[The Bands Of Traction]

The Bands of Traction

 

If you saw the last GP in Portugal this past weekend you couldn’t help but be impressed with the traction capabilities of the tires. The corner speeds, lean angles and how quickly the riders could flick the bikes is astounding. Clearly, that level of riding can only be achieved by those who are able to trust the tires. How do you arrive at the point of being able to use current tire technology?

 

The Edge

 

Anyone would like to be able to read and sense traction at a pro level. That would mean something like: to always know when you were at the edge of traction and feel comfortable enough to bring it there when and if you wished to.

 

For a professional rider that “edge” has to be pretty wide. Think of it this way: you must be able to ride in that band of traction or you don’t get paid. That is a different perspective than most sportbike enthusiasts have on the subject of traction.

 

Bands of Traction

 

Feeling in control of tire grip would mean reading the signs of losing grip and knowing what those signs meant. If there was a nice long, tapering curve to losing traction, where the signs of it ramped up very gradually from a squirm to a little slip and then to a slip & grip and then on to a nice, clean, power-on slide we’d all be traction masters. The fact is, tires do have signs and signals just like that but talking about it doesn’t make it any more real or comfortable without some personal experience to back it up.

 

Reading the Signs

 

By questioning a track day or club race rider you could pretty well figure out what lap times they’d be able to turn by what traction signals they had experienced and were comfortable with. You would find most riders stuck right at the “squirm” band of traction.

 

Not too bad really, providing that the rider’s basic riding techniques were firm, he could go quite quick at the squirm band of riding. This would typically give lap times that were within 8 to 12 seconds of AMA Pro 600 Supersport times. The squirm band starts right when the rider has enough pressure on the tires to get a decent sized footprint on the pavement, which is the technological magic of radial tire design.

 

Many riders think there is less rubber on the ground when the bike is leaned over but it is the opposite, there is more. They think that because they can’t add gobs of throttle when it is leaned over. In actual fact, as we bring the bike up we can add more throttle because the tires do not have to deal with the leaned over side-loading from the cornering. When the bike is straight up it has the least rubber on the ground but no side loading to take away from the available traction.

 

Technical Skills

 

Having good technical skills is the only sane route to mastering the bands of traction and reading their signs. In other words, without a firm grounding in basics, it’s easy for riders to misidentify what they think is a loss of traction when it isn’t or because of poor technique they may skip a band or two and get themselves into trouble.

 

Sloppy throttle control gives a false sense of tire grip. Using lean angle in the wrong part of the turn for the wrong reasons gives a distorted feel for it. How the rider sits on the bike can have a huge effect on it. Confusing inputs into the handlebars is another classic way of misreading the signs your tires can give you. All of them will set you up to miss the signals completely.

 

These, and others, are all technical aspects of riding that can be adjusted by the rider without having to touch the bike’s suspension. Being coached through these points is the way to go and leads to control of the mysterious traction questions riders have.

 

Tire Technology

 

Riders know that 21st century motorcycles and tires are better than they are. Fine. What security does anyone have that this is true beside the thin hope that if they do get into trouble the bike and tires will save their bacon?

 

One aspect is tire warmers and the security they seem to give riders. Tire warmers are a fact of life these days even at track day events. What many riders fail to realize is that by the time they get around a lap or two the tires can actually cool down.

 

Tire temperature is based on tire usage. The higher loads the hotter they get. If you aren’t in the band of traction that will take you over the tire warmer temp you really are looking at a security blanket that isn’t totally real. For sure it can save a rider from the embarrassment of a first lap, cold tire crash and that is the good news.

 

New Skins

 

Aside from crashing, tires are the single most expensive, consumable cost riders have for track days and racing. Tires do wear out and that wear is part of the key to their ability to grip.

 

Take the tire’s viewpoint for a moment. They are willing to stick provided there is rubber covering the cords; the temperature is up to the loads being demanded by the rider’s speed; lean angle; braking and drive off the corners. Tires wear out just like skin. As the outer layer becomes dry it is swept away by friction. On your clothes when it comes to skin. On the pavement when it comes to tires.

 

Tires, like skin, dry out from age or from heat. Exposing the next layer of fresh, pliable rubber underneath to the road is critical to performance. If the dry rubber remains on top, traction isn’t as good. To expose the new, fresh rubber, enough load must be put on the tires to “clean” them. It has been theorized that 10% tire slippage is the ideal situation for tires because it keeps the temperature up and at the same time “cleans” them.

 

Heat Cycles

 

How many heat cycles a tire has gone through, theoretically, has a huge effect on how well they work. The heating and cooling is supposed to reduce their grip by changing the chemistry that holds the rubber together and riders sometimes worry about it.

