface area of the tire that is in contact with the road surface. Ideally you want a tire contact patch to be equal in pressure at all points where it is in contact with the ground. On a bias ply racing tire, you can run it very low on air, maximize contact patch and since the side wall will wrinkle, you still get even pressure across a large contact patch. With a steel belted radial, this is NOT the case.
4. Laws of physics tell you that moving air molecules collide and make heat. if you run a tire very soft, the tire flex is causing the molecules to move around more and much faster...colliding more frequently and thus making heat in the tire. An over inflated tire has less flex, less molecular movement, and thus builds less heat.
5. Given a fixed tire size, more mass takes more pressure in the tire to hold up said mass. So if you put a standard car tire under a 2000# load vs a 4000# load...you will need more air to hold up the heavier weight.
6. Static pressure is cold tire pressure as set after the car has been sitting, say overnight. Dynamic pressure is where the pressure ends up after being driven. Dynamic pressure will always be higher...point 4 above explains why.

With those facts in mind...where should you run your tire pressure.
At 32 PSI you are too soft, the center of the contact patch will have significantly less load on it than the outer edges of the tire will have (concave). Sure the center is still touching the ground, but with significantly less pressure than the outer edges. You will have more rubber on the ground as the tire is softer, but load on the contact patch is not even. The more rubber on the ground may help on track days...more on that in a minute (there is a heat variable built into that). But for street driving, this is NOT optimal. You will wear the outer edges much faster, you have far less overall grip across the contact patch. You will generate more heat and that is harder on the tire...but you do not build enough heat in street driving to bring the tire pressure up to where you have consistent contact patch pressure.

Some say 32 PSI and TRACK results prove this. That is actually true! Why? Because when tracking the car, you are working the shit out of the tires, and building a lot of heat...thus you will get significant pressure gain! You can expect to gain 6-8 PSI in the tire working it that hard. So you end up at...38-40psi and grip is fantastic for you! This is fine for the track.

But on the street, if you start at 32psi, you will likely gain 2-3psi no matter how you drive. Ya, you can say you drive aggressively and that may be...for short durations. It is not the same as a track day where you are running hard continuously while on the track. So you end up running 34psi on the street...still not enough for good even contact pressure and optimal tire grip, wear, heat, and rolling resistance (which affects fuel mileage).

By starting at 37 and 38psi in my tires, they build 2-3psi depending on how I drive the car...city or highway. So I end up around 40psi. At this pressure, contact patch is solid, heat is normalized across the tire surface (checked it with a tire pyrometer), rolling resistance is giving me optimal mileage, and tire wear is perfectly even side to side to middle. If I have good even contact patch pressure, I have the best street grip I can expect.

On the 1LE, the rims are different sizes and thus the tires hold a very tiny delta in volume. Little more volume means little less pressure. (remember fact 1 above). Also, the weight ratio is about 60% front, 40% rear. Thus it takes a little more pressure to hold up the front than the rear due to the weight delta.

So, on the street, I run 37 and 38psi. In my daily drivers I always run 3-5psi higher static pressure than the tire calls for. I do this to maximize tire life, reduce heat, and minimize rolling resistance for best fuel mileage. I always get full life plus from my tires. My Chevy Traverse tires are rated at 60,000 miles. I have 189,000 miles on my Traverse and I have pulled 64,000, 62,000, and 63,000 miles out of my 3 sets of tires I have put on the car...and they are due now for replacement again! Yes, I drive my DD a LOT for work...part of why I don't drive my Camaro's as DD's!

As for the car getting darty as you hit ruts and grooves in the road...contact pressure being even will help reduce this. If you have them at 32psi...you are running on 2 rails on each tire...the loaded outer edges created by the stiff sidewalls pushing down harder than the center since it is buckled upward. If you run too much pressure, you are riding more on the center and less on the outside...thus like riding on one rail in the center of the tire. These situation are going to make the grooves less manageable. If you run pressure that gives you even pressure across the contact patch...you will ride over and through these road imperfections more easily.

