Tire Pyrometer

[Apex50]

Does anyone use one? I took a couple measurements over the weekend at VIR full course. Any thoughts on what the tires are trying to tell me?

Session 1:

Set pressure to 39psi all around before a 30 min session

Drivers front:
Outside 50C Middle 53C Inside 55C

Drivers rear:

Outside 55C Middle 57C Inside 56C

Passenger front:

Inside 55C. Middle 54C. Outside 53C

Passenger rear:

Inside 55C. Middle 56C. Outside 55C

Session 2:

(Checked tire pressures after the session this time)

DF

Out 52C Mid 56C In 56C 46.4psi

DR

Out 57C Mid 60C In 58C 47.2psi

PF

In 57C Mid 56 Out 55C 45.4psi

PR

In 56C Mid 60C Out 58C 46.0 psi

Tires are 295/35R18 BFG G Force Rivals,
Konis set to 3/4 firm in front, 1/2 firm in rear, camber set at -1.5 degrees.

Thanks for any guidance

 

[ocpony]

These are the tires I am running in the USCA events. BFG reps are at these events and recommend hot pressures around 36 psi and best temps at 180 degrees F. over 210 F and they get greasy. I start at 29 psi cold and have been getting temps in the 160s when checking after my runs in the pits. The last event I did was at Daytona Super Speedway. We did the Roval. Infield course and the big Oval. I hit over 155mph on the banks.
They are great tires and are fairly easily drivable at their limits. They will talk to you at the limits which I find very helpful.
Also, you don't really want to see more than 20 F difference of temps from edge to edge according to the BFG engineer.

 

[ocpony]

Also, if temps are highest in the middle that is indication of too high a pressure. Your rears show indicate that. The fronts are not as obvious since camber can tweak the numbers on the edges.

 

[marcspaz]

You using an IR or a touch probe? How long between peak heat and the time you took the hot readings? Paved all the way to stopping to measure?

Without watching you drive, just looking at your readings... looks like you are slightly over inflating (maybe 2 psi) or while you are airing up, one side is in the sun and the other side is not.

Also, you might need to check your balance. If the tire pressure is okay, the load disbursement may be off. Increased friction due to load over the rear driver's side can give you the same results (all other things being equal). It could be that the driver's rear dampener just needs to be firmed up for that particular track.

 

[csamsh]

Need less camber!

Need A LOT LESS pressure!

 

[sheizasosay]

DriverFront- less camber
DriverRear- tad less psi
PassFfront-less camber
PassRear-tad less psi

 

[dontlifttoshift]

, camber set at -1.5 degrees.

Thanks for any guidance

Need less camber!

DriverFront- less camber
PassFfront-less camber

Nobody thinks that's weird? That's not a lot of camber compared to what we are used to seeing but the temperatures definitely say less camber......

I believe overinflated all around and not drving it very hard. 140* just isn't very hot for a 30 minute session.

Try 32 psi cold and see where that puts you, pretty sure that will still be too high.

 

[marcspaz]

That is why I mentioned load balance on the corners. Excessive body roll can give you the same results on the tires.

 

[sheizasosay]

Nobody thinks that's weird? That's not a lot of camber compared to what we are used to seeing but the temperatures definitely say less camber......

I believe overinflated all around and not drving it very hard. 140* just isn't very hot for a 30 minute session.

Try 32 psi cold and see where that puts you, pretty sure that will still be too high.

Yeah 32 psi cold is probably a good move. It's certainly a lot easier than changing camber. I have run psi as high as he has, but tires are very different in what they want. When I was looking for a baseline to run for psi I found out what Roush was using and it was about 39 cold. But I wasn't running the same tires. Camber is the same way. Not all tires want as much camber.

I have no experience with Rivals. Vorshlag and CSamsh do though.

 

[Apex50]

These are the tires I am running in the USCA events. BFG reps are at these events and recommend hot pressures around 36 psi and best temps at 180 degrees F. over 210 F and they get greasy. I start at 29 psi cold and have been getting temps in the 160s when checking after my runs in the pits. The last event I did was at Daytona Super Speedway. We did the Roval. Infield course and the big Oval. I hit over 155mph on the banks.
They are great tires and are fairly easily drivable at their limits. They will talk to you at the limits which I find very helpful.
Also, you don't really want to see more than 20 F difference of temps from edge to edge according to the BFG engineer.

Thanks, I'll try dropping pressures to 36psi hot and see if that increases temps. Like hearing what a BFG engineer says...

You using an IR or a touch probe? How long between peak heat and the time you took the hot readings? Paved all the way to stopping to measure?

Touch, and measuring right after. VIR paddock is now paved, woohoo!

Need less camber!

