How To: Choose New Tires

So your bike is ready for new tires. What do you do now? What if you just want the original tire or a similar tire from another brand? Hopefully I can help you make a more educated decision by learning to decipher a tire company's rating language.

[Cover Photo By: Kevin Tong]

Every tire has a set of numbers and letters that denote size and tire capability. Sizes are identified most often in a set of three numbers. The first number is the section width, this is a measurement in millimeters of what the manufacturer says the total width from sidewall to sidewall of their tire is on a specific sized rim. Use another size rim and the section width will be different. This is not the tread width and it does not include any letters or other adornments on the side of the tires. So a 150 sized tire is 150 mm section width on the proper sized rim.

The next set of numbers is called the aspect ratio or section height.  This is generally a two digit number and represents the tires sidewall height as a percentage of the section width. A 150 mm section width, with a 50 for the aspect ratio, will have a sidewall that is 75 mm tall as measured from the bead to the tread surface. This is again affected by the rim width. Placing it on a wider rim results in a shorter measurement because the tire gets spread out and made flatter.

Between the aspect ratio and rim size is the speed rating. Indicated by a letter designation ranging from M to ZR it indicates the maximum safe speed that tire is designed to perform. The higher the letters the faster it is designed to go safely.

The last two digits indicate the rim size the tire was designed to fit.

Let's now talk about the UTQG rating. What's that you ask? This is the "standard" for describing a tires capability. I placed the word "standard" in quotes because it's an industry standard but one interpreted by each manufacturer. In other words you cannot compare a Michelin to a Dunlop based on this rating. You can compare tires from the same company, so it's not entirely useless.

UTQG stands for Uniform Tire Quality Grade. It's a multi part rating that gives a rating for tread wear, traction, and temperature. The higher the designation in each category the better the tire will perform in those conditions. Tread wear is shown as three digit number. The higher the number the longer the tire will last. For example a tire with a 150 rating should last 1.5 times longer than a 100 rated tire. Take this with a grain of salt, it's a manufacturer's extrapolated calculation based on limited wear in testing. Useful for deciding between tires from the same brand but again not helpful comparing two different brands. Go by the manufacturers tread life warranty and use that to compare competitors. Traction is either a single or double letter rating, AA is the highest. This is a rating of the tires ability to stop on wet pavement in the mandated Government test. It does not include cornering as a criteria. Finally is the temperature rating. There are three ratings for temperature, A, B, or C. A is the best, meaning it not only resists heat better but also dissipates heat better.

Bridgestone-BW-501

Now that we have covered what the labels mean let's talk about wading through all of that and finding the tire you need. The first thing to look at is who made the original equipment tire for your bike. This will make it easier to compare tires and get the characteristics you want. For this discussion I will use my personal bike and go through the tire selection process. My bike, Tiger Explorer 1200, came with a Metzler Tourance EXP sizes 110/80/19 front and 150/70/17 rear. If I want to get tires that perform similarly to what I have, but a different brand, I need to look at several factors. Overall tire diameter, tire profile, and tread. Tire diameter is the distance from tread to tread when measured directly across the tire. The best place to find this is a tire retailer or manufacturer's website. Not every manufacturer lists this measurement so it can be hard to discover (Metzler in fact does not have this information available). I found two tires that fit my needs, Dunlop's Trailmax TR91 is 26.02 inches tall, and the Bridgestone BW501 in the same size is 26.06 inches in diameter. Not a lot of difference in the case of the front tires so how do the rear tires compare? The Dunlop is 25.13 inches and the Bridgestone is 25.43 inches. Here we have a difference of over a quarter inch in diameter despite both of these tires appearing to have similar tire profiles. This minor difference in tire diameter results in a different ride height in the rear, changing handling characteristics and may require a suspension change in order to return it to a setting you like. These are all things to keep in mind when that new tire doesn’t feel the same as the old one. It also explains why some people prefer certain brands on a bike versus others. Their riding style suits that tire with their settings, in most cases a small adjustment to their suspension could give them a very similar feel.

There are even more factors when you decide you need to change your riding from 100% street to mixed riding, more race oriented tires, colder weather, the list goes on.

Tell us what your tire buying experience has been. What did you you ended up choosing?

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