I checked my tires for the first time, and found all 4 at 40 or slightly above. per the recommendation in the door panel, I lowered them to 29 in front, 36 in rear (cold pressure). Well, I forgot about the TPMS and the next time I drove it, I noticed that the light was on solid. I stopped at nearest gas station and rechecked all the tires, which were slightly above what I'd left them at. Got the manual out right then, read up on the TPMS, and pushed the reset button (tho they were a little warm/off). Well, the light went off for about a couple miles. I have subsequently tried a couple times to hit the reset button when the tires were cold, but it still comes on after a mile or so of driving.
Any ideas about this stupid thing? 29 psi seems low for a tire rated to 40, is that right? why do we have to have these stupid things--can't we just all be more responsible citizens and check our air at least once per month and give the tires a glance before driving it every day? geez!!
Haven't had any issues like yours. I always press the reset button after changing the pressure and before driving....while they're still cold. Never had a problem with the light. The only time that mine has ever come on was when the car was loaded with me, my wife, and the entire back-end with luggage for the Prosser, WA Rally! I also run 29 front/36 rear in mine. The problem I had was when I didn't change lanes quickly enough on the interstate when it was loaded, and hit 3-4 road reflectors in a row, and the TPMS warning light came on for just a few seconds, then went off! Got my attention, but went away quickly!
Trena, the maximum pressure on the tire sidewall is just that - the maximum the tire should ever be inflated to. smart, and other manufacturers, may decide on different pressures based on vehicle application, hence the 29/36 settings on the smart. Some tire stores, and even dealerships, don't seem to understand this. Stay with the settings recommended by smart.
The PSI is specified by the manufacturer depends on the weight of the car at that wheel to give the proper tread "footprint." A 500 lb car would need very few pounds per square inch to support the 500 lbs across the appropriate square inches for the 4 tires' contact area. If the engine were in the front, higher PSI would be required on the front to avoid extra wear on the edges and the back would have to be lower to avoid wearing down a stripe in the middle.
Are you sure you followed the full reset procedure? My older car was a little more involved than just pressing a switch - had to look for an indicator color change before releasing. I haven't had a tempermental TPMS to research any closer on my Smart.
Problem might be in the Gauge you are using. Recently I bought expensive ($20) digital tire pressure gauge, and realized that my air pump gauge and small analog one are way off.
My light came on, so I got the old tire gauge out and found that the front tires were way over inflated. I lowered the pressure to the recommended 29psi and reset the light and have had no further issues. What I don't understand is that the manuel states that the light will not come on for an over inflated tire. It only comes on when there is a significant loss of pressure. So this means that one of my tires must have been really over inflated.
Doesn't suprise me that a car with a rear engine has more air presure in the back. More weight back there! Years ago Corvairs (rear engined) used 16 psi up front and 30 psi in the rear, those were non-radial tires. The infamous flipping Corvair that Ralph Nader made famous was caused by a mechanic who rotated the tires, front to back, back to front. One guess why it flipped over....
Trena, a good air pressure gauge can make all the difference in the world. If you get a cheap pressure gague, your pressure can be 5 to 7 PSI off. I would invest in a digital ACCUGAGE. Those have worked for me and I have checked them with gauges that are $50.00 plus.
Well, guys, thanks for all the info and suggestions on gauges, but that doesn't help my TPMS light problem. Any more suggestions out there? I am NOT driving the thing 2 hours to the dealer when my tires are fine. If my gauge is not calibrated well, it would have the same calibration (surely) for before, during and after changing the air in my tires. The TPMS should reset to whatever pressure I put in them. Stupid fancy electronics. I wanted to get this car to simplify when I first got the bug in my head. Then I wanted the cabrio (don't regret that part), then wanted the leather and ps, then the dealer installed the fancy schmancy kenwood head unit and i had to make all the bells and whistles work on it, so added some accessories. what happened to my good idea of simplicity??? ;)
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per the recommendation in the door panel, I lowered them to 29 in front, 36 in rear (cold pressure). Well, I forgot about the TPMS and the next time I drove it, I noticed that the light was on solid. I stopped at nearest gas station and rechecked all the tires, which were slightly above what I'd left them at. Got the manual out right then, read up on the TPMS, and pushed the reset button (tho they were a little warm/off). Well, the light went off for about a couple miles. I have subsequently tried a couple times to hit the reset button when the tires were cold, but it still comes on after a mile or so of driving.
29 psi seems low for a tire rated to 40, is that right?
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