Tire Pressure Monitoring System - Need vs. Want

[Jon Wehrenberg]

I don't think there is a silver bullet when it comes to tires and monitoring their condition.

No tire pressure monitoring device is going to warn of an impending blowout from a tire that is properly inflated. It won't warn of tread separation. It will warn of loss of air pressure but it could also fail to warn as Kevin points out.

Doing a pre-trip and periodic tire pressure check and inspection may also fail to detect issues.

I think the bottom line is that we should not place all our trust in any one method of checking tires and no matter what steps we take, or what devices we employ we still can have problems. Where I see red flags is when I hear owners place 100% faith in their method of checking tires. I have heard owners tell me they do not check their tires the old fashioned way because they can see the pressures on their tire monitoring system. Maybe they are comfortable relying on a mechanical device, but stuff fails. If I had such a device I would still feel the need to verify at least once the readings were accurate, and I would never stop my practice of visually looking at my tires on a walk around combined with running my hands over the portion of the tread I can easily reach to feel for nails or other defects such as cuts. Nothing is perfect, but we can approach perfection by stacking the deck in our favor by using multiple methods to verify tire condition, including using a temperature reading gun right after stopping to make sure all tire temps are the same.

If I were to stress any single issue that I see with tires it would be to never ever allow tire pressures to drop 20% below the required pressure for the weight the tire carries. As soon as a tire has been run at low pressure it is scrap, and while it may look perfect, and have good tread depth it may be damaged so bad it will fail catastrophically and without warning.

[phorner]

I guess over my RV driving career I've been a bit obsessive about checking my tires. Nothing gives me more concern than a catastrophic tire failure at highway speed.

And, to be realistic, there are some failures that I simply cannot protect myself against. As Jon says, the best I can do is try to stack the odds in my favor as best I can.

To that end, I recently installed a Pressure Pro TPMS on the bus and Hummer (thanks, Tom!) and yet I still cannot bring myself to rely solely on this system. To me, it is another tool, another source of information, that I can use to help keep the odds in my favor.

It offers some peace of mind knowing that while I am driving, I can still monitor tire pressures. This of course is not possible without a TPMS of some kind.

But, the Pressure Pro will not replace my visual inspections before starting out each day and routinely at rest stops.

And I'll keep that rabbits foot right next to my 4 leaf clover and always step out of the bed with my left foot first in the morning and wear my lucky socks while driving the bus....just for luck

Can't hurt...

[rahangman]

John & All....I agree with most all that has been discussed, but wonder about the IR Gun ( I use it for enroute stops & visual) anyway, is there any particular Temp? Mine all check pretty even, through one side (sunny) might be a bit warmer. They also seem to cool real quick. I have the "Tattle Trail" system but am considering a TPMS also on in lieu of.

[phorner]

I use an infrared thermometer at rest stops and look more for uniformity than an absolute temperature.

Sunny side of the bus is definitely warmer....

[pwf252]

Although I have an infrared gun I tend to relay on the temperature readings given to me by my Tire Pro System, which leads me to this question. Typically it shows a variance between the temps on the steer versus drive versus tags. I always assumed that to be standard given the verying tire functions/locations. Specifically the drives run hotter then the steers by maybe 10 degrees and the tags by 25 or so. Does anyone think thats not typical??
And Paul , while I can certainly buy into the rabbits foot and 4 leaf clover the lucky socks thing just seems like nonsense and I would suggest not relying on that to heavily.

[Jon Wehrenberg]

Patrick and Rodger bring up some interesting points. I'm not sure we have anything but anecdotal evidence, and we have little of that.

I inflate my tires according to the Michelin tire pressure tables. Why the engineers pick those pressures is beyond my pay grade, but on my coach if I get out and use the IR gun as soon as I am stopped the temperatures at about the center of the tread on every tire is almost identical regardless of position. The sunny side is slightly higher, but I think when driving both sides are equal but I have no way to prove that. Maybe the folks with the temperature sensing capability can recite if there is a sunny / shade side temperature difference when driving.

The outside air temperature affects the tire temperature (and the tire pressure increase) but after a run at 80 degrees ambient on a sunny day I am not surprised to see 135 degrees. I have never recorded the outside temps relative to tire temps relative to speed so I have no clue what normal is, nor do I know the impact of higher ambient temps. I am only looking for consistency as Paul mentions with an abnormal high temp being a clue to low pressure.

For Patricks variation between axles, and my consistency between axles we would have to compare axle weights, tire pressures (as compared to Michelin charts), speeds driven and probably ambient temps. I suspect, but do not know that at higher speeds the drives are delivering more HP to the road and tire slippage may contribute to the higer temps. Higher than specified tag axle pressures could explain the 25 degree spread as can the steer axle tire pressures.

[TerryM]

Thanks for all the input.

A TPMS sounds like cheap insurance and peace-of-mind. I realize it can't predict a blowout or road hazard but it sounds to me like it is better to have more information then less.

I'm going continue my visual inspections before every trip and when we stop during the day and I'm going to invest in a TPMS. I fired off an email to Tom about Pressure Pro this afternoon.

Thanks for your help.

Terry

[jack14r]

Terry,I agree that it is cheap insurance and a TPMS just adds to our knowledge.

[rahangman]

Ooops, I should have brought this up with my previous post. Where do "We" use the IR gun. I tend to spot about the middle of the sidewall, this being the thinnest (weakest) point of construction. Yes, the tread hits the ground, but with our sidewalls thinner I am thinking it gives a truer temperature? Hmmmm

[Jon Wehrenberg]

Being thinner the sidewalls also give up heat faster than areas of greater mass, such as the tread. A problem with sidewall readings is the inability to read the inner drive. If you are going to lay on the ground to get a shot at the sidewall on the inner tires you might just as well use a tire gauge.

While using a tire gauge on hot tires will not give you an accurate measurment of what cold tire pressures are, checking tire pressures when the bus has just stopped is also a good way to get a quick idea of the tire pressure when cold. We all know when tires heat up pressures rise. If tire pressures are taken when cold, then when hot keeping a short record to make a chart based on various outside temperatures a person would have a very good idea if pressures (cold) have changed. As long as a person understands you do not let air out of the tires to bring the pressures down when the tires are hot the readings are a good reference point.

A second point to check temperatures for those using an IR gun is at the wheel very close to the hub. This will give an indication that the bearings are not overheating such as due to low fluid and that the brakes are not dragging. We can do the same thing to the tires and wheels on the toad.

If we are still looking for something to do we can open the engine doors and do a complete engine inspection to make sure the belts are OK, fluid levels are OK, etc. By the time we do all this however we won't have time left to drive.