Never thought I would need/use such a thing until today. I am always checking the tire pressure on all of our vehicles. Well we had the 30' toy hauler pretty well loaded up. On our way home from REW PA the warning light came on. thought I had a flat tire coming on. Nope, not at all. Temp was cooler before we left when i set TP at 65psi as I was towing max load for our truck. The temp was blazing. Tire pressure went up to 70psi with increase in temp. So they work if too low or too high to avoid a blow out. Reset to 65 psi hot and light went off. Wayyy cool. :rck:
Ours say 65psi max cold air pressure right on the side of each tire. 80 psi is for load range E. They do not make a BFG All Terrain in 285/70/17 in load range E that i am aware of. Ours are load range D.
Although the 5 psi you removed wouldn't make a huge difference, you really shouldn't take air out of hot tires, as long as the pressure was set correctly when the tires were cold. It's simple physics - when the tires heat up (either from use, direct sunlight or even just the ambient temp), the pressure inside will rise accordingly. Tire manufacturers take this into account when designing their tires. They are more than capable of withstanding the extra pressure created when they heat up.
When your tires (now set at 65 psi hot) cool off, the pressure inside will drop & you will be below your desired psi. In an extreme case, this could lead to a dangerous underinflation of the tires, which in turn could cause a catastrophic failure. Most tire failures on highways are actually due to underinflation - it causes the tires to overheat and then separate, resulting in a blow-out.
The problem is, it also moniters the spare tire as well. So it sets off the warning because there is more than a 3lb difference. the spare does not heat up as it is not on the road. OOPs, they did'nt figure on that. I suppose I will have to put a few extra pounds in the spare when I tow the camper.
That is just bizarre!? Why would you need to monitor the pressure in the spare? If it loses pressure, it's not going to be a life-threatening situation, just a PITA if you have another flat (which are fairly low odds).
Is there any way to disconnect or disable the monitor on the spare? It just seems a bit unnecessary, and would regularly cause the issue you had.
I'm constantly amazed at how engineers (presumably very bright people) can be so out of touch with the systems they design. For example, anyone ever try to change spark plugs on a V-6 Pontiac Fiero...
Believe me, I totally agree. I think they do things just to justify(at least they think so) thier jobs. But it is nice to know if the spare needs air too, especially if it is low and you are towing and need it. I had to buy a digital tire gauge, it goes to the .5 lb. I feel like a NASCAR driver now-need .5lb in the right rear LOL.
Quick update- set tires to 63psi cold before Adirondak trip. Spare was at 65psi. I thought I was good until the light went off and started dinging. Pulled over and checked again with same digital gauge that rezeros itself for accuracy everytime it is turned on. Fronts said 68psi-rears said 72psi. This is now starting to be a pain in the butt. Like NASCAR I constantly have to check the air pressure / especially when towing. For the ride home I did 65psi for spare-62psi for front and 60psi rear. The light did not come on all the way home- but it was much cooler outside temp than the day we went. So as it stands 62 front-60 rear and 65 spare seems to be the ticket when towing our camper.
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