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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.

Simply put, a single layer of material on the inside of thetyre’s carcass.All the materials used in a tyre are about performance – abalance of grip, flexibility and durability. It may surprise you to hear thatthe ideal mix of rubber is actually porous, so will slowly leak air. In thepast, this was overcome by fitting a tube with a completely different rubbermix that would contain the air much better and have little effect on theoverall performance of the tyre.The biggest issue with this design is that if it’s subjected toa puncture, the tube will lose all of its air suddenly, which would havetypically escaped rapidly through the spoke heads on the wheel. Rapid deflationof a tyre on any vehicle is not good, particularly when travelling at speed.Created predominantly with safety in mind, the tubeless tyre wasdesigned by taking a section of tube material and making a single continuouslayer on the inside of the tyre carcass, and also saving weight.Of course, a tubeless tyre can still be punctured, but theoffending object usually stays stuck in the tread and the tyre deflates slowly,giving the rider an opportunity to slow down. At the same time, cast wheelsmean spokes are no longer needed, so the entire unit has become sealed.Now, instead of manufacturing both tubed and tubeless tyres inthe same size, most companies only make tubeless, and recommend that tubes canbe fitted if required. The disadvantage to this is that it adds additionalweight to the total wheel assembly, which can lead to more heat generation,which ultimately means faster tyre wear.If a tyre states that it is ‘tube type’, then it will have notubeless liner, so it will not hold air and therefore must be fitted with aninner tube.

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.

In this photo we have a 180/55 ZR17 (73W) tyre, whichmeans it’s 180mm wide, and the profile height is 55% of that, so 99mm. The 17relates to the rim size – 17inches – while the 71W is the speed and loadrating; 365kg and 168mph (270kmh). Because that rating is in brackets, it meansthe tyre is capable of speeds above the figure, but if there were no brackets,it’d mean the rating was the maximum. The ‘M/C’ simply denotes that the tyre’sintended for use on a motorcycle. You can also see the direction of rotation –if this is the wrong way round, your bike will fail its MoT.

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.