Planet 9

I recently picked up the following product off the intenet--from a friend--which provides real time tire pressures and temps.Not sure what you can do with the temps but the ability to get accurate pressures at each tire--real time--at your dash i thought would come in handy at the track.

The sensors screw on and the LCD display attaches to the dash either by Velcro or a clip to the vents, which I did.

Took 10 minutes to get everything mounted and having checked the pressures with my digital Longacre gauge, the readout was dead on.

From under $200 i thought this represented a good value--as long as it doesn't die on me after 30 days. I'm not comfortable leaving these sensors on all the time for fear they could get taken but for track use they work just fine.

I've attached two pics.

Attached Images

	pressure display unit01.JPG (166.1 KB, 31 views)
	tire sensor.jpg (413.7 KB, 41 views)

Is this a "direct" (reads the pressure from inside the tire and is not impacted by environmental conditions) or "indirect" measurement system? Temps are pretty handy as well. With the factory system that measures direct pressure it is good to watch the changes as tire temps change.

I had to look up the difference between the direct and indirect systems to be sure.

Since they are mounted on the top of the valve stems and do a direct measurement of air pressure, rather than wheel rotational speed, they qualify as direct.

I think the max they will do on the temp side is 85Deg. C. That is the air temp at the sensor on the end of the valve stem. Since it's not a cross section like a pyrometer being placed across the tread, what will one temperature measurement at the track tell you?

One other feature are presets for over and under inflation audible warnings.

So it measures the pressures from the outside of the tire rather than internally like the OEM unit? Some people might like that better since they like the comfort of comparing it to an external air gauge which for obvious reasons will usually differ from a factory system. TPMS is a great safety feature. Let us know how yours works after some driving.

I would be concerned about the additional mass at the end of the rubber valve stem during high speeds. This may cause a valve stem failure. Porsche does make some rubber valve stem supports that I remember. My 951 & 911 SC had them on. I've had a couple of rubber valve stems fail even on the street--one mid corner in a rear tire on my GTi. That was fun! Now I only run metal stems or the fixed stems from the TPMS systems. I even think they say you can't run the metal valve stem covers on the TPMS units due to the potential for valve stem failure.

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Nov 16, 2007 build:
'08 CS Midnight blue metallic--6 spd
Black sport seats, Delete model designation
Fire extinguisher,Floor mats, Sport steering wheel

Interesting thought. I'll get the weight on the sensors. They don't feel like they weigh much but at XXX revs per mile that may be a problem for rubber stems at speed.

That was due to possible signal transmission interference, not valve stem failure. Indeed, Porsche sells metal valve stem covers and I remember reading that Michelin recommends metal covers for track use because of the risk of heat deformation of plastic caps.

While not as beneficial as a tire pyrometer, general tire air temps can be useful for track use when adjusting pressures to get your tires into the ideal temp range.

The stick on valve stem supports are still available.

Attached Images

valve stem supports.jpg (6.6 KB, 5 views)

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Dan

I saw those in a magazine and thought about getting a set for the 370Z. The only problem was that about the same time the tires got up to temp the Z went into limp mode with hot oil.

Has anyone checked the delta on the factory TPMS? Mine reads low as others have noted. When I come in from a drive and check the pressures with a gauge the delta appears to be the same as the cold delta.

Alan, there are a ton of posts about the difference in TPMS and tire gauges. It is probably the most misunderstood feature since the direct measurement system was mandated on new cars. This FAQ explains more Planet Porsche - FAQ: Cayman Options

I did a search on TPMS systems and the names Doran and Pressure Pro were the first two to come up.
They use sensors that look identical to mine and their sensor units are used on RV's, police cars, heavy trucks as well as cars.

Besides the fact that my friend that is selling these units has had them on his track car for 2 years without a failure, my view is that if this technology wasn't appropriate for the application, it wouldn't be on the market for very long before any failings became apparent. If valve stems were failing due to wear, I'd expect complaints to be raised with the DOT, with an investigation into it and the product would get pulled.

FWIW, Vulcan tire is selling a unit with these types of screw on sensors.