| Author |
Message |
Bill Sebestyen (Bill308)
Member
Username: Bill308
Post Number: 410
Registered: 5-2001
| | Posted on Wednesday, December 04, 2002 - 7:58 pm: | |
Bernard,
I've got a lot of experience using probe or thermocouple type systems and some experience with high end (military type) infrared systems. I use these instruments to evaluate the temperatures of electronic components and PC boards.
Both types of systems are subject to inaccuracies.
Probe or thermocouple based systems require the sensor end be in intimate contact with the surface or media for good accuracy. Some systems act more quickly than others, but usually 5 seconds of contact will get you pretty close. They can be used to measure surface and fluid temperatures and don't require a direct view. Their absolute accuracy can be quite good for most applications. Their upper temperature limit is based upon their construction. Probe based systems work pretty well on tires but you need to work quickly and be consistant with where you measure the temperature on the tire and how hard you make contact with the probe. Some probes resemble needles and can be pushed in to penetrate a surface like rubber. Obviously, you don't want to do this with tires you intend to drive on.
Infared systems can be of the spot or field reading variety. Inexpensive ones will read spot temperatures while very expensive ones are basically infrared cameras and will read temperatures across the viewing field. The absolute accuracy of infrared systems requires direct visualization of the target and is highly dependent upon the material and surface finish which affects emissivity, a measure of how much heat is being radiated by the object. As an example, if you had 2-pieces of steel at the same temperature, one of which was painted(and paint color doesn't really matter because is only affects the visible spectrum) and one highly polished, the infrared probe would show the painted piece was hotter. If you really needed to know the temperature of the polished piece and your only method of measurement was an infared instrument, you could improve accuracy by putting a piece of electrical tape on the polished piece and view it's temperature, or get this, Desenex spray foot powder could be sprayed on the polished surface prior to viewing with the infrared instrument. Infrared spot systems should work pretty well on rubber, which has an emissivity of about 0.86, where an emissivity of 1.0 is equivalent to a black body. Emissivity of black electrical tape and Desenex is probably better that 0.95. Highly emissive surfaces will give more accurate readings. |
Mitch Alsup (Mitch_alsup)
Junior Member
Username: Mitch_alsup
Post Number: 247
Registered: 4-2002
| | Posted on Wednesday, December 04, 2002 - 2:56 pm: | |
I used the Longacre $130 pyrometer to determine that my S03s needed to be closer to 40 PSI than 32 PSI. Easy as cake to use: 1) drive hard; 2) stop; 3) measure tire temps at 3 positions accross 4 tires takes about 5 seconds per tire--longer if you write down the numbers.
By the way, the pyrometer is capable of measuring all sorts of temperatures, tongue, skin, water, basically everything lower than 400 degrees. There is an attachment probe that can be used on brake rotors up to 1200 degrees. |
Bernard Sharp (Fanatic)
New member
Username: Fanatic
Post Number: 5
Registered: 11-2002
| | Posted on Wednesday, December 04, 2002 - 1:30 pm: | |
Hmmm, it gets even more complicated. It sounds like you have to use a probe type pyrometer just right, or you get inaccurate results.
http://www.longacreracing.com/articles/art.asp?artid=16
Can anyone with experience using one verify if they are easy to use correctly?
Thanks! |
Bernard Sharp (Fanatic)
New member
Username: Fanatic
Post Number: 4
Registered: 11-2002
| | Posted on Wednesday, December 04, 2002 - 1:16 pm: | |
Hey, check these guys out:
Longacre Racing at www.longacreracing.com has both probe and infrared pyrometers. They even have a tech article discussing the advantages and disadvantages of each type at http://www.longacreracing.com/articles/art.asp?artid=9
Now I can't decide which one to get. The probe type apparently gives more accurate readings for tires, but it only works for tires. The infrared type works for any kind of temperature measurement.
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Jim DeRespino (Jimbo)
New member
Username: Jimbo
Post Number: 26
Registered: 10-2001
| | Posted on Tuesday, December 03, 2002 - 9:47 pm: | |
The gadgets are called "Non-Contact Thermometers". Mine is made by Raytek and is sold by Northern Hydraulics (now Northern Tool & Equipment) $89.99 - 129.99, depending on the bells and whistles (1-800-533-5545). When the AC electricals cut out on my 512TR, I used it to check the temp of all the connections at the fuse box. One was twice as hot as the others, and sure enough it was fried. Instead of buying a $700 fuse box (as I was advised by many), a 1 cent spade terminal did the trick. So I guess my 89 bucks paid for itself right there. Plus you can check the temp from the ac vents, exhaust manifold temp, etc. Ask Santa for one. |
BretM (Bretm)
Advanced Member
Username: Bretm
Post Number: 3000
Registered: 2-2001
| | Posted on Tuesday, December 03, 2002 - 6:22 pm: | |
Usually they say about 1PSI for every 10 degrees. I'm sure there are more accurate formulas, but that's usually pretty damn close. |
Lawrence Coppari (Lawrence)
Member
Username: Lawrence
Post Number: 414
Registered: 4-2002
| | Posted on Tuesday, December 03, 2002 - 5:53 pm: | |
Entirely depends on how hot. |
stu cordova (Balataboy)
Member
Username: Balataboy
Post Number: 302
Registered: 4-2001
| | Posted on Tuesday, December 03, 2002 - 4:20 pm: | |
Another question; what's the difference, in PSI's, between a cold & hot reading? IOW, a 40 psi reading when cold would be ? reading when hot? |
Mitch Alsup (Mitch_alsup)
Junior Member
Username: Mitch_alsup
Post Number: 239
Registered: 4-2002
| | Posted on Tuesday, December 03, 2002 - 12:10 pm: | |
As a point of reference, in my F355 I am using S03s (225/40-18 F and 275/40-18 R). I found these tires wanting at the stock setings of ~32 PSI. I ended up with the rears at 41 PSI and the fronts at 40 PSI. These tires have much more grip at these pressures than at lower pressures.
