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Reading tire pressures from inside my house!
- Thread starter artsci
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- Driving Dynamics Model S
Andyw2100
Well-Known Member
jcaspar
Member
Just hope the o-rings are durable and carry a pump. I got the old school version of this for my mom's XJR Jaguar (had tire gage on each cap). When o-rings would go bad the tires would loose air fast!I am sure these are much better but to work I believe they have to keep the Schrader valve open such that only the seal on the cap is preventing the tire from losing air.
If a digital gauge is self admittedly accurate only to +/- 1 psi, why does it report to the nearest tenth of a psi?
That seems misleading confidence. Shouldnt it just do the rounding and truncate the hell up at the single units digit?
I'm sorry, I think these things look goober on a car.. and are completely redundant with tpms inside the wheel where they belong (see schrader valve comment above, thats a real issue of lowering reliability).
That seems misleading confidence. Shouldnt it just do the rounding and truncate the hell up at the single units digit?
I'm sorry, I think these things look goober on a car.. and are completely redundant with tpms inside the wheel where they belong (see schrader valve comment above, thats a real issue of lowering reliability).
It's a marketing gimmick to make people believe that digital is more accurate. The sad part is that it seems to work. You can get some very accurate digital gauges, but the price would be 2x or 3x the price of an analogue gauge of the same accuracy.
bylund
Member
Isn't 45.6 still more than 45.2 even if the accuracy is +/-1? You can still see that it went down approximately 0.4 psi, but you still only know that the pressure is somewhere between 44.2 and 46.2 psi if it changed from 45.6 to 45.2 (given that the accuracy is accurate).
I checked the accuracy of the FoboTire sensors today with a gauge I bought from Griot's Garage about 15 years ago. The gauge is quite accurate and reads differences of 0.1 psi. It also has a relief valve.
To test the accuracy of the FoboTire sensors I removed the sensors, overinflated all four tires, used the gauge to bleed each tire back to precisely 44 psi, then screwed the FoboTires sensors back on each valve cap. The FoboTire app in the car showed readings that varied by plus or minus 0.5, psi, which in my book is quite accurate.
1. The primary air seal is the valve cap (which shouldn't be the flexible rubber kind) the Schroeder valve is a convenience to keep the air in while you check the pressures.
2. The problem is that the unit on the valve stem is large and susceptible to being knocked off if you scrap a curb.
3. Long term sealing ability won't be any more of a problem than it is on any other kind of valve cap.
SteveS0353
Member
The valve cap is sometimes called a "dust cap" and it's purpose is to keep crap out of the valve stem. Without these monitoring caps, the primary air seal is the Schrader valve at the bottom of the stem. Without the valve cap, dirt and water can get to the top of the valve, potentially jamming it open a bit causing a leak. In areas where they de-ice the roads in winter, without a dust cap, salt or other chemicals can corrode the brass components and similarly cause a leak. The value cap is important, but it's not the primary air seal.
These remote pressure monitor caps keep the Schrader valve open permanently (they have to do that so that the sensor in the cap can measure the tire pressure), and therefore the monitoring cap must provide the primary air seal, not the Schrader valve. In reality, if you knock one off on a kerb, the Schrader valve will close and seal the tire.
Time will tell, but I question the reliability of such a system for it's intended purpose. The external and vulnerable monitor cap providing the primary seal seems risky.
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dont confuse resolution with accuracy
45.6 is a measurement that is just as accurate as 45.2 coming from the same device, which is accurate to +/- 1
both could be reports of a tire that is actually between 44 and 47 psi as measured by a more accurate device, say, the perfect gauge
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gzerninplatz
Member
I'm currently in communication with Fobo about the bluetooth music skipping issue that users have reported...follow it in this thread if you like:
Fobo Tire Pressure monitor for smart phones - Page 6
Fobo Tire Pressure monitor for smart phones - Page 6
Hi,
It's my understanding (not scientific) that the stem has a valve which keeps in the pressure, and the cap was for dirt.
However, according to Michelin, this is what they say in their manufacturers guide for their tires:
http://www.michelinman.com/mediabin/Approved/Michelin/Visuals/Digital/Promise_Owners_Manual.pdf
"Old valves may leak. When new tubeless tires are mounted, have new valves of the correct type installed. Tubeless tires must only be mounted on wheels designed for tubeless tires i.e., wheels which have safety humps or ledges. As with any other tire air valve, the PAX System valve stem-pressure sensor combination must be in good condition to assure its performance. Always utilize valve caps capable of containing the tire’s air pressure, should the valve core leak. The valve cap is the primary seal against air loss."
However, I think that in most cases, the valve is the seal, but for added safety, if the seal of the valve fails, the valve cap will keep in the air if it has the capability to hold.
Seems like we assume that the valve is the primary, but based on this, it would seem even tire manufacturers feel the valve could fail and the cap is the primary seal. (If I am interpreting that right)
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