Idiots Guide To Motorcycle Tyres - Part Deux

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Details

Details

Parent Category: Nurburgring

Category: Motorcycles

Created on Friday, 22 June 2012 20:34

Last Updated on Friday, 22 June 2012 21:04

Published on Friday, 22 June 2012 20:34

Written by Andy

An idiot on a motorcycle, sometime last decade.

So I (this is Andy writing - Dale) have a few minutes spare, and I thought BTG could tidy up some of the loose ends from the first idiot's guide I wrote here. Now first things first. Riders generally do something that causes crashing. True mechanical failure is a rare thing, thankfully. So all of this is about the detail of helping along someone with half an idea to start with. Good tyres cannot overcome all bad riding. Right, less of being old and boring and on with the show...

So, what is it?

If this guide is to be useful, then we need to establish the environment. From the tyre’s viewpoint is the Nürburgring a road or a track? Might be neither, could be both. It might look like a racetrack but the vast majority of riders will not brake or corner like they could on a short circuit. Or think they could. Acceleration might be at a higher rate, but not for long. Speeds will be a lot lower as almost every rider does not know the track intimately enough to be confident of holding the throttle open. So it’s decided, we’re not track riding.

But many riders want to go fast on a racetrack. So the rider tries a lot harder than he would on another unsighted road. Acceleration is harder, top speeds are up a bit, braking is harder and more frequent. Maybe a bit erratic. Hmm, that’s not road riding. Well, it shouldn’t be.

Usage affects optimum tyre pressure. Two up with camping kit and a heavy bike, speedy across Europe is very different from alone on a lighter bike scratching around the local bands. But we broadly  stick to the same sizes, brands and pressures. Can’t both be right.

Under pressure?

Recommended tyre pressures generally err on the side of caution to cope with high load and speed without the risk of failure. But this isn’t helping you accomplish successful track riding. So what do you drop them down to? Established race lore is way too low for 90% of us – very few are going fast enough to justify this approach. But road pressures can still be too high.

Aiming half way between the two is a good start point. Now what exactly “half way” is might take some establishing. A very important piece of your tyre is the carcass – it provides the stability and directional control. The outer bit you can see does the gripping. Broadly, tyre engineers will be muttering its more complicated than that, and they’d be right. The problem is what to say next. Track day knowledge will not say 30 psi front and back set cold, maybe a smidge less if its a hot day. Aiming for 36psi hot. STOP RIGHT THERE!!! This was about right, but it took a few years to be known, by which time technology has moved on. It fitted the bill (past tense, you noticed that right) for most tyres (not all). Metzeler, Dunlop, Bridgestone have definitely made advances/changes that render the above value obsolete. I’ve not so much experience of the other brands recent products but do you think they have stood still?

So you either experiment yourself, or you ask the manufacturer's technical department. Asking will often get you very useful advice if you think about your question and include enough information. Just don’t expect a speedy reply – technical departments may in fact only be 1 or 2 blokes, who live in a van with a laptop. Either which way, good information helps the product, so they have a vested interest to help you. That and dead riders can’t buy new tyres...

Failing that, experiment yourself. Remember the cool kids will do small changes and see what happens incrementally. 10% away from manufacturer's recommended per experiment or less. No crying if you decide -50% is a good first stab and later, when all the bits come to rest, it dawns on you what incrementally means and why you were an idiot.

Now that, and idiots guide part 1, was thinking about cold problems. What about hot problems? The temperature range the Nurburgring experiences is quite wide. -20 degrees C up to plus 40. We can forget the minus range, but riding on a dry sunny day with snow all around happens. 40 degrees is rare, but 25 to 35 is common through the summer. Charging about on hot day if you started on road pressures sometimes results in riders finishing laps with tyre pressures off the scale of my 0 – 50 psi gauge!

I only write ‘sometimes’ because it involves so much slithering about nearly everyone either scares themselves and slows down, or falls off. (I wouldn't measure the tyre pressure on a crashed bike, it gets me some funny looks off the marshalls - Dale) Its only the loons that forget to check the odd tyre that complete the example. The riders of heavier bikes (eg sports tourers) shod with ‘roady spec’ tyres fit this bill because roady spec have a lot lower operating range. Don’t ruin your holiday with this oft repeated mistake.

Temperatures, types and self-delusion

Operating range. We’ve all grasped tyres work better warm. Cold is bad. But so is too hot. Some numbers then... oh boy. Approximately; road tyres will want 40 deg C and 20 deg C either side of this will be ok. Road legal track tires need more heat to start working properly, around 60 to 80 degrees C. Customer race tyres eg proper slicks not track day stuff will be higher still, and full race factory supported type tyres? Perhaps core temp of 150 deg C. To apply this to you; most riders are reducing safety as they do not have the track knowledge to push hard enough to keep a track orientated tyre in its optimum range on anything bar the hottest day. A road tyre has a lot friendlier operating range, and heat up acceptably sooner and forgive more mistakes. They also last longer which tight northerners like.

