An idiot's guide to motorcycle tyres
- Details
- Parent Category: Nurburgring
- Created on Friday, 13 April 2012 17:44
- Last Updated on Tuesday, 24 April 2012 22:04
- Published on Friday, 13 April 2012 17:44
- Written by Andy
I love the English language. Read the title again and ask yourself a little question. Who’s the idiot? Is it you, dear reader? If you don’t know the ins and outs of tyres by now, it must be you!
But it must also be me. Because the subject is so chock-full of variables that only an idiot would attempt to write something about it.
All sorts of things will influence whether a tyre is up to temperature. Words can only go so far, thereafter you need to ‘feel’ the problems for yourself. But we get ahead of ourselves; first we need an idiot. Bring forth #1....
Clearly an idiot? Maybe not. Aside from having the wherewithal to bash the credit card to the tune of a new GSXR1000. What if it was just a bit too much excitement alongside not quite enough experience. And doesn't that just sound like the vast majority of newbies to the Nordschleife?
Since you're reading this its possible you're trying to self-help yourself away from a silly accident. So any moment now you're going to ask the obvious question. That is; "How long should I wait before the tyres are warm?" Or as people tend to ask me; "Which corner before I’m good to go?"
If you're hoping for a definitive statement, you are not getting one just yet.
Variable means things change. This is clear, not all bikes are the same. They are fitted with tyres meant for different purposes. The intention changes, some want more fasterness others just wobble a lap and buy a sticker. And a whole host of other physical reasons like weather, suspension settings and road surface. But first....
What is the cold tyre problem? From the top... Grip comes from abrasion and adherence. Abrasion is friction. Its everywhere, must be, otherwise you couldn’t move anything. Adherence means how sticky it is. If a tyre is at its operating temperature it will literally try to stick to the road. Sometimes tyres get sticky enough to lift stones and rubbish of the floor, or lift the paint off garage floors (especially after you just paid hundreds of quid for super-duper PVC paint - Dale).
So you set off from the barriers and you have abrasion, but you will have little adherence. Tyres are not round either. Where they touch the ground they spread out a little, and this working area is generating friction. Upon leaving the ground due to rotation they return to being round. This constant working and flexing causes the tyre to heat up. And this is where your adherence comes from. Easy, the tyre is now warm.
Generally road rides are done upright, and there is ample time to let heat soak through the tyre. The Nürburgring however gives you about 800 metres of easy section before ooh 18,200 metres of harder. 800 metres is not enough to warm a cold tyre so how do you cope?
If you wander along slowly you will generate less friction than if you try a bit harder. So accelerate briskly. Briskly does not mean highside into orbit, m’kay? And use the brakes.
Arriving at reasonable speed then braking in a firm but progressive manner – you might be surprised at how much grip there is here. The first section of the track is kind-of-straight and will allow 130kph without scaring all but the most timid. And happily you have several hundred metres notice before the first slow section at Hohenrain chicane. You could shut the throttle early and roll in. But that slows the rate the front tyre will warm up. Keeping the speed up a little then braking firmly will help. Happily all this can be done at angles approaching upright. Which is safer.
Leaning over and accelerating or braking hard on cold tyres will end in tears (I crashed an Aprilia RS125 at T13 right this way - Dale). But some lean and only enough throttle to keep the thing balanced will be fine. Likewise trail braking (that is braking into or around corners) has to be done very softly to start with. But if you braked hard earlier, the middle of the tyre is warmer, so brake firmly again whilst straight before the corner, then let the brakes off and coast into the corner. On the way out use only enough to balance the bike, resist the urge to play at racers just yet.
If you like think of grip as 10 euro note. If you spend 9 euro on braking roughly there is very little to spend on turning for the next corner. And if it was only a little 1 euro corner... you wouldn’t need to spend 9 euro on brakes.
Watch the ZX10 in the above video. Bad luck Mr Adi. He’s slower in, then winds the throttle on slowly. Chris curve was done well, decisive, good line, fair speed. Shame he forgot the left side of the tyre wasn’t ready. Some consider the run off at Cadwell to be a bit small in places. Small is a relative term.
What does this mean in practice on a dry Nurburgring?
The first tyres problem is the cone chicane a little after the barriers. Don’t zoom off from the barriers. Crashing at the cones is very embarrassing, isn’t it Mr Ghostrider?
The next problem only affects loons using race tyre pressures, but the little jump on the way into Tiergarten can cause instability for the fast right – only applicable to high speeds. Hohenrain chicane. Its tighter but you see it early so no drama. You can now see the GP track area directly ahead, and there is a ‘link road’ that goes sharp right. This is the route you take to remain with the Nordschleife (there will be a tyre wall to stop you straying). Being sharp and unexpected (because of the barriers that line the track you can’t see the corner) causes problems with riders shutting the throttle. At the very moment they get scared there are several bumps that harm front end grip. Also because its a blind unexpected entry its common to hear car tyres squeal and this can spook some riders. You can now see a blue painted wall to your right as the track goes slightly uphill. Beyond this you know nothing of what’s coming and the sanctuary of the car park feels a thousand miles away, even though its probably less than a mile...
What happens is the track bends slightly right up and over a bridge, then it falls sharply into a right that hooks itself tighter. And the surface is a bit mismatched. So you come in a bit too hot, the bike is ‘light’ over the crest and you start braking just as the back is trying to reconnect with the ground, which is now falling away down hill. The front tyre might be warm in the middle, but asking it to cope with braking (a load increase) turning (another one) and going down hill (another) then you change line (yet more load). Oh and the suspension might still be cold so the damping oil will be slower to react. The area is called T13 on your map. Next is Hatzenbach Bogen. The faster right adjacent the 2km board needs care. A good line in makes it easy. Novices trying to stay out of the way of faster traffic will find the corner kinkier [ooh matron!].
Also the corner for odd geological reasons can feel ‘colder’ sometimes, I avoid aggressive throttle. The next left kink (un-named) has a bump only a problem for those going proper fast,or overloaded badly suspended buses. The next section is what your map says is Hatzenbach. It is a gift for warming tyres – the section resembles a snake like series of right after left after... seven in all if you count Hoheichen. All in 2nd gear for most people, open so you can see a quite a lot, and there are no surprises until you reach the pace of doing them at full throttle in first gear on a newish sports bike. Just watch for the kerbs, the ones on the way in are high, getting too close can knock holes in generator cases on older engine designs.
The only bit that’s missed out from the above diatribe is tyre pressures, which type of tyre is suitable or otherwise its operating temperature, how the weather might affect things and which size works. Might have to be another day. Anyway if you have reached this far... you might still fall off. But it won’t be because of cold tyres. Away you go...
