Pressure reductions are speculated to have higher danger of hydroplaning in addition to compromised handling and safety. Most tire blow outs could be prevented detecting low air pressures early and having the tires repaired professionally.

One of the nine changes Congress made that affect the tire industry are TPMS. The TREAD Act mandated every new car must be equipped with TPMS starting in 2007.

Sensors installed in new vehicle wheels send a signal to the dashboard alerting the driver if pressure falls below 25% of recommended cold psi for the tire.

How do I identify TPMS on a vehicle?
*Look for the identifying traits below to check if a vehicle has TPMS.
1. TPMS symbol lights up on dash board indicator when vehicle is turned on. The symbol should be noted in your owner’s manual.
Most look like a “half oval shape flat on the bottom” with an exclamation mark in the middle.
2. Tire pressure of each tire displayed on the instrument panel.
3. Aluminum colored valve caps, Hex Nuts and valve stems.

Many aftermarket wheels may need these rings to prevent off-centering during installation that can cause vibration.

*BACK SPACING: The distance from the backside of the wheel mounting pad to outside of the rim flange.
*HUB DIAMETER: (or center bore) The hole at the center of the wheel & used to center the wheel.
*BOLT PATTERN: (or lug nut pattern) Spacing or distance b/t lug studs.
*OFFSET: The distance from the centerline of the wheel to the mounting surface.
*POSITIVE OFFSET: When the back of the bolt pad is closer to the street side of the wheel; when mounting surface is outboard of the rim centerline.
*NEGATIVE OFFSET: When the back of the bolt pad is closer to the inside of the wheel; when mounting surface is inboard of the rim centerline.

When determining that selected wheel meets the requirements of a particular vehicle, make sure it is compatible with the mechanical aspects, such as suspension clearance. Tie rod ends, A-arms, brake calipers, shocks & mounts may be potential trouble spots. Another area of concern is both the inside and outside fender clearance. This should be checked by turning steering wheel lock to lock from left to right with suspension fully collapsed.

4×4.25 = 4×108
4×4.50 = 4×4.5

5×4.25 = 5×108
5×4.50 = 5×4.5
5×4.75 = 5×120.7
5×5.00 = 5×127
5×5.50 = 5×139.7

6×4.50 = 6×114.3
6×5.00 = 6×127
6×5.50 = 6×139.7

8×6.50 = 6×165.1

FORMULA for Standard to Metric Conversion =
1 inch + 25.4

To convert inches to millimeters: multiply by 25.4
example: 4.75 x 25. = 120.65
To convert millimeters to inches: divide by 25.4
example: 100 mm divided by 25.4 = 3.937″

The process will not change for the vehicle owner other than not receiving an actual sticker but instead will get an “electronic authorization.”

Consumer Reports wanted to find out if nitrogen is worth the price, so we purchased a Nitrogen Inflation System and checked out how well the inflation held up over a one year period. We evaluated pairs of 31 tire models of H- and V-speed rated, all-season tires used in our tread wear test from 2006. We filled one tire per model with air and the other with nitrogen. The test was quite simple: fill and set the inflation pressure at room temperature to 30 psi (pounds per square inch); set the tire outdoors for one year; and then recheck the inflation pressure at room temperature after a one year period.

The tires were filled and deflated three times with nitrogen to purge the air out of the tire cavity. We also used an oxygen analyzer to be sure we had 95-percent nitrogen purity in the tire–the claimed purity limit of our nitrogen system, which generates nitrogen gas from ambient air.

The test started on September 20, 2006 and the final measurements were taken on September 20, 2007. The results show nitrogen does reduce pressure loss over time, but the reduction is only a 1.3 psi difference from air-filled tires. The average loss of air-filled tires was just 3.5 psi from the initial 30 pressure setting. Nitrogen-filled tires lost an average of 2.2 psi from the initial 30 psi setting. More important, all tires lost air pressure regardless of the inflation medium, so consumers should check their tires’ air pressure routinely. No evaluation was done to assess the aging claim.

Bottom line: Overall, consumers can use nitrogen and might enjoy the slight improvement in air retention provided, but it’s not a substitute for regular inflation checks.