I purchased the second generation SmarTire system from Eddie for my '00 S4, including four extra sensors for my snows on separate wheels. (I also bought four S-03 PPs, but I won't be driving on them until April or so, when the snow subsides in Denver).

Mounting went pretty well, although it's very tough to get the guys at the tire place in town to actually read the instructions I copied for them. There was a lot of:

Me: "Uh, I don't think the sensor's supposed to be pushing against the valve stem like that."

Them (in a deep voice): "Please stand behind the line, sir, this is a restricted area."

In the end, everything was installed OK. I had the extra sensors installed in my snows and when I drove away, I was disappointed to see no indication that the system was detecting that any information was being sent to the display. So I got home, put the system in 'learn mode' and one by one, let a bunch of air out of each tire, then refilled it, after telling the system which tire I was working on. Low and behold, the next time I took off, all the tires were sending their wonderful pressure and temperature signals to the display. I reset the alarms the way I wanted them and proceeded to mount the remote display on the wood trim just to the right of my steering column (Thanks to all for the recommendations on this location). This all went very smoothly.

So, how do I like the system? I like it a lot. I bought it because of two flats I didn't see coming with these narrow walled tires. I think this will protect my tires and my drive.

One thing that took getting used to was the understanding that the temperature compensation of the pressure reading works in both directions (hot and cold). I set the cold inflation target on the unit to 38 psi and filled the tires to 38 psi, as measured by two different pressure gauges. The SmarTire readout said that each of the tires had 34 psi but also said that the pressure deviation from the set pressure was zero. The readout also said that the temperature in the tires was 38 degrees F. The manual says that the cold inflation pressure of the tire is calculated at 64 degrees. It turns out that as I drove and the temperature of the tires rose, the pressure in the tires hit 38 psi just as the temp got to 64 degrees. I assume that, just as there is pressure compensation for high temps there is the same for low temps. As a demonstration of this, througout the rise from 34 to 38 psi, the pressure deviation reading for each tire remained at zero.

The only thing I don't understand is why my pressure gauges said the pressure in the tires was 38 psi (when filled at 38 degrees). Perhaps just matching, inaccurate gauges. Or maybe an undocumented feature of the Accutire gauge that Audi sent me as a thank you gift is that it automatically compensates for temperature! Not!

 

Good feedback on the SmarTire system, Sandy, Thanks!