A Closer Look at Tires

A Closer Look at Tires

Posted by Ben Baker on Oct 29th 2016

Rubber, tubes, tread, balonies, hides, skins, stones, tub, wide whites, whitewall. These are nicknames tires. But what’s in a tire? What’s this history behind this highly modified wheel? What kinds of tires are available to the motorcycle community today?
No one knows who invented the wheel or when it happened. What we do know is the wheel changed over the years. The first wheel was probably a log. For centuries nothing changed. Then, someone got the idea to put a band of metal on the outside of the wheel. This greatly increased the life of the wheel and made it more durable. Spoked wheels with an outer iron rim came next, delivering stability, strength and a lot less weight.
The next revolution (pun intended) in wheel technology had to wait until the mid-1800s. Charles Goodyear created vulcanization in 1839. He patented the vulcanization process in the United States in 1844. Thomas Hancock patented vulcanization in Great Britain in 1843. Vulcanization comes from the name for the Roman god of fire and metal forging, Vulcan. Vulcanizing rubber turns it from a goopy liquid into the solid form we’re familiar with today.
Sadly, Mr. Goodyear never managed to make money with his invention. He died bankrupt. The Goodyear company was formed 40 years after his death.
The first rubber tires were pneumatic (air-filled like standard motorcycle tires of today) and solid. Exactly who created these first is not known. Mr. Hancock filed the first patent for a solid rubber tire in 1846 in Great Britain. During his life, he filed several more patents for tires and tire technology.
The solid tires were heavy, compared to the hollow tires of today, but certainly provided a more comfortable ride than iron-wrapped wood.
Fellow Brit Robert Thomson got the first patent for the pneumatic tire in 1845. He received patents in other countries for his work.
For the riding community, the next big change was in 1888. British citizen John Dunlop (of the tire company fame) gets the credit for inventing the first air-filled tire for a bicycle. A later patent conflict gave the official rights to the bike tire invention to Thomson.
1. The most familiar tire is the pneumatic, or air-filled tire. This is what most people use. Tires that need the inner tube are much less common than they used to be. Some rides do require tubes in the tires. Today’s tubeless tires seal to the rim very well and can hold air quite well. Even the best tires lose air pressure. Air gradually seeps through the rubber.
2. Solid rubber tires are most common in industrial applications. These are found on small trailers or wagons, forklifts, hand trucks and such. Because of their weight, they are not common on motorcycles.
3. A third tire is a rubber web around a rim. These airless tires look like black Swiss cheese. They cannot go flat because there’s no pressurized air in them. They provide more shock absorption than any other tire. These are used in industrial and military applications where flat pneumatic tires are common or having a flat is dangerous.
4. A fourth type is uncommon and rarely seen outside heavy industry or agriculture. Tires are sliced into rectangles, stacked and then pinned to a rim like spokes. It looks like a Rolodex. This tire does not have a band around the outside.
Pneumatic tires come in two basic construction types. Each has advantages and disadvantages.
Bias Ply Tires
A bias ply tire has “plies” on the inside. These are layers of wires or cords that are embedded at angles to make a criss-cross pattern. These tires flex very well which is important when riding on rough surfaces.
Bloomberg Business says bias ply tires can also carry heavier loads than radial tires. “A smaller bias-ply tire can carry more load than a radial tire of similar size,” says an article on the website.
Bias ply tires are cheaper to produce than radials. They also wear out faster than radial tires.
Radial Tires
A radial tire also has wires or cords inside the tire. But, these wires run perpendicular to the tire. In other words, when the tire is rolling straight down the road, the tire is parallel to road stripes. Wires inside the tire are at 90 degrees to the stripes.
Radial tires offer some significant advantages over bias ply tires.
Tougher. The wire construction inside the tire make the tire stronger and more durable. It’s harder to tear one of these apart.
Punctures. The wires also make the tire more puncture resistant. Not puncture proof as anyone who has picked up a nail knows.
Run cooler. The wires help the tires stay cool. This matters when you’re on the road for a long time. Cooler tires mean less chance of a blowout.
Quiet. Well, quiet within limits. The same tread on a radial is going to be quieter than the same tread on a bias ply. But when you are running giant knobby tires at 50 miles an hour on pavement, the tires are going to roar.
This tire tech for bikes is younger than most of today’s riders. The first mass-produced radial motorcycle hit the market 28 years ago. Radials hit the market in the 50s for cages, but for some reason the biker market was slow to catch on. Pirelli has the claim for the first radial for a bike, a tire made specifically for the Honda VF1000. Michelin lays claim to the first non-ride specific tire with its offering in 1987.
Dunlop offers a clue behind why it took so long. “The introduction of the radial tire led to such things as modified frames, wider wheels, new steering geometries and suspensions. Therefore, it is recommended that a motorcycle be used with the type of tire construction that it came with originally,” the website says.
The same web page offers a warning: “If a change is to be made, then it should only be done if the motorcycle or tire manufacturer has approved the change. Above all, do not mix bias ply and radial tires on the same motorcycle unless it is with the approval of the motorcycle or tire manufacturer.”
The basic parts of a tire are:
Tread. This is where the rubber literally meets the road. More in a moment.
Bead. The thick inner rim of the tire. This is what seals to the rim.
Carcass. Just like it sounds, the body of the tire.
Sidewall. The side of the tire and the place where construction is thinnest and weakest.
The tread is what matters. That’s what grips the road, mud, dirt, rocks, etc. Tread ranges from a completely smooth racing tire to knobby off-roaders that look like someone stuck a bunch of blocks onto a bald tire.
Technically, the tread is only the part of the tire that touches the road. Those grooves in the tire are not truly part of the tread.
Street Tire
The MotorCycle Safety Foundation has published a short ebook on motorcycle street tires. It’s full of safety tips like when to change your tire, what air pressure to use and some tips on selecting a tire. It says, “Your motorcycle was designed to work in harmony with a limited selection of tires. The owner’s manual will specify tire size, construction (radial or bias, tube-type or tubeless), load range, and speed index, and may identify the brand installed as original equipment. In addition, tires are specifically designed for use only on the front or rear wheel – because each tire has a different function – and the front and rear tires should match each other by being from the same brand and model line.”
Pep Boys has a good primer on tread types for cages. The tread types here, for street tires, are similar to many street bike tires.
The patterns are designed to grip a variety of surfaces a rider will encounter on the street. Some issues are: water on the road (most important), sand or gravel and uneven surfaces. The tire has to be able to cope with all these.
To get general riding capability, a street tire has to sacrifice some grip on the road. Everywhere the tire has a groove means there’s no rubber contacting pavement. That means no traction at all. These grooves channel water away and provide some cooling effects, like vents on the motor.
Racing Tire
To the uninformed, an asphalt surface racing tire looks like a bald tire. There are no grooves or cuts in it. It’s uncut rubber. This is because the racer wants as much tire on the pavement as possible. More tire on the road means more traction and grip and maximum control.
Racing tires are sometimes called racing slicks.
Racing surfaces are just about as smooth as can be. They are dry: rain can postpone some races. Racing slicks will hydroplane. They are also kept clean, no sand or gravel or such. The racing pavement is as close to perfect as the track builder can get.
So, there’s no need for water-channeling grooves in the tires or big knobs to bite through sand.
Off Road Tire

