Tires seem to be a pretty simple proposition. They’re round and they’re black. All we ask of them is that that they grip well, last a decent number of miles and don’t cost too much. However, beneath this rather bland exterior lies a tremendous amount of technology born of relentless research. To understand them, one must recognize the series of compromises that go into the development of motorcycle tires.
Consider first a tire’s job—we need for them to grip well so that we don’t go clattering down the road on our sides. The type of tire that provides the most amount of grip is the racing slick, which is essentially a solid curving slab of rubber without tread grooves. So why not run racing slicks on the street?
The first problem is that if there’s rain or grit on the road, that solid block of rubber provides no outlet to channel it away. Because of this, as soon as the track becomes wet the racers pull in to change to grooved rain tires, a compromise that will continue to provide grip under the changing circumstances. The grooves not only break up the surface tension of puddles, but also provide channels for the water to escape so the tires don’t hydroplane.
But further compromises are needed. To provide maximum grip, racing slicks need to be warmed up so their extremely soft rubber compound becomes tacky and conforms to the surface of the track. At the highest levels, the slicks are intended to last only one race, as they trade longevity for grip.
At the other end of the spectrum, if we wanted our tires to last forever we’d build them out of iron, and they would rattle along for many thousands of miles. Of course, as soon as we began to push them hard and lean them, these iron hoops would slip and send us crashing to the pavement. Again, we have to compromise and build our street tires of a relatively hard rubber compound that will grip well enough as it also wears acceptably.
Manufacturers will often run a belt of Kevlar, aramid fiber or steel circumferentially around the tire beneath the tread to stabilize it and prevent it from squirming, which induces uncertain handling and causes greater wear. Next come the plies. The body of the tire, the carcass, is made up of layers of flexible plies. Until about 25 years ago, motorcycle tires were all of bias-ply construction, which means that their plies run at an angle (on a bias) of maybe 20 or 30 degrees from side to side (bead to bead) of the tire. Overlapping these layers of plies stiffens the sidewalls, which contributes to the higher load rating of bias-ply tires, though it diminishes ride comfort. Those overlapping plies also rub against each other, generating heat. Bias-ply tires tend to run hotter than radials and heat softens the rubber compound, causing it to wear at an accelerated rate.
Following the radial tire revolution in automobiles in the 1970s, in the ’80s some manufacturers introduced radial motorcycle tires. Their plies run mostly radially, straight across from bead to bead, near or at 90 degrees to the direction of rotation. The benefit of a radial tire is that its sidewalls are more compliant, leading to a more comfortable ride, and the flexible sidewall allows the tire to conform better to the road surface so it grips well without generating as much heat. The limiting factor is that a too-soft sidewall can lead to uncertain handling (which is why some companies run the plies at a slight angle to enhance stiffness, and sport tires have low-profile sidewalls), and with its more flexible sidewall, a radial may offer less relative load-carrying capability. Speaking in general, radial tires are more common on bikes on which handling is a priority, while bias-ply tires are more common on heavier bikes that carry greater loads. Because they flex in different ways, never pair a radial tire with a bias-ply on your bike.
Touring and Sport-Touring Tires
Tires are defined by their use. Touring riders tend to ride bigger, heavier bikes and often ride two-up. Sport tourers tend to ride long distances at high speeds on somewhat lighter but more powerful bikes. Both ride in all sorts of weather, so durability and grip, especially in wet weather, are important considerations. Sport tourers will often place more emphasis on handling, while touring riders will often prioritize load capacity and durability.
How to make your tires last longer
To keep your tires rolling well, keep them properly inflated. The recommended inflation pressures will be listed in the owner’s manual and on a plate mounted to the bike. This will usually be around 32 to 36 psi for front tires, and 36 to 42 for rears. Check inflation at least weekly, and check for tread wear and cracking periodically.
Touring and Sport-Touring Tire Buyers Guide
We asked each manufacturer listed below to send us info on one touring and one sport-touring tire to spotlight for this article. The manufacturers have provided the information here, and the touring tire is listed first.
Specially designed for the Honda Gold Wing, the Cobra GL1800 tires from Avon allow for powerful launches, fast acceleration, hard cornering and hard braking. When compared with the stock tires, Avon says its Cobra rear tire offers an increased load index and triple compounding. This includes a longer lasting compound in the center, a softer shoulder compound for improved grip and cornering performance, and a third compound underneath. This six-ply tire includes two Aramid belts and a nylon belt to reinforce and stabilize the tire carcass, reduce tire flex under heavier loads, and provide for a more comfortable ride.
