MOTORCYCLE TIRE GUIDE

MOTORCYCLE TIRE GUIDE
What riders need to know about street motorcycle tires.  The information in this booklet represents the collective knowledge of a number of motorcycle tire manufacturers, the U.S Tire Manufacturers Association, and Motorcycle Industry Council staff and is intended to be a useful resource for motorcyclists. This booklet, however, cannot cover every possible example or aspect of tire usage. Consult the appropriate motorcycle or tire manufacturer for issues not addressed in this booklet.


INTRODUCTION 
Never underestimate the importance of having good, properly inflated tires on your motorcycle.  The small contact patches provided by the front and rear tires are the motorcycle’s only source of traction. Deterioration of your tires’ condition can jeopardize this contact patch and bring a good ride to a quick end. Safe riding depends on selecting the right tires, inspecting and maintaining them, and replacing them as necessary.

INSPECTION AND MAINTENANCE
Inflation Pressure
It’s all about inflation, inflation, inflation. Proper air pressure is critical for tire performance and tire life. Under-inflation or overloading can 
cause heavy steering, irregular wear, and internal damage due to overflexing, and can cause the tire to separate from the rim. Over-inflation can reduce the contact area (and therefore available traction), and can make the motorcycle react harshly to bumps. Check the air pressure with a gauge when the tires are cold (at least three hours since the last ride), as part of your pre-ride “T-CLOCS” inspection (T-CLOCS) means Tires and Wheels, Controls, Lights, Oil, Chassis, and Stands; see page 14 for a complete 
MSF T-CLOCS checklist), and adjust it according to your motorcycle’s owner’s manual or the tire information label on the chain 
guard, frame or swingarm. There may be two sets of recommendations for tire pressure (as well as suspension settings): one for solo riding and one for riding with a passenger and/or cargo. Do not exceed the maximum inflation pressure listed on the tire’s sidewall. And 
never exceed the motorcycle’s or tire’s load limit (combined weight of operator, passenger, cargo, and accessories), since that can cause tire failure. (Refer to the Load Limit Calculator on page 17.)  At a minimum, check your tires’ cold inflation pressures at least once a week and before long trips. Visually inspect tires for surface conditions before each ride. However, be aware that it is impossible to determine proper inflation by appearance alone. An accurate pressure gauge is needed, even if your motorcycle is equipped with a Tire Pressure Monitoring System that gives specific pressure readouts.  Regularly inspect the tire tread depth to ensure that adequate tread 
remains. Tires have small wear bars molded into the tread grooves. When the tread is worn down to the level of the wear bars (indicating 1/32 inches of tread remaining), the wear bars become exposed and the tire should be replaced. Some tire manufacturers recommend replacing the tire when there are 2/32 or 3/32 inches of tread remaining, before the wear bars are exposed. Although it may look like there is a sufficient amount, it may not be enough to maintain traction in wet conditions.  The deep grooves in new tires help channel water away from the contact patch, and worn tires are thinner and easier to puncture. For a quick check, if you insert a penny into a groove in the center of your tire, 2/32 of an inch is right at the top of Lincoln’s head. In addition to tread depth, glance over the tires’ surface for any evidence of uneven wear, cuts, embedded objects, bulges, or sidewall cracking.

Heat Cycles and Tire Age

Every time you ride, the tires go through a “heat cycle” as they go from ambient to operating temperature and back down again. Each successive heat cycle slowly hardens the tread. Also, chemical reactions over time may cause the rubber to harden, even with nonuse. Whether through heat cycles or aging, the tire’s surface becomes less spongy and less able to interlock with the protrusions and pores in the road surface, thereby decreasing maximum traction capability. (If you have an old tire and a new tire, you can press your fingernail into the surfaces of each to see the difference in how they react.) So, tires eventually have to be replaced, even if they have plenty of tread left. However, tires don’t have an “expiration date,” since operating conditions, storage conditions, exposure to sunlight, number of heat cycles, and wear are the primary factors that determine their usable tread life. Consult your motorcycle service professional or 
tire manufacturer for guidelines. We recommend against buying used tires; you don’t know how many heat cycles they’ve gone through. This also means that when you buy a used motorcycle, you should thoroughly inspect the tires, and replace them if their condition is questionable. 

