I just wanted to post a follow up to my post a few months back on these in the "What did ou do today" thread. I have a R171, but these could be used on a R170 as well and just about anything else.
A few weeks ago I noticed 1 of the pressures and temps never changed, then I noticed another wheel say "lo" briefly which I assumed was a low battery warning. The other one might have done that as well, not sure. The kit came with tools to hold the caps and unscrew them so you can change the battery in them. I have read other reviews that suggest putting new batteries in before you even try them. The 2 sensors that acted up did have dead batteries, and the other 2 are weak. I bough a 4 pack of 5 from Amazon shipped for under $9 (They are Toshibas)
I will re-install them today and see if they all work again. FWIW, they use 1632 batteries. Also I decided to weigh them for kicks, they are very light, but they have to affect balance even if unnoticeable. I used them on my 1967 El Camino when I drove it to Woodward Dream Cruise in Detroit this August, and one front wheel that I normally would feel at highway speeds actually stopped, so it affected balance in a good way...
ANYWAY, they weigh about .45 ounces US, or about 12 grams according to a cheap digital scale I have. And the plastic caps they replace weigh about .5 grams. Pretty amazing considering that about 1/3 of that is the battery and the brass lock nut you thread on first and back against it (with a tool) to prevent theft.
As for the functionality of them, my only complaint is the display on the cigarette lighter plug deal is not easy to read. But considering it is infinitely more convenient then manually checking pressures, and getting instant notification if a tire is actively leaking via a beeping sound, the display is still very good. It will beep at 28PSI or less, which is a bit annoying in the fall when they will be 27,28 in the am one day, but you know it will be on average 30 degrees warmer the rest of the week, but a tap of the side button will silence it, or just unplug the display altogether. The temperature functionality is cool, but useless. In heavy traffic on a hot day, (even worse in a tunnel traffic jam) the fronts will really climb. I assume more from the hot air around them and engine heat coming out from under the front. They can show 40 degrees hotter than ambient in a situation like that. When driving it is cool to see the temps and pressures change typically 4-5 psi when warm. The temperature sensors measure within 1 degree of the car's outside sensor when driving in the rain, so I assume they are extremely accurate, just not useful, but hey, more info is always cool.
My only concern is durability. Being in the Pittsburgh area, our communities take horrible pride in keeping the roads clear and use a ton of salt and other ice/snow melting crap on the roads. As long as they stay sealed they should work great, but if any saltwater/slush crap gets in I assume they will die.
Admins feel free to move this to another section if it fits better.