Tires are without a doubt, in my mind, the most important component on a motorcycle, or a car for that matter. When you buy a bike new or buy one with a new set of tires, it may be a couple of years before you even have to think about buying tires. Or if you’re a real hooligan or a road-trip addict, you may need to buy new ones every few months.

Whatever your personal situation, at some point you are going to have to buy new tires. It may be tempting to just buy a set that’s identical to the ones that you’ve taken off the bike, but as time goes by the OEM (original equipment manufacturer) model tire may no longer be available. It may also be that tire technology has improved in the meantime and you can actually improve the overall performance of your bike by fitting a new generation of tire to it.

How do you know if you are fitting the right tire, though? In this quick buyer’s guide I’ll go over the different aspects of bike tires that you need to pay attention to, as well as some general tips that will serve you well in the hunt for new rubber to burn. Don’t forget that I also have a review page where I highlight a few notable products.

Don’t Supersize It

Before we get to all the technical stuff, let’s first address a common mistake that many bike owners make – oversizing tires. There’s always a temptation to put on a fatter, bigger tire. Some people think they just look cool; others are under the impression that they will perform better.

I’m telling you right now that unless you know exactly what you are doing (and since you are reading this I presume that you don’t) you should stick to the size specifications that the manufacturer of your bike recommends. If you put a different size tire on there you are messing with the tire geometry that has been designed and set up for the rest of the bike. This can seriously mess with the handling of the bike and can even be dangerous.

You also shouldn’t change the type of ply, which is something I discuss below.

Made From The Right Stuff

There are basically four parts to a tire that you should be aware of or that matter when it comes to your decisions.

There’s the tread, which varies depending on what the tire is supposed to do. A motocross tire may be knobbly to handle dirt, while a sports touring tire may be smooth with deep grooves to channel away water. Racing slicks, on the other hand, have no tread at all, making sure that as much rubber meets the road as possible. Incidentally, racing slicks are illegal on the road in most parts of the world.

Then you have the carcass of the tire. This is essentially the supporting structure of the tire that sits right beneath the tread. Usually the carcass is constructed from steel cords or sometimes fiber of some sort. The carcass runs from bead to bead.

Speaking of which, the bead is the part of the tire that attaches to the wheel. There are a bunch of steel cords here too, which ensure a tight fit, especially in the case of tubeless tires.

Finally we have the sidewall. The sidewall is more than just a place for white wall decoration and information labels to go. This is the part of the tire that greatly influences load carrying capacity and handling characteristics. How well the sidewalls handle the forces you put the tire through will determine a bunch of things, such as how quickly the tire wears or how much lean you can get out of them.

Don’t Be Biased Man, That’s Not Radial

Traditional tire design implemented something called “bias ply” and you can still get tires that use this design today. Unlike radial tires that have cords running from bead to bead, bias ply tires have cords laid directionally at an angle. The bottom line is that radial tires offer better heat dissipation and flexible sidewalls that offer better handling. However, since bias ply tires have such stiff sidewalls they are the preferred choice for many very heavy bikes, such as Harley Davidson cruisers. These bikes don’t have high handling demands, but they do need strong tires to cart their porky butts around.

The Writing’s On The Wall

The sidewall that is. You’ll notice a bunch of numbers on the sidewall of the tire, in either metric or alphanumeric format.
A metric spec can look like this: 170/90 R15 67 W

The “170” indicates the width of the tire in millimeters; this is called the section width. The “90” refers to the aspect ratio of the tire; in this case the sidewalls are 90% as tall as the tire is wide. The “R” is for radial it can also be “B” for bias. The “15” is the wheel size in inches. The “67” is the load index – an index of 67 gives a load capacity of 661 lbs. You can refer to a load index chart to look up each value. The letter at the end refers to the speed category that the tire is rated for. A “W” rating is good for over 168 miles per hour, for example. You should have tires that match the top speed of your bike, or at least exceed the top speed you intend to ever ride.

Alphanumeric specs give you the same info, but are formatted differently. The first letter is always “M” for motorcycle, followed by a letter code representing the width. Then there is a number with the aspect ratio, and then the rim diameter in inches and the speed range code. You’ll have to look up the codes to get the exact numbers.

Compound Interest

Apart from getting the size and specifications right, you’ll also want to consider the tire compound. Broadly, you get three compounds: soft, intermediate, and hard.

The softer a tire compound is, the better it grips but the faster it wears, so you have to make a decision about where your needs lie. For example, if you aren’t a rider that pushes the bike to its limit you really don’t need soft compound tires.

But these days things are not as simple anymore. Some tires are now multi-compound; they’ll have hard or intermediate compound in the center of the tire that eats the most miles, and then softer compound towards the outer edges of the tread where grip is most needed in the corners.

Tire makers are also now experimenting with other substances such as Kevlar in their rubber compounds, in order to find ways of extending tire life without compromising grip. So pay close attention to what the manufacturer says their compound is designed to do.

Rolling Away

Buying tires isn’t rocket science, but if you don’t do your homework things may go badly in different ways. If you are in doubt you can always give the dealer or manufacturer a ring and find out if the tires you are considering would be a good idea or not. Happy hunting!