Whether you ride a sportsbike or a Harley, an adventure machine or scooter, you need tyres. And regardless of if you’re a learner or a seasoned biker, tyres can seem something of a black art – how long should they last, do they go hard, what pressures should you run them at, what’s the minimum tread depth? We spoke to Graham Matcham, tyre expert at Cambrian Tyres, and brand manager of Continental Motorcycle UK for the lowdown on bike rubber…

How do I choose the best motorcycle tyre? It sounds obvious, but the most important point is that the tyre must be the right size for your motorcycle, with the correct speed and load ratings. Then, be honest with yourself, and choose rubber that’s recommended by the tyre manufacturers to suit your needs. A good example is sports tyres – many people think they should buy the stickiest race rubber they can, but unless you’re riding hard on track, it won’t get up to temperature properly, so potentially won’t perform as well as a more road-focussed tyre, and could sacrifice wet weather safety too. Durability, performance, all-weather capability, the types of road you ride, the luggage you take, if you carry a pillion and even the climate you’ll be riding in should all be considered; there is no best all-round tyre, but technology has moved on so far in the last few years that you can expect good wet and dry grip, as well as longer life from much of today’s road rubber. What makes a good tyre for different conditions, like dry, rain, snow etc? The design of a decent motorcycle tyre is all about its construction, compound and tread pattern. Advances in the materials used have developed dramatically, with new elements offering manufacturers multiple options for both carcass design and compound variation. The traditional balance of a hard compound for mileage and a soft compound for grip has been modified by 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 to improve performance. What really matters when looking at tread patterns? Effective water clearance on a road tyre of course, as well as generating heat. On adventure, enduro, motocross and other off-road tyres, grip on loose surfaces is important, but also durability and mud clearance – it’s no good having a knobbly hoop if it clogs with mud. But in addition to that, tyre designers might need to consider how they can make a tyre that can put the power down, without tearing up the surface too much. While knobbly tyres are a trend on many custom bikes at the moment, be careful that you don’t compromise the road holding if you’re riding on tarmac – the more extreme tyres will not only have reduced hard-surface grip, they’ll also give a much less comfortable ride.

What does the writing on the side of my tyre mean? In this photo we have a 180/55 ZR17 (73W) tyre, which means it’s 180mm wide, and the profile height is 55% of that, so 99mm. The 17 relates to the rim size – 17inches – while the 71W is the speed and load rating; 365kg and 168mph (270kmh). Because that rating is in brackets, it means the 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’s intended 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.

The maximum load – here it’s 365kg – is the most the tyre can support at a standardised pressure – in this case 42psi. This isn’t necessarily the pressure recommended for your bike, so check your owners’ manual or the tyre manufacturer’s fitment guide.

This circle shows that the tyre is homologated for use in Europe, with the number indicating the country in which the approval was made – in this case Netherlands.

