HPDE on PS4

[nextcar]

Originally Posted by Desertnate

I find chalking my tires helps with seeing how close I'm getting to the sidewalls.

Wouldn't something like this work for checking the temp of your tires? Just shoot a beam at multiple points across the contact patch to read how hot they are getting. You can find quite a few which are affordable.

I too started with chalk...

As far as the infrared thermometers go, the only problem is that they measure surface temperature, and the surface cools quickly when you come off the track. The tire pyrometer probes are designed to be stuck into the tread itself (the probe linked is set to 5mm depth) to read internal temp, which does not cool as quickly. Never tested with the infrared (even though I have one!). My base assumption was that if all the tire pyrometer kits used the insertion probes, there is probably some benefit. Then again, I may be a bit of a tool junkie looking for an excuse to buy another tool...

[NoHaveMSG]

Originally Posted by nextcar

I too started with chalk...

As far as the infrared thermometers go, the only problem is that they measure surface temperature, and the surface cools quickly when you come off the track. The tire pyrometer probes are designed to be stuck into the tread itself (the probe linked is set to 5mm depth) to read internal temp, which does not cool as quickly. Never tested with the infrared (even though I have one!). My base assumption was that if all the tire pyrometer kits used the insertion probes, there is probably some benefit. Then again, I may be a bit of a tool junkie looking for an excuse to buy another tool...

This ^

My inside always shows hotter with an IR gun since the outside cools faster due to the amount of camber I run.

[mr.whiskers]

Originally Posted by Desertnate

I think the weight of the car, suspension balance, and drivetrain have a lot to do with how you set the tire pressures.

On my GTI, since it was FWD and understeared, I had to add about 5 PSI to keep the tires off the sidewalls. On my BMW 435 which is a very heavy car that tended to understeer on it's staggered set up I had to add 15 PSI to keep the summer tires off the sidewalls (still under max PSI for the tire, surprisingly). Even when I moved to 200TW tires on a square set up I was adding around 10PSI. I constantly chalked my tires and kept a log to dial things in and make sure I was adding too much.

For a lightweight RWD car like my 22 BRZ I'm looking forward to not having to play around with the air pressures so much.

EDIT: This is for autocross, not a track day.

Yes Infiniti was understeering too, riding the sidewalls a lot

I guess I will have to wait until autocross season starts to see what will happen with premacies and if additional PSI's are needed on the fronts

[WolfpackS2k]

I saw the thread title and thought it meant there was an HPDE game on the PlayStation4, whoops!

PS4 tires are fine for an HPDE, especially for someone's very first HPDE. Stock brake pads are usually fine for beginners as well (personally I wouldn't do it, so don't interpret it as an endorsement). Most first timers aren't very hard on their cars. And PS4 tires are very competent. I typically would get 20,000 street miles and 3-4 weekend events out of a set of PSS on my Cayman (PSS was precursor to PS4).

So what if tires loose grip from heat cycling? Unless you're competing in an event, or have unlimited funds, that's just the name of the game and is unavoidable. These events are about having fun and learning car control. Super sticky tires will make it harder to learn car control IMO. As long as the tires aren't chunking and/or failing everything should be good

Check your tire pressure after every session. As long as there's no wear on your sidewalls keep lowering the pressure if you think you can gain traction. A paint pen is also good to use for marking your sidewalls.

As a final HPDE comment, I can't speak highly enough about the durability of Hankook RS4 tires. They take a beating and keep going. Cheap and long lasting. They don't look like they've been dealing with the 4000 lb weight of my C63.

[ZDan]

Originally Posted by nextcar

Disclaimer: There are a LOT of people more serious about their track days than I am... and as always opinions differ.

Troof! Mine follow...

So, how do you tell what tire pressure is best for your car, your driving, track conditions, and tire differences? The answer is a tire pyrometer, a fancy name for a digital thermometer that can measure the tire temperature at the outter, middle, and inner portions of the tread. Ideally you want them to be as even as possible. If the center is hotter, you have too much air. If the outsides are hotter you have too little.

A setup optimized for quickest lap times will almost always have the insides of the treads hotter than the center and outside.

It will vary based on the car, tire used, setup, and the venue but generally speaking with a semi-optimized setup (i.e., some decent negative camber), you're putting heat into the inside tread down every straightaway *and* around every turn (including the inside tires). While the outside portion of the tread gets a break on the straights (and outside portion of inside tires gets a break every turn).

Most of us are gonna be better off just aiming for a "known good" hot pressure near the middle of accepted range and just stick with that. Modern 200tw tires have a *very* broad pressure range over which lap times aren't very sensitive to pressure.

I bought a pyrometer years ago and basically it told me what I already knew, I needed more front camber... Unless you are able to do dedicated test days to home in on optimal setup *and* optimal pressures for each setup, IMO pyrometer isn't really going to help a lot, will just be a possibly misleading distraction.

Originally Posted by Desertnate

I find chalking my tires helps with seeing how close I'm getting to the sidewalls.

IMO, chalking for modern radials, not so useful... If you don't have significant front camber, you're going to be rolling onto the sidewall to some degree. I don't think pumping up the front tires until you don't see any rollover is a good method. If I had low front camber, I *might* go as high as 38psi hot for the fronts but I wouldn't bother going any higher than that.

Originally Posted by WolfpackS2k

Check your tire pressure after every session. As long as there's no wear on your sidewalls keep lowering the pressure if you think you can gain traction. A paint pen is also good to use for marking your sidewalls.

I really disagree with the approach of lowering pressure as much as you *think* you can. Hear it all the time at the track, it's like a "how low can you go" competition. People seem to think "less pressure = more grip", but this isn't exactly true. Again, modern trackworthy radials are going to have a very broad pressure range over which they'll give near-optimal performance.

I'm attaching data from a Grassroots Motorsports test of skidpad grip vs. pressure for RT615K+, RT660 , and RE71R tires. https://grassrootsmotorsports.com/ar...oss-and-track/
They did three laps each run, I'm showing the average at each pressure setting. As you can see there is a lot of scatter. Note this data is strictly for continuous lateral grip in one direction for just a few seconds and doesn't account for the negative effects lower pressure might have for track lap times (higher rolling resistance, slower response in transitions, greater heat buildup over time).

Personally, at the track I just aim for 34-36psi hot and don't worry about trying to "optimize" as I know I don't have enough dedicated uninterrupted laps under identical conditions to actually determine optimal with any kind of reasonable accuracy.

Better to err a bit on the high side than on the low side IMO. And not to get caught up in misguided "how low can I go?" experiments...

[Ohio Enthusiast]

Originally Posted by ZDan

A setup optimized for quickest lap times will almost always have the insides of the treads hotter than the center and outside.

It will vary based on the car, tire used, setup, and the venue but generally speaking with a semi-optimized setup (i.e., some decent negative camber), you're putting heat into the inside tread down every straightaway *and* around every turn (including the inside tires). While the outside portion of the tread gets a break on the straights (and outside portion of inside tires gets a break every turn).

There are plenty of IR camera footage of Formula 1 cars. They show about the same tire temps as you described. This one of Vettel is particularly illustrative:

[WolfpackS2k]

I can't really disagree with ZDan, I was certainly generalizing a bit. And I have experienced performance going down from lowering the pressure too much (while still not having sidewall scrub).