Know Your… ................................... Andy Notman from Öhlins gives us the lowdown on everything to do with electronic suspenders.
What on earth is cold tear, why does it happen, and how do you stop it?
If I got a pound for every time someone came to me complaining of cold tear on a race tyre, then I'd be a very rich man. Most cold tear we see is tyre temperature related, but incorrect compound selection also plays a factor in a cold tear occurring as well. Let’s look at correct compound choice first ....
All proper race tyres are compounded. In some brands we have as many as four fronts and five rears to choose from! The reason for this, is we need a tyre that suits different track surface severity and track temperatures depending on the grip level and longevity we desire. Be aware, circuit conditions can change by the hour, never mind by the day, so what works in the morning, may not work in the afternoon. When the track surface is hotter, we would (as a wide sweeping rule as each rider is different) go harder on a Pirelli front, and harder on the rear. With Michelin, we would go soft on both front and rear. Always ask your tyre professional for advice on compound choice, as the wrong one could end up costing you a couple of hundred quid in a short space of time!
A temperature related cold tear occurs when the surface of the tyre is much hotter than the core, which is the bit a few mm below the surface. Race tyres are designed to operate at temperatures higher than 85 degrees, but if the core is sitting at a lower temperature, it means that that elements that make up the tyre compound won't work together correctly. Pretty quickly you'll find yourself with that thick and heavy horrible looking 'tear' type wear. The hotter outside of the compound literally tears itself away from the colder core.
Tyre warmers need to be used to help a race tyre get to operating temperature. Running a race tyre with no tyre warmer, or not long enough on the warmer before use, is a quick way to damage a tyre with cold tear. Look at what your tyre manufacturer recommends with regards to heat management and stick to it. If they say an hour at 80 degrees, don’t expect them to work properly after 30 minutes at 60 degrees. Getting the whole tyre, the air in it and the wheel at the same temperature is what you are aiming to achieve. If we can get everything working at a constant temperature, correct compound selection and with correct pressure, we will get the tyre to perform as it was designed. So how do we work out the temperature?
For us, we need to know the core temperature. You've probably seen the technicians on TV – or me in the NLR paddock – sticking something pointy in a tyre. This is called a pyrometer. We use this to measure the core temperature below the surface to make sure the compound is working correctly below the surface. If you buy one of these to use, good on you, but make sure you don't stick the needle in too deeply... you can puncture the tyre!
Another thing we need to consider with cold tear, is pressures. When you are using a race tyre, you need to be on top of both the tyre temperature and pressures.
Pressures are the source of most tyre issues we see, and more often than not it’s because riders are running the tyre pressure far too low. What we need to do, as amateur racers and track day riders, is to start by working within the recommended tyre pressure range set by the tyre manufacturer.
To resist cold tear occurring, especially at the colder start and end to the season, we need to increase the pressure in the tyre pressure! Starting with a higher tyre pressure forces the tyre to reach a higher operating temperature.
All levels of professional racing now have minimum pressures they are allowed to go to and they are monitored by TPMS sensors. Moto2 on Dunlops is 22psi. WSBK and BSB on Pirellis is 24psi ... worth considering that if these riders are only allowed to run to these parameters, maybe having more pressure in a tyre is worth considering.
A final chapter in the cold tear section is looking away from out-andout race tyres for your track day use. All of the above is relevant to a race tyre.
We all love the look and the feeling of a race tyre, but many cases, it is just not the correct solution to your needs. A simple thing to remember about race tyres is that if you cannot generate good operating temperatures in the tyre, grip will suffer. We don't want that!
A more track day focused tyre is what you are best considering. Something that is designed to work with YOU, notaBSBracer.
More and more we are seeing track day specific tyres being made, but they aren’t just cheap, hard-as-concrete compounds like so many seem to think. The latest generation of track day tyres have technology in them far superior to some race compounds. High contents of silica help with generating heat and providing high levels of grip, very quickly. These latest generations of product are the manufacturers understanding the needs of the track day rider. You want a tyre that grips, gives feel, lasts well, doesn’t cost the earth and won’t tear...