BEST TIRE PRESSURE TO RUN TRACK

[karma003]

this has been a thing that's been bugging me since I went out to the track & saw a exp driver out there doing. He had a 1st gen completely stock miata, so Idk how he beat me. Well my first time out he did, I got him this month. Either way, the question remains. Does tire pressure make a big difference? If so, what's the best pressure to run on the track w our cars?

[RYU]

HUGE difference. Insideline (Edmunds) like 38 psi hot. Buy a pyrometer and learn about measuring tire temps. There's no right answer only a right answer for you.

[gmookher]

experiment and see..

[NemeGuero]

^ This. There is no magic pressure.

[Im_SPEED]

Originally Posted by gmookher

experiment and see..

^this is the best thing to do. i tried the 38/38 and didnt like it one bit. im running 35/29 but thats just me and doent mean its right.

[AJUSA.com]

use these two guides to help determine your best tire pressure

http://toyotires.com/tire/pattern/pr...petition-tires

click on Spec Miata guide



http://www.hoosiertire.com/pdfs/tctR6_A6.pdf

Knowledge is power (and better lap times)

[MarkRacerX]

Stock tires? Aftermarket ?

Mark the sidewalls and adjust from there! These cars stock have very little front camber at all so I have had to run front pretty high psi to keep from rolling at Autocross. Last event was close to 50psi up front and 38psi in rear seemed to stick good and use most of tire. But like I said depending on tire, speed of course , no set Psi #.

Good luck!

[BlaineWasHere]

You're surprised an experienced driver was faster than you?

[BAE]

Originally Posted by MarkRacerX

Stock tires? Aftermarket ?

Mark the sidewalls and adjust from there! These cars stock have very little front camber at all so I have had to run front pretty high psi to keep from rolling at Autocross. Last event was close to 50psi up front and 38psi in rear seemed to stick good and use most of tire. But like I said depending on tire, speed of course , no set Psi #.

Good luck!

You are talking about Autocross and 1 minute runs where you start with cold tires. It could be dangerous when people mix up autocross and track driving.

On the track I have seen 6-8 psi gain on 20 minute sessions. The tires felt greasy when I came in at 41-42 psi. I think 38 psi hot is a good starting point. On a warm day I would start out with 32-33 psi cold and reduce pressure if you come in above 38 psi. On cold days and in rain you need to start higher.

[RYU]

Also, when you're experimenting keep in mind that nitrogen expands less under heat. Some air compressors also contain a lot of moisture (i.e. water). Water expands into gas greater than air. If you pump your tires from a compressor that doesn't have a dryer don't be surprised to see 10-12+ psi in heat expansion.

[jstn]

Originally Posted by MarkRacerX

Stock tires? Aftermarket ?

Mark the sidewalls and adjust from there! These cars stock have very little front camber at all so I have had to run front pretty high psi to keep from rolling at Autocross. Last event was close to 50psi up front and 38psi in rear seemed to stick good and use most of tire. But like I said depending on tire, speed of course , no set Psi #.

Good luck!

This is pretty reasonable I think. After a couple of autox runs I felt happiest at 41F/36R on the stock tires.

[rice_classic]

Originally Posted by RYU

Also, when you're experimenting keep in mind that nitrogen expands less under heat. Some air compressors also contain a lot of moisture (i.e. water). Water expands into gas greater than air. If you pump your tires from a compressor that doesn't have a dryer don't be surprised to see 10-12+ psi in heat expansion.

Good post RYU, you mind if I expand on it a bit for the OP?

Regular air is 70% Nitrogen. Nitrogen expands at the same rate (essentially) as the other gasses that make up AIR (the non-H20 Gasses). (Roughly 1 PSI for every 10 Degree F in temp change)

The point of running pure nitrogen is the reason you suggest regarding moisture because Nitrogen is a dry-gas. When moisture is present it will exacerbate the expansion but more importantly the presence of moisture yields unpredictable expansion rates.

