What Do I Need To Know About Tires?

When it's time to shop for tires, it pays to understand some of the numbers written on the sidewall of the tire. The first thing you must do is to determine the size of the tire you intend to buy. Normally this number is on the sidewall of the tire you are going to replace. The tire size will be written as P215/75R15.

The "P" says the tire is a passenger tire. The 215 says the tire tread is 215 millimeters in width. The 75 means the tire's height is 75% as great as the width. The "R" means it's a radial tire and the 15 indicates the overall wheel size in inches. So a P255/60R15 is wider and shorter than a P215/75R15. Also written on the sidewall will be maximum load as well as inflation information.

To allow you to compare brands, there is three other ratings normally written on the sidewall of the tire. The first is likely to say "Treadware 300". A rule of thumb is a 300 rated tire is twice as good as one rated 150. Another way to compare this rating is to take the number, 300 and times it by 2 and add 2 zeros. In this case the number 300 would turn into 60,000. This represents the expected mileage under ideal inflation and rotation conditions.

The second rating is written as "Traction B". This is a rating of either A, B or C with A representing the best grade a tire can receive for it's traction abilities. A mud and snow tire or an all season tire will almost always have an A rating. A highway tread could have a B or a C.

The third rating will be written as "Temperature C". This rating represents the tire's ability to stand up to high temperatures with A the highest grade and C being the worst.

So armed with this rating information which tire is a better deal?

TIRE #1 Treadware 200, Traction B, Temperature B for $49.95.

TIRE #2 Treadware 300, Traction A, Temperature A for $59.95.

Tire #2 is expected to last 33% longer than Tire #1, yet it only costs 17% more. Tire #2 can also handle heat better than Tire #1. That should make a big difference if you plan on driving in Arizona. Clearly, Tire #2 is a better deal.

Shop for a tire with a Treadware rating of at least 200. The Traction rating may not be very important unless you drive in snow or rain a lot. Stay away from tires with Temperature ratings of C.

Allowing a tire to be run low on air or loading the car with people or cargo causes a tire to heat up. An A rated tire will handle this or any other heat much better than a C rated tire.

Shopping for tires at home can now be a lot easier if you know what size the tire is and you know the three ratings and the price of the new tire you're considering.

What's a good deal when buying a set of tires? Price is not everything. After the sale, SERVICE is also important. Free tire rotations and free flat repairs are often part of a four tire sale. These free services, used properly, will provide over $75 worth of value. So if one set of tires comes with free rotations and free flat repairs and it's only $50 more than the other set that doesn't provide those services, it's easy to determine which deal is best.

Most shops offer a variety of tires, however, if you want a good top of the line tire, buy a Michelin or a Toyo.

When I have a flat, should I have it plugged
or patched?

When you experience a flat tire and take it in for repair, you should ask that they patch the tire from the inside instead of plugging the tire from the outside.

You see if a tire is patched, the hole is covered by a patch on the inside. A plug is a piece of rubber type compound that is lubricated by glue and inserted into the hole. The plug will vulcanize or fuse to the tire and is supposed to stop the flow of air.

It is my opinion that plugging a tire is the wrong way to repair it. First, some tire manufacturers will void your warranty if there is a plug present in the area of a defect on the tire.

To properly patch a tire, the weights used to balance the tire are marked and the tire is deflated and removed from the wheel. The area around the hole in the inner liner of the tire is lightly buffed and a cleaner is applied. Next, a glue is brushed on and allowed to dry. A patch is laid over the hole and rolled on. The patch covers the hole from the inside.

This is far more labor intensive, yet a much better repair. It may cost between $8 and $15 depending on if the tire had to be removed and/or reinstalled on the car. Plugging a tire will cost $8 or so.

A repair using a plug is far different. While the tire is on the car, the nail can be removed and a plug installed. The first problem I generally see while patching a plugged tire is the plug installer was able to hit the hole on the outside portion of the tread, yet they missed the hole on the inside portion of the tire.

I can't tell you how many times I've seen a plug sticking through the inside of a tire and seen a hole right next to it. I know the plug installer was unable to insert the plug exactly in the path of the object that punctured the tire, so he made different hole as he rammed the plug through the tire tread.

Plugging a tire can trap air between the layers of tread. When the plug is dipped into the glue and inserted into the hole, the plug glues itself to every layer it passes through.

As the tire heats up, the air between the layers begins to heat up and expand. The air has no place to go, so as it expands, it causes the tread to separate from the rest of the tire.

If the tire was patched, the patch prevents any air from inside the tire from escaping, but allows any air trapped between the layers to escape out of the entrance hole in the outer tread area.

The same thing happens when the plug is not inserted exactly into the path the puncture occurred in. The air inside the tire tries to exit using the hole that was missed. As the air moves towards the outside of the tread, it becomes blocked by the plug that was inserted into the outer hole. Again, the air is between the layers of the tire, it gets hot, expands and causes a tread separation.

The choice you make, patch vs plug, may not make a big difference today, but it may be costly later if the tire becomes defective and the warranty claim is denied. Ask that your flat tires be patched.

WARNING--It is my opinion and many experts that you should never put a can of flat fix or tire sealer in your tire. There are many products on the market which come in an aerosol can. You are supposed to push or screw the can nozzle onto the valve stem and squirt this chemical into the tire to seal leaks. The danger is to the person who attempts to repair the tire by patching or plugging it.

This is what happens. If you install these sealers in the tire, it makes it very difficult to properly patch the tire. First, you must clean out all of this jello looking sealer. Then you must clean the area to be patched so the glue can be applied and the patch will stick. Sometimes this operation is impossible.

The danger occurs if someone attempts to plug the tire. Often a rasp-like tool is used to prepare the hole for a plug. As the worker rasps out the hole, he is rubbing a steel rasp against the steel belt and if a spark is created, BOOM, the tire will blow up.

How much air should I carry in my tires?

There are three different places tire inflation information can be found. Your owners manual will deal with proper tire inflation, there may be a tag describing proper tire inflation procedures in the drivers door area, either on the door or on the jamb or there is inflation information on the sidewall of the tire. Don’t be surprised if all three don’t match.

The inflation information on the tire will describe the maximum inflation of that tire cold. This is the most that tire should ever be aired to. The owners manual may describe a slightly lower inflation number. Anywhere in between will be fine for any car or SUV or light truck. But remember this:

Using the higher inflation numbers (35-44 psi) will keep the tire cooler, give you better fuel economy but you will sacrifice ride quality. The ride of the car will be harsher than with softer tire pressures.

Using the lower inflation numbers (28-35 psi) will give you a soft, smooth ride but your tires will run hotter and your fuel economy will be between 1-5% less than with fully inflated tires.

I always inflate my customers tires to the maximum inflation figure written on the side of their tire. The only exception is a "Z" rated high performance tire, like ones on a Corvette, Camaro, 300ZX. I do not inflate them to their maximum of 44 psi, but use 35 psi as our upper limit on these tires. Otherwise the ride is way too harsh.

Next FAQ

Back to FAQs Index

Copyright ©1997-, Mark Salem, Salem Boys Auto, All Rights Reserved