This new sport-touring tire is designed to combine the performance of its predecessor, the Storm 2 Ultra, while offering increased longevity. The Storm 3D utilizes the technology found in the 3D performance tire family, but recalculates it with features such as interlocking three-dimensional points hidden in its smallest grooves that are designed to improve stability, grip and warm-up times, while limiting tread flex. The single- and multi-compound silica-rich tread is designed to enhance wet grip. These tires are designed for sport tourers such as the Yamaha FJR1300 and BMW K 1200, for Hayabusa riders who want more mileage, and to transform the performance of older-model hyper bikes.
These tires are original equipment on the 2012 and 2013 Honda GL1800 Gold Wing, as well as the new Honda F6B. They are part of Bridgestone’s Exedra family of touring and cruiser tires, and were designed specifically for the GL1800 with input from Honda. They are radials designed to provide excellent handling characteristics, a smooth and quiet ride, good comfort for touring and exceptional grip in both wet and dry conditions. The G704/G709 combo is not used on any other motorcycle fitment, but some design influences can be seen in Bridgestone’s latest cruiser replacement line of Exedra Max.
This sport-touring radial is now available in two versions, a standard along with a GT, the latter of which is designed specifically for heavyweight motorcycles. The rear tire has a wider contact patch in the center to provide enhanced grip, wear life and smoothness. Also, the vertical grooves are for enhanced contact feel and comfort, while the angle grooves are for wet-weather performance. The compound utilizes silica and an RC polymer to further enhance wet performance and tread life. There are likewise two versions of the front tire, a standard and a GT version with a slightly different tread pattern.
According to Conti, its new Trail Attack 2 is intended for riders who demand ultra high performance and mileage from their large-capacity adventure touring/enduro machines. It features zero-degree steel-belt construction on the rear tire for stability and comfort, even at high cruising speeds and high loads. There’s a reinforced carcass on the front tire along with a new tread pattern for higher precision and optimized wear. The improved touring compound is for enhanced wet grip while still offering high levels of dry grip and mileage. Finally, Conti says a temperature-controlled curing process called Continuous Compound Technology utilizes a homogeneous grip grading with just a single compound.
The new Classic Attack is a radial tire built specifically to enhance and sharpen the handling of older classic machines originally designed to run on bias-ply tires. According to Continental, its Classic Attack tires will upgrade the handling of these bikes to the level of a modern radial-tire bike. They have zero-degree, steel-belted construction front and rear for stability, and their Continuous Compound Technology is designed to deliver homogeneous grip grading with a single compound thanks to the temperature-controlled curing process. Traction Skin is Conti’s raw tread surface designed to provide an extremely safe and short tire break-in period.
The Elite 3 has been available in both radial construction for the Honda GL1800 Gold Wing, as well as in a bias-ply version for the GL1500 Gold Wing. For 2013, the rear E3 tire now incorporates Dunlop’s MT multi-compound technology. As with all Dunlop MT Multi-Tread rear tires, these new versions incorporate a long-wearing compound in the center, with a special lateral-grip compound on the shoulders to enhance cornering performance and to help provide a new level of feel and grip. Because their profile is modeled after that of modern radials, the bias-ply E3s share many of the benefits of the radial E3.
Utilizing technology gleaned from Dunlop’s racing tires, the Roadsmart II offers new tread patterns front and rear, additional grooves for wet-weather riding, increased tread depth for water dispersal and greater tread life, and new compounds to accelerate tire warm-up and wear characteristics. These radials incorporate Flex Steel Jointless Belt construction that utilizes two body plies arranged at opposing angles and optimized for shock absorption and riding comfort. Its MT Multi-Tread construction incorporates a long-wearing compound in the center of the tread flanked by lateral-grip compounds on the shoulders. The compounds also contain silica for performance in wet conditions while also extending wear.
Kenda offers several street and dual-sport motorcycle tires but wanted to focus on its new RetroActive for this article. Early sportbikes from the 1970s and ’80s (such as the Suzuki GS and Honda CB models) are now considered classics, yet are still a load of fun to ride. Because tire design and sizing has moved on, it’s not easy to find tires for these bikes any longer. However, Kenda has brought back a line of V-rated sporty bias-belted tires for them that feature an all-weather tread pattern with a new rubber compound for improved durability and mileage. Their improved crown radius also offers a larger footprint in corners, but note that they are not recommended for heavy load-carrying vehicles.
Metzeler has been a development partner with BMW for many years, and the new Tourance Next is the third generation in its Tourance range that is specifically designed for the latest generation of street enduro and adventure-touring bikes. The structure and profiles were designed for large-displacement bikes with particular attention to high-speed stability, even when loaded with a top box and passenger. Profiles are designed for bump absorption to provide greater stability, and the carcass is designed for rigidity to promote easier handling. New tread and compounds are designed for a significant improvement in mileage thanks to better and more even tread wear.