These tires are characterized by big knobs. These gaps around the knobs channel water better than any other tire. They also claw at the terrain, working through mud and sand. When riding on unpredictable ground, this is the best choice. The sacrifice is not much of the tire comes in contact with a flat, even surface. Off-roaders deliver less control when on the highway.
Hybrid Tire
This is a combination of street tire and off road. It has knobs, but they are smaller than the off-roader. This means less stability and grip on uneven surfaces. At the same time, there is less rubber hitting a paved road than with a street tire. Again, this means less control.
Special Purpose
Some special purpose motorcycle tires look like paddle wheels. Raised ridges cross the tire parallel to the axle and perpendicular to the direction of travel. These tires are used on some dirt tracks for racing, running in sand and tractor-pull-style racing.
Another special purpose tire looks like it ran through a box of nails. Metal spikes or screw stick out from the tread area. These tires are used for racing bikes on ice.
So why do street motorcycle tires manage 10,000-12,000 miles before they need to be replaced and car tires can go four times that long or longer?
The main reason is the compound or the composition of the rubber in the tire. Racing slicks have a very sticky, soft compound. This helps the tire grip the pavement better. The trade off is the tire wears out much faster.
Street tires have a tougher, harder compound that is less sticky. So, they last longer.
However, even the hardest motorcycle street tire is going to be softer than a typical cage tire. Think about it. A bike is always on two wheels. This matters a lot when turning and cornering. You need that tire to really grip the surface to keep you from going down.
A cage has four or more tires. Each tire has a lot more surface area in contact with the ground than a motorcycle tire. Because of the lower central of gravity, a car won’t flip nearly as easily as a bike.
It’s a compromise between riding safety and longevity.
The rear tire wears out faster than the front tire because it is supporting more weight and it’s the drive tire. That means more pressure and more friction, which means the tire wears out faster. This same wear pattern can be seen in vehicle tires. That’s why car tires need to be rotated.