tire pressures

Inner duals:

Out of air flow
Passenger side close to tailpipe (at least on Ford)
Crown of road increases load

Inner Passenger side dual:

Even worse
When we drop the outer dual off the pavement (unintentional of course) the inner takes all its load.

I have always wondered about the ambient temperature and the cold pressure setting. I don't let pressure out because the morning temperature is a bit warmer one day versus the next. I set mine the other day and was at 81 and 81 for the two rear tires. Temperature was around 70. This morning the temps were under 60 degrees and the pressure had dropped to 76 and 77. We are moving into summer so if I will watch and may need to make a slight adjustment one way or the other. That should do it for the next several months. I do get frustrated with garages. Some seem to take it upon themselves to change the tire pressures when I go in for an oil change. I usually remember to tell them to leave the tires alone. Once I pulled in to a quick change for an oil change. The tires had been running on hot pavement all day. The shop lowered the pressures on the rear tires to about 70 psi. That was probably equivalent to around 60 psi cold.

I have Michelin tires on my Class C. I run mine at 78 to 80 lb. cold. I run the fronts at 75 lb. cold. I do not use a tire monitoring system.

What matters is what the tire pressure reads after the tires have cooled back down. Do all the tires read the same (within 2 lbs. for duals)? Do not lower the cold pressure on the inside duals. That could cause them to overheat.

The problem I ran into after replacing my original 10 year old Michelin tires is that all the standard rubber valve stems leaked within 3 years. The valve stems must have been from a bad batch. I now use steel valve-stems with extensions so I can test tire pressure as often as I need with a good quality pressure gauge.

I check tire pressure every morning before driving on a multiday trip. "Cold" means ambient temperature for that day (per my RV manual. If the next day is hotter you might need to release air to get back to 80 lb. maximum before driving that day.

DO NOT LOWER THE PRESSURE! The inside tire will always run hotter than the outside tide because of less airflow around the tire to cool it.

pianotuna wrote:
Hi,

I have a tire pressure monitoring system.

I'm noticing a trend while driving that the inner dual tires on both sides are warmer and exhibiting higher pressure than the outside ones. On my last trip this caused the over pressure alarm to ring on the inside duals. (and the first alarm scared me) The rear axle alarms at 97 lbs.

At the moment I'm running 65 lbs in the front, and 80 in the rear. (cold pressure)

I'm considering putting a little less pressure in the inside duals.

An old rule of thumb for tires: You don't want more than a 10 percent build up in tire pressure. If you get more than 15 percent, take immediate action to reduce.

Dude, you're over 20 percent!

First, SLOW DOWN. Until you figure out what is going on, reduce your speed to generate less heat. Heat is the tire killer.

Second, verify the pressure build up manually. You need to be sure what you are seeing is accurate.

Third, weigh the truck - fully loaded and by individual wheel position if possible. Compare those values to the GAWR. It might be your truck is too small, or you might have a bent axle.

Lastly, your tires are likely damaged by the heat. Make it a habit to rub your gloved hand over the circumference of each tire before every major tow. You are looking for bulges. If you find one, immediate go to the tire shop and replace those tires.

Can you turn off the HP alarm?

I have a SRW. The rear tires start at 80 psi and the pressure rapidly builds at highway speeds especially on a warm day. When the pressures go over 93 psi, the system stops working. I don't get an alarm but the pressures read "254". Again, I cannot see the final temperature but it must continue to build in to the range of 95 to 100 psi.

Do not put less pressure into tires that are working hard. Be sure you are at 80 with totally cold tires.

I know my tires are running at close to maximum load. Unfortunately I have 17 inch rims and the only feasible upgrade seems to be to spend a small fortune going to 19.5 rims and tires.

17 psi is not a huge increase in pressure while driving, in my opinion, though I don't claim to be a tire expert. I would generally expect the inners to heat up more than the outers, both because of somewhat reduced airflow around them and because they're closer to the brakes (and bearings, but bearings should not be generating much heat).

Reducing the pressure doesn't seem like a good idea to me, and may well be counterproductive, making the tires heat up even more. I understand it's always best to have both twinned tires in a dually at the same (cold) pressure.