 

The Dunlops on our school coach’s bikes are usually take-offs; they’ve already been raced on and often raced on by pro riders who can get them up to full temperature. We then use them for days of track riding and all the coaches can go quick enough to run club race lap times and most of them could qualify for an AMA Supersport race. While our coaches don’t ride hot laps every moment of every day the tires do get a minimum of 30 heat cycles a day.

 

Here’s the point: The record for a front tire is 38 school days. The record for a rear is 18 days. The average laps per day would be around 90. I think Dunlop knows something about tires and taking up the devils advocate, these are the stickiest, most expensive ones so perhaps, at least for the quicker riders, there is economy in buying the good stuff after all.

 

NOTE: We change the Dunlops on our ’07 ZX6 student bikes every three or four days.

 

The Sticky Stuff

 

Everyone wants to have the stickiest rubber they can afford but it isn’t sticky until they can put the big load on the tires. Most riders would do better and learn heaps more about traction with something lesser than full race, factory rider developed tires. Why? They don’t have to put the big loads on the tires to start to experience the bands of traction as listed above.

 

Look at it this way. If you are using the tire at the bottom end of where it was developed by pro riders would it actually save you if you got brave for a moment? The answer is no. Pushing the loads on the tires up for a moment when the rest of the lap was at your normal pace will not give the tire enough time to warm up to the level you momentarily demand from it to handle the situation.

 

In other words, your potential and that of the tires have to come up together for you to take advantage of what the tire has to offer. To a large degree, the security of the stickiest rubber is false. Until you arrive at some consistency in your levels of speed and lean angle and throttle control and the other technical parts of riding it is no more then blind faith.

 

Trusting the Tires

 

In the end it isn’t about the tires it is about the rider. It’s about using good technique and having good technical skills. It’s about gaining some consistency with them and knowing you can do it. After that, it’s not so difficult to trust your tires because you trust yourself.

 

 

Keith Code

 

Copyright 2007, all rights reserved. No part of this article may be reproduced by any means without express written permission of the author.

[/quote AS usual you give food for thought,perhaps you could take it further and describe in your own inimitable style the sensations felt when approaching these limits.I don't do much track riding but I've been riding sports bikes without any breaks for the last 26 years and as ahabitual suspension twiddler for the last 15 I've experienced the edge more times than is healthy.The three main types are the "oh my god Ican see the tailpeice(too much preload)and "what up this things not going forward"(too much rear comp) and by far the most enjoyable(if your not chasing lap times)the fast constant radius where you're working the steering so hard to keep it down in the corner you feel sure the first thing to let go will be the front but slowly the limit arrives as a gradual lightening of the rear(little too much preload up front).Anyhoo the suspension settings arent really my point the first one I suppose doesn't count as there is no sensation except mabye hot and wet but the other two are directly related to throttle input and not at all scary.The last one in particular I found out later through video footage the rear was leaving rubber on the road through some seriously fast corners and interests me the most.As I've said I'm just a guy who rides on roads for pleasure,I love riding fast but am fairly cautious by nature and won't put myself into a situation I don't think is safe.So why in this situation do I feel it's comfortable and safe to explore the abilities of the tyres in an enviroment which would by many considered to be completely wrong.Since learning this I have observed other riders of bigger sports biikes(I've been riding 750s for the last 15 years) leaving short strips on initial acceleration and some of the quicker riders leaving them as they exit a corner and hit the throttle but I don't think they even have time to feel this and they're not really exercising any control over the situation because it really doesn't warrant any.I know both theirs and my tyres aren't sliding in these situations and it's just the top layer of rubber stripping away but there is a difference in doing it for 200m at 130mph and snapping the throttle a bit quick on a 1000 cc.Please note this isn't about percieved riding skills(I'm long past that)It's about percieved traction and why some people read it different from others.I realise that racers mostly find it by necessity(sink or swim)but for me there is no pressure only pleasure .

[Front Tire Skid]

I have noticed when making an aggressive down shift from med RPM to high RPM the front tire skids for

a split second, the back tire is fine, very stable but the front seems out of control for as split second.

Then it regains traction very quickly, and the bike is stable, this happens just before I start to make the bike lean.

 

James.

 

 

While hard on the brakes? maybe, but still highly unlikely.

 

A front tire skid on a race tire that is up to temp is VERY hard to do. About the only way you can do it is to bottom the suspension and then 'pogo' the front end where it hops off the ground a bit. Otherwise, you're more likely to go over the bars...

 

now I'm not outright calling you a 'liar', but I really think that if you had some video you would see something different from a front end slide/skid...

 

 

Not I can clearly hear the skid, no brakes

I,ve got to agree even a badly set bike shouldn't unload the front end whilst on the brakes.Are you sure you are not doing something with the bars or the brake lever when you're blipping the throttle.ie tensing your arms or releasing the brake lever enough to let the front pop back on you.