Tire pressures at a track day, help me learn

So, continuing my threads on my SW20 and new wheel and tire set up, Im going to VIR on Wednesday with some fresh RT660 tires. This will be my second track day.

First time I saw a lot of guys in my group (novice) adjusting tire pressures between sessions etc, I did none of that. I dont know enough about it I didnt want to mess something up. I do have the ryobi battery powered inflator and three fresh batteries packed up already for it.

So what do you recommend? Like, what's SOP for tire pressures when doing track days?

Couple things to think about. First is that cold pressure is going to be 5-10 psi lower than hot pressure and how much pressure goes up is telling you something about how you're working your tires. At the beginner level you're adjusting for tire wear and feel, to what degree each of those is important depends on you and the car. Generally one end of the car will be harder on tires than the other. You need to adjust pressures to minimize that, and then adjust the other end to keep the car balanced. Ideally you'd have a pyrometer and be taking temperatures to further help you dial in pressure and alignment, but that's for the future. 

Find someone with your car or your tires, preferably both, and ask what they are running. Once you get a baseline of what works for someone else, bump one end up or down a couple pounds and see if you can feel a difference.  

If the person you ask is in the same boat as you and doesn't know either, you now have a friend to walk around with to find a person with the knowledge.

Lots of people mess with things they shouldn't mess with because they see other people messing with things.  Seriously.

If you aren't doing this with a plan or reason behind it, it's often better to do nothing.

The SW20 has staggered tires right and more weight on the rear?  What did Toyota recommend from the factory?  Start there.

Porsche recommends higher pressure in the rear on staggered setups.  Lower pressure in the front on lighter tires helps them grip more compared to bigger rears at higher pressure.

You can use a paint pen or chalk to see how far you are taxing your sidewalks.  Higher pressure will stiffen the sidewall.

There is really a lot to consider.  Want my dad's number?  He could talk for hours about tires.

I'm a set mine up at home, check at event, but I only adjust pressures for odd wear or a handling issue that requires a pressure change.  I do not bleed out air pressure gained due to heating of tires.  If you do that, you should air them back up to drive home, and I do not trailer cars for fun.  I drive there and back.

Do a quick search on the SW20 forums and use that as a starting point. Initially you won't put has much heat in the tire so they won't go up as much so you're cold pressures and hot pressures will be close. 

I've had my cars long enough that I simply set the cold pressures then double check them after the first session.

I've heard all sorts of advice on this topic, but ultimately experimentation is the only way to dial it in.  Truthfully, most rookies that are obsessing over tire pressure don't know what they're trying to accomplish and it wouldn't matter much anyway as far as lap times are concerned.  A realistic goal is avoiding premature tire wear.

First things first- if you haven't gotten a good performance alignment, start there.  In terms of handling performance, alignment is a can of spraypaint and tire pressure is a ballpoint pen.

 Get an accurate tire gauge and a notebook. Set the cold pressure the same in all tires before you start, document. When you come off after a session, look at the wear.  If you're using all the tread, great.  If you're on the sidewalls, you need more air.  If you're not using all the tread, let out 1/2 psi.  Document.  Rinse and repeat.  If you have oversteer, let some air out of the rear tires.  If you have understeer, let some air out of the front tires. You might need more on the right or left side based on whether it's a clockwise or counterclockwise track. 

Measure, document.  measure, document.  etc.  By the time you're putting down consistent laps within 1 second of each other you'll know what you should be looking for. 

After a weekend of clutch problems at CMP last month (new clutch should fix that), I'll be at VIR's TNIA with you, and will hopefully have a much more successful evening.  I'll be in a white E36, with probably one of the few enclosed trailers (black with black Tundra), as I know this is not the spirit of TNIA.  Had to get a waiver to run my not street registered car, and convince the arbiter of such things that it could be registered if I wanted it to be.  Stop by and introduce yourself.

I'm quite sure I've got a tire marker in the trailer you are welcome to use, but I'd vote with the others to not over think it initially.  Ignore those people standing outside their DE1 classroom musing about how they added a 1/2 pound to the front left and it made all the difference.  That is as silly as being at a BMWCCA event a number of years ago, one of my first HPDEs, and listening to the people outside of the classroom brag about how much over sticker they paid for their new M3s.  I got screwed, no I got screwed harder than you did....great, I'll just be over here in my E36 track rat with 250k on it, with lots of decent parts sourced cheaply.

Go online with whatever forum is appropriate for your car, get a good starting point, focus on safety, consistency and having fun.  I always glance over my car and tires between sessions just to see if anything doesn't smell, feel, look right as good practice. Lots of time to stress on the other stuff as you get more seat time under your belt.

From the GRM archives: Good talk on using a skidpad to set tire pressures. 

