Tire pressure, how high is to high ?

[DMTTRANSPORT]

Originally Posted by gnlandrus

My question is, what would be considered a dangerously high pressure that would require me to pull over and deal with it ? Lets use a steer tire with a cold pressure set to 110 lbs. as an example. At what pressure should I take action, assuming all other conditions are normal.



Sent from my iPhone using iRV2 - RV Forum

This is an example of my statement, you are talking of a high AP which will happen in a normal case and in a low tire/leak/puncture case, are you going to pull over every time the pressure seems high?? bump the tires every evening and when fueling...

[IASM]

Greg-I don't think that's something under your control unless the tire is overloaded or running under inflated and building to much heat.
The manufacture is assuming temp and pressure increase in there charts. I would make sure the weights are known and cold pressure within guidelines.
Rod

[britcon]

Originally Posted by DMTTRANSPORT

This is why I do not own a TPMS, sure it will let you know if you have a tire going down/flat, but thats it, rolling down the road you will get unrealistic readings depending on the tire temp., OAT, ALT, etc.

To each his own. Personally, I want to know if my inside dual is going flat before it comes apart and rips the heck out of the wheel well. Cheap insurance IMHO.

[DMTTRANSPORT]

Originally Posted by britcon

To each his own. Personally, I want to know if my inside dual is going flat before it comes apart and rips the heck out of the wheel well. Cheap insurance IMHO.

Never needed one with 58 tires rollin and a heavy load, it's like the auto slack adjusters they also keep you from hands on issues....JMHO!

[Greytraveler]

Tire pressures will vary with the temperature. For every ten degrees the pressure will change by a pound.

[JumboJet]

Originally Posted by DMTTRANSPORT

This is why I do not own a TPMS, sure it will let you know if you have a tire going down/flat, but thats it, rolling down the road you will get unrealistic readings depending on the tire temp., OAT, ALT, etc.

After checking tire pressures before our most recent trip, I monitored the TPMS screen the entire trip. 155 miles from home a tire began losing 1 PSI every 10 miles. The pressure was within range when I stopped 90 miles later but, the next morning the tire was down to 15 PSI (Flat) and was taken in for repair.

TPMS works for some things.

[Betr2Trvl]

Setting the alarm levels on the TPMS does not have to be an exact science......

For low pressure, I set mine about 5#s below my minimum cold pressure settings.

For high pressures, set it initially about 20-25#s higher than your cold settings. Then simply see what you get across all the tires too after driving a while, then adjust your alarm setting from there. I have mine about 10#s higher than what I saw on hot tires on hot summer afternoons.

As noted, if I get a low pressure alarm after driving, I would have lost about 20#s of air pressure from the hot pressures at that point which would indicate a leak of some sort, which is what I (and I would think most people) are most concerned with. We usually check the monitor throughout the day when we are driving just to make sure all seems good. And I am really just as concerned with the toad pressures as I am the coach, since you have no feel if a toad tire is going down, or for instance, the parking brake is left engaged and you get a heat or high pressure warning from dragging a tire.....

Btw, on high pressure tires on a MH your pressure deviation is closer to 2#s per 10 degrees ambient while your car is about 1# per 10 degrees (rounding both to keep it simple). So the OP gained about 6-8#s just based on ambient temp.

The other thing to keep in mind is that you drive very little on cold tires, just a few miles before they heat up and you see the pressure gains which can vary quite a bit even from the same cold setting depending on sun, sun on one side or the other, rain, ambient temp changes, etc. Cold tire pressures are just that, cold minimum pressure settings. Even so, on my cars and MH, I'll set a bit higher in the fall if I set my tires when it is 70 degrees for instance and expect to drive in cooler temps where I'll loose a few pounds due to lower ambient temps.

Regards

[Selah]

My TPMS cost a little over $300. Friend of mine saved $300 by not having one. Same friend had a flat on his toad that cost over $1800 to repair. Friend now has a $2100 TPMS.

