Motorcycle Tires 101

Beyond the obvious of keeping your rims off the ground, tires are an important part of your motorcycle’s operation. Tires are part of the suspension and braking functions of your motorcycle.

For your tires to do their job, they need to be inflated to the correct pressure. Discussion on motorcycle tire pressures could be a whole book. All tires (car, motorcycle, airplane, etc.) are designed to have a certain amount of air pressure. The pressure keeps them from failing. Air pressure and internal heat/temperature are related. Motorcycle tires need to be warm to function. Too little pressure and the tire overheats, wears unevenly and changes it’s contact patch with the road. Many motorcyclists will allow their tires to get under inflated or have too low air pressure. And too little tire pressure = bad!

Tire pressures are almost always different between front and rear wheels. They are designed to be different as the front tire does different things (turning the motorcycle for example) than the rear tire (propelling your bike forward). The difference can be as much as 4-6 PSI. The tires on my BMW seem to lose a pound of air per month if left uncorrected. When you check your tire pressures, you should use a good quality pressure gauge. Many of the cheap pressure gauges won’t accurately measure a small difference in pressure of 4-6 PSI. So keep that ‘pencil’ gauge for your car and buy a good gauge. Get one that measures 0-60 PSI and avoid the ones that measure 0-100 PSI or more as these will be less accurate at the PSIs our motorcycle tires run at.

So much for my rant on tire pressures. Moving on to what tires do;

Your motorcycle’s tires have a significant effect on how my motorcycle will stop and how the bike responds to the road. Tires compress enough that they form part of your suspension. A properly inflated tire will absorb some of the bumps and irregularities in the road surface allowing your bike to maintain adhesion to the ground. Different brands of tire will do this differently and even different models from the same brand will differ. Some of the differences are hard to notice and some dramatic. Again ask a lot of questions.

As a tire ages, it gets harder. A harder tire will not flex as much as it did when it was young (like us humans). Less flex means that it will absorb less of the road imperfections and make your suspension work a bit more. A too hard tire (like when you put a car tire on your motorcycle) will not grip the road surface as effectively. That isn’t a problem on 4/6/8 lane superslab highways but can be problematic on the tight on/off ramps onto the highway.

Tires are also there to be part of your ability to stop or ‘brake’. Braking forces can be extreme on a tire. When a tire reaches its limit of adhesion, it will start to slide. The adhesion thing again. Old hard tires will start to slide earlier than new tires. Sliding tires limit your ability to stop in time. Stopping distances are not just a function of the motorcycle’s braking system, it is also dependant on the tire doing its job against the pavement.

While the tires that came new on your bike were likely part of the overall motorcycle design process, tire choice for the manufacturer is also cost driven. The manufacturers had to pick a tire that met everyone’s needs and cost less for them to buy. Once the bike is a few years old, you may find that the tire specified from new isn’t even available anymore. My 2011 BMW came with a Michelin tire set that has been superseded by the next generation of that tire three times in 4 years!

Tires, like some people I know…perform best when new and perform worse when they get old. If your motorcycles are more than 5 years old, they are suspect. Check the build date on the tire to be sure.

When your tires have worn out, you get to choose a tire that meets your needs. This is where your dealer can help point you at the best choice for you. Model specific web groups are also useful for this kind of advice. Ask the tire retailer what to buy in a replacement tire and they will ask you “what are you going to use your bike for?”. They will suggest a tire based on what kind of riding you do, your bike type and price point. Let’s say you have a Kawasaki Versys like I recently tested. It comes with 17” street tires. They are a decent compromise tire. However, if you want to do mostly gravel roads around your cottage your dealer can help you pick out a more off road/dirt oriented tire set. Want to tour on highways, there is a high mileage tire available for that too. If you are like me and want to carve the twisty back roads, a choice of a more sport tire is likely available.

It used to be easy to categorize tires as hard and long lasting or soft/sticky and shorter lived. While that difference is still true, tire makers are now capable of putting soft rubber on the sides of the tire for great traction and harder rubber in the center for long wear (higher mileage). Generally, sport bike owners want soft tires to enhance cornering. Cruiser riders want harder tires to get the highest mileage possible before having to change tires. Touring bike riders also want harder tires to get high mileage. Sport touring bike owners are likely to look for a compromise between mileage and handling.

Your motorcycle tire retailer can point out which tire for your bike is the hardest available or softest available. The best tires will always cost more to make than the ones designed to be sold at a lower price point.

Hard-soft what is that?? One of the most confusing things when considering what tire to buy is tire compound. Hard Compound/Soft Compound. Most riders have likely heard people talk about hard or soft tires. Tires are made of a chemical ‘soup’ of ingredients. What we would call “rubber” is in fact a highly refined product that is designed for a specific purpose. Just like a cake mix is different from a brownie mix. Both can be delicious and chocolate coloured but they are different.

Mmmm chocolate…sorry I was distracted. To best understand what soft VS hard means, I suggest we start by sticking your fingernail into the tire. You should be able to tell the soft compound tire by the way you can move your nail into the rubber and jiggle it around. A hard compound tire will be less likely to allow you to get your fingernail into the tire. Generally speaking, soft tires are designed to maximize traction in cornering and give up some tire life for the extra tire traction. Hard tires are designed to give long life but limit your traction in cornering.

Another basic part of motorcycle tires are the grooves or tread patterns that are on the tires surface. The pattern of the tire grooves is a significant part of the tire’s design. This is another area where extensive engineering and testing has changed what a tire looks like and how it functions. Just look at a tire rack in any motorcycle dealership and you will see a multitude of different tread patterns. Sport bike tires will have the fewest grooves on the tire’s surface and off road tires will have the most grooves. The grooves depth (how far below the surface of the tire the groove goes), pattern (square/long following lines/short pencil thin/etc.) and shape all affect how the tire works.

When the tires have worn, the wear is indicated in the tire groove. Some of the tire grooves will have a small raised area that is called a wear bar. When you get to it. The tire should be replaced.

BTW, tires like to be naked. Do not use car tire “dressing” products or rubber preservative products on your tires. Remove any chain lube that got on your tires and if storing your bike over the winter, try to get both wheels off the ground.

Ok class, if your tires aren’t underinflated and not worn out you get a B+.