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I'm looking for 245/50/20 snow tires for a 2010 Dodge Nitro, and dropping down to 17 inch steel wheels to get less expensive winter tires sounded like a good idea, but what do I do to prevent my tire pressure monitoring system from detecting low tire pressure all winter? – Steve Fox If you don't want to bask in the warm glow of the tire pressure warning light until spring, you'll probably have to buy a new set of sensors for your winter tires.

"Generally, you can either spend $70 or so for a sensor for each wheel," says David Weatherhead, automotive professor at Centennial College in Toronto. "Or, don't worry about the light and just check the pressure regularly, which you should be doing anyway."

The Nitro uses a direct system that relies on a short range radio signal transmitted to a receiver by a battery-powered sensor in each tire.

If your Nitro has the premium system, the computer display tells you the current pressure in each tire and warns you if any tire is low. If you have the standard system, the receiver will trigger the alert light on your dash just when the pressure is low. If the receiver's getting no signal at all – say, because your new tires don't have sensors and the original sensors are sitting in the old tires stacked in your garage – you'll get a TPMS warning until the receiver can find the signal again.

"We've all experienced a dropped call on a cell phone," Weatherhead says. "If you take away the sensors and don't replace them, it will be interpreted as a lost signal and the tire pressure warning light will stay on."

His advice would be the same for any vehicle with a direct system, but not all vehicles use a direct TPMS.

An indirect system doesn't use special sensors in each wheels. Instead, it uses data from the anti-lock brake (ABS) system to see how fast your wheels are spinning. If the tires are smaller, because of a sudden leak, they'll spin faster and that will trigger the tire pressure warning.

"If you have an indirect system you just change the tire normally and the TPMS will still work," Weatherhead says.

In the U.S., the TREAD (Transportation Recall Enhancement, Accountability and Documentation) act requires TPMS on all new cars sold there after 2007. The act – a response to the August, 2000 recall of some 6.5 million Firestone tires after complaints of Ford Explorer rollovers – also forbids tampering with or disabling the system.

Canada, though, doesn't require TPMS on new cars and there are no federal or provincial rules against disabling it, Transport Canada says.

Could you disconnect the warning light? Probably not easily. My editor suggests (jokingly, I think) putting a piece of tape over the offending light. Could you get your mechanic to take the sensors from the existing tires and put them onto your new winter tires? It's possible, but the sensors could get damaged pretty easily, Weatherhead says.

Older direct systems use a sensor inside the rim: newer systems use a sensor on the valve stem.

"With either style, the sensor is going to be inside the tire," Weatherhead says.

Do you have to go to a Dodge dealership to get these installed and set, or can you do it at any tire shop?

"The sensors do not need to be installed at the dealer," said Chrysler spokesman Eric Mayne. "But the sensors need to be the appropriate type in order to communicate with the receiver in the vehicle."

"Again, If any sensors are missing (or have a dead battery) then the system sees this as an error," Mayne said.

Some owner's manuals walk you through the reset process so you can do it yourself –but I checked the Nitro's manual and it doesn't.

Whether or not you have TPMS, you should be regularly checking tire pressure with a tire gauge, Weatherhead says.

That pressure needs to be the number shown on the driver's side door pillar (200 kPa or 29 PSI for the Nitro) and not the maximum on the side of the tire.

"You should be checking at least every time you get the oil changed," Weatherhead says. "I'm a bad example because I'm terrible for checking them when I should."

And if you do have TPMS, don't rely in it to tell you when it's time to inflate your tires.

In the U.S. at least, "TPMS isn't required to issue a warning until pressure is 25 per cent below the vehicle manufacturer's recommendation" writes Popular Mechanics' Mac Demere.

"TPMS is intended as a last-minute warning before imminent tire failure, not as a monitor to make sure your tires are properly inflated," Demere says.

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