RE71R - Competition Tire Pressures - Track and Autoslalom

[Red5OH]

For those with RE71Rs

So I am involved in both Regional Track and Autoslalom events and have been experimenting with different tire pressure setups this past season.

I've always felt the need to run higher pressures for Autoslalom vs. track to take into account temperature increases during track use.

Track: 32psi (F)/ 28psi (R) Cold
Autoslalom: 36 psi (F)/ 32psi (R) Cold

Though usually competitive in the mid-pack or 2nd place in both disciplines, the all-out "win" had been elusive this year. Until I kept my track pressures for autoslalom. On track, 32F/28R has been the most comfortable and most even temps, with hot pressures at 38F/34R between sessions.

Last weekend I topped a field of 8 CAM-C entrants (all regulars), by a margin of -3.9 sec. from the 2nd place entrant, at times holding FTD, beaten out by a Miata +0.439 secs.

I thought it may have been temperature, but its been colder as of late, and the tires still managed an even temperature across, as if I was running the higher pressures.

Have other RE71R users found this to be a sweet spot? And are there any negatives with competitive driving at pressures this low (32F/28R - both increased by only 2psi during the 50 sec. course), if temps are still even across (slightly higher on the inner fronts due to camber)?

 

[Grant 302]

Take your 'cold' temps...as well as your hot temps, and you'll see a lot more correlation in your data.

@blacksheep-1 might have more to add...

 

[Red5OH]

Take your 'cold' temps...as well as your hot temps, and you'll see a lot more correlation in your data.

@blacksheep-1 might have more to add...

Thanks. Will definitely do.

 

[blacksheep-1]

Here's a couple of things, unless you make a temperature notation, along with the pressure run, it's really hard to tell you what to do. You may have actually been running the colder pressures at the track and not actually realized it..even though the pressure gauge says otherwise. as an example..30 psi at 60 degrees is roughly 32 psi at 80 degrees, so unless you have a temp notation, you have no way to tell. Running a split from front to rear is pretty normal, although you may want to change that up if the car is loose (add front/subtract rear)) or tight (add rear/ subtract front).I wouldn't recommend a wider split than what you have..
Also do you check tire temps with a probe, or IR gun? The probe is preferred, but it takes 2 people.
Don't fall into the trap of believing the tire has to be even across the tread to be operating properly.
Lastly, you are correct in running higher pressures at the autocross track, I do as well.

 

[blacksheep-1]

One other thing Red50H, it's ALWAYS the hot pressures that determine the cold, not the other way around. It doesn't matter if you start them with 5psi if the hots are where they need to be...good luck keeping those on the bead though.

 

[DaveW]

With autocross, the hot/cold thing is much harder to pin down. What is important is that you pick a time to do it after each run and repeat that every run. I do mine right when I get back from a run.

As mentioned already, even heat across the tire is barely relevant.

Once you nail down the hot/cold/when you check them thing, then you just need to experiment with what works. In my experience, track pressures are higher (especially hot) than autocross pressures.

I wouldn't be scared of either pressure you are running. I ran my RE71's this past weekend at 29 psi all around.

DaveW

 

[Red5OH]

Thanks Blacksheep and Dave W.

Good thing to know about the "heat across", since I thought it would be a relevant indicator of contact patch.

Unfortunately, I did use an IR temp indicator, so the temps may have not been the greatest data set.

Good thing to note about using the "hots" to determine the "cold". Looks like I'll redo the testing for both track and autoslalom with your suggestions, to get that better correlation that Grant mentioned.

 

[carver]

So I.m just curious if anyone uses chalk on the tire sidewall to monitor the tire roll?
It's an easy way to track the tires wear / roll giving you a visual record of whats happening on each session.

 

[Red5OH]

So I.m just curious if anyone uses chalk on the tire sidewall to monitor the tire roll?
It's an easy way to track the tires wear / roll giving you a visual record of whats happening on each session.