So, some will be asking, who the hell is this dude. To give myself a little credibility...but NOT bragging about anything as I sure as hell don't know it all. But know enough to be dangerous most of the time! LOL I have 2 engineering degrees, worked as an engineer for a couple automotive companies over the years, and now am a self employed engineering consultant. I also owned racing teams for 23 years. Seventeen years as an owner/driver of my own dirt late model team. I did not build my own engines because I am not a motor guy...I paid builders to build my power plants...I just tuned them. But racing chassis are my forte. I did not build the power, but set the car up to put it to the ground and go extremely fast around an oval track. Won 86 races as a driver. I studied the racing chassis a lot, designed my own suspensions in 3D modeling programs and then incorporated them onto my cars. I also attended chassis and tire schools at AFCO, Rocket, and CJ Rayburn Chassis. I quit racing after 17 years and started working with my son racing quarter midgets for 7 years...from age 10-17. He won several track championships and finished 5th in National USAC Unrestricted Animal points twice. Again, I purchased the motors from motor builders, but did all the chassis and tire setup myself. I always ran on dirt, but 90% of my son's racing was on pavement...so had to learn pavement tires too! To kinda show the tire pressure/volume thing...on my Late Model with very large bias ply tires I ran 12 PSI on the right side, 10 in the LF, and 6-8 in the LR. Why the difference? In the corner the right side tires are loaded extremely heavily and needed 12psi...they would typically gain 8 psi in a race! Yes, almost double their pressure...on dirt! Again...molecular movement and collision makes heat and the extreme flexing of the tire makes this event happen at an extreme rate. On the LF...needed max contact patch with the way we setup the cars. The LF...well, it was just along for the ride...often it was not even on the ground! LOL Now in the quarter midget...that basically runs carting tires...we ran 12 psi right, 10psi LF, and 6 psi LR. Hmmm, almost the same at the full size dirt late model! Smaller tire, FAR less weight....lots less volume...but on pavement. When we took the quarter midgets to Eldora and other dirt tracks...we would run 6psi right sides and about 3ps in the LR. Bias ply tires...wrinkle wall, maximum contact patch and since side walls give, pressure was fairly equal across the contact patch.

So...that's it...that's all I got! Again, run the pressure that works best for you! I am NOT telling you what to do! I am just explaining why I run what I run and how I came to that conclusion. Hope this helps some of you though.

Thanks for this interesting info. I just got my 1LE on 6/17/16, and when I checked the air pressure the next morning, all tires were @ 30 lbs. I read the sidewall (max 51 lbs) and the doorjamb sticker (32 lbs), and aired up all 4 to 45 lbs. It was 86 degrees yesterday, and after putting about 100 miles on her, 45 lbs seemed to be a little to harsh. So I lowered all 4 down to 40 lbs this morning, and I'm going out for a cruise this afternoon. Hopefully this will be a good street tire pressure #.

[Kendall421]

Originally Posted by Gstick

Thanks for this interesting info. I just got my 1LE on 6/17/16, and when I checked the air pressure the next morning, all tires were @ 30 lbs. I read the sidewall (max 51 lbs) and the doorjamb sticker (32 lbs), and aired up all 4 to 45 lbs. It was 86 degrees yesterday, and after putting about 100 miles on her, 45 lbs seemed to be a little to harsh. So I lowered all 4 down to 40 lbs this morning, and I'm going out for a cruise this afternoon. Hopefully this will be a good street tire pressure #.

Run them 36-38 COLD. They will gain 3# when warmed up and you will like it.

[vinman]

Originally Posted by Kendall421

Run them 36-38 COLD. They will gain 3# when warmed up and you will like it.

That's what I've been doing since I read this thread

[Jayjellyfish212]

Are we still talking the stock f1 tires or all in general? Interesting subject ...

[pbsinternet1le]

Weight is 52% front 48% back....not sure where the 60 40 comes from?

[Kendall421]

Originally Posted by pbsinternet1le

Weight is 52% front 48% back....not sure where the 60 40 comes from?

You are correct! Wrote that before I put my car on my scales. This is a very old thread. I got about 52/48 as well. So I run 37 or 38 pretty square now.