Encyclopedia of motorcycle tyre

Eventually tires wear out, and needreplaced. Typically the rear tires start to square up, losing their roundedprofile, as the center of the tread wears away faster than the shoulders. Fronttires generally wear more evenly across their tread, but may begin to developscalloped wear known as cupping. Knobby tires are more obvious as the knobs startto wear, tear or break-off over time.Inspect your tires for adequate treaddepth. When the tire is worn to the built-in indicators at 1/32nd inch (0.8millimeters) or less tread groove depth, or the tire cord or fabric is exposed,the tire is dangerously worn and must be replaced immediately. Also inspecttires for uneven wear. Wear on one side of the tread, or flat spots in thetread may indicate a problem with the tire or bike. Consult your local dealeror mechanic for help. Inspect your rims also. If you have a bent or crackedrim, it must be replaced.A good practice is to plan ahead and havereplacement tires lined up and ready to install before the old ones are totallyworn out. Tubes should be replaced at the same time as the tires, on tube types. Old tubes deteriorate and are prone to cracking, which can lead to suddenfailure, so a new tube should be installed whenever the tire is replaced. Makesure the tube (if it is used) is the right size and is compatible with radialsif need be. Rim strips should also be replaced if they look deteriorated.

The design of a decent motorcycle tyre is all about itsconstruction, compound and tread pattern. Advances in the materials used havedeveloped dramatically, with new elements offering manufacturers multipleoptions for both carcass design and compound variation. The traditional balanceof a hard compound for mileage and a soft compound for grip has been modifiedby additional elements that make the rubber behave in very different ways.Tread design is crucially important for water clearance,while also allowing movement, which helps to generate heat in the tyre and toimprove performance.

Crossply (or bias) tyres have a relatively simplestructure with sturdy sidewalls and are particularly suited to off-road use asthey resist impact well. They can’t be used at speeds over 150mph (240kmh)Radial tyres – which have an ‘R’ in the designation onthe side – have a casing that sits at 90° to the rolling direction, and a beltthat’s between around 0 and 25° off it. This belt, which sits under the tread(it’s what you see poking through on really badly worn tyres), adds stabilityand allows for far higher speeds as the deformation due to centripetal force isgreatly reduced.Because the sidewalls are thinner, the tyre heats upless, so high speed strength is improved. Modern motorcycles are geared to useradial tyres, as they only expand by a few millimetres at speed; a crossplytyre can expand by around 20mm at 130mph!The other tyre of note is the ‘bias-belted’ – effectivelya crossply with belts below the tread for additional support, and is suitablefor use up to 150mph. These tyres have a ‘B’ in their designation; in thepicture below you can see one on the 2018 Harley-Davidson Sport Glide.

The legal tread depth limit for motorcycles, mopeds and scootersover 50cc in the UK is 1mm across three quarters of the width of the treadpattern, and with visible tread still remaining on the other quarter. At thispoint though, the ability of your tyre to disperse water will be limited, andit will be performing far from its best in the dry.For anything under 50cc, the law simply states that you must beable to see the original tread pattern across the whole tyre.

It sounds obvious, but the most important point is thatthe tyre must be the right size for your motorcycle, with the correct speed andload ratings. Then, be honest with yourself, and choose rubber that’srecommended by the tyre manufacturers to suit your needs.A good example is sports tyres – many people think theyshould buy the stickiest race rubber they can, but unless you’re riding hard ontrack, it won’t get up to temperature properly, so potentially won’t perform aswell as a more road-focussed tyre, and could sacrifice wet weather safety too.Durability, performance, all-weather capability, thetypes of road you ride, the luggage you take, if you carry a pillion and eventhe climate you’ll be riding in should all be considered; there is no bestall-round tyre, but technology has moved on so far in the last few years thatyou can expect good wet and dry grip, as well as longer life from much oftoday’s road rubber.