So I'm paronoid about getting a flat, shredding a tire or worse !
Around where I live I seem to get a flat every 6 months or so.
As a precaution I installed some valve stem pressure caps - the type which change color from green to orange to red if the pressure starts to drop.

However I'm thinking of replacing them with a proper internal system because recently one of them worked loose somehow and reduced the pressure to 11psi. I thought I'd got another flat, but is was the pressure cap itself not sealing on the valve stem properly !!

This incident has made me resolve to change to a 'proper' pressure measuring system which can sound an alarm in the car should any tire loose pressure.

So any suggestions for a system which has a smallish display ?
The ones on the web seem to be made for RV and are pretty big.


Thanks Tim

 

https://www.6speedonline.com/forums/...ad.php?t=62314

 

Tire Pressure Monitoring Systems

some good info I found elsewhere, interesting read thought I'd share..


"The invention has wide-ranging application across many fields of industry. It is particularly suited to pressure measurement in harsh or dynamic environments that would preclude many other pressure sensors. These applications include, but are not limited to: monitoring engine pressure (cars, aircraft, ships, fuel cells) sensors for high speed wind tunnels sensors to monitor explosions sensors for boilers sensors for dish-washing machines sensors for irons (both domestic and industrial) sensors for other steam based machines where overpressure can lead to destruction and loss of life

However, in the interests of brevity, the invention will be described with particular reference to a tire pressure monitor and an associated method of production. It will be appreciated that the Tire Pressure Monitoring System (TPMS) described herein is purely illustrative and the invention has much broader application.

Transportation Recall Enhancement, Accountability and Documentation (TREAD) legislation in the United States seeks to require all U.S. motor vehicles to be fitted with a tire pressure monitoring system (TPMS). This is outlined in U.S. Dept. of Transportation, "Federal Motor Vehicle Safety Standards: Tire Pressure Monitoring Systems; Controls and Displays", US Federal Register, Vol. 66, No. 144, 2001, pp. 38982-39004. The impetus for this development comes from recent Firestone/Ford Explorer incidents which led to a number of fatal accidents. A careful assessment of tire inflation data found that approximately 35% of in-use tires are under inflated, whilst an assessment of the effect of a TPMS found that between 50 to 80 fatalities, and 6000 to 10,000 non-fatal injuries, per annum could possibly be prevented. This is discussed in U.S. Dept. of Transportation, "Tire Pressure Monitoring System," FMVSS No. 138,2001. European legislation also appears likely to require the fitting of a TPMS to increase tire life, in an effort to reduce the number of tires in use by 60% in the next 20 years, so as to minimise the environmental impacts.

Two different kinds of TPMS are currently known to be available in the marketplace. One kind of TPMS is based on differences in rotational speed of wheels when a tire is low in pressure. The asynchronicity in rotational speed can be detected using a vehicle's anti-braking system (ABS), if present. The second kind of TPMS measures tire pressure directly and transmits a signal to a central processor. FIG. 1 (prior art) illustrates a schematic of a typical pressure measurement based TPMS 10. Sensors 12, provided with a transmitter, measure pressure in tires 13 and transmit a signal 14 to antenna 16. The data can then be relayed to a receiver 15 and processed and displayed to a driver of the vehicle 17 on display 18.

Table 1 lists some presently known TPMS manufacturers/providers. Motorola and Pacific Industries have each developed a TPMS, whilst other companies listed in Table 1 act as suppliers for TPMS manufacturers, including some automobile producers that install their own TPMS.

TABLE 1 Pressure sensor manufacturers involved in TPMS. Company Supplier to Type of Sensor Motorola Motorola Capacitance Pacific Industries Pacific Industries Piezoresistive SensoNor Siemens, TRW, Beru, Piezoresistive Porsche, BMW, Ferrari, Mercedes, Toyota Siemens Goodyear Piezoresistive Transense Under development Surface Acoustic Wave Technologies TRW/Novasensor Smartire, Michelin, Piezoresistive Schrader, Cycloid"

(Note that the Porsche system is Piezoresistive,--made by SensoNor.)

"There are two main types of pressure sensor; resistive or capacitive. Both types of these sensors rely on deflection of a membrane under an applied pressure difference. One side of the membrane is exposed to internal pressure of a tire while the other side of the membrane forms one wall of a sealed cavity filled with gas at a reference pressure.

The resistive-type sensors typically employ silicon-based micro-machining to form a Wheatstone bridge with four piezoresistors on one face of the membrane. The sensor responds to stress induced in the membrane. For capacitive-type sensors, the membrane forms one plate of a capacitor. In this case, the sensor responds to deflection induced in the membrane. Preferably, the responses should be linear with pressure, for predicability, up to at least a critical point."

"To increase battery life, most TPMS are in stand-by mode for the majority of time, only operating at set intervals. The U.S. legislation requires the system to alert the driver within a set time of detecting significant tire under-inflation conditions. It also requires a warning light to signal when the tire is either 20% or 25% under-inflated. Most of the devices presently available in the market are accurate to within .+-.1 psi, which represents .+-.3% for a tire pressure of 30 psi. More generally, the sensor should perform in a harsh environment, with temperatures up to 130.degree. C. and accelerations of 1000 g or more. Tire pressure increases and decreases in response to corresponding changes in temperature. Most systems presently available include a sensor to account for thermally induced changes in tire pressure sensor sensitivity..."

"Supplying power to pressure sensors within tires poses several problems. The simplest option is a long life battery however, this significantly increases the overall size of the sensor which can limit the installation sites. Reducing the size of the battery risks reducing the battery life less than the tire life.
..."

You may also elect to look it up yourself. If not an account holder you can't get the diagrams and images, but at least you can extract the narratives. You can do a general search with "TPMS" on the URL: http://patft.uspto.gov



here is a site..........

BERU is the OEM for the Porsche TSS (TPMS)
Click Here

The BERU tire pressure control system has been developed in close co-operation with the car manufacturers in the VDA working group — Audi, BMW, DaimlerChrysler, Porsche and VW.

 

Hi Doc,
Would you happen to know if this system from Tirerack fit will our hollow spoke wheels ok ?
Seems like an ideal system.

Thanks Tim

 

I have the SmarTire system installed (Tirerack carries them) and it works well. Occasional false alarms, but like with a radar detector you learn to recognize the likely "reals" from the falses. In addition to providing early warning about flats (which fortunately I have not needed), it has beenvery helpful in reminding me to put air in when the tires are a little low.

I can't see any reason hollow spoke wheels would make any difference. The sensor uses a wireless transmitter and is attached to the inside of the wheel, so I can't see how the wheel design would matter.

 

Contact Damon. Let us know what you end up getting. It's one of those things I want to do but haven't (I have about a thousand of those things).

damon@tirerack.com
877-522-8473 ext. 643

 

Yes Tim it does!!

tom

 

I've just ordered one.
I figure the so called 'safety pressure caps' from Accu-pressure are anything but safe after one of them let go on the freeway - hence my interest in a better measuring system.

FYI the pressure cap which failed was seated correctly on the valve stem, but something internal to it failed causing the rapid deflation.

Regards Tim

 

Here's a blast from the past that may be helpful:

http://www.heumann.com/smartire/index.html

 

I lost my TPMS once I went aftermarket. Good thing I carry my AAA card.

Off -topic: One of my patient owns the patent for TPM and is expanding its use for anything with wheels on it. Took him eight years, but now he's on easy street.

 

switch to nitrogen in the tires