I think this has to do with the original tires having a 44 PSI maximum and the modern max-performance tires having a 51 PSI max.
Funny thing is that the ride was actually better with the tires at 40 PSI than with them at 32 PSI. |
stu cordova (Balataboy)
Member
Username: Balataboy
Post Number: 298
Registered: 4-2001
| | Posted on Saturday, November 30, 2002 - 9:01 pm: | |
Thanks guys - looks like starting at 33 and adjusting from there is a good place to start!
I'll have to get me one of those fancy laser thingamajiggys!! |
Bernard Sharp (Fanatic)
New member
Username: Fanatic
Post Number: 3
Registered: 11-2002
| | Posted on Saturday, November 30, 2002 - 2:41 pm: | |
Wow, I guess I haven't been paying attention to the latest gadgets. It almost makes it too easy! Who builds and sells these meters, and how much do they cost?
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Jim DeRespino (Jimbo)
New member
Username: Jimbo
Post Number: 25
Registered: 10-2001
| | Posted on Saturday, November 30, 2002 - 2:27 pm: | |
OK, I guess I qualify as a fanatic. I have one of those hand-held laser-pointer infrared thermometers. Drive your card hard to get the tires hot, then immediately take readings at the center and outer tread areas. If the center is hotter, the tire is over-inflated. If the outer areas are hotter, it needs more air. Keep playing until the temp is even across the whole tread and you have the optimum pressure for your tires, your vehicle and your style of driving. Record this for future reference. Simple, huh? Ain't technology wonderful? |
Bernard Sharp (Fanatic)
New member
Username: Fanatic
Post Number: 2
Registered: 11-2002
| | Posted on Saturday, November 30, 2002 - 1:54 pm: | |
Stu,
I would start with all four tires at 33 psi for street driving, and then raise or lower them in 1 psi increments until you find the balance of ride and handling you like. Keep all four tires at equal pressures until you find the basic ride/handling/traction setting you like.
Then you can experiment with front tires at slightly lower or higher pressures than the rears, but be cautious! Anything more than a 3 or 4 psi differential front/rear could lead to unexpected and possibly unpleasant results at the handling limits.
Most Ferrari's have plenty of power to adjust understeer and oversteer by modulating the brakes and throttle, so I prefer keeping the tires at equal settings to avoid surprises.
For track use I would start at 35 psi all around, and then adjust up or down in 1 psi increments based on the handling characteristics and the wear on the shoulders of the tires. I guess a real fanatic would use a tire pyrometer to check the temperature balance across each tire, but I haven't gone that far yet.
Have fun!
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Vince Canipelli (F308vc)
Junior Member
Username: F308vc
Post Number: 57
Registered: 2-2002
| | Posted on Friday, November 29, 2002 - 4:38 pm: | |
Stu.....I have the same tires on my 80, 308GTBi. The car seems to like 35lbs allaround. |
Randy (Schatten)
Member
Username: Schatten
Post Number: 493
Registered: 4-2001
| | Posted on Friday, November 29, 2002 - 5:09 am: | |
First, check the recommended tire pressure for them. They are typically at 32psi. Make sure your tires are C O L D when you do it. Even driving around for a few minutes and the temps get up there. Fill them up to the recommended temps, or even a few pounds higher.
When tuning the tires correctly, it all depends on 1) how you drive and 2) how much comfort you want. Depending on how aggressive you drive - i.e. - when you feel the sidewall roll over on the street (aggressive), you need to tune it to your driving habits. Sometimes higher pressures can yield a harsher ride. The Lincoln town cars have pressure set at 28psi from the factory, and hence a softer ride. It doesn't mean it handles better, it actually doesn't. Its less precise, but that doesn't matter for that particular car.
The best way to fine tune the pressures in the car are getting the air up in the front and the rear, and then down'ing the rear for traction. The front is all about turning, the rear is all about traction and tuning the oversteer/understeer characteristics. Keep in mind, even 1psi of pressure can be felt, but on street tires, 1-2psi is usually where you'll notice a change.
One note - the Michelins, like all tires are different, so different tires in different cars like different pressures. So, try to take a guidline and run with it while being very subjective.
Hope this helps!
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stu cordova (Balataboy)
Member
Username: Balataboy
Post Number: 295
Registered: 4-2001
| | Posted on Friday, November 29, 2002 - 12:23 am: | |
I'm running on Michelin Pilots - 205/55/16 & 255/50/16. I just realized I don't know what the correct pressure is for these tires.
Any tire experts out there that can enlighten me? I think they're a bit low but I'm not sure how much to fill 'em up! Thanks in advance.
-Stu |