Go figure, size doesn't matter

John Mahler

SPECIAL TO THE STAR

Q: We have a set of P225/55R17 winter Blizzaks (used two months on a 2004 Nissan) and a set of P225/60R16, standard sized tires for a Subaru Outback. I have worked out the diameter of these tires as follows: P225/55R17 is 26.744 inches and the P225/60R16 tires are 26.629 inches. Are these figures correct and, if so, could we use the Blizzaks on the Subaru Outback?

A: Your math is perfect. Yes, you can sub these tires without any problems, though generally one moves down in diameter for winter. This is done because moving down in diameter usually means a narrower tire. In your case, this does not matter as both tires are the same width and the Subaru AWD system gives you an extra edge.

Q: Our Honda CR-V has AWD and carries a full-sized spare. I understand that you cannot put a mini-spare on a vehicle with AWD. The winter tires we have are unidirectional which creates a problem for the spare. Do we carry a non-unidirectional spare or a unidirectional spare? If we use a non-unidirectional spare to limp home, do we put that spare on the front or back (i.e. if we get a flat on the front, do we move the rear tire to the front and put the spare on the back)?

A: You are correct about never using a mini spare tire on an AWD vehicle. All the tires need to be the same size or the AWD system thinks one wheel is in trouble. The AWD system then works overtime and may end up damaged.

If you are using the spare tire that came with the car, it will no doubt be an all-season tire. Should you get a flat tire, it will be fine to use it with your unidirectional winter tires for the short distance home or to a shop. You will experience less traction and should drive accordingly. If you can put the spare on the front, that would be best.

The best tires should always be on the rear of any vehicle, no matter what the drive system, FWD, RWD or AWD. The AWD drive system will be able to compensate for the one tire with less traction in terms of getting you going, and the two good tires matching traction on the rear will ensure you can stop straight without a skid.

Q: I have a Land Rover Discovery 3 that has all-season tires. My dealer has been encouraging me to buy winter tires but taking in the expense, are they really necessary? I live in Geneva, Switzerland, and often go to the mountains where the roads are icy and snowy, but not as bad as Canada.

A: Yes, you need winter tires for your Land Rover. AWD can help get you going but stopping and turning are as important if not more important. Winter tires are designed to maintain grip levels as temperatures drop. All-season tires lose grip as temperatures drop. Then add snow or ice to the mix and stopping becomes more of a problem with all seasons. I would consider looking at the Pirelli, the Hakkapeliitta/Nokian, or a Goodyear Ice line of tires.

Email tire questions to John Mahler at thetireguy_1@hotmail.com. Please include vehicle's make, model and year, tire brand and size, as well as your name, address and phone number. Volume of mail prevents us from answering all queries or providing personal replies.

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