tire pressure

[AFChap]

Kix ... I don't like to get up before sunrise either so I am likely to check the tire pressure the night before departure!!

When I check 'em when the sun is shining, if the one or two in the sun are a few psi higher I just ignore it as long as they are relatively close to "right" -- I do like things to be exact, but I just let that one slide. I have learned that my "good" tire pressure gauge is apx 5 psi higher than my TST TPMS ... so which pressure should I try to match the tires to?? ... very distressing to a details guy like myself, but I am trying to get used to the idea that 5 psi one direction or the other isn't a big deal. Since I decided I needed to put 5psi more than the tire mfg chart calls for "just for good measure," that has been easier to do.

Here's the one that I am puzzling about right now ... my TST TPMS system shows temp in addition to pressure. While driving, the pressures may go up as much as 10 psi, and the temps as much as 30 degrees on the MH and 40 on the toad fronts. But when we stop for lunch, the temp on the passenger side duals goes up more ... the outside 5-10 degrees over the other tires and the inside as much as 20 degrees or emore!! As soon as we get back on the highway, the temps rapidly drop back to match the other tires. My first thought was that the engine exhaust is on that side, but it is pretty much behind the tires rather than beside them. The other possibility is the motoraid heat piped to the WH immediately in front of those tires -- I haven't look underneath, but maybe the coolant tubing is running close to the inside tire?

[KIX]

Hi Paul, What you do is the same as I'm doing. I have a Pressure Pro.

Having crawled all under my UA I can't think of anything near the RR tire set that's not near the LR set that would cause higher temps on the RR. I sure would like to hear what you figure out on that one.

[Ed_G]

Originally Posted by Rudolph

When you say cold do you mean 55 degrees or 90 degrees? I have my MH inside a building. Early morning temperature at 55 degrees tire pressure is 95, afternoon temperature at 90 degrees tire pressure is 100 to 105.

"Cold" inflation is spec'd somewhere near 70 degrees.. I don't recall the exact figure, but close. As far as pressure, fill the tire to at least the minimum cold pressure specified for your weight load. NOTE: that listed pressure is minimum. You CAN exceed it, and you will when the temperature climbs, but that is expected and OK.

[Broadstone]

I am very attentive to tire pressures ever since we had a blowout on an inside rear tire about 20 years ago. It sounded like a bomb went off inside the coach filling the cabin with rubber chunks and smoke. It left a hole in the floor about two by three feet in size, ruined the refrigerator, part of the leveling system hydraulics and the generator. We had it towed, replaced the tire and traded it 2 days later. We now carry an infrared thermometer which we use at fuel stops to monitor tire and hub temperatures on the MH and Toad at fuel stops. This practice may also have saved us a potential big expense when we discovered a hot wheel on the toad caused by the sticking aux braking system in the toad. We don't have tire pressure monitors on our MH (we will) but do on two of our cars and I've noticed that there can be an increase (2-3 #) in tire pressures after as little as 10 minutes of driving starting at recommended pressures. If tire pressure is allowed to become low, however, the pressure change is much greater over the same time and speed. BTW, we now use nitrogen and inflation pressures are extremely stable.

[dsbike]

Sorry for the long post, But I feel I have important info for all to read.

As an aircraft mechanic on large jets I have some experience with using nitrogen in tires. Nitrogen has been used in aircraft tires long before I started working on aircraft, about 30+ years. First myth to be discarded, " nitrogen does not leak down or change with temps" Nitrogen does leak down but at a much smaller rate than air. Nitrogen can change pressure at a much smaller rate also due to temp changes. We check tire pressures everyday on our aircraft and in the warmer months we service them with nitrogen about every 3-5 days. Leak rate of about 5-10 lbs for an average pressure of 210lbs. In the cold months we service about every 10-14 days. If the aircraft has landed with in the past 60 minutes we add up to 15psi. The biggest advantage to using nitrogen in aircraft is due to moisture or the lack of moisture. An aircraft flying at 30k' for an hour is subject to extreme temp changes and if we used air instead of nitrogen then we could have water form inside the tires and freeze causing an out of balanced wheel which could be catastrophic. For those who use nitrogen keep checking those tire pressure as a saftey measure. You never know when you may pick up a nail or get a leak in a valve stem.