The Z8 Interact gets a new contour that’s designed to improve handling while reducing steering effort significantly and optimizing the tire footprint. It offers a new high-silica compound for performance and safety in all weather conditions, but is specially targeted for wet-weather performance. The rear tire offers a dual compound mixture with 70-percent silica content in the center for higher mileage and stability at high speeds, while the shoulders have a 100-percent silica compound for increased chemical grip in the wet. The front tire, meanwhile, is a single compound of 100-percent silica. Quicker warm-ups and dry grip are enhanced by new polymers and filler configurations.
Michelin calls its Commander II a new standard in cruiser tire longevity. The company states that third-party tests show that the Commander II rear tire lasts almost twice as long its main competitors. It attributes this to its Amplified Density Technology, which is a highly dense, more rigid tire casing that helps deliver feedback and handling. Aramid tread plies on the rear tire resist centrifugal growth, reduce weight and enhance stability. There’s a new rubber compound for improved wet grip without compromising durability, and a square bead-wire package for improved casing rigidity, handling and ease of installation. New sizes are available for 2013.
According to Michelin, its new Pilot Road 3 surpasses the performance of its predecessor, the Pilot Road 2, with enhanced grip in the wet from its X-Sipe design. It also is intended for exceptional durability with its latest-generation 2CT dual-compound technology. The company states that its XST sipes contribute to even wear and longer performance because of their full-depth design. Finally, Michelin has introduced two new sizes, 180/55-ZR17 and 190/55-ZR17, which are also available in a “B” version specifically designed for loaded sport-touring or two-up riding. They’re recommended for bikes such as the BMW K 1600 six-cylinder and Triumph Trophy SE Triple.
Pirelli’s Night Dragon is a new premium tire designed for the performance-oriented Harley-Davidson and metric cruiser rider who desires more grip, handling, style and miles. Today’s V-twin custom cruisers have increased engine displacement and upgraded suspensions, which creates more demands on their tires. To compensate, the Night Dragon’s contact patch has a new shape, larger dimension and new compounds for increased durability and traction. The radial structure utilizes a zero-degree steel belt with five plies, and its new front and rear tire profiles create linear steering response and quick handling. The tire’s sporty feeling comes from a proprietary compound mixed from Pirelli’s racing and street experience.
The Angel GT is the successor to the Angel ST, which, according to Pirelli, holds seven world durability records. The GT’s new rayon carcass offers 32-percent more linear density and 60-percent higher rigidity compared with the Angel ST, which translates to 30-percent increased mileage and reduced braking distance, while also offering improved grip and handling in the wet. The tread was primarily designed for more regular and reduced wear, with improved water drainage. Pirelli states that the GT is ideal for riders who travel long distances with a passenger and fully loaded bike, but will also satisfy recreational riders and commuters.
Shinko’s goal with the 230 Tour Master was to design a tire capable of carrying high loads for long distances in both wet and dry weather. To achieve this, it has given the Tour Master belted construction for improved handling and ride comfort, yet it’s also V-rated for use at speeds of up to 149 mph. The staggered tread pattern is intended to prevent hydroplaning in the rain while providing a quiet ride. The Tour Master is tubeless and has a four-ply nylon carcass.
Shinko’s 011 Verge is designed to deliver performance combined with extended tread life for sport touring. The rear tire features zero-degree JLSB (Joint-Less Steel Belted) construction for added stability and strength, while the front is Aramid belted for enhanced high-speed performance. Both of these feature a compound that has been created to provide excellent grip with extended tread life. The 011 also has a tread radius designed for enhanced high-speed cornering and, with a W speed rating, it’s capable of handling speeds of up to 168 mph.
The 302 Twin has Vee Rubber’s most advanced construction and is intended for the heaviest touring motorcycles, including everything from heavyweight metric cruisers to Harley-Davidson dressers. The construction is paired with Vee Rubber’s most advanced compound for high mileage and a tread pattern designed for all-weather riding, even extremely wet weather. And if you want to go stylish, the 302 Twin is also available in whitewall versions for all baggers and most metric cruisers. According to Vee Rubber, the 302 Twin is an excellent choice for cruising, touring and two-up riding.
Billed as an affordable product that provides all the features riders want in a sport-touring tire, the 387 Traveler has a specially designed tread to disperse water from the surface for excellent wet-weather riding characteristics. This is in addition to a specially formulated deep tread design for extended mileage. The Traveler also boasts an advanced compound in both the center and sidewalls to allow for even wear throughout the life of the tire. Its load-carrying capacity is designed to accommodate the needs of two-up riding, along with hauling the luggage required by the sport rider on extended trips.
(This Buyers Guide was published in the August 2013 issue of Rider magazine.)