Performance Technic Tip: That might not be the right tyre you’re running
Performance Technic is the new technical facility in Kyalami, run by the same team behind the phenomenally successful Fire It Up and Bike Buyers. Every Tuesday they will be providing some technical know-how that could make your biking life a better and easier one. Today, we bust some myths about tyres.
We know tyres are important because, otherwise, everyone would be riding around on the floor. There are two spellings for the word – Tyre in British English and Tire in American English. While we normally scoff at the pitiful American attempts at spelling, in this rare case they are correct.
The word comes “attire” as in a dress for the wheel, that was later shortened to “tire”. The English started using “tyre” in 1900 probably because it looks cooler, but the actual correct spelling is “tire”.
We will, of course, completely ignore this undeniable fact and move on with a few more facts and myths about the pieces of rubber surrounding your wheels.
The first myth is that they are not technically made of rubber, at least not the traditional sort that is milked from trees. Since 1920, rubber has been surpassed by a concoction of materials that are, luckily, black. Rubber is still used in certain tyre markets, especially the heavy utility vehicles, but not in motorcycle production. We still use the word rubber because this newfound concoction is conveniently called “synthetic rubber”.
This is good news for riders because it means that tyre performance has reached levels that natural rubber can only dream of, especially at a wider range of temperatures. In the old days – by that we mean ten years ago – a sport tyre had to be warm before it would even half decently grip. This is because sport tyres, especially race tyres, were traditionally made using a material called Carbon Black. It creates a hardy tyre that does not deform as easily and can handle very high temperatures. In fact, it needs high temperatures because it doesn’t grip when cold. This why racers make use of tyre warmers. Also, don’t try anything with it while it is raining, partially because it won’t get up to temperature and also because Carbon Black tends to repel water, something you don’t want when you’re trying to grip on it.
Things have changed in the last decade as tyre manufacturers have made strides with a material called Silica. It started life as a bonding agent in tyres used in the cold and wet regions of the far up Northern Hemisphere. Silica is able to grip when cold and also has a mild chemical attraction to water, meaning it creates chemical grip in the rain. This sounds perfect, but the problem is that Silica has never coped well with high temperatures and tended to overheat on tracks or when ridden hard on mountain passes.
This is where the laboratory people at tyre makers have made their strides because they have managed to make Silica that has a wider temperature range, meaning it works better at higher temperatures. This is why most modern road-sports tyres are now so good – they grip beautifully in cold weather with riders able to put their knees down even without tyre warmers, they are better able to cope when the tyres get up to temperature and rain will not end play. In fact, modern road-sports tyres grip incredibly will in wet conditions even without the aid of a huge amount of tread.
The proper track tyres and slicks still use Carbon Black and that doesn’t look likely to change, but the road-sports tyres are now on a new level compared to their predecessors.
With materials out the way, we get to sizes. It is believed that the bigger the tyre, the bigger the contact patch and therefore the more grip. This is a fallacy, however, because a bigger contact patch does not create more grip. Yeah, we were shocked at this news too, and even some senior track coaches still teach this wrongly.
Grip is formed by the tyre pressing into the rough tar, meaning the little spikey bits in the road poke into the tyre and stop it sliding. The further the spikey bits stick into the tyre, the more grip they create – we are sorry about the simplistic nature of this explanation, but bear with us. The spike bits on the road stick into the tyre because the tyre is being pushed downwards into them, and the more the tyre is pushed downwards the more the spikey bits stick into the tyre. When the contact patch is increased, it covers more spike bits in the road which do indeed create more grip, but the force pushing the tyre downwards is still the same but spread over a bigger area. This means that each spikey bit in the road is not sticking into the tyre as much, cancelling out the gains from the bigger contact patch.
We hope you’re still with us because this has some interesting implications – the bigger contact patch might not have any more immediate grip but will be under less duress. This means it generates less heat and is subject to less wear and tear. We have seen this in 24 Hour endurance races when we previously ran a Triumph Daytona 675. In the first year, we ran a 180 rear and the tyre was poked after four hours. In the second year, we ran the same tyres but using the bigger 190s, and found we could push them to as much as six hours. The tyre ran at a slightly cooler temperature under the summer heat plus suffered less wear and tear.
This is the benefit of running a bigger tyre with a larger contact patch, but the downside is that it is a heavier tyre that will slow the straight line speed slightly, and will also make the bike feel a little heavier when tipping into corners. For the racers or road riders running Carbon Black rubber, the bigger tyre also might not get up to temperature on cooler days. It’s because of these reasons that Moto3 GP bikes run a 140 rear tyre and not the bigger 150 or 160 sizes.
Obviously the type of tyre is important – a tyre that the top racers use and has the most grip for them is not the same tyre that has the most grip on the way to work in the morning. Especially on a rainy, winter morning. As we have already discussed, the top race and track tyres are made using Carbon Black, and will not work when they are cold or wet. A sport road tyre, on the other hand, with Silica foundations, can do all of the above and grip almost as well as a full race tyre that is up to temperature.
Fire It Up has a special on all Bridgestone BT-021/015 tyres with prices as low as R2199 fitted.
Performance Technic Contacts:
Tel: 010 880 2849