[fastereddie]

Help me settle an issue I'm having with my boss. The truck is a 3 axle straight truck with a drop axle (=4 axles). He says the tires get hot because the heat gets transferred from the brake drum to the rim and then to the tire. I say it is more from the flexing of the tire sidewall because gross weight is 76,000. I check the axle hubs and they are warm to the touch.
The second issue is tire pressures. The other driver doesn't like to have tire pressures up to the spec. He says that stresses the tires more to have them at max pressure and they will fail because of that. I say they will fail more likely due to overheating from running at lower pressures.
....I set the cold pressure according to the door sticker inflation numbers.

[GMAN]

I have had several tire people tell me that under inflated tires will heat up more and fail more often that tires that are at the proper weight. One guy who worked for BF Goodrich, in Akron, OH, told me that there are more failures from heat than anything else.

[Birken Vogt]

You are correct on both counts, higher pressure will result in less heat. It is better to have a tire overinflated than underinflated! (Within reason)

Also tire pressures are checked cold, when warm (even sitting in the sun) they will increase significantly and if run at the max to start they will be over the max when warm, and that is OK.

Birken

[kc0iv]

Originally Posted by Birken Vogt

You are correct on both counts, higher pressure will result in less heat. It is better to have a tire overinflated than underinflated! (Within reason)

Also tire pressures are checked cold, when warm (even sitting in the sun) they will increase significantly and if run at the max to start they will be over the max when warm, and that is OK.

Birken

From the website:
http://www.landlinemag.com/Archives/...t/maint_qa.htm

One comment that should be repeated " Our compliments for gauging your tires instead of just thumping them. You’ll benefit with better fuel mileage and longer tire life." Every driver should have their own tire gauge and throw away their tire thumper. Nor should they use one installed on the hose.

Have a Merry Cristmas and Happy New Year.

kc0iv

[yoopr]

when you have a under inflated tire you're putting more load weight on the other tire on your trailer tandem or drives and it builds heat. That's why equal air pressures are important to keep your eye on.

[TK THE TRUCKER]

Also, look on the inside of the drivers door frame. Most trucks have a recommended tire pressure sticker to tell you what pressure the tires should be at on each axle. Don't go by what the max pressure is on the tire. I have this problem with my Dad all the time. The tires on his pick up have a max pressure of 60 lbs or so but if you look at the manufacturers tire pressure sticker on the door frame it says 35 lbs of air. If you go over inflating the tire the truck will ride rough and the suspension will wear out prematurely. Most big trucks have to have at least 100 lbs in the tires but range up to 120 lbs and not usually over that.

[slider64683]

That is only true for the tires that came on the truck. you can go anywhere and look at 5 sets of tires of diffrent bands and find diffrent specs. the specs are not set for the truck. the specs are set for the tires. We run nitrogen in all our tires in our personal cars (racing background) to keep pressure level. But in a semi the spec pressure is not always the same. Keep the pressure at what is says on the tire not on the door.

Happy Holidays

[NevadaJim]

Originally Posted by fastereddie

Help me settle an issue I'm having with my boss. The truck is a 3 axle straight truck with a drop axle (=4 axles). He says the tires get hot because the heat gets transferred from the brake drum to the rim and then to the tire. I say it is more from the flexing of the tire sidewall because gross weight is 76,000. I check the axle hubs and they are warm to the touch.
The second issue is tire pressures. The other driver doesn't like to have tire pressures up to the spec. He says that stresses the tires more to have them at max pressure and they will fail because of that. I say they will fail more likely due to overheating from running at lower pressures.

Any heat generated from the drums should be minimal. If your drums are heating up it's more than likely due to a lining dragging, which needs to be corrected. Or, from someone that drives with his foot resting on the brake pedal. Drums are designed to dissipate heat pretty quickly. Most of the heat is generated from friction. The tires job is not only to roll, but to create traction. Traction equals friction, and friction equals heat. Sure, the flexing will create heat, but unless its a constant back and forth bending it will be minimal.

Most tires will only change pressure of 4 -5 psi from cold to warm. I was always taught to check them after driving for a few miles, and run them at the recommended pressure, not the max.

Tire pressure has little to do with weight distribution. Unless, of course, your talking about a total flat and the truck is leaning excesively to one side. What happens when one tire is at a different pressure is the vehicle will pull to one side. This creates friction, and thus heat. That's why tires wear crazy when front ends are out of alignment.

Tires need to flex a certain amount to provide a decent ride. Too much pressure doesn't allow them to flex, which creates excessive stress. Too little pressure allows them to flex too much. I'm not a rocket scientist but I would guess an underinflated tire would give out faster than and overinflated tire.

[Rawlco]

Anytime that you have three axles sliding around a corner it will cause heating. When you turn the steering wheel to the right the truck will pivot on the center drive axle. The axle in front of that will slide to the right and the rearmost axle will slide to the left. This will cause excess heat and tire wear over a single or tandem drive configuration.