In 2014 we have been working closely with our partners at California Superbike School UK and the team at RiDE magazine to publish our six part “Tyre Tech Talk” series which helps to give riders across the UK the tyre knowledge they need to find the right tyre for them, and get the most out of their rubber once it is on the road. In the 4th instalment of the series which was released in the July edition of RiDE magazine we took a look at motorcycle tyre shelf life and this is what you missed!
The biggest change in technology in terms of motorcycle tyres in recent years is the compounds that we now use to provide riders with both grip and durability. Originally tyres were made from natural rubber which is sticky but lacks durability. In order to improve durability carbon black soot was added to stiffen the compound, which is why tyres are black in colour. After the addition of carbon black in order for the tyre to grip properly the tyre would need to have a certain amount of heat in it.
As Deputy Chief Riding Instructor at California Superbike School UK Andy Peck goes on to explain, the biggest change they have seen in recent years is the window of usability over a wider range of temperatures. In the past when out on track Andy explains that riders would either have to ride cautiously for a few laps whilst the tyres warmed up, or at the opposite end of the spectrum the tyres would be good to go straight away but would then overheat and lose traction halfway through a session. As on 2013 California Superbike School UK switched to using the street legal ContiSportAttack 2 hypersport tyre on all of their track bikes. The difference is clearly noticeable with grip at the very start of the day, with a minimal amount of work required to bring them up to temperature whilst also offering consistent levels of performance right throughout the day until the last session at 5pm. Amazingly Andy says “Even at minus 5°C at the start of the year we were getting our knees down”.
Nowadays we manufacture tyres using a synthetic rubber, adding fine grains of silica that create a compound with the flexibility to grip even at low operating temperatures. More recently the goal in terms of tyre development has been to attain a greater level of dispersion of these components within the compound to achieve improved uniformity and performance. A number of Continental products such as the ContiSportAttack 2 and the brand new ContiRoadAttack 2 EVO sport touring tyre use Traction Skin technology, which consists of microscopic rough particles on the tyres surface to increase adhesion between the tyre and the road, reducing the need for scrubbing in.
Modern day tyres may be more advanced than their predecessors, but they are not immortal. When a tyre leaves the mould it will slowly continue to cure, which means that it is of the upmost importance that tyres are stored and handled correctly to minimise the effects of exposure to the atmosphere. Stored in optimum conditions in a dark room at a constant 20°C most tyres will remain in good condition for over five years. However once fitted to your bike and inflated a tyre is placed under stress as well as being exposed to direct sunlight as well as the extremes of heat and cold which accelerates the process of deterioration.
One of the common signs of tyre ageing is known as “Crazing”, which is when hairline cracks appear in the tyre wall or at the base of tread grooves. The crazing is caused when oils in the tyre leach out, and you can use a torch to help you spot whether or not a tyre is starting to perish. When buying an older bike it is important to ask the dealer when the tyres were manufactured, even if they appear to have a good amount of tread left on them.
Andy goes on to explain how California Superbike School UK recently coached a student who decided to ride his own Yamaha R1 track bike. Whilst out on track he was running on a pair of slick race tyres, but struggling to find any real grip. When Andy took a look at the sidewall it was clear as to why he was struggling. The four digit date code allows you to date your tyre, and the first two numbers represent a week of manufacture with the last two numbers representing a year of manufacture. In this case the date code was 0809 meaning that the tyre had been made in the 8th week of 2009 so it was now over five years old. Attempting to change the tyres for some new rubber the team struggled to remove the old slick tyres from their rims because they had the consistency of wood.
In order to spot a tyre that is past its prime, try sticking your fingernail into the tread. The texture of the tyre should be soft like rubber, not hard like plastic. Try comparing your tyres to some that you know are fresh to get a good feel for it. In order to minimise the effects of tyre ageing once they are fitted to your bike ensure that you inflate the tyres right up so that they keep their shape when the bike is being stored. You should also use front and rear paddock stands to keep both wheels off the ground. This will stop pressure from the weight of the bike creating flat spots on your tyres.
If you have missed any of the other parts in the “Tyre Tech Talk” series then you can catch them all via this link.