Initially, when I first ran the tires, to get the initial range of pressures to work with. However, by the end of the season, the changes in tire pressure i was making didn't affect rollover noticeably yet made a huge difference in times.

 

[blacksheep-1]

I've used chalk, especially on banks to check rollover

 

[JDee]

So I.m just curious if anyone uses chalk on the tire sidewall to monitor the tire roll?
It's an easy way to track the tires wear / roll giving you a visual record of whats happening on each session.

A lot of tires have a little indicator on the sidewall right below the tread edge that serve as a roll indicator guide. If you're getting into it you're getting too much roll. As I understand it these indicators can be any shape, mine are a tiny rendition of the tire company's logo, but they should be pretty apparent.

 

[carver]

A lot of tires have a little indicator on the sidewall right below the tread edge that serve as a roll indicator guide. If you're getting into it you're getting too much roll. As I understand it these indicators can be any shape, mine are a tiny rendition of the tire company's logo, but they should be pretty apparent.

Chalk or crayon was always my go to guide but admittedly with tires getting so wide with such a low profile I'm not sure how effective it is these days. Nowadays if you roll the edge to hard.... you grenade the rim!!!

 

[blacksheep-1]

use the chalk..

 

[racer47]

A lot of tires have a little indicator on the sidewall right below the tread edge that serve as a roll indicator guide. If you're getting into it you're getting too much roll. As I understand it these indicators can be any shape, mine are a tiny rendition of the tire company's logo, but they should be pretty apparent.

Those marks show where the treadwear indicators are. They are not roll indicators.

https://thetiredigest.michelin.com/every-day-check-for-wear

https://www.google.com/search?rlz=1...JRK0KHVD8BOYQsAR6BAgAEAE#imgrc=Pr2uS2cuLmXYvM:

 

[JDee]

Really. Who knew? The guy who told me that had a garage and sold tires!!!!
But they still will indicate roll though, won't they? I got into the tops of mine when I was trying to find the best cold pressure.

 

[racer47]

Its a common misconception. Its not necessarily a bad indicator but its not like its a factory recommendation either. Plus they are not all in the same place relative to the tread shoulder, some will be higher or lower than others. There is no hard standard where they need to be.

Marking the sidewall with chalk or paint stick is common for autox but less so for road race. Its just another tool in the box. I do it but don't live or die by it. Maybe there is only 1 part of 1 corner or 1 curb that runs down too low on the shoulder. Do you want to give up time on all the other corners for that 1 spot? On the other hand, autox is usually a flat parking lot so marking shoulders is usually a better measure of where the tire is spending most of its cornering time.

 

[blacksheep-1]

I think where you will find the chalk most useful is on a banked racetrack like Homestead, the mustangs are required to run tiny little 275 tires and it is very difficult to get them to last the race and also be competitive. I use it once in awhile just to check, sort of like using plastigauge when building an engine, it's a tool, but you wouldn't want to live or die by it.

 

[drano38]

I've been using a set of RE-71R for the last couple years. Hot temps after road course session I think are in the 42-44 psi range. I use an IR gun to check tread temp in 3 places across the face, and my hot temp gets me fairly even across the tread.
Like said above, find the hot temp that gives even tread temps or desired performance. Then see what psi that is when cold - so you know where to start at your next track day.

 

[j3st3r]

Ok, I have been running RE71s for years and your pressures seem high. Your AutoX cold pressures should be higher than your cold track pressures. Your should only be seeing 2-3 psi increase hot

I run mine at:
Track:
27/25 Cold

AutoX:
29/28 Cold

I run quite a bit of both as you can see here: www.youtube.com/bsowde

 

[s9669s]

I am only autocrossing, not tracking. Also, wheel and tire width, camber, and surface also matter. I set my pressures based on what the outer shoulder is doing, working the tire to a little above the arrows on the shoulders with RE71's.

For what it's worth, my typical setup:

Wheels: 19x10.5
Tires: 285/35-19
Camber (F): -2.7 degrees
Pressures: 30F / 29R, +/- ~1psi
(Before every run, like DaveW mentioned...)