Some more talk about setting tire pressures here, too. TL;DR: Andy uses a skidpad to set tire pressures. 

I start at 5 psi below what I think is optimal (start at 25 hoping to build to 30 in my case). Don't know if that's ideal but the car doesn't do anything particularly evil so it can't be that bad.

FWIW I will also be at TNIA VIR tomorrow (later today?) Silver & black NC Miata #139.

Green MR2, look forward to meeting some GRMers

Tire pyrometer.

It will tell you about tire pressures AND your alignment.  It is easily the single best tool for car setup.

It's easy to use, easy to understand, and you only need to be able to average 2 numbers together to get all the data.

If it saves 1 tire from premature wear, it just paid for itself.

If you think you are gonna do this track driving thing more than a handful of times, get an actual tire probe.  Not a non contact temperature gun.

One of the above links explains how to use it.

wvumtnbkr said:

Tire pyrometer.

 

It will tell you about tire pressures AND your alignment.  It is easily the single best tool for car setup.

 

It's easy to use, easy to understand, and you only need to be able to average 2 numbers together to get all the data.

 

If it saves 1 tire from premature wear, it just paid for itself.

 

If you think you are gonna do this track driving thing more than a handful of times, get an actual tire probe.  Not a non contact temperature gun.

 

One of the above links explains how to use it.

 

 

THIS IS your answer

If you decide to go with a tire temp probe here is what I bought - Tire temp probe on the cheap

Note - I still have not gotten to use it at the track and see what the actual difference is between it and an IR gun as things are still shut down here in to June. I will follow up when I do, there's lots of comments like above saying that IR guns aren't good enough but I've never seen any data to support that. IR guns do take a larger average sample depending on the focus of a particular gun where the probe is the temp at that exact spot where it is pushed in.

For starting out like you are I wouldn't worry about this as much though, if you already have the IR gun I would bring it along as it will still give you an idea of where the heat is in your tires and can help you make decisions on pressure adjustments right away and alignment down the road. 

We made a video for you about this very subject:

Very cool, great video.

I took someone upstream's advice, just didnt mess with it and focused on learning the track. But I will be looking into this stuff more as I get more track time and more comfortable at a track (say VIR).

Again, great video, I always enjoy the GRM content, keep up the good work!

adam525i said:

If you decide to go with a tire temp probe here is what I bought - Tire temp probe on the cheap

Note - I still have not gotten to use it at the track and see what the actual difference is between it and an IR gun as things are still shut down here in to June. I will follow up when I do, there's lots of comments like above saying that IR guns aren't good enough but I've never seen any data to support that. IR guns do take a larger average sample depending on the focus of a particular gun where the probe is the temp at that exact spot where it is pushed in.

For starting out like you are I wouldn't worry about this as much though, if you already have the IR gun I would bring it along as it will still give you an idea of where the heat is in your tires and can help you make decisions on pressure adjustments right away and alignment down the road. 

The problem I have with your approach is called the cool down lap. After the checked flag  you get one more lap to cool off your tires and brakes.

      IR will tell temps faster than a prob will because you need to leave the probe in long enough to stabilize. Stick a tire in 3 locations of a tire   takes more time than shine a red dot on 3 locations.  
 Besides you don't care what the number is. Because there usually will be different temps.   You are looking for patterns.  Inside too hot? Reduce chamber, center too hot? lower pressure. Back too hot? reduce over steering.  Etc. 

In reply to frenchyd :

But a red dot only tells you the surface temp, which drops rapidly after a cooldown lap.  A probe will be far more accurate.

However, any system works as long as you do it consistently.  I can come pretty close on inflations by laying my hand across the face of the tire.

Taking a cooldown lap screws up the data regardless of what measurement method you're using. The right way to do it is to come in straight off of a hot lap and take temperatures while the tires are as hot as possible. Or have live measurement, but that's really cost prohibitive.

I know the event has already passed but if you caught the bug and are making this a habit, invest in a notebook and pen/pencil. Maybe a fancy little zipper cased to keep it all together or a clipboard. Write down what you think throughout a track day, even if you're not adjusting anything. As you go you'll be able to look back at notes written when things were fresh and remember something particular about a corner, the reason a change, or just general thoughts to pick up where you left off from last time.

Streetwiseguy said:

In reply to frenchyd :

But a red dot only tells you the surface temp, which drops rapidly after a cooldown lap.  A probe will be far more accurate.

However, any system works as long as you do it consistently.  I can come pretty close on inflations by laying my hand across the face of the tire.

Good point.  Street tires cool off quick enough that you can lay your hand and feel the tire. 
Race tires though hold tire temps longer and you can get your hand burnt.  
     As far as temp differences between in rubber and the surface, again what does it matter?   You aren't worried about exact temps, but patterns. Inside, center,  outside, front, rear.