Tire Monitoring Systems

Keeping tabs on air pressure can reduce premature tire wear and help assure a safe ride.

By Mark Quasius, F333630

September 2015

Tires are one of the most important parts of a motorhome. It’s impossible to drive and maneuver without them, yet they often are overlooked when it comes to safety. Think about it: That heavy box of steel, wood, and fiberglass rides on only a few rubber balloons filled with air. A safe arrival at your destination depends on those balloons not failing.

Fortunately, more engineering goes into tires than a basic dime-store balloon. Tread patterns, sidewalls, and overall tire construction are designed to provide good handling, a smooth ride, and a reasonable lifespan. Yet, everything riding on those tires is supported by the air inside them. Without air, you go nowhere. Raising the air pressure in tires increases their ability to carry more weight. If tires are filled to the correct pressure according to the tire manufacturer’s inflation charts and actual vehicle wheel weights, everything works great.

Tire pressures are rated according to cold inflation pressure, or CIP, and can be measured accurately with a tire pressure gauge. However, driving heats up a tire and increases the air pressure, which is why a reading taken after pulling into a rest stop is much higher. Checking the tires each morning while they’re cold is a good practice, but it doesn’t offer protection against a loss of pressure while driving. For that, a tire pressure monitoring system, or TPMS, is needed.

A TPMS consists of sensors located on each rotating wheel. The sensors communicate wirelessly with a monitor in the cockpit to provide a real-time warning to the driver when a tire’s air pressure falls below a preset pressure threshold. A number of systems are on the market and accomplish this in various ways. Antenna options also are available, depending on the TPMS brand. Some sensors are capable of providing tire temperature as well as pressure information.

Two basic versions of TPMS sensors are available: internal and external. An internal sensor is mounted on the inside of the wheel rim and most often replaces the valve stem, because the sensor incorporates its own valve stem. This version is used on virtually all cars and light trucks manufactured today.

External sensors screw onto the outside of existing valve stems. External sensors generally do not interfere with a factory-installed TPMS on a towed vehicle; the monitor will learn the location of each sensor. External sensors require rigid valve stems, so if a towed vehicle has the flexible rubber type, they will have to be replaced with metal stems. This prevents centrifugal force from the weight of the external sensor from flexing the valve stem, which can cause the stem to leak at first, and eventually fail.

Because external sensors can be stolen, many manufacturers are now using a theft-proof design. External sensors also can be damaged or destroyed by rocks, especially when off-roading in a vehicle such as a Jeep. Internal sensors, on the other hand, are theft-proof and damage-proof. However, if a vehicle already has a factory-installed internal TPMS, it’s possible to use external sensors on the valve stems for the RV monitoring system. Fortunately, some systems allow a second monitor to be placed in a towed vehicle so the TPMS can be used when that vehicle is driven away from the motorhome.

As previously noted, a tire heats up when driven. It is normal for a properly inflated tire to reach 120 degrees Fahrenheit. However, an underinflated tire can reach much higher temperatures, depending on the air pressure. Low air pressure causes the layers, or plies, in a tire to flex and rub against each other, creating heat. Tires usually are cured at temperatures well above 200 degrees. If tires overheat and reach that temperature, reversion can occur, which returns the rubber to its uncured state. Any tire that reaches 175 degrees should trigger a warning, regardless of pressure.

Normally, if a loss of air pressure causes temperature increases, the TPMS will signal the pressure problem before temperatures get anywhere close to 175 degrees. In such a case, having a TPMS that monitors temperature is redundant. However, at times other factors can contribute to a serious rise in temperature. I had a personal incident that further underscores the benefits of a TPMS with temperature monitoring.

We had just left our campsite in Custer State Park in South Dakota with the motorhome towing our Jeep Wrangler. We had driven about 20 minutes through the park when suddenly the SmarTire TPMS sounded an alert. I pulled over and found that the alert was triggered by the Jeep’s rear tires reaching 175 degrees.

The pneumatic breakaway solenoid had failed on the auxiliary braking system; the air pressure was causing the rear brakes to drag on the Jeep. If I didn’t have a high-temperature alert, I would not have known, because the air pressure in the tires was fine. Continuing to drive would have overheated the tires to the point of reversion, and they would have failed. It’s also possible the brake fluid could have caught fire. Since then, I have determined that I will have a TPMS that monitors temperature as well as pressure.

The SmarTire system was purchased by Bendix Commercial Vehicle Systems LLC, which now uses the technology to monitor 18-wheelers that frequently swap trailers. Unfortunately, the company has dropped support for the RV industry, so this state-of-the-art system is no longer available for motorhomes. However, many other manufacturers have systems tailored for RVs.

