Instructor: Jon Edwards, Les Schwab Tires, Junction City, OR
This is about tire monitors in a coach. Transmitters are wireless, and xmit to montior mounted near driver. Small antennae in back of unit receives signal, and monitor displays data on each of six tires..
Sensors are mounted with stainless steel strap to inside of tire. They have lithium battery on a kinetic switch. As motion occurs, the're flipped on, and they transmit information. The warranty is for 3 yrs/50K miles. But actual experience is closer to 7 years on commercial trucks, with "expected" life of 7 yrs or 70,000 miles. .
What does it do? Why do you need it?
Peace of mind. It monitors actual pressure (right now) in each tire. It toggles between each of the six tires on a motorhome.
It also monitors temperature. We care about air pressure because it creates heat. If you can guard against temperature, you can best monitor and mange tires. Heat always occurs BEFORE a problem. Gives driver an early warning. Monitoring temperature is the most important feature.
If you know temperature, you also know "required" pressure. You first tell it what the cold pressure should be. It's the RV owner's responsibility to know what it should be for his own coach.
It will tell you whether you are over inflated or under inflated based on the "slope" -- the changing requirements as heat builds as the RV is underway.
Warning: Two forms of low pressure warnings. Low pressure alert is more like an advisory. If you have 100 psi cold pressure, first warning level might be set to 92 psi. Any time it gets to 92 or less, an early "alert" (red light) comes on. Next is a "warning" which might be set at e.g. 90 psi. Third warning is where tire gets above a certain temperature. Truck industry recognizes that any sustained tire pressure above 195-200 psi will cause tire failure. Coming down hills w/brakes on will heat the tires. Problem is where you're on straight road and the heat goes up. Tire separation, sidewall deterioration, etc. may not be far behind. Going across the desert at 115 degrees, asphalt might be 140 degrees. Long term driving over 200 degrees will cause tire failure. Slow down, or even stop and let it cool.
What about tow car? There's a need, but no solutions yet. (??? I thought I saw one...)
Status: Difference between actual and required pressure. It's a built in sloping warning device. Start at 100 psi might go to 120 psi. "Required pressure" is now 120 psi too. Don't want to wait until tire pressure drops 30% before a warning is given. As air pressure ramps up, tire pressure ramps up, but status floats w/the new "required pressure" -- so if you're down 8-10 pounds, you'll get same warnings. Again, temperature is really what you want to be monitoring, so this is probably the most valuable feature.
All the programming is done at the monitor using two buttons. Entire programming sequence can be done from "setup" throught the various parameters used for your own coach.
Any overlap of signals from a nearby coach also equipped with SmarTire? If so, warnings would go off. It's conceivable, since they're on the same frequency. But it retransmits every 30 seconds, so any false readings would be momentary and quickly corrected.
Recommends "unplugging" after the day's trip. Nothing is transmitted until you start moving. So when you first fire up in the day, tire pressure isn't registering. You need to drive a few blocks.
One RVer with the SmarTire installed reported --Temperature: O/S temps in AZ at 100 degrees, registering 185 degrees; slowed to 60 mph and the tire pressure dropped 10 degrees.
Note: 127 pounds is the highest it will display (this can be a problem for coaches with high "cold" pressures.)
Temp will be more important. Inside dually will have less airflow, and two inner duals will run "hotter".
Push both buttons to 'standby' -- it shows six dots. One way to leave it while underway.
Accuracy of pressure compared to air guage. Guage is +/- 3 pounds; SmarTire is +/- 1 pound.
Problem: Intermittant operation of inside duals. When antenna is pulled out, that seems to solve it.
NOTE: This is going to be replaced by a newer model that will not have the 127# limit, and monitor more tires. Will be entirely newly designed system.
Status: Warnings should be around 12-15.
Bottom Line -- Better fuel economy with less tire wire, and enhanced safety.