Kelly's Garage - Active Green and Ross - February 2015


header patricks day 2015


Well I hope everyone is surviving winter. I sure hope March is warmer than February and that spring is just around the corner.  With this brutally cold weather some people have had their water pipes freeze up in their homes, water mains have been bursting and some of you may have been dealing with the Tire Pressure light coming on on  your dash. My vehicle doesn’t have TPMS sensors but I did have a rental car that had them and I unfortunately hit a curb as I was driving.  Within seconds the low tire pressure light came up on the dash.  As I like to say “ the joys of winter “.  Be safe with properly inflated tires and have a happy St.Patrick’s Day on March 17.





In 2007, the US government passed the Transportation Recall Enhancement, Accountability Documentation Act. (TREAD Act.)  This act requires all vehicles coming into the US to have Tire Pressure Monitoring Systems. (TPMS)

This month's topic: Tire Pressure Monitoring Systems

What does a TPMS sensor do?
The TPMS sensor monitors either the air in the tire or the rotation of the tire and sends this information to a central command centre. If the tire is low in air pressure or the tire is spinning faster than it should be, the computer will activate a light on the dash to alert the driver. Some vehicles will only activate a light and others will actually tell you the tire pressure of each tire. (See the symbol and photo below.)

Where did TPMS sensors originate?
TPMS sensors have been around since the 1980’s in European luxury cars and the first North American car to have sensors was the 1996 Chevrolet Corvette. Although it has been law in the US that all vehicles coming into the country have TPMS sensors, it is not law in Canada. However, many vehicles do come equipped with TPMS sensors.

What types of TPMS sensors are there?
There are two types of TPMS sensors; direct and indirect sensors. There are photos below of each style. The direct sensor is actually in each wheel and actually monitors the air. The sensor sends the information wirelessly to the central command center. This type of sensor tends to be more accurate than the indirect sensor and they don’t need to be reset after a tire rotation. The battery is supposed to last between 3-10 years. When the battery is finished the whole sensor will need to be replaced since it is a sealed unit.
The Indirect sensor actually measures the rotation of the tire rather than the air in the tire. This is done by using wheel speed sensors that are also used by the Anti Lock braking system. The wheel speed sensor is using located around the hub. This type of system can sometimes be less accurate and may be unreliable is the tires are unevenly worn.

How the weather affects the TPMS sensors.
The low tire pressure light may come on when you first start your car up and then go out after a few kilometers. This is due to the ambient air pressure. With every 5 degrees drop in air pressure your tires will lose 1 psi. So potentially overnight with a big temperature shift yoru tires could be under inflated.

Why to keep your tire pressures at proper inflation?
Proper tire pressure is very important since your tires are the only thing you have in contact with the road. Tires with low air pressure can make your vehicle handle poorly when you have to make an emergency maneuver. Low tire pressure also creates greater rolling resistance thus reducing fuel economy; decreases water dispersion creating a greater chance of hydroplaning; greater heat build up increasing the chance of a blowout and premature tire wear.

TPMS sensors are a great tool to have in our vehicles but it doesn’t replace manually checking your tire pressures once a month. Make sure you have a tire pressure gauge in your vehicle!

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