Another major concern as stated above should be the date of manufacture. If you are not sure how to read this do a search on the internet. There are plenty of websites listing this info. 6-7 years is all you should be running your tires.

[Flagelpater]

FWIW My Tire Gage reads exactly the same as my TPM System after I service the tires. Last coach had nitrogen in all tires and almost no increase in TP as I went down the road according the the TPM System. Present coach still has Air, soon to be Nitrogen, and I see about 10 psi rise within 10 miles driven with 100 psi as set pressure, as read on the TPM System. The tire pressure is part on the suspension system design - Tire Pressure Too High will transmit more load to the rest of the suspension system, possibly leading to premature failure of components. I can see, on the TPM System, the effect of the sun on one side while driving. Before I had a TPM System I drove over a mile without realizing I had a flat on the Toad. And, another time, I drove many miles without knowing I had an inside dual tire with the valve extender hose severed! I had checked all tires before both trips. Depending on road conditions you may not feel the problem. One flat dual may overheat and take out the other tire!

[CLIFFTALL]

What aux brake system did you ?

Cliff

[Flagelpater]

Tire Condition should be should be very high, if not the highest, priority in coach safety. Professional drivers are always monitoring their tires, and we should also. The more you check them the more you understand what is normal. I used to think the chunks of tire we see on the road were from Recaps, not true, most are from tires that overheated and separated the tread. The tire manufactures have a name for this "Tread Off." The tread is the last part applied during assembly. When it comes off, it unravels and whips off. This whipping action can, and usually does, cause catastrophic damage, especially to a MH! I have the PressurePro, over 3 years and 30,000 miles, no problem.

[Broadstone]

Clifftall, I was using the Brake Buddy and to say that it was sticking misrepresents what actually happened; I had positioned the seat too far forward disallowing the piston to completely return to its unactuated resting point. Maybe I shouldn't be telling on myself but this was not my first experience with this issue. Coming back from the Fla Keys, after a warning from a following driver, we checked our toad and all 4 wheels were smoking and the front 2 hubcaps had melted off. We made it home (75 more miles) and ended up having to replace rotors, pads, front wheel bearings and McPherson struts. There, I said it. It doesn't reflect well on my attention to detail but if it helps anyone avoid this mistake it will have been worth it I suppose.

[Flagelpater]

I don't think any of us would be on this Forum if we were not trying to learn from others. Many times reading someone else describe a situation "turns my light on too." IMO We all need to be willing to share.

[Dick L]

All tire pressures are suppose to be set at 65 degrees F according to Goodyear RV information. If you are having problems with the sun raising the pressures a bit before you are able to get up in the morning and check them, try shielding the tires from the sun. It is good to keep the sun off the tires whenever possible anyway.

That is one cause of early tire failure - dry cracking from the sun. Same thing that causes wrinkles and aging on skin does the same with tires. I have seen excessive cracking on tires that are only 2 1/2 years old depending on how they are cared for. Bottom line - 4 corner weigh and adjust pressure based on weights and tires and check pressures often and be safe,

[Triker56]

Good thread. So far I have learned to never drive my MH at 30K feet without 100% nitrogen in the tires.
Air contains roughly 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, trace amounts of other gases, and a variable amount (average around 1%) of water vapor.

Will the expense of a added 22% more of nitrogen really be worth it?
Will it make the tires last years longer?

Using Pressure Pro I put only dry regular air into my tires.
Every May I drop the PSI in them down to 100 PSI(that's plus 10 by weight chart) and install the sensors.
In first of Oct. I take sensors off. And fill tires back up to 120 PSI for winter storage. Then next May do same.

I have never needed to add any air between putting the sensors on & taking them off the last several years. The pressure does change a little down & up all summer depending on temperature.

But it is always a little above the weight chart. So regular air will & does work. Your experience may be different.

[Flagelpater]

FWIW I should have mentioned that I had free access to nitrogen. If I had to pay a lot to have it installed I would have just put up with air from my MH system as well. One other benefit with nitrogen is that because it is so stable it is easier to see a trend when you are monitoring the pressure on a daily basis. The ambient temperature does not cloud up what would otherwise be obvious.

[Ray,IN]

I agree with you triker56.All one needs is to use a small moisture filter to remove nearly all moisture from your air compressor output. Many folks attempt to convince others that pure nitrogen does not expand/contract, unless they now how to change the laws of physics it's not possible.