falken 615 tire pressure

[olds350]

Hello all... I need a recommendation please. Recently picked up a set of 295/40-18 Falken 615+ for autocross. It's been a while since I've run a decent sticky tire. I'm looking for air pressure recommendations. In the past, I've generally run in the 36# range, but that was on a stock all season. I'm not sure where to start on these. Would appreciate some feedback please.

As for the car, '08 bullitt on lowering springs and updated suspension parts. I was going to start at 32 and then watch the roll on the tire edge and go from there, but if you have any insight on these tires, I'd like to know what pressures you run please...

 

[Juice]

32 psi COLD is a good starting point. I have an infa red thermometer to check my tire temps (inside, center, outside) right after a session. You want the middle temp in between the outside temps. The center will be hotter if over inflated, or colder under inflated. Adjust pressures accordingly.
Front tires will be hottest on the inside from negative camber. The rears I get almost even across the tire.

 

[olds350]

32 psi COLD is a good starting point. I have an infa red thermometer to check my tire temps (inside, center, outside) right after a session. You want the middle temp in between the outside temps. The center will be hotter if over inflated, or colder under inflated. Adjust pressures accordingly.
Front tires will be hottest on the inside from negative camber. The rears I get almost even across the tire.

That brings up a great point. What infrared reader to you have? That would be the best way to see how the tire is performing...

 

[Juice]

Its a cheap piece, about the size of a keyless entry fob. A friend gave it to me, but its perfect for track days.

 

[Pentalab]

I have a Fluke 62...bought it 15 yrs ago. It will depict the highest temp, and also the current temp. ( 2 x displays). It can also be switched from F to C. Max range is -22F to +932F (-30C to +500C). It can be used for all sorts of stuff, like finding exhaust leaks, tire temps, eng bay temps, individual component temps etc, leaking gaskets, etc. I used it around the home to find where insulation was lacking, air temps of output of AC units, fridge and freezer actual temps, oven temps etc. I also use it on electronic components, where dangerous high dc and ac voltages are involved. Comes with a laser pointing aid..which also works as a great cat exercising toy. Fluke 62 has been around for a long time, and is an industry standard.

This is the latest version, which includes distance, as well as min, max, average,difference between 2 x temps. Backlit, drop proof, water proof etc. https://www.fluke-direct.com/product/fluke-62-max-infrared-thermometer?search=

 

[Racer47]

That brings up a great point. What infrared reader to you have? That would be the best way to see how the tire is performing...

The best way is with a pyrometer. This is a good read.

https://949racing.com/using-a-tire-pyrometer-949-Racing.aspx

 

[QuickShift281]

On my 275/35/18 615's I start around 32 cold front and rear, they typically rise about 4-6psi on the first lap. Then I will adjust accordingly.

 

[Vorshlag-Fair]

#500psi!

 

[DocB]

Don't waste your time with an IR temp gun. It only reads the surface temp and will give you meaningless data.
You will want to use a pyrometer with a probe that sticks into the tire at least 1/8".
Additionally, pull into the hot pits with hot tires and take the temps.
Not after a cool down lap, and not in the paddock.
Just something to consider.

 

[Mrerob]

That brings up a great point. What infrared reader to you have? That would be the best way to see how the tire is performing...

I don’t know if it matters of if you care, but I did an experiment with a cheap infrared reader (general from Lowe’s) and a snap-on one,(because I do shit like that from time to time, and I don’t know why) the general was consistently 8 degrees colder than the snap-on changed batteries in both still 8 degrees colder, depending on what you are measuring that might or might not matter.

 

[01yellerCobra]

I don’t know if it matters of if you care, but I did an experiment with a cheap infrared reader (general from Lowe’s) and a snap-on one,(because I do shit like that from time to time, and I don’t know why) the general was consistently 8 degrees colder than the snap-on changed batteries in both still 8 degrees colder, depending on what you are measuring that might or might not matter.

That doesn't really tell you anything though. The Snap On is just as likely to be out of calibration as the General. I've seen Harbor Freight specials do better than Flukes in my line of work.

However, if they're both reading consistently that might work in this case. As I think temp across the tire is more important than what the number actually is.

 

[Mrerob]

That doesn't really tell you anything though. The Snap On is just as likely to be out of calibration as the General. I've seen Harbor Freight specials do better than Flukes in my line of work.

However, if they're both reading consistently that might work in this case. As I think temp across the tire is more important than what the number actually is.

Yes it mostly just for comparison or relative value, I have not yet found a “calibration mode” on either gun.

 

[Juice]

It is the temp range across the tire that matters. Once I found the pressures that gave me good readings across the tire, I can feel a 1/2 psi change in the feel of the car on track.

 

[01yellerCobra]

Yes it mostly just for comparison or relative value, I have not yet found a “calibration mode” on either gun.

There usually isn't. At least that's not easy to find. It usually involves a button sequence or actually opening the unit up and flipping a switch. I still wouldn't recommend it if you managed to find it though. It requires a special piece of equipment to calibrate them properly.

 

[Pentalab]

That doesn't really tell you anything though. The Snap On is just as likely to be out of calibration as the General. I've seen Harbor Freight specials do better than Flukes in my line of work.

However, if they're both reading consistently that might work in this case. As I think temp across the tire is more important than what the number actually is.

With the extremes in min to max of say the Fluke 62, I wonder what the actual temp the unit is calibrated to, or if individual calibration points...across the entire range are used? But an 8 deg F change between 2 x IR devices is a bunch..and both pointed at the same heat source. I should try pointing at an ice cube...sitting out on the counter, just to see what it indicates. Or near the digital T stat for my gas furnace...when its at say 70 deg.

But you are correct, temp readings across the tread width, and their variations, is what will be useful.

 

[Norm Peterson]

IR readers are based on a material thermal property known as "emissivity", and the short version here is that it's not a constant among materials or necessarily constant for the same material at different temperatures, different surface finishes or textures, different colors, etc.

https://www.thermoworks.com/emissivity_table

https://en.wikipedia.org/wiki/Emissivity

Basically, IR measurements of tire temperatures are more valuable for comparison purposes than for the displayed temperatures themselves.


Norm

 

[01yellerCobra]

With the extremes in min to max of say the Fluke 62, I wonder what the actual temp the unit is calibrated to, or if individual calibration points...across the entire range are used? But an 8 deg F change between 2 x IR devices is a bunch..and both pointed at the same heat source. I should try pointing at an ice cube...sitting out on the counter, just to see what it indicates. Or near the digital T stat for my gas furnace...when its at say 70 deg.

But you are correct, temp readings across the tread width, and their variations, is what will be useful.

It depends on who's doing the calibrations. Some places only check 1 or 2 points. I've checked as many as 5. As for the tolerance, it should be listed in the manual under specs.

If you want to get an idea you can do the ice cube and then point it at boiling water. It won't be exact, but it should give you an idea where it's reading.