Cleaning
To clean your sidewalls, use a mild soap solution and rinse off with plain water. Do not use chemical cleaners or protectants, as they may degrade the rubber, causing cracks in the sidewalls, and spread to the contact patch, causing loss of traction.  Storage If you’ll be storing your motorcycle for more than a month, and it has a center stand, set the bike on its center stand to raise the rear tire off 
the ground and use blocks under the frame or fork to lift the front tire slightly off the ground. If it doesn’t have a center stand, periodically roll the bike forward or backward a few inches so the tires don’t develop flat spots in the tread. Store the motorcycle in a dry, well-ventilated area, away from electric motors and generators, and ensure the tires do not come in contact with petroleum-based products or solvents.

THE RIDE 
Rubber is harder when it’s cold than when warmed up. Motorcycle tires are designed to provide maximum traction at specific temperatures. Riding moderately for the first few miles on the street will allow your tires to come up to proper operating temperature. Don’t take the freeway on-ramp near your home at maximum lean angle and cornering speed before your tires come up to temperature. Tire temperature is so important that professional racers actually use electric tire blankets to preheat the tires so they’ll have maximum grip when the green flag drops out on the track.

SELECTING A TIRE
Your motorcycle was designed to work in harmony with a limited selection of tires. The owner’s manual and tire information label will 
specify tire size, construction (radial or bias, tube-type or tubeless), load range, and service description (load index and speed symbol), 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. Tires must also be mounted so the sidewall directional arrows correspond to the direction of travel.  Motorcycle dealerships can recommend a variety of types within brands that best match your motorcycle and style of riding, whether 
commuting, touring, sport riding, or on- and off-road adventure riding. Some tires even use two different rubber compounds in the tread: a harder compound in the center for extra life when riding in a straight line and a softer compound on the outer edges for extra traction while leaning through turns. Note, too, that different tread patterns can make a difference in how your bike handles. For example, some patterns will resist tracking on the rain grooves that are cut into some highways. It is unsafe to install passenger car tires on motorcycle rims. The flat tread profile of a car tire is incompatible with the dynamics of a vehicle that leans as it corners. Plus, motorcycle tires and rims are designed with a different bead seat area than passenger car tires and rims. Ignoring this fact may cause inflation pressure loss while riding or the beads to break with explosive force resulting in possible serious injury or death. 

TIRE SIDEWALL INFORMATION
Every street-legal tire sold in the U.S. will have a Department of Transportation (DOT) tire identification number (TIN) on the sidewall. The TIN begins with the letters “DOT” and ends with a four-digit date code. The four digits represent the week and year of production. For example, a date code of “4510” means the tire was produced in the 45th week of 2010.  The sidewall will also have a code indicating the size, plus a load index and a speed symbol.  Replacement tires must match or exceed the speed rating specified in the owner’s manual and tire information label to maintain motorcycle speed and handling capabilities. However, tire speed ratings do 
not imply that any particular motorcycle can be safely ridden at the maximum speed for which the tire is rated. Consult the motorcycle 
manufacturer or tire manufacturer for recommendations.

NEW TIRE INSTALLATION AND PRECAUTIONS
Tires should be replaced and balanced by a professional mechanic. Professionals have the right tools to prevent damage to the bead of the tire which must seat firmly against the rim to provide an airtight seal, and they have equipment that can perform dynamic, high-speed balancing to guard against wheel vibration. Install a new tube every time a tube-type tire is replaced. If equipped with a rubber rim band, replace it with an equivalent band. For a tubeless rim, replace the rubber valve stem, or replace the valve core and rubber grommet in a metal valve assembly. For motorcycles equipped with a TPMS, consult the owner’s manual or TPMS manufacturer for service recommendations.  Certain Harley-Davidson® motorcycles use spoked, tubeless-type rims identified as “MTM” which require a rim seal for proper tire-to-rim fitment. Consult your owner’s manual.