Advantage PressurePro manufactures two systems that are suitable for RVs. Both are made in the United States and use external sensors.

PressurePro’s 16 Wheel TPMS Monitor not only alerts users to low and high pressure and high temperature, it also features built-in data-logging capabilities so that up to 45 days of tire performance history can be viewed using PressurePro’s free management software. Tethering to other devices is also possible. The PressurePro 6.5-inch-by-3-inch monitor uses an easy-to-see LED readout as well as red LED graphical representations of each wheel position. The system can be powered by a hardwired cord, a 120-volt wall plug adapter, or a standard 12-volt receptacle plug. A compact rubber ducky antenna can be placed directly on the monitor; a cabled antenna kit and repeaters are available for larger coaches. The sensors are 0.7 ounce each, and 1.1 inches in diameter, and a sensor locking kit is available. The sensors do not have user-replaceable batteries; rather, the sensors are sealed in order to enhance durability and performance in all weather conditions. The sensors reportedly last five to six years in RV applications. Various mounting options are available for the monitor.

The new PressurePro Pulse system marks the launch of PressurePro’s TPMS+ line. The 4 1/2-inch-by-3-inch LED monitor is customizable, allowing users to choose from common setups or create their own. Pulse displays can monitor up to 80 tires and up to five vehicles, so the system easily can be moved from one vehicle to another. Changing setups or switching between different towed vehicles is a simple two-button operation. Pulse also allows data logging for those who want to take a proactive approach to tire wear by monitoring historical data using an SD card to transfer information to a PC. Six customizable alerts include low pressure (two settings); upper pressure; high temperature; quick leak; and cross axle. A J1939 data buss is also included, which allows tire information to interface with a networked multifunction display, such as the SilverLeaf Total Coach system or VMS/PC.

The Doran 360RV system features valve-stem-mounted sensors and a 5.7-inch-by-2.2-inch LCD display. The system, which includes a prewired 12-volt plug, is designed to be programmed and installed in less than an hour. It can handle up to 36 wheel positions.

The system allows for customized baseline tire pressures and provides multiple visual and audible tire pressure warnings, including the patent-pending FastLeak alert, which is triggered when pressure in a tire drops by at least 4 psi in less than 16 seconds.

A lithium-ion battery, with an expected life of at least five years, is built into each Doran sensor. The sensors are spin welded and the components are encapsulated in potting material to protect against vibration, temperature change, and impact, so the batteries are not replaceable. However, replacement sensors are easily programmed.

The system comes with a variety of mounting options, and optional sensor locks are available. A signal booster or remote antenna kit is recommended for use with diesel pusher motorhomes to ensure reliable signal reception and to maximize the useful life of the sensors.

Tire-SafeGuard, from HCI Corporation, claims that its systems have superior signal reception and therefore do not need a signal booster for most RVs.

The wireless portable monitor can support up to 20 tires on two vehicles. The monitor, which is powered by a rechargeable battery, mounts on the dash and uses a rubber ducky antenna to communicate with cap-style or flow-through sensors; the latter allow air in the tire to be refilled without removing the sensor. The sensors have user-replaceable batteries.

The system can be configured to monitor only the motorhome or only the towed vehicle, when not towing.

Hopkins Manufacturing Corporation, the makers of BrakeBuddy, offers nVision, a portable unit with a flip-up display. This system monitors both pressure and temperature via external sensors. The system has four memory positions, so it’s easy to connect to up to four vehicles without reprogramming. The system uses external cap-style sensors. The base TPMS system includes four sensors; additional sensors can be purchased in sets of two. A repeater is available to boost the signal on larger motorhomes.

The TireMinder A1A from Minder Research communicates with up to 22 external sensors. Its 1.8-inch-by-2.6-inch LCD display can be placed in the included window bracket. Sensor updates occur every four minutes (whether the vehicle is moving or not), and the system performs self-diagnostics every five seconds to warn of unstable tire conditions. The display shows each wheel position and provides low-pressure and high-pressure alerts, as well as temperature information. Current pressure or temperature readings can be seen by manually toggling through each wheel position. The lithium-ion battery in the monitor has a service life of 5 to 10 years. The charge life is about 48 hours, which, depending on how much driving you do, may last for one to four weeks. Charging is done via a standard micro-USB cable. The sensors are secured with Allen screw antitheft locking rings and weigh 0.5 ounce each.

A user-replaceable CR1632 watch-type battery powers each sensor. TireMinder includes a free battery exchange program; you send back old batteries, and the company sends free replacements, as well as any O-ring seals or sensor caps you may need. A spare set of batteries is included, so you won’t ever be caught without them during the exchange process. The system features a temporary disconnect mode to facilitate separating the motorhome and towed vehicle when not towing. The kit also comes with a hardwired booster to eliminate electronic interference.

