Using Tire Temp to Adjust Pressure

[TN10R]

Would using a laser temp gauge be a good way to fine tune air pressure? I've been running tire pressures in the low 30s hot on the track, but exactly where seems to be very subjective.

Checking to tire temp immediately after coming off the track would seem to be an objective way to make the remaining small adjustments? Drop pressure a little to increase temp vs add a little pressure if the temp is too high.

Does anyone do this? What would be considered ideal temperature?

For the record, I'm running DC3 rear and Dragon SC Pro SC2 on the front. I would assume that each may have a difference ideal temp.

 

[beechkingd]

Maybe in Motogp they would adjust pressures that way. Just measure the pressure when you come off the track. The surface temp of the tire would vary way to much.

 

[Joe Vital]

Last year at the races the some of the tire dudes were suggesting we check the air pressures right off the track. Just for shits and giggles I also checked the tread surface temp with a little infra-red gizmo. We found the temps to be comparable to what we had hot off the warmers.

 

[Sklossmonster]

FYI, the laser temp guages are nice for track temps and double checking to make sure your tire warmers are actually coming up to setpoint, but for actual tire temps you really need to use a pyrometer.

The pyrometer has a small needle that we use to stab the tire at various points so you can measure the actual carcass temp, which varies considerably from left to center to right side.

You can learn a lot from a pyrometer, especially at tracks that are predominately left or right turning. The readings we've been taking over the last couple of seasons explain a lot of low sides at tracks like Putnam Park and Road America.

Food for thought from the motorcycle buffet.

 

[Sklossmonster]

Not that I expect everyone to go out and get a pyrometer, but that's why "hot off the track" is a preferred method of checking pressures, because with no pyrometer available to most people that's the next best way to get consistent performance from your tires/pressures.

 

[jaren warren]

what's that about Marshall and learning from a pyro?

 

[jas0336]

FWIW, I had a bad crash last July. When they got my bike off the crash truck they checked my pressure and told me it was high by about 7 or 8 pounds in the front. I couldn't understand why since I set my pressure hot off the warmers. Well turns out my warmers were going green at 130 degrees rear and 110 degrees front (checked with infrared thermometer).
From everything I've found, you can estimate about 1 psi for every 10 degrees. If you go by the rule of 175 degrees operating temp (give or take) then that explains part of the discrepency.
I plan on contacting Chicken Hawk to see if it's worth having them check them out.
I think the infrared thermometers are good for that purpose...keeping the warmers in check. You need to check the accuracy of the tool though. You can get them for about $30 but they are only accurate to around +-7 C. Thats almost 45 degrees F. If you want something accurate, you'll spend around $80-100 and it will be accurate to within +- 4 F.

As for setting pressure, I agree that hot off the track is as accurate as you're gonna get. But this means you check pressure before you talk to CRs. I would say, put a gauge inside your leathers, run until you're up to pace for 2-3 laps and then pit in and check pressure just inside paddock gate.

 

[Sklossmonster]

what's that about Marshall and learning from a pyro?

Nicely done, Jarren!



Regarding jas0336, you're absolutely right. I can't tell you how many problems we trace back to a tire warmer not coming all the way up to temperature. It's dangerous and far more common than you might think.

This is the single biggest reason to pony up the extra cash for digital tire warmers. At least when your digitals aren't making set point you know it.

By the way, another common problem we see that is similarly avoidable are crummy air guages that are several pounds off. Race tracks are extremely unforgiving environmnets, that's part of the attraction for me, but it means if you don't come correct it may well cost you dearly.

 

[Meat]

Sklossmonster;108251 wrote:

The pyrometer has a small needle that we use to stab the tire at various points so you can measure the actual carcass temp, which varies considerably from left to center to right side.

You can learn a lot from a pyrometer, especially at tracks that are predominately left or right turning. The readings we've been taking over the last couple of seasons explain a lot of low sides at tracks like Putnam Park and Road America.

I've had a tire pyrometer ever since I got into track days and I just need to use the darn thing. I used it when I was a beginner to show me that I was too slow to get my tires up to temp.

It is just something I need to do, but I really don't know what I am looking for. I am guessing the trends and what to look for will become apparent.

It is difficult to get the tire pyrometer out, take the shield off the needle probe and stick it into my tire, when it is 95 degrees and 96% humidity. But, I just need to do it.

Marshall, do you have any info as far as tire temps go that I can look for until I figure things out on my own? If it makes any difference I plan on running the GP or GPA D211 this year, most of the time.

 

[Meat]

Oh, and most of you probably already know this but those surface pyrometers (the ones with a laser), the laser is only a pointer and has no impact on the infrared readings that the tool is actually measuring.

 

[Ruhe52]

Meat isn't it proper superhero protocol to step into a phone booth before getting into costume?

 

[Meat]

cyclerant;108427 wrote: Meat isn't it proper superhero protocol to step into a phone booth before getting into costume?

HEY! Where the heck did you get my shirt!

 

[Sklossmonster]

Unfortunately, you really need someone else to help with this because the temps drop very, very quickly as soon as you start slowing down, and especially once you're off the track. I recommend a friend in Hot Pit Lane ready and waiting to stab your tires as you come off a hot lap. It's really best way to check your tire temps with a pyrometer.

If your race tires aren't coming up to temp, then either the compound is too hard and/or the pressures are too high. There's a window of acceptable pressures and the lower the pressure the higher the tire temp will be, due to flex in the carcass.

The range we look for is very broad, but most manufacturers design race tires to operate between roughly 175 and 210 degrees farenheit. A little lower on the front, usually.

There's a common misconception in the track day communities that only "fast guys" can get race tires up to temp. This is patently untrue. Tire compounds and tire pressures that work for a faster rider will not work as well for a slower rider.

The only time a faster "B" group rider can't get a soft compund up to temp with the low end of pressures is when it's extremely cold and overcast on a Spring or Fall day.

More important for the fast "B" riders and Intermediate folks is using tire warmers to minimize heat cycles, because as you heat cycle a race tire you are increasing the temperature necessary to make it work right. More heat cycles = higher operating temperature

 

[Meat]

Sklossmonster;108442 wrote: ...as you heat cycle a race tire you are increasing the temperature necessary to make it work right. More heat cycles = higher operating temperature

That is very good to know and actually makes since, only after you told me.

 

[Sklossmonster]

No worries, Bro, it's my pleasure to shine a little light in the dark corners of this crazy game we love to play.

 

[stow]

Sklossmonster;108442 wrote: More heat cycles = higher operating temperature
Meat;108468 wrote: That is very good to know and actually makes since, only after you told me.

Meat I need a graph that shows initial operating temperature and pressure and how it should change with heat cycles. I will need this by Barber or Jennings.