: Tire Temp



john d
09-17-07, 10:07 PM
Using a no contact infrared thermometer my front tires read 15-20 degrees hotter on their outside edges than the inside edges. The rears seems to be uniform across the tread.
What does this mean and is it the expected result?

MortnCyn
09-18-07, 07:32 AM
john d: First question is, what cold air pressure in the front and rear?
Are the temps taken after driving in town turning corners?

TSS
09-18-07, 08:32 AM
Using a no contact infrared thermometer my front tires read 15-20 degrees hotter on their outside edges than the inside edges. The rears seems to be uniform across the tread.
What does this mean and is it the expected result?

This means that you are far more technologically saavy than me. :worship:

MortnCyn
09-18-07, 08:46 AM
Another question. RWD or AWD?

n7don_srx
09-18-07, 05:13 PM
Suggest taking similar measurements on another vehicle for comparison. Alignment can effect tire temp but unless there's some tire company folks lurking I doubt there's a good answer.

dkozloski
09-18-07, 05:43 PM
Cornering ,AWD, toe-in, and camber all affect tread temps. It sounds normal to me. Are the inside edges feathered?

z32drifter
09-18-07, 10:00 PM
It really depends on how you were driving before the temps were taken. If you were setting up for the track I would say add neg camber. If you were driving on a twisty back road I would expect higher temps on the outer edges. What was the tire temps on the inside?? Keep in mind most cars have a little toe in to increase stability on the interstate, so I would expect some increased outer edge temp from that alone. If I check my track cars temps after driving on the interstate the inside edge the front tires will be about 20 degrees hotter due to some toe out and about 2.5 degrees of neg camber. The rears stay closer mabey 10 degrees at 0 toe and 1.5 degrees of neg camber. On track temps stay within about 10 degrees across the tires.

MortnCyn
09-21-07, 11:08 AM
I emailed a friend that used to be in the tire business and mentioned air pressure and asked if john d had been cornering would make much difference? His reply was as follows and is pretty much what z32drifter said.

Well yes, Mr. Rudd, bending the tie rods at 120 going into the tunnel turn at Darlington will build up some additional heat in the outer sidewalls. For the temperature differential that john d mentioned; there would have to be a mechanical effect causing that. Low tire pressure will cause a tire to heat up, but consistently throughout the tire, the tread area would be hotter than the rim side, but evenly.
If there is a right to left or vicey versy correlation in temperature, then the front end is exhibiting what the NASCAR boys refer to as 'push'. It won't be extraordinary and it would take a really good analyst to feel it in the wheel. But it would be there, if you could take the SRX to a perfectly flat surface, (some really big parking lots will have this, also airport runways....) and set the wheel at horizontal, you should be able to drive it in a straight line without touching the wheel.
Years ago, there was an Oldsmobile dealership across the street from the tire shop. They would send their better customers with the 98's and 88's over straight off the showroom and have us set the front end for the curve/slope of the two lane roads. We set the tire pressures, one or two pounds higher on the right than left, and front to back, depending on just how finicky the customer was.
Our front end man, a little Italian who probably could have taught physics at the U, was a master on front ends. He taught me how to simply draw my hand across the surface of a tire to check caster, camber and toe.
Another simple test is the old thumbtack and string. You place a thumbtack at the center of the tread on the left and right tire in the 9:00 and 3:00 positions respectively. Take a string and draw it across the tacks and mark it. Roll the car one half of one tire revolution and try it again. Depending on factory settings, the mark on the string should be within a 1/8th of an inch.
A plumb bob can be used to drop from the right or left fender well and measure the tip angle of the front tires as well.
All of this can be done on independent rear suspensions as well, but you'll need a physics professor to align that without throwing off the front end.