I did extensive pure nitrogen vs AIR testing this season. I ran an actual experiment (it was a college course I was completing during my racing season). I ran data on 8 tires during a triple race weekend comparing AIR and NIT. Then on a following weekend I ran pure NIT on all 8 tires to increase the pool of data of pure NIT and the predictability of expansion rates. I also use wheels with dual valve stems allowing me to "purge" the AIR and replace it with pure NIT effectively.

After extensive testing and loads of data collected I found... it doesn't matter. The pure NIT was no more predictable than regular compressed AIR.

The reason: It's damn near impossible to get 100% of the moisture out from inside the tires.

1: Tires are typically mounted with tire lube. So from the get go, you're screwed.
2: Most wheels have single valve stems. Purging the air/moisture is very difficult in this case unless you have a vacuum machine.
3: Even with lots of purging or a vacuum to suck out the AIR if any of the moisture is in liquid form you won't be able to purge it. You will first need to heat the tire enough to convert the moisture into a gas before purging.

The best way to avoid air/moisture is to:
1: Heat unmounted tire to evaporate ANY moisture.
2: Dry-Mount tires on rim (no mount lube).
3: During mounting use only pure NIT to fill tire.
4: Verify that the source of pure NIT is indeed pure.

The likelihood of this taking place for your average joe or even your average club racer is highly unlikely (I've only met one and they indeed do those things and are a well funded Spec Miata outfit).

To the OP.

Always set your COLD temp PSI with the goal of achieving your HOT temp PSI with the 1 PSI per 10F expectation. After each session, check temps and pressures, record data and adjust accordingly.

Have fun good luck.

[Texas BRZ]

Originally Posted by karma003

this has been a thing that's been bugging me since I went out to the track & saw a exp driver out there doing. He had a 1st gen completely stock miata, so Idk how he beat me. Well my first time out he did, I got him this month. Either way, the question remains. Does tire pressure make a big difference? If so, what's the best pressure to run on the track w our cars?

Good topic you bring up... I feel managing your tire pressure all around is very crucial. I learned this even more after this past DE weekend I completed.

I had a very experienced instructor with me, and he was giving me pointers on how much psi I needed to bleed out of my front tires because he felt my car needed to turn-in better. I followed his advice and was disappointed afterwards... Not because he was wrong by any means, and he was only trying to help me. The problem was that every car and every driver are different. He was driving an E30 M3 racecar, and I was only in a stock FR-S. He was speaking from his experience and how his car benefits from the changes he advised.

And I didn't want to be stubborn and only follow what I thought was right... I gave his advice a chance for the first day because I knew that this was something to learn upon (trial and error), and the changes just didn't work out, unfortunately. After repeatedly bleeding more and more air from the tires after each session, expecially more in the fronts... My car began to feel less responsive. It lacked that 'spring' that I was expecting out of the tires, and it simply lacked that better feeling I had experienced during my prior track events with this car.

After the first day was completed, I opened up to my instructor about what I (as the driver) was feeling. I told him that the tires were feeling very 'spongy' and weren't giving me that 'spring' that I was looking for. My instructor was very understanding of what I was saying, and he supported me and my thoughts of trying differently... My instructor informed me of how every car and its driver can be unique in preferring a certain air pressure setting.

For the second day of the event, I set my tire pressures all around to the factory recommended 35 psi cold... And I worked my way from there. It resulted better for me.

I admit that I'm not the most experienced driver out there (and I don't want to sound like that either), but I truly feel that setting tire pressures are specific to each driver and definitely to the car he / she drives.

You don't want to release too much air, and you also don't want too much air in the tires... It comes down to the psi which is the most appropriate compromise for the car and its driver. Try to really FEEL the behavior of the car, and don't worry about another driver or car being faster or slower than you. If you go in with the mindset worrying about the other car(s) least, you can excel as a better driver much more progressively.

All the best to you.

[TheFirstScion]

it really depends on the tires and road conditions, I was running 35(cold) on the stock tires on an old run way in RI on a warm day (for October) this weekend. 2 laps in and they felt as good as they were going to get. Ended up spinning one lap because I had let the car sit for an hour before driving and the tires got cold again.
The instructor on the course said "run them high in the beginning, you can always take air out, but those harbor freight pumps will take forever to put it back in"