Take it easy on new tires for your first 100 miles. The tire’s surface will be a bit smooth and needs to be “scuffed in” for maximum grip. Also, its cross-section shape will be more round than a worn tire, which likely has flattened out over time in the central tread area. This wear happens so gradually that you likely won’t notice how sluggish (relatively speaking) your bike’s handling has become until your first ride with new tires. The fresh tires may respond more quickly to cornering input, and during this break-in period you may have to re-adjust to this “restored” feeling. 

HOW MOTORCYCLE TIRES WORK
Because a motorcycle is a single-track vehicle and leans as it turns, motorcycle tires are quite different than car tires. Whereas car tires 
have a fairly flat profile and a contact patch that varies little in size or shape, motorcycle tires have a U-shaped profile and a contact patch that changes size and shape during cornering. Motorcycle tires are also relatively narrow, which makes their gripping capability (“traction”) a limited commodity. Plus, this limited amount of traction is divided up among multiple forces created when braking, cornering, and accelerating. The more you lean in a corner, for example, the less traction is available for braking; the quicker you accelerate, the less traction is available for turning. If any one of these actions uses an excessive share of available traction, you 
might lose control of the motorcycle. For more information on how motorcyclists can manage braking, cornering, and acceleration forces, please read the Motorcycle Safety Foundation’s Guide to Motorcycling Excellence (Second Edition), or any number of in-depth books on the art and science of motorcycling.  Traction can be thought of as the mechanical adhesion between tires and road surface. 

Predictable traction is essential in all riding situations, especially cornering. To enable this connection to transmit as much force as 
possible, it is necessary for the tire’s rubber surface to interlock at the microscopic level with the protrusions and pores of the road. That 
means there must be sufficient tread thickness, and it must be flexible to provide adequate traction.  There are several ways in which the adhesion between rubber and road can be compromised:
• The tire surface has lost its elasticity, because of cold temperatures, aging, or other factors 
• The asphalt or concrete has been “polished” down and made smooth by automobile and truck tires
• The interface between tire and road is “lubricated” or obstructed by any number of substances: rainwater, engine oil, leaves, gravel, sand, dirt, etc.

SUDDEN AIR LOSS AND TIRE REPAIR
Fortunately, sudden air loss is uncommon and generally preventable by maintaining proper air pressure. Sudden air loss may occur due 
to a puncture, overloading, under-inflation, impact, etc. Sudden air loss may occur without warning and can induce panic even in experienced riders. The symptoms may include vibration or sluggish handling. If a sudden air loss should occur, keep a firm grip on the handlebars, steer smoothly, and gently ease off the throttle. Avoid downshifting or hard braking, as these actions can upset the now-unstable chassis. If traffic permits, slow gradually and move off to the side of the road. If you must brake, limit your braking to the wheel with the good tire. Applying the brake to the wheel with the bad tire can cause the tire to separate from the rim, leading to a loss of control.  If a tire is punctured, it might be possible to repair it. However, repairs should be considered a temporary measure at best, and speeds should be kept low. Repairs to the sidewall are not permitted. Some tire manufacturers do not recommend repairing motorcycle tires or using liquid sealants. If permissible, repairs should be limited to a combination plug/patch repair of tread punctures no larger than 1/4” in diameter on a demounted tire. Never perform an exterior repair and never use an inner tube as a substitute for a proper repair. Speeds should not exceed 50 mph for the first 24 hours after the repair, and the repaired tire should never be used over 80 mph (not recommended to exceed the legal speed limit in any event). Remember, motorcycle tires experience tremendous sideways forces and deformation when cornering. For detailed information on repairing your tire, contact the specific tire manufacturer.

CONCLUSION
Buy the right tires, have them professionally installed, maintain proper air pressure, inspect them regularly, don’t ride over sharp 
objects, and avoid slick surfaces. Treat your tires well and they’ll treat you to many miles of safe, comfortable riding.
Danger lurks beyond the wear bars. Once the rubber is gone, so is your tire’s ability to grip the road.