What is a good tire pressure monitoring system?

 

“What is recommended to monitor RV tire pressure? I check my dual tires with a hammer when on the road. I also use a gauge from time to time, but I’m looking for something a little better.”

As you may know, I monitor a number of RV Forums. I recently saw the above question. So here is my answer:

I am currently running the ONLY (as far as I know) direct comparison of Tire Pressure Monitoring Systems (TPMS): a TireTraker™ external vs. TST^® internal.

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TPMS “reviews”

Every “review” I see on the internet is basically someone’s opinion based on the use of one system, but I do not see anyone presenting actual data showing the accuracy of either the Pressure readings or Temperature readings. Sometimes I have noticed the “review” has links to sell the units that someone has “recommended,” but I do not see any direct comparison data or test results. I’m wondering if those posting the “review” are just interested in selling products?

I have more than 40 posts covering various aspects of TPMS on my BLOG and at RVtravel.com, if you want to do a “deep dive.” But the basic question you probably have is:

Prior report on what is the “best” TPMS?

I started my direct comparison of TPMS brands/types in March 2018 and have test data on Pressure and Temperature readings from 26°F to 98°F in actual service, along with a direct comparison of all 12 sensors for pressure accuracy measured on a custom-built test fixture.

While internal TPMS normally report hotter temperatures because the sensor is not being cooled from external air, I can report that the temperature difference runs about 20°F cooler on external sensors. Except for that difference, I would consider BOTH systems essentially identical when it comes to reporting pressure, which is more important than temperature readings.

The original poster on the Forum said he was looking for something better than the “Hammer Test”. Here are my observations on that test.

Tire pressure “Hammer Test”

While working as a Tire Design engineer (about 45 years) I was able to observe the “Hammer Test” when a dozen experienced (more than 500,000 miles driven) truck drivers were all presented with the opportunity to “Check” the pressure on two truck tires. As I recall, one tire was properly inflated to 105 psi and the other was set to 50 psi. We ran the test twice over the day and switched the tires around. Half the drivers could not consistently or correctly identify the tire with low pressure. Three of the remaining six did identify the low tire in both tests, but provided estimates from 30 to 75 psi. Only three truck drivers were able to correctly and consistently identify the 50 psi tire as being between 45 and 55 psi both times.

If you remember that any tire operated with a 20% or more significant loss of air is considered “flat,” the test results do not support the value of a Hammer Test other than the fact that if a tire has lost 75% or more of its air the “hammer” might tell you something was wrong.

What TPMS do I recommend?

With some 30,000-plus miles of use, I feel comfortable recommending either system, as the small variation in PSI reading and temperature readings are not, in my expert opinion, meaningful to the average user. I have replaced a number of batteries in the external system and expect the internals to need new batteries soon.

What is important, even if you get or already have a different system, is to be sure you test your system at least once a year, as I covered in this post.

It is also important that you program the warning levels for your RV, as the factory setting of the TPMS may or may not provide sufficient advanced warnings for you. Here is what I do.

Bottom line. I can recommend either system. I do suggest that any TPMS be purchased from someone that supports the RV community and that has a phone number and web page with info on the TPMS. There are some low-price units. But, personally, I think a TPMS with Lifetime Warranty is a good deal.

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Can you change a tire on your RV?

 

Can you change a tire on your RV? This is not a question of your physical ability. While that is something you need to consider, let us set that question aside for this post. Let’s imagine we are in great physical shape; or even if we can’t lift 150 pounds off the floor, we might be in a situation where there are others around who can lend a hand with the physical aspect of doing the task.

The intention of this post is to help people focus on the parts, information, and tools that might be needed to change a tire on the side of the road.

#1 Safety: You need to be sure it is possible to change the tire without putting you or others in danger. This means getting far enough off the highway that moving traffic isn’t going to be involved. There are almost an infinite variety of locations or situations, so I can only remind you to think first and review where you are. Since you have considered the proximity to moving traffic let’s move on.

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Even if you are not going to change the tire yourself you should probably have a couple of wheel chocks to place in front and behind the tire on the opposite side of the one you would change. This will help stabilize the RV when it is jacked up. When I was racing and towing my Camaro in a 26′ box trailer and needed to re-pack wheel bearings, I would leave the trailer hooked up to my 1-ton dually truck AND still I used wheel chocks.

#2 Information: No, tools are not the first thing to consider as there is some minimal information I would need to know before I even reached for a wrench.

A. Do I have a spare? Yes/No? That’s pretty basic, but I bet there are some folks that assume they have a spare when in fact they do not, as many RVs are sold and delivered without a spare.

B. Is the spare mounted on a wheel and is it inflated? Have you confirmed the inflation in the last year? Wouldn’t do you much good to change out a tire if the spare is also flat. I have suggested that sometimes having a dismounted spare can save you hundreds of pounds and dollars by not forcing you to pay the service truck premium price or even having to wait days for a tire of the proper size and load range for your RV to be located and shipped in. Some folks have found they have space for a spare and save the cost and weight by having just a tire that is not mounted. There is a lot of space in the center of an unmounted tire, so having one still allows you to place some of your “stuff” in the tire. This is most likely something owners of Class A RVs might consider.

C. Service trucks can mount and inflate a tire by the side of the road, but you need to know before the service truck is called that you have a tire. Or, if you do not have a tire, Question C is exactly what size (the numbers) and what Load Range, “F”, “G”, “H”, etc., you need. Are all of your tires the same size and Load Range? Many Class A’s have different-size tires front and rear. You do not want to pay for a service truck to come out only to find they did not bring the correct size. This is some of the basic information you need to have written down and easy to find so when calling for service you can give them that information. If you are going to rely on a service truck, the other questions about tools and air will not apply. Can you reinflate the spare if it is just low?