How can I tell how old my tyres are? The production date of any tyre made since 2000 can be found on one of the sidewalls, at the end of the ‘DOT’ (Department of Transport) code. The last four figures – typically after other letters and numbers – show the production date. The first two are the week it was made, and the last are the year. So this tyre was made in the 9th week of the year 2017. Tyres used to have a three-digit date code, as it was considered that none would be used for more than a decade. Unfortunately, this made it very hard to tell if the rubber on a bike you were buying in 2005 with a 327 code was made in the 32nd week of 1997, or the 32nd week of 1987. Just know that a tyre with a three digit code on now is too old. Can I run tubes in a tubeless tyre? Yes, but it’s worth checking that there are no loose labels on the inside of the tyre that could cause a problem with the tube. Does running a tube reduce my tyre's speed rating The addition of a tube has no effect on a tyre’s speed rating up to a maximum of 130mph (210kmh), beyond that the tyre would typically be rated at the next speed down. What is the difference between tube and tubeless tyres? Simply put, a single layer of material on the inside of the tyre’s carcass. All the materials used in a tyre are about performance – a balance of grip, flexibility and durability. It may surprise you to hear that the ideal mix of rubber is actually porous, so will slowly leak air. In the past, this was overcome by fitting a tube with a completely different rubber mix that would contain the air much better and have little effect on the overall performance of the tyre. The biggest issue with this design is that if it’s subjected to a puncture, the tube will lose all of its air suddenly, which would have typically escaped rapidly through the spoke heads on the wheel. Rapid deflation of a tyre on any vehicle is not good, particularly when travelling at speed. Created predominantly with safety in mind, the tubeless tyre was designed by taking a section of tube material and making a single continuous layer on the inside of the tyre carcass, and also saving weight. Of course, a tubeless tyre can still be punctured, but the offending 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 wheels mean spokes are no longer needed, so the entire unit has become sealed. Now, instead of manufacturing both tubed and tubeless tyres in the same size, most companies only make tubeless, and recommend that tubes can be fitted if required. The disadvantage to this is that it adds additional weight 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 no tubeless liner, so it will not hold air and therefore must be fitted with an inner tube. Why are tyres so slippery when they are new? The final part of manufacturing a tyre is the curing process – a carcass containing all the component materials is typically placed into a very hot mould and cured under high pressure for about thirty minutes. To assist in the removal of a cured tyre from its mould, a small amount of release agent can be applied before the process begins. A thin residue of this remains on the surface of the tyre, leading to the warnings issued about scrubbing in new rubber. Some manufacturers have got around this process now, and Continental for instance has developed a unique way of modifying premium tyre moulds, negating the need for any mould release agents; the finish is slightly rough and provides instant grip when the tyre’s used for the first time – it’s called ‘Traction Skin’. A new tyre will always feel significantly different to your old, worn one, so we still recommend riding with care at first, building up speed and lean angle over time.

Continental’s ‘Traction Skin’ prevents the slippery feeling some new tyres have What is the minimum tread depth on motorcycle tyres? The legal tread depth limit for motorcycles, mopeds and scooters over 50cc in the UK is 1mm across three quarters of the width of the tread pattern, and with visible tread still remaining on the other quarter. At this point though, the ability of your tyre to disperse water will be limited, and it will be performing far from its best in the dry. For anything under 50cc, the law simply states that you must be able to see the original tread pattern across the whole tyre. If I don't ride many miles, how long will my tyres last? Will they go hard? As long as a tyre is stored in a cool, dry place, and away from direct sunlight, chemicals or other ozone effects, it will be fine for a long time. Tyres do slowly age, but Continentals for instance can be sold and used unconditionally as a new tyre from up to five years after the date of manufacture. The warranty period on a Continental tyre commences at the date of purchase, regardless of the production date. We recommend replacing any tyres that are more than ten years past the date they were made, but advise against buying or running used tyres that have an unknown history. Do I need to put my bike on stands when I'm not using it? Bikers sometimes worry that they’ll get flat spots on their motorcycle’s tyres if they leave it standing for any length of time. In fact, the most important thing to do is simply keep them inflated correctly; with your tyres at the correct pressure there’s no need to lift the bike off the ground. How do I check my bike's tyre pressures? Check the pressures when the tyres are cold. As you ride a bike on the road, the tyre warms up, and can increase up to around 0.5 bar (about 7psi) – don’t let your tyres down to remove this as they’ll be under-inflated when you next ride. Use a quality stand-alone pressure gauge, not the one fitted to your pump, or on an airline.

