Toad tire temps

[sheridany]

I drove to La quinta,ca from Las Vegas and I was watching my toad tire temps. It was close to 100 today there and when I got off the freeway my right tire was registering 123 degrees F. The pressure only moved up one pound. I actually touched the tire and it wasn’t that hot. My bus exhaust is turned away from discharging right on the tire. At what temp is the tire considered dangerous or does that even matter if the pressure stays the same? I would imagine if pressure rises as a result of temperature then that would be a problem to cause a tire to blow.

 

[Bigblockyeti]

It shouldn't matter even if you had the coach exhaust blasting right on it. The wind and road contact could remove any excessive heat even if the exhaust was capable of putting substantial thermal energy into the toad tire. They're designed to operate quite hot. The only tire failures I've heard of where heat was a consideration was where they were already dangerously underinflated. Tires can be mechanically undermined by UV and age as well, always replace road going tires before they're 10 years old, for some applications, sooner.

 

[sheridany]

I found this googling this morning. From Bendix Corp. I don’t know if they are sme’s on this topic.

Most experts consider 195 degrees Fahrenheit as the “line in the sand” when it comes to tire temperature: Beyond that point, the temperature will start impacting tire life. At 250 degrees, a tire will start to lose structural strength, could begin experiencing tread reversion and the tire will begin to lose strength.

Avoiding weakening or damaging your tires is reason enough to use a Tire Pressure Monitoring System (TPMS) that includes temperature sensors and high temp alerts – but there’s also the pressure side of things. As a tire heats up, its pressure increases. A typical tire inflated to 100 psi, undergoing normal use at 68 degrees Fahrenheit, tends to build up enough heat to increase 10 to 15 psi as it reaches thermal equilibrium. A general rule of thumb is that for every 10 degree increase in tire temperature, the tire’s pressure will increase by 2 psi.

 

[Kevin D Pem]

I found this googling this morning. From Bendix Corp. I don’t know if they are sme’s on this topic.

Most experts consider 195 degrees Fahrenheit as the “line in the sand” when it comes to tire temperature: Beyond that point, the temperature will start impacting tire life. At 250 degrees, a tire will start to lose structural strength, could begin experiencing tread reversion and the tire will begin to lose strength.

Avoiding weakening or damaging your tires is reason enough to use a Tire Pressure Monitoring System (TPMS) that includes temperature sensors and high temp alerts – but there’s also the pressure side of things. As a tire heats up, its pressure increases. A typical tire inflated to 100 psi, undergoing normal use at 68 degrees Fahrenheit, tends to build up enough heat to increase 10 to 15 psi as it reaches thermal equilibrium. A general rule of thumb is that for every 10 degree increase in tire temperature, the tire’s pressure will increase by 2 psi.

Good find! However it Beggs the question. Why only 1 psi? Should have been 4 psi according to your find.

Ambient temperature is measured at eye level in the shade. Does that mean the temperature measurement was tire temperature of 100? But still! Only 1 psi with an increase of 21 degrees?


Did you adjust the tire pressure after you drove the toad? If so you had low tire pressure from the start, unless you calculated for an increase in tire pressure over Ambient.

The problem with to much information, is learning how to use it, right?

 

[sheridany]

Right. Too much can cause the wrong action to take. I didn’t adjust the pressures. My pressures were the same measured with a gauge versus the tpms set to tire spec. As the drive went on I was watching the temperature rising and it made me wonder what is the max. I need to reset my temp warnings so they don’t go off in the event of higher temperatures which will inevitably happen as I travel this summer.

 

[MemoriesByTheMile]

This post has me googling tire temps. I was familiar with tread ratings and traction ratings, but never paid much attention to temperature ratings. Something new to learn!
Have noticed tire temps and pressures changing during a drive, and even changing based on which side the sun was on.
Need to look up my tires to learn what the manufacturer says for each of them.

 

[Joe Hogan]

Here is an answer regarding tire temps that have some interesting points. Excess temps apparently do not register on the surface of the tire but remain on the interior of the tire and the inside temps are what is measured by the TPMS..

"Regarding critical temperature: For short term (minutes or seconds), I would consider structural temperatures in the 205 F – 230 F to be critical. Size, brand or design – doesn’t make much difference. The problem is there is no way to measure the temperature as the hottest location is at the edges of the radial belts. In racing, like at Indy, we use a needle probe and stick this into the tire about 1/4″ to 3/8″ deep.

External surface temperatures are much cooler because of external air moving over the surface. With rubber being such a good insulator, the heat does not travel to the surface fast enough (minutes) relative to the ability of the temperature to rise (seconds) at the critical location we see it, so it’s possible to have internal rubber failure before the surface temperature gets to a critical point.

I think you can understand that the rubber can get softer with an increase in temperature. As it gets softer, it stretches more, and as it stretches more it gets hotter, etc. Up to about 210 F, this increased softness can be managed with construction and thickness design changes, but each of those changes can result in some other property getting worse. Also, that 210 F point changes with time and temperature history.

Tire design is a balancing act and a series of trade-offs. One thing that happens with a loss of strength and increased bending is the potential for tearing of the rubber at the molecular level, which can result ultimately with the tearing to grow to the width of the belts, which in turn results in a belt separation.

BUT the key thing to understand is that temperature damage is cumulative and the chemical reaction that occurs can eventually result in a loss of elasticity at higher temperatures so the rubber tears, which leads to a separation. The rate of these changes can itself change over time and the rate is also affected by the temperature.

Even for a single rubber compound, there is no exact temperature for it to “fail.” The physical properties of rubber changes with temperature, but here there is no exact point at which the strength goes from 100% to zero.

A TPMS gives an approximate temperature of the air inside a tire, which is also lower than the critical temperature. Most TPMSs have a high-temperature warning set to 158 F, and if you see that reading then you do not have enough pressure for the load you have or are driving too fast. This does not mean you can lower pressure till you see a reading of 158 as you are still doing damage and “consuming” the finite life of the rubber in a tire.

Read my blog, learn the actual load (when the RV is its heaviest) for each tire position (4 corner weights), consult the tables, learn the MINIMUM inflation pressure, add a +10% inflation margin to learn your “cold set pressure” for each axle based on the heaviest axle end, and adjust your TPMS low pressure level to never be lower than the minimum. Then go and enjoy your RV.

Read more from Roger Marble on his blog at RVtiresafety.net."

 

[J&JD]

I have seen my right front tire ( nearest the DS exhaust) exceed 140 degrees with no ill effects after being towed over 50k miles.

 

[CaptainGizmo]

It shouldn't matter even if you had the coach exhaust blasting right on it. The wind and road contact could remove any excessive heat even if the exhaust was capable of putting substantial thermal energy into the toad tire.

Sheridan,

Increased right front TOAD tire temps is absolutely common on the big diesels! The exhaust doesn’t have to be pointing right at the tire at all.

You have to keep in mind that, especially during a regen, the exhaust temps can be 700°. That constant blast of higher temperature air hitting that right front tire area will cause the tire temperature to go up; haven’t met a big coach owner who hasn't experienced the same…especially us western state desert goers!

Your increased temperature is nothing to worry about, however.

 

[JRS]

IMHO it's a good move to tilt the exhaust away. Per above and via my experience, I wouldn't worry about that temperature.