Making sense of the numbers on your tires
Question: I just started shopping for new tires and am confused by all the numbers used to list each tire. What do the numbers 98V mean? They’re listed right after the P225/60VR16 on the tire I’m considering.
W.M. Answer: Good question. Let’s look at all the numbers you mentioned. P indicates the tire is intended for use on a passenger vehicle (LT is light truck, ST is for special trailer, T is for temporary/spare use, and European spec tires have no letter). 225 is the section width of the tire in millimetres, and 60 is the aspect ratio (height/width — a lower number is shorter-wider). V is the speed rating and R means this as a radial tire. And finally, 16 is the wheel diameter in inches.
The 98V, listed after the above groups of digits indicates the load index (weight capacity) and speed rating of the tire. The number 98 indicates the tire can safely carry — when properly inflated — 1,653 pounds. This scale ranges from a low of 60 (551 lb.) to a high of 114 (2601 lb.) for passenger tires. The speed rating ranges from the letter L (75 mph) to Z (149+ mph). In general, the higher the letter, the better the rating. For reasons I can’t fathom, the letter H (130 mph) is inserted between U and V of the scale. Also, W and Y speed ratings are actually higher, and more specific than Z, at 168 and 186 mph.
Tire age can be determined by locating the DOT (U.S. Department of Transportation) tire information number; (DOT followed by approximately 12 digits). The final four digits are the week and year the tire was manufactured (3114 would be the 31st week of 2014). This is listed only on one side of the tire, hopefully facing out! Maximum safe tire life is approximately 10 years, possibly sooner. You may also see the letters M and S listed (M/S, M+S, MS), indicating the tire’s tread is optimized for allseason (including snow) use.
Elsewhere on the tire are the UTQG (uniform tire quality grade) letters, indicating a tread wear, wet traction, and temperature rating. Expected tread life is assigned a number ranging between 100 and 500. Tires are tested by the manufacturer relative to a baseline of 100. A 400rated tire could be expected to last twice as long as a 200-rated tire. It’s best to take this number with a grain of salt, as the computation process leaves plenty of wiggle room. Keep in mind also that many factors affect actual tire life, such as inflation pressure, wheel alignment, vehicle load, shock absorber condition, road conditions and driving habits. Straight-line wet-surface traction is also assigned a letter, with AA being the very highest, then A, B and C being the lowest. The tire’s resistance to heat is the final letter, with A again being the best and C the worst.
Confused? My head is spinning as well. A good starting point when shopping for tires is the tire information placard (sticker) on your vehicle’s door or door post, or the owner’s manual. The original tire specifications are listed for your vehicle and it’s important that a replacement tire equals or exceeds them. For a wonderfully informative source of tire information, go to www.tirerack.com, select Research and Advice, and Tech Center. I find and learn new things every time I go there.
Q: I need your advice about the 2014 Subaru Outback that we recently bought from a dealer. I went to check the oil and saw that the positive and negative battery terminals were full of white corrosion. The dealer cleaned it up. A week later I found the same corrosion. I purchased felt circles and grease. I cleaned the corrosion and used baking soda. This lasted through the winter. I checked again the other day and the positive terminal is corroded again. What is causing this? What can I do to fix it?
A.P. A: The corrosion is due to venting from the battery. Felt washers placed around the battery terminals seem to work somewhat. And covering the battery terminals with grease is an old favourite for keeping the connections protected, but I like to use aerosol battery-terminal protector or aerosol discbrake quiet that gets into the nooks and crannies. Since it is unlikely you will ever use a whole can, ask nicely and your local shop might give you a courtesy spritz.
Q: My wife drove a BMW 3-Series for 13 years and had no issues with the car. When the 4-Series two-door was introduced, she fell in love but is now in a bad relationship. The seat belt catches her in either the neck or the jaw. She is 5 feet, 6 inches tall. Her test drive was in the winter and she surmises her coat probably held the seat belt and she didn’t notice the problem. She called her salesman and he responded that plenty of people have the same problem. This seems like something everyone planning to buy a
4-Series should know, as BMW has no solution. She has fewer than 1,600 kilometres on the car.
C.W. A: I have experienced the same problem in various vehicles I have driven. There are devices that alleviate the chafing, and my favourite is a simple, wool-like wrap-around that slips around the belt and closes with a Velcro fastener. Check your local auto parts store.
Q: I do not believe enough attention is given for proper torque of wheel nuts. A few years ago I had to almost beg a wellknown tire dealer to use the torque stick or wrench. They seemed to think they were good enough with the impact wrench to go with that. Not so. Many warped
brake disc/drums could be avoided if proper torque is used.
R.A. A: Torque sticks are good, but not the best. Attaching a socket to the end of one of these calibrated sticks and then the stick to the impact wrench will at least allow all of the lug nuts to be tightened to the same degree. But the amount of torque might not be as exact at that achieved with a torque wrench. Even torque wrenches should be sent in for recalibration from time to time.