What tyre pressures should I use on my motorcycle? Your bike’s owners’ manual will tell you the recommended pressures, or sometimes a sticker on the swing-arm or hugger. Use them – the bike will have been thoroughly tested to find a safe recommendation based on getting heat into the rubber, and the load you’re likely to carry. Incorrect pressures reduce the life of your tyres, and can affect the handling; if you run them low, the contact patch can be reduced – not increased – because the tyre deforms, lifting the middle section away from the road. They’ll also easily overheat and can be damaged. If you over-inflate your tyres, they’ll again wear unevenly, handle poorly and give an uncomfortable ride. You might find different pressures recommended for different loads and riding – Continental recommends that you ride at the highest pressure stated in your owner’s manual. If you don’t have the bike manual, check the tyre manufacture’s website. Should I reduce my tyre pressures in wet and bad weather? No. They’re designed to work at a specific pressure. Some people reduce the pressure of their tyres in the winter, believing they’ll grip better. They’ll get warmer as they move around more, but the contact patch will be reduced due to deformation, and the tread pattern will perform less efficiently; they’ll wear out quicker and be potentially dangerous. Should I reduce my tyre pressures for a track day? If it’s your first time on track, then no – just get out there and enjoy it. Because manufacturers test bikes for safe pressures on the road, if worked very hard, the tyres can get too hot. The air inside your tyres is, of course, the same as the atmosphere around us – it contains water. As the temperature inside increases, the water expands, and the pressure goes up. You could avoid this by using nitrogen, but it can feel odd when pulling away, as you don’t get that ‘bedding in’ feeling you expect from a cold tyre – the bike can feel ‘wooden’ at first, and once a bike feels odd, you lose confidence. How far you need to reduce the pressure on your tyres at a track day will depend how hard you ride. Keep in mind that you don’t need to reduce them for any form of road riding, so be honest about how hard you can push you bike. My recommendation, if you are riding hard, would be to take a pressure gauge with you – ride the first session at road pressures, then check the tyre while it’s still hot. As a rule of thumb on sportsbikes, reduce the rear to 42psi if it’s above that as soon as you get in (so the tyre’s still hot), and the front to 36. At the end of each session, just check the hot pressures again and reduce only if they’ve gone over 36/42psi as you get quicker through the day. Just remember to pump them back up when they’re cold at the end of the day before you ride home. True racers will go a lot further – the recommendation for a Continental race tyre is just 26psi when it’s hot! This takes into account just how hard the tyre will be working under race conditions – this is way in excess of any track day pressures, even in the fast group, and would feel awful to a rider who wasn’t trying to win a race. Interestingly, I’ve found that for every 10°C change in temperature, the tyre pressure will typically change by 1psi, which as a percentage of the overall pressure is significant. If your pressures are off, you won’t be getting the best out of your tyres or your track day – you’ll be wasting money and track time.

What is the difference between a crossply and radial tyre? Crossply (or bias) tyres have a relatively simple structure with sturdy sidewalls and are particularly suited to off-road use as they resist impact well. They can’t be used at speeds over 150mph (240kmh) Radial tyres – which have an ‘R’ in the designation on the side – have a casing that sits at 90° to the rolling direction, and a belt that’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 stability and allows for far higher speeds as the deformation due to centripetal force is greatly reduced. Because the sidewalls are thinner, the tyre heats up less, so high speed strength is improved. Modern motorcycles are geared to use radial tyres, as they only expand by a few millimetres at speed; a crossply tyre can expand by around 20mm at 130mph! The other tyre of note is the ‘bias-belted’ – effectively a crossply with belts below the tread for additional support, and is suitable for use up to 150mph. These tyres have a ‘B’ in their designation; in the picture below you can see one on the 2018 Harley-Davidson Sport Glide.

Is it safe to repair a motorcycle tyre after a puncture? There’s a British Standards recommendation, but it is just that – a recommendation – so you will find some differences between manufacturers and dealers. Personally, I’d go with the following: Tyre speed rating Up to J Above J, up to V Above V Max speed equivalent 62mph (100kmh) Up to 149mph (240kmh) Over 150mph (240kmh) Max diameter

of damage 6mm

(1/4 inch) 3mm

(1/8 inch) No repair permitted Max number of repairs 2 1 0 These repairs need to be carried out using a plug inserted from the inside of the tyre and vulcanised in place. Only the central 50% of a motorcycle tyre’s width can carry a repair, and not the sidewall. It’s also not recommended to attempt to repair a tyre with less than 0.8mm of tread – if it’s that worn, invest in a new one. Roadside repair kits aren’t considered a permanent fix, and should only be used to get you home; most manufacturers will still tell you that you’re best off having the bike picked up if you suffer a puncture at the roadside. A blow-out on a bike is extremely dangerous, and as your tyres are all that connect you to the road, it’s worth using common sense when considering a repair… Motorcycle tyres explained