One of the most challenging experiences for many motorhome drivers is checking and managing the tire pressure on their (usually) six wheeled chassis. We experienced this dilemma with our new Intrigue; and when we asked other motorhome owners for their suggested solutions, we found we were hardly alone.
We think it's a given that proper tire inflation is crucial not only to tire life and fuel economy -- it's a major safety issue as well. It's extremely important for RV owners (of any type rig) to know the fully loaded corner weights -- by having it actually weighed -- and then set the tire pressures to the manufacturers specifications. This is usually provided in the form of a small chart (and written in very fine print) which is provided with every new tire. But wanting to check and maintain the proper tire pressures is one thing -- accomplishing it is something else. Many RV tires have difficult to access valves. The inside dually is a special challenge, because it's very difficult to reach without either a special tool or the use of valve extensions. While valve extensions make the task much easier, many tire experts will tell you that perhaps the greatest cause of deflated tires on duallies is the use of valve extensions.
What's really needed, though, is not just the ability to check and adjust tire pressure from time to time. It's the added ability to actually monitor tire pressure at all times. Without some sort of aftermarket device, this is obviously not possible.
Enter what could be for some the perfect solution -- "SmarTire". While this product doesn't facilitate adjusting air pressure, it does something we think is extremely important: It provides a continuous digital monitoring of the actual pressure and temperature in each of the motorhome's six tires. It is espcially "SmarT" because it has the ability (within limits later described) to calculate what the "required" pressure of each tire is as it begins to heat up from road friction. With this intelligence, it can also (subject also to the caveat below) provide a continuous read out of the difference between the "actual" tire pressure and the "required" tire pressure at any temperature. If at any time the monitor detects that any of the six tires has gone below what the driver has set as the minimum pressure (e.g., perhaps 10 pounds below the cold inflation pressure required), a visual alarm goes on. If the pressure goes even lower (beyond a set value), an audible alarm sounds. As the tire heats up, the "required pressure" of course goes up. But this same low pressure warning system (e.g., a visible alarm at 10 pounds below "required" pressure at ANY temperature) continues to work regardless of tire temperature. A second set of alarms monitors temperature only, and if any tire goes above a set value (e.g., 195 degrees), the alarm is triggered. In this case excessive heat build up is frequently the immediate precurser of tire failure. But with this on board warning system, the driver has time to move quickly to the side of the road to determine the status of the situation before proceeding.
The system itself consists of a monitor for use somewhere in the cockpit, plus six small transmitters -- one mounted inside each wheel with an equal counterweight opposite to keep the wheel properly balanced. Obviously each wheel needs to be dismounted to accomplish the installation. The tiny batteries reportedly have a life well in excess of 50,000 miles. We had a rare case of signal interference caused by the addition of a VMS unit. However, this unusual problem can be cured by adding an antenna to the SmarTire monitor. We had no such interference with the VMS unit "off".
What we have described so far is an outstanding -- and we think extremely important -- source of safety information. But there are two limitations which you will often not hear or fully appreciate from the sales presentation of this product. For some these two items will be inconsequential. But we think it's important that we highlight them.
First, the present generation of SmarTire can only "read" tire pressures to 127 pounds. That's high, but not high enough for some RV tire applications. Our own Toyo tires have a factory recommended setting of 125 pounds, even though our own calculations show a setting of 115 is more appropriate to the actual fully loaded weight. Many RV tires will run at 80 pounds or less when properly inflated according to the manufacturers recommendations. Because our tires have a relatively high cold pressure setting (we use 115 pounds), it is fairly easy on a hot day to get the "actual" tire pressure above 127 pounds. When that happens, the temperature monitor continues to send back "real" temperature values, but the monitor "thinks" the tire still has only 127 pounds. As a consequence, at some point we get a false alarm -- in effect a reading which says something like "according to the actual temperature in your tires your actual tire pressure should be 140 pounds, but it's only 127 pounds, so I'm going to flash a red warning light". Of course this is not caused by a low tire pressure -- it's caused by a low tire pressure reading (i.e., 127 pounds). Reportedly this problem will be cured by the "next generation" of SmarTire products. The sales folks will advise there's no date certain for the release of the "new" type units, but with a problem of this magnitude one would have to assume it won't take very long!
Second, and this is purely a matter of cosmetics, a "permanent" installation of the monitor may not be a piece of cake either. While the monitor looks like something that should be part of the dash instruments, as a practical matter it is a stand alone unit with a long cord which plugs into a cigarette lighter. Most tire dealers, such as Les Schwab, won't want to deal with making a permanent electrical connection or finding a useful and "professional" looking permanent mounting. We've consulted with the Country Coach factory and getting the job done correctly will be a bit costly. Purchasers of the product will want to factor this cost into the purchase price of the product.
One final observation: We found the transmitter unit is capable of providing tire pressure values within the first 1/8 mile or less; while the temperature values often require running in excess of a mile. On an extremely cold morning this can cause a false alarm if the outside temperature causes the tire pressure to go below the set value for a warning. E.g., if the unit is programmed to issue a "red light" warning if any tire goes more than 10 pounds below the cold inflation pressure value, the first "pressure" readings transmitted may be 10 pounds or more "low" because of the cold outside temperature -- and for the first mile or so the "real" tire temperature won't yet be recording. This, too, is a rare occurence -- and we think not troubling.
Our bottom line is that even with the two "caveats" mentioned, the SmarTire unit on our rig is something that provides us not only essential information, but is an onboard "insurance package" which can greatly reduce the risk of running at dangerous pressure levels; and which can often signal a serious tire problem in time to respond to the situation. We think it's a good investment -- and with the "new generation" models will be even more valuable.