A neat product, but...

As wireless technology continues to improve, manufacturers are coming out with some innovative products. Over the last couple of years, one of the neat things is wireless tire pressure monitoring systems.

I'm a stickler for checking my tire pressure, both on the motorhome and the car. It's important to have the proper tire pressure, and I learned from my years in the automotive business that many people don't check their tire pressure often enough. With the proper pressure, your tires last longer, you get better gas mileage and ride quality, and it's safer.

A couple of weeks ago, I received a small package. Here's what was inside the box...

• Four sending units
• One display module with USB port
• Small tool kit
• Intructions
• Warranty card

I waited until we got back to Cabri, and I installed the sending units on the little blue car. Simply remove the valve stem cap, spin on a little lock nut, screw the sending unit on to the valve stem, and tighten up the lock nut. Simple.

Then, plug the display unit into your cigarette lighter power outlet.

Within 30 seconds, the display unit had read the signals coming from each tire.

But there's a problem.

The car had been sitting all winter and I had just topped up the tires to the recommended 30 psi pressure. Yet the sending unit was telling me there was only 28 psi in each tire. I removed one of the sending units and double checked the pressure with the guage that I keep in the motorhome. Yep, 30 psi. I then triple checked with a guage that I have in the shop. Yep, 30 psi.

So that's the first problem, the sending units aren't accurate.

The display unit has high and low settings that give you warning if the tire pressure starts to drop. I set the low at 24 psi and the high at 36 psi. It also gives temperature readings (in Celcius only) of each tire, and you set parameters there as well.

Then, we drove into Swift Current and back, a total distance of about 140 kms (87 miles) return.

As the tires warmed up, the readings went up to about 32 psi. This is normal, but they were still reading lower than what they should be. When we returned home, one of the tires had dropped down to 29 psi and I figured out that I simply didn't have that sending unit tight enough on the valve stem so it was slowly leaking. Hey, at least it was telling me there was a problem!

Everything went fine....except for one thing.

The sending units are actually fairly heavy for their size. And the valve stems are only rubber. So what happens is that the centrifugal force of the spinning tire causes the valve stem to bend outwards, and in the case of the little blue car this causes the wheel cover to actually cut into the rubber valve stem.

Notice the gap between the valve stem and the silver wheel cover.

When the wheel is spinning, the valve stem presses into the edge of the wheel cover. You can actually see in the first photo where it has slightly cut into the valve stem.

The display unit.

So, because of the valve stem problem, this won't work in the little blue car. In order to make it work, I would have to replace all of the valve stems with metal ones such as these...

Aluminum Bolt In Valve Stem and Cap (Set of 4)

So, you could make it work if you want to. Instead, I'm going to try it out on the motorhome. I'll install all four sending units on the rear wheels so at least I can monitor the duallies. I tried out the one furthest away, and the distance still works with the sending unit plugged into the dash of the motorhome. Plus, the motorhome already has steel valve stems.

I don't like the fact that the numbers are off by a couple of pounds, but if it's across the board and you know it then it's not that big of a deal. I mean the whole idea is that it warns you when it's going down. And, possibly it's just this unit that's slightly defective, although given that all four read a couple of pounds low, I doubt it.

SNAN Tire Pressure Monitoring System

For $90, I think it's probably priced right, but better quality systems are available at higher prices. And, you can get systems that specifically come with six sending units for use on vehicles with more than four tires.