[Crasher]

When you first install a good TPMS, it's a good idea to just monitor what is happening as you drive. The OAT and heat from the rolling tire will increase the pressure and to some extent the temp readings. I don't pay much attention to the temp reading, because it is influenced both up and down by the OAT. For the first few trips don't be alarmed by what you see. After several trips, you will know what is normal for the tires on your motor home. This assumes that you started with the correct pressure in each position. Now, after seven years of experience with a TPMS, I know what is normal and when to be concerned. In that time, I have had a blown trailer tire at night. I had no idea it had blown except for the monitor alarm which showed me what position had lost pressure and that the other tire on that side was increasing in psi and temp at an alarming rate due to the added weight it had to carry. I stopped, changed the tire and was on my way. I can only imagine what the damage and cost would have been without my TPMS when the second tire failed. Needless to say, I'm a believer.

[Gary RVRoamer]

rolling down the road you will get unrealistic readings depending on the tire temp.

What's unrealistic about that? It is the actual pressure in the tire at that time.

Tire pressure increase about 2% for every 10 degrees of temperature change. If you set the pressure when the tire was at 20 F. ambient, and then drove it 20+ miles, the tire itself probably climbed to 90+ degrees. Maybe more under some conditions. On a warm day it is not unusual for a tire to hit 110+ degrees. That's an easy 15% increase, and 20-25% is not out of the question. Nor is that necessarily a problem, but it is worthwhile to be warned it is happening, in case the cause is something else, e.g. an overheated wheel bearing or a dragging brake.

[Ray,IN]

According to Goodyear:
"IMPORTANT: It's a common practice for RV owners to lower tire pressure in their search for a smoother ride. This is not only dangerous, it's relatively ineffective, as the difference in ride quality is not significant."

When you run the minimum air pressure for your load instead of mfgrs tire placard, you make your MH more susceptible to sway from wind, passing large vehicles, and sudden maneuvers.
As to how high pressure must get to be dangerous, Tireman9 is IMO the best person to actually know. If I remember correctly, he was a tire design engineer when working.

[Crasher]

Originally Posted by Ray,IN

According to Goodyear:
"IMPORTANT: It's a common practice for RV owners to lower tire pressure in their search for a smoother ride. This is not only dangerous, it's relatively ineffective, as the difference in ride quality is not significant."

When you run the minimum air pressure for your load instead of mfgrs tire placard, you make your MH more susceptible to sway from wind, passing large vehicles, and sudden maneuvers.
As to how high pressure must get to be dangerous, Tireman9 is IMO the best person to actually know. If I remember correctly, he was a tire design engineer when working.

So who's recommendation do we follow, the Motor home manufacturer who must cover any liability of some owners irresponsible loading and assumes maximum weight or the tire manufacturers load chart that through testing has determined the correct pressure for any given load? The load chart may give the minimum pressure, but it is also the correct pressure. I had an Avalanche that the placard said 35 psi in the tires. Depending on the load, I carried as low as 26 psi using the load chart. At 80,000 miles the tread wear was even and still safe to drive. The load chart recommendations work, but require an operator that is diligent in following it.

[Ray,IN]

Crasher, follow the MH tire placard air pressure, tire mfgrs do not know how their tires will be used, that is beyond their control.According to the RMA/Rubber Manufacturers Association, over 90% of all tire failures are due to underinflation/overloading.

Back to the original question; bursting pressure of MH/truck tires. This 1983 study from U of Michigan says a radial truck tire will burst somewhere around 341 PSI. This is also enough pressure to deform the bead surface of a one-piece truck rim, making is unusable.
That said, the sidewall listed air pressure is self-explanatory, but tire mfgrs.also say 10-15 PSI over that is still safe.

[Mr_D]

Originally Posted by Ray,IN

That said, the sidewall listed air pressure is self-explanatory, but tire mfgrs.also say 10-15 PSI over that is still safe.

If that was true then why does it keep coming up time after time?