- Written by Carole Nash Editor
- Created: 10 April 2014
Motorbike tyres are arguably the most costly element of being a track day rider. It’s therefore crucial that we know the warning signs so we’re best equipped to deal with any problems with tyres as and when they arise. Keeping your eyes peeled will mean you can nip any tyre issues in the bud before they are completely ruined. But is reading your tyres that easy? With so many different types of tear, it can be hard to diagnose the problem. So we’ve put together a guide on the various tyre wears, and what causes them in the first place.
These fingernail-shaped, half-moon tears can be cut a millimetre into a tyre within 10 minutes. They are a sure sign of over-inflation and mean that the whole tyre has not been able to reach proper operating temperature, so it starts to rip itself apart. This is because the surface of the tyre has heated up extremely quickly while the carcass remains below the operating temperature. It will look as if tweezers have been put into the tyre and pulled out.
How do I know if I’ve got a cold tear? Do the fingernail test: if you can get a fingernail under the tear and pick back a chunk of rubber from the tyre’s surface it’s almost certainly a cold tear.
A hot tear is almost always the result of under-inflation. This, in turn, means the contact patch is too big which makes the tyre overheat. When you have a tyre that is extremely hot, the surface melts at a rapid pace and is thrown off as a result of the centrifugal force.
How do I know if I’ve got a hot tear? A hot tear can be confusing as the markings can also represent an incorrect spring rate. The bike’s sag should therefore be measured to make sure it falls within manufacturers’ recommended specs, and this will eliminate the spring rate from the equation. You then know that it’s a hot tear. Similarly, at first glance it can resemble a cold tear, but because it’s happened due to the entire tyre overheating (not just the surface) the rubber can be removed with a lot less effort. The tears are also shaped differently – hot tears arc towards the direction of travel at the outside edge near the shoulder. Hot tears are pretty shallow and you shouldn’t be able to get a fingernail deep underneath them (like you can with a cold tear).
Geometry Tear – too much weight on the front
Although not as common as cold or hot tears, it comes as a result of too much weight being put on the front wheel. The tear is therefore caused from the front end suspension being too soft and the back end too hard. When the bike goes into a corner, for example, it pushes across the ground or stalls (rather than rolling across it as it should) and then goes, meaning once the bike straightens up and the weight returns to the back tyre the front tyre can start rolling properly again.
How do I know if I’ve got this type of geometry tear? A geometry tear will follow the circumference of a tyre and will be around 5mm wide, typically around half way between the middle and edge of the tyre.
Geometry tear – not enough weight on the front
This type of geometry tear is a result of a lack of weight on the front tyre so it can’t reach its proper operating temperature. This results in the tyre not getting proper traction. When the rider gets on the throttle, the front tyre pushes and drags across the ground meaning the surface of the tyre gets over-heated and torn to shreds.
How do I know if I’ve got this kind of geometry tear? The affected area will be relatively big and the part closest to the centre of the tyre will follow the circumference of the tyre in a somewhat uniform fashion.
Suspension-related Tyre Wear
If you don’t look closely enough, tyre wear as a result of incorrect suspension settings could be confused with a pressure-related issue (i.e. a hot or cold tear). However, there are specific differences to look out for. If your rear suspension settings (compression, sag, rebound, spring rate) are not set correctly, it can sometimes cause the tyre to act as part of the suspension. Tyres are not designed to do this, so straight away you’ll start to notice unusual wear and (literally) tear.
How do I know if it’s suspension-related or not? Check the thickness of the tear. If there’s no uniformity to the tear and it changes as it goes around the tyre, this typically indicates it’s something to do with the suspension. If the tear goes all the way around it could be a result of poor geometry or tyre pressure. Your spring may be too hard or too soft for your weight, in which case the carcass of the tyre will have been put under immense pressure. As a result, the tyre will shred. Do you have a raised patch on the leading or back edge of the tread? This could be a sure-fire sign that rebound damping on the shock or forks is set too fast or slow.
It doesn’t fall under the ‘tear’ category, but many riders will experience blue tyres as a result of the oils coming to the surface of the tyre. This is often perceived as the end of a tyre’s life. However, this is simply not the case.
Why does this happen? Once the tyres have reached a certain temperature and then are allowed to cool down, the oils often come to the surface. This is known as a ‘heat cycle’. It’s nothing to worry about – once you go back out and ride again the oils will be scrubbed off. However, the more heat cycles you put your bike through, the more oils your tyre is losing and the less effective the rubber will be.
The trick is to look out for these tell-tale signs. While there are many other factors that come into play (how you ride your bike, suspension make up, and the type of track, for example), hopefully this will have shown the small differences between the disfigurations so that you can fix any problems that come up in the correct way.