Wait... What?

Nobody thinks that's weird? That's not a lot of camber compared to what we are used to seeing but the temperatures definitely say less camber......

I believe overinflated all around and not drving it very hard. 140* just isn't very hot for a 30 minute session.

Try 32 psi cold and see where that puts you, pretty sure that will still be too high.

I never claimed to be fast. I'm hell on brake rotors though, think I could do that swap in my sleep at this point.

That is why I mentioned load balance on the corners. Excessive body roll can give you the same results on the tires.

Not experiencing much body roll, could bump up the sway bars by one position though. Hopefully that doesn't mess with the balance, finally got rid of the oversteer with current settings.

Thanks everyone.

 

[sheizasosay]

LMAO on the Will Farrel pic!

 

[dontlifttoshift]

That is why I mentioned load balance on the corners. Excessive body roll can give you the same results on the tires.

Excessive body roll will cause front camber to go positive so the outside would read hotter.

Apex, I wasn't implying you were slow, sorry. I haven't had the Rivals on track yet on my car but autocross at 32 psi cold/ 36 hot.....ish.

What size wheels are you on? My 295s are on 11s.

 

[Apex50]

Excessive body roll will cause front camber to go positive so the outside would read hotter.

Apex, I wasn't implying you were slow, sorry. I haven't had the Rivals on track yet on my car but autocross at 32 psi cold/ 36 hot.....ish.

What size wheels are you on? My 295s are on 11s.

No worries, just going for a laugh.

I'm on 10" D Forces

 

[modernbeat]

Before you get a lot more responses that may or may not know what it takes to make a tire happy, learn about it yourself. Augment your pyrometer and buy the Paul Haney book on Performance Tires. There's more to adjusting tires than camber and pressure, though those are the biggies that will make the most difference.

 

[marcspaz]

Excessive body roll will cause front camber to go positive so the outside would read hotter.

Apex, I wasn't implying you were slow, sorry. I haven't had the Rivals on track yet on my car but autocross at 32 psi cold/ 36 hot.....ish.

What size wheels are you on? My 295s are on 11s.

I see what you are saying. I was thinking that body roll on a right curve/corner/bank/etc. would cause the inside tires to go positive, but the outside would go negative, heating the inside line of the tire. Makes sense given the VIR Full Course is mostly hard right curves.

But again, all that is based off of not seeing him drive. And he said he isn't experiencing much roll anyway.

 

[csamsh]

If the insides of your tire are hotter than the outsides...don't you need a decrease in camber? Or...change some other degree of freedom to make the temperature more even?

I run my Rivals in the low 30's cold, and 33/31 for autox, 35/34 for track (hot). I set a cold temp before the first session, bleed 10+psi after session one, and then make small adjustments through the rest of the day. Those are numbers I just kind of arrived at based on feel. It's a little lower than what the BFG guy suggested, but who knows what the rest of his setup was. I run ~3 degrees of camber. I've checked temps a couple times, and they are high (160? 180?), and pretty even across the tread, but I don't remember what they were. I wasn't too concerned with absolute temps, just differential. I'll look at an absolute temp next time I go out and try to write it down.

 

[csamsh]

duplicate post

 

[modernbeat]

If the insides of your tire are hotter than the outsides...don't you need a decrease in camber? Or...change some other degree of freedom to make the temperature more even?...

Maybe. But it depends. If you have a lot of camber the outer part of the tire can cool off faster than the inside, even if they were the same temp mid corner. Even running just 100 feet from the corner before probing the tire will result in a cooling of not just the surface, but also the carcass. If you are taking real-time temps with IR sensors during the drive, you will see the changes that happen between actual cornering (and using the tire) and the quick cooling and temp changes that occur as soon as you leave the corner.

 

[modernbeat]

FWIW, you should be making the tires as happy as they can be, but the ultimate tool to decide whether you have enough air pressure, camber, toe, caster, rear squat, rear steer, spring rate and damping is...

The stopwatch.

 

[csamsh]

Maybe. But it depends. If you have a lot of camber the outer part of the tire can cool off faster than the inside, even if they were the same temp mid corner. Even running just 100 feet from the corner before probing the tire will result in a cooling of not just the surface, but also the carcass. If you are taking real-time temps with IR sensors during the drive, you will see the changes that happen between actual cornering (and using the tire) and the quick cooling and temp changes that occur as soon as you leave the corner.

Good point. I suppose cool-down laps, which I always take prior to measuring, well, anything, will also affect temperatures.

FWIW, you should be making the tires as happy as they can be, but the ultimate tool to decide whether you have enough air pressure, camber, toe, caster, rear squat, rear steer, spring rate and damping is...

The stopwatch.

Even better point!