An idiot, who just crashed on cold tyres. Suddenly the L-plate wasn't so funny

That more or less answers what type of tyre fits the bill for most people – a sporty road tyre. Without rattling on too long (who me?). If you're still considering track orientated tyres, well I like them and want them, but... If you don’t know the track sporty road stuff will easily do sub 8 mins BTG all day! Granted they get a bit hot and bothered and torquier stuff must be ridden with a bit less throttle out the bends due to them sliding (gotten over operating range y’see, even though I said you wouldn't, sue me), but it will do tank after tank of this. An article on times will appear soon, but note; sub 8 is hopelessly unrealistic for almost everyone – even the odd national supersport riding journo hasn’t managed it when towed around by people that can (naming no names, right? Guy Martin got dragged under 8mins within 20 laps though Dale). So road tyres are plenty good enough. True race tyres won’t be helpful or allowed on the track if they are not E marked. Don’t bother.

What size?

Have you heard of the power circuit? This is where the bike with a powerful engine is odds on to win the race. The Nurburgring is NOT a power circuit. Done right it is one long corner with few opportunities to truly hit high speed. Lots of it is multiple direction changes in second and third gear. So something that handles nicely is better, easier and safer. Personal preference for 1000cc bikes on a 6” rear rim is a 190/55. These tend to steer in a fast but progressive fashion. 190/50’s then tend to steer slower and the profile may not be linear. This is considered numpty-proof, which is why suits and uniforms love them. 180/55’s on 6” rear rims? I would advise against this. In very specific circumstances in could be a benefit, but TF isn’t it. The tyre tends to be slightly out of profile on the rim and leads to very quick steering – too quick in fact and novices have enough to do with adjusting their line from their own errors, let alone the bike behaving oddly. [When I tried it almost feels like I imagine same-phase two wheel steered bikes would. Perhaps the roll centre/resultant is being deflected – anyone care to comment?] No one seems to keen to fit 190 tyres to 5.5” rims so I’m stopping now.

Damaged goods

Nearly there. Squared off tyres, well the track is one enormous corner, it can feels never ending to the point of fatigue and disorientation to novices. If its excessive you have a problem to ride around for a time (avoid too much throttle on the way out of corners).

Damaged tyres. Unlikely to be caused on the track. Worth checking for splits, cuts, nails etc before the day starts. Damage that is common and is caused on track is tearing. Heavy throttle hands coupled with low corner speed, powerful bikes and poorly set up suspension often rips the right rear to pieces. If this is you, you are at risk of two things. The first is the highside risk – standard stuff and just its just the same as any other piece of tarmac. The other is on the way into a corner just after a crest / bump/jump, some lean angle, and maybe a rough gear change to finish the job. Nurburgring has a lot of crests, bumps and jumps. Either fix it, change your riding style, change tyres or slow down. The alternative might be a helicopter ride... isn’t it Stefan?

Lastly on damage. Those bored of the police’s tiresome belief that all the world’s evils can be rectified with a speed limit may wish to exploit the odd autobahn. Re-read the bit about manufacturers erring on the side of caution for speed and load. Flat in top on with rubber set to track pressures has reduced an evening or two old BT-002R to scrap inside 50km. Longer would have resulted in catastrophic tyre failure, but Koblenz arrived before that did.

Getting new ones? Loads of folk ride bikes in Germany, thus the dealers are adept at ordering the tyre they think you ought to have, in almost the size you wanted inside 2 or 3 days. Its genius. And well expensive. Be a boy-scout.

The wet, the wild and the waffle

That’s now 3000 words of accumulated tyre waffle... and no mention of wet weather. It rains in Germany sometimes. Some people might have the option of bring wets on wheels. This seems a sound idea, and you can get road legal wets before anyone flies off the handle, but its not a good idea. The Nurburgring suffers from an odd problem. The tarmac grip level changes, both in its position on track and as it degrades over time. This is a whole subject in itself. There is no way to predict where the grip level changes, you have to find out yourself. I could warn you about Maddock’s bend/129 but how will you recognise where this is? I can explain one of the biggest and most sudden grip level changes is, in my opinion Wippermann. The fast right and medium left have been re-surfaced and they feel, and are good. But at the worst possible moment, just about on max lean and throttle on for the tighter right exit you cross to a perpendicular line onto greased fucking lighting. However this is not a problem. How so? Because any faster inexperienced rider will have fallen off at any one of a dozen places before you get to Wippermann!

The only sound routes for bike wet laps are;

1. Go to the pub instead.
2. Get/hire/blag 4 wheels and sample this variable grip level for yourself (odd’s on you won’t get to Hatzenbach 2.5 km in before declaring ‘by jove, that was a tad close’) (come and see me at Rent4Ring to get a Swift, I'll do you a good price if you stand there looking glum in sodden leathers - Dale)
3. Go to the pub instead.  
4. Go careful – an awfully unclear statement... so hows this? Aim for 14 to 18 mins for the lap. (14 ish and 51 mph average for heavier sports tourer on road rubber / 18 and a mahoosive 39mph average for firmly sprung race rep on track tyres – and you still might get caught out!) Stay to the right side, out the way of all other traffic as the speed differential can be quite high. Avoid trail braking like the plague, easier said than done. Be aware the ideal line is also the rubber line, and you cannot help but cross it sometimes. If its a downhill corner the front tyre load is already increased. Leave the missus in the cafe.

Scared? Think this is over-cautious? Firstly I write as a 33 year old having ridden every winter since I was 16 on a bike. Second, have a look how many bikes are in the car park when its raining. You might see some, but its highly unlikely you will see any local plates venture out. Enjoy. Slowly.

- Andy C

A sports tourer on road tyres, going fast for 20 minutes at a time. No problems.

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