The TireTraker TPMS from RV Safety Accessories range from four-wheel to 22-wheel versions. The system includes a 2.2-inch-by-3.5-inch monitor with a built-in antenna. The backlit LCD screen shows three stages of low-pressure alerts and two stages of high-temperature alerts. A rechargeable battery in the monitor holds a charge for up to 30 days. A dedicated charger is included with the system. The sensors weigh 0.4 ounce each and use CR1632 batteries, which are user-replaceable. The TT100A hardwired 12-volt signal booster is an optional accessory. When no motion occurs for 15 minutes, this system goes into sleep mode to conserve battery life.

Tire-Protector can monitor up to 22 tires. Its low-profile LCD monitor displays both high-pressure and low-pressure warnings, as well as high-temperature alerts. All of these alert settings are user-adjustable. The sensors detect tire pressure and temperature readings every five seconds. A loss of pressure or rise in temperature immediately triggers an alert that warns the driver.

The system uses either standard external cap-style sensors or external flow-through sensors. All sensors include an antitheft locking collar that secures the sensor to the valve stem. The flow-through sensors allow filling of tires without requiring removal of the sensors.

The sensors have a battery life of two to three years. A battery-replacement features allows batteries to be installed without changing the sensors.

Truck System Technologies (TST) offers a wide selection of RV tire pressure monitoring systems that can handle from one to 22 tires, depending on the system. Truck System Technologies reps claim that the company was the first in the industry to offer sensors with user-replaceable batteries. Its products are ISO certified.

The TST 507RV series uses 1-inch-tall external sensors that are powered by user-replaceable CR1632 batteries. The theft-resistant sensors are designed to last indefinitely, with typical battery life of about one year. The sensors come with a special wrench for removal from the valve stems. The sensor’s outer housing will spin free unless the wrench is applied to the sensor’s base. The 3.5-inch-by-2.4-inch monitor can be powered by a rechargeable lithium-ion battery or by a power cord that fits a standard 12-volt power receptacle; the power cord also can recharge the battery. The unit has a built-in rubber ducky antenna, and a remote extender is available to expand the operating range. A breakaway feature allows the towed vehicle to be removed from the coach monitor when not towing. A second monitor can be added and placed in the towed vehicle to monitor pressures when driving away from the RV.

The TST 507 Flow-Thru system comes with larger — 2 1/2-inch-long — flow-through sensors that allow air to be added to tires without removing the sensors.

The TST 507 Internal series uses the same monitor as the TST 507RV, but the sensors are internal rather than external. Internal sensors do not require replacement of the valve stems; adapters allow the current valve stems to be used. However, if desired, new valve stems are available in 1-inch, 2-inch, and 3-inch stem lengths. The internal sensors have a seven-year battery life, thanks to a movement-based charging mechanism that was developed by TST engineers working in conjunction with a University of Maryland professor.

The internal sensors are popular with Jeep owners who travel off-road, where external sensors easily can be damaged. Such owners must replace the towed vehicle’s factory-installed sensors and add a second TST monitor to the towed vehicle so its tires are monitored when it is driven. The detailed information on the TST monitor is more helpful than the factory-installed systems, which generally issue a warning only when the tire pressure is low.

The TST 510 series uses external sensors that are similar to the TST 507RV, but they include a five-year military-grade battery.

All TST units measure temperature as well as pressure. The internal sensors are the most accurate and pick up the heat of the wheel rim much faster. TST has found that external sensors, which sample the air inside the tire, have about a four-degree lag when compared to internal sensors.

Regardless of which system you choose, it’s important to monitor tire pressures. A loss of more than a couple of pounds per square inch of air pressure will cause a tire to work harder than it was designed to. This will lead to premature wear and failure that can have serious consequences. A TPMS provides a warning so an issue can be resolved before it becomes critical.

For more information and pricing on tire pressure monitoring systems, please contact the following manufacturers:

205 W. Wall St.

Harrisonville, MO 64701

(816) 887-3505

2851 Massachusetts Ave.

Cincinnati, OH 45225

(866) 816-7233

11245 E. 183rd St.

Cerritos, CA 90703

(818) 400-9976

P.O. Box 1157

Emporia, KS 66801

(800) 835-0129

P.O. Box 47

Port Salerno, FL 34992

(772) 463-6522

13833 S. Schechert Way #13

Yuma, AZ 85367

(866) 200-9773

11775 Encino Ave.

Granada Hills, CA 91344

(800) 659-6339

4250 Keith Bridge Road, Suite 200

Cumming, GA 30041

(770) 889-9102

*FMCA commercial member