#3 Tools: So, moving on, let’s assume you and your co-driver and passengers or friends have the physical strength to change a tire and you have a mounted and inflated spare of the appropriate size.

Some basic items I carry myself:

Lug nut socket of the correct size. Have you confirmed the “6-point” socket fits the nuts on your wheels? 6-point sockets are less likely to slip and round out your nuts as seen here. Don’t just look, but confirm the socket is not too large. A 13/16″ socket will fit over a 21mm nut, but might be so loose that the socket spins on a tight nut and now you are stuck with a nut you cannot remove. Some nuts come with chrome covers that make proper fit difficult. Ask a mechanic, if you are not sure.

Socket extension. I have a Class C with dual rear wheels. The nuts are deep into the wheel so I needed a 12″ extension (be sure the extension is long enough) to allow a proper 90° between the socket and my “breaker bar“.

The 2-foot breaker bar allows me to generate the torque needed to loosen the tight lug nuts. My wheel nut torque spec is 140 In-Lbs., so I am using the extra leverage the 25″ bar provides to make it easier to loosen the nuts.

Speaking of lug-nut torque, what is the spec for your RV? Do you have it written down in an easy-to-find location? While we are on the topic of torque: Do you have a torque wrench that can measure at least 120% of the torque you need to ensure your nuts are properly torqued? When I am tightening the nuts I use the appropriate pattern or sequence of tightening the nuts, as covered in THIS post from my blog. Maybe in your notes you should include the sequence along with the torque spec.

For my Class C, GM specified 140 Ft-Lbs. I start with all 6 nuts “snug,” which means I turn the nut till it bottoms on the wheel. Then I step up in about 1/3 of the ultimate level so I set my “clicker” torque wrench to 50 Ft-Lbs. and, after following the sequence back and forth around the wheel, I then set for the second step at 100 Ft-Lbs., and again move back and forth in the sequence. Finally, I set the wrench to 140 Ft-Lbs. and tighten all the nuts. Side note: Checking torque does not mean removing the nuts and torquing again, but rather setting the wrench to your value and applying the appropriate torque. I would suggest you check torque every 50 miles until you find there is no movement of the nut. If you see a nut still turning after 100 miles, there is something amiss and you should learn why and take appropriate action.

Jack. Also under tools is the jack you use to raise the tire off the ground. There are many options, but I prefer a “bottle jack” as this doesn’t take up much space in the RV basement. I selected an 8-ton model as my rear axle “weight” is 10,256 lbs., so my 16,000-lb. jack is adequate. You need a jack with more capacity or the safety valve in the 5-ton jack may not allow you to lift 10,256 pounds reliably. I also carry a piece of 2″x8″x8″ board to help stabilize the base of the bottle jack if I am parked on sand or soft dirt.

Regarding jacking the RV and replacing the tire/wheel assembly: READ your owner’s manual as some RVs have a specific location on the RV that if not used could result in damage to the RV.

Suggestion: Once you have reviewed your owner’s manual and have confirmed you have the spare tire and all the tools and information you need, you can decide if you need to practice changing a tire or just review with a fellow RV owner.

Tires without traditional rubber? A tire expert’s opinion

 

The concept of tires made without rubber from “rubber trees” has been around for many decades. World War II and the potential of no “natural rubber” aka latex from rubber trees became a concern for the Allies. Plantations in Asia were under threat of attack and so were the plantations in West Africa. This spurred the development of “synthetic rubber” made from petroleum products.

Synthetic rubber

Firestone produced the program’s first bale of synthetic rubber on April 26, 1942, followed by Goodyear on May 18, United States Rubber Corporation (aka Uniroyal) on September 4, and Goodrich on November 27. In 1942, these four plants produced 2,241 tons of synthetic rubber. The American Chemical Society has a booklet on “The United States Synthetic Rubber Program, 1939-1945” if you want to learn more about the joint war effort.

Following the war, various tire and rubber companies expanded their work on developing “synthetic rubber” made from petroleum and many of today’s passenger and light truck tires are made with up to 100% synthetic rubber. Some of the properties used in mining, off-road, and heavy truck tires including sizes that might be used in a Class-A RV, typically require about 65 percent natural rubber and 35 percent synthetic rubber, as some properties such as cut resistances of natural rubber have not been completely matched by synthetic rubber.

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Race tires from guayule desert shrub

Last year Bridgestone Americas (Bridgestone) celebrated its first-year milestone of using Firestone Firehawk race tires with sidewalls made of natural rubber derived from the guayule (pronounced why-YOU-lee) desert shrub, grown in America’s Desert Southwest.

These tires are built in Firestone’s race tire facility in Akron, Ohio. Firestone has been working on the project of using guayule latex in tires for many years and, according to this Release, it looks like there have been some breakthroughs as Firestone has been using guayule latex for the sidewall rubber on its Indianapolis tires.

 

Does this mean that your RV tires might soon be made of guayule latex? Well, I would not hold my breath for a few different reasons. Volume production would require hundreds if not thousands of acres of guayule to be cultivated and grown to maturity. The use in Indianapolis tires is clearly a “Demonstration Project” and low cost is not a high priority.

Will Bridgestone enter the RV tire market?

Finally, I have not heard of any interest on Bridgestone’s part to enter the RV market, especially for ST-type tires. While currently Bridgestone and Firestone’s tires are available in LT and Class A sizes, I see little reason for the company to push to expand in the RV market as long as the majority of the tires are being overloaded and/or underinflated by the users.

While I have no current knowledge of the status of the program or what the plans are to expand the evaluation beyond Indianapolis race tires, if and when Bridgestone is ready and I hear anything more about guayule latex, I will let you know with an article here.