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I have a 2008 Lincoln MKZ, with 57,000 km. I recently installed snow tires; ever since, the tire pressure monitor shows faulty tire pressure gauge. I took it back to the dealer that installed the tires; they kept it 30 minutes, then told me that when I start the car the gauge will show faulty but will reset itself. That that was three weeks ago. I use Highway 401 daily and want it to work right. – Nigel in Port Hope, Ont.

I'd take it back to the dealer, complete with any records of the purchase and subsequent visit, and tell them you will be waiting until they reset or replace the Tire Pressure Monitor Sending (TPMS) units.

They most probably do not need replacing, just resetting.

Obviously the dealership did not do so properly at the time of installing the tires.

There are a variety of TPMS units, most of which will "re-learn" when tires are changed or replaced. It is also possible to manually reset them using a tool designed specifically for that purpose.

Since your sensors did not "re-learn" the pressure when the winter tires were installed, they should be reset manually.

I purchased a generously discounted 2011 Mazda6 in late November and negotiated the inclusion of snow tires on rims in the purchase price. I asked the dealer to install the snow tires for delivery of the vehicle. My wife gave me wheel covers for Christmas and in attempting to install them I realized that the snow tires are 16-inch, not the 17-inch size that the all seasons that came with this model are. (I've checked in my garage and the all seasons are in fact 17-inch). While I recognize that the base Mazda comes with 16-inch tires as standard, I cannot find out anywhere whether there is any problem with using 16-inch snow tires in the winter and 17-inch tires the rest of the year. Is there a problem? – Paul

There is nothing wrong with the choice of 16-inch tires. Not only were they less expensive, as would be the steel wheels – important to the dealer – they will be better in the snow than the 17-inch ones.

The 17-inch tire is slightly wider and the sidewall – distance from rim to road – slightly less. The added width provides a larger contact patch – the actual area of the tire tread in contact with the road. The lower profile or sidewall provides less flex, keeping more of that contact patch in touch with the road in the corners.

The truth be told, in your car and the vast majority on the road today, the choice of the larger wheel has little if anything to do with the desire for better grip and cornering ability and is all about style – the ability to use a larger and more stylish wheel, something every designer in the world relishes. Thus, the move to 19, 20 and even 22-inch wheels lately.

But you do get the benefit of the smaller wheels in winter. The difference is in the width – the 16-inch tires will be slightly narrower, allowing them to dig through the snow and reach the road surface instead of riding on top of it, which the wider tires might do. A second consideration will be a more supple ride thanks to the taller sidewall which acts like shock absorbers.

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