1. ## The Traction Circle reloaded

Before we even step in to traction, let's take a look at what it actually is first. As you all should know, traction (or friction) comes by having two different surfaces going against each other. In the case of a bike, that would be the tire having to go against the road.

To make it easier, we draw a simple circle and put in the forces acting on the bike when we ride. Traction has two components which consists of the straight-line component and the lateral component as illustrated in this simple diagram. The vertical line depicts the friction associated with accelerating and braking whereas the horizontal line depicts the traction associated with left and right turning.

While riding/leaning, when we take a corner to the limit point of the bike, soft or maybe familiar skidding sounds can be felt or heard. A bike will twitch as well as the front and rear traction is lost alternatively. This shows that the bike is right at the end of the limit in the circle. If we actually exceed the traction circle limits while turning, the amount of slip felt will increase VERY quickly. If you lose traction on the rear then find it again very quickly you WILL highside. In short, in order to ride fast, we have to ride within the limit, which means taking the bike as smooth as possible and right to its traction limit.

Anything within the limit of the circle does not take full advantage of the tires' traction capacity and anything outside of the circle will induce loss of traction. Also don't forget tire locking that increases the braking distance. If the limit is exceeded while turning, the bike may not be able respond as efficiently to the control input, causing it to go down or wide.

The points not on the vertical or the horizontal line are a combination of acceleration or deceleration and turning. Many people think "trail braking" is really in fashion these days and let's explore it's relation to the traction circle. The traction circle represents 100% of traction capacity, if we use 100% for braking then we would have ZERO room to turn the bike. In order to actually turn the bike while: on the brakes, accelrerating or decelerating, then we would have to ease off the brakes, ease on/or off the throttle according to how much percentage we wish to put into turning.

Example: Turn 3 on track XXX, long straight leads into a tight left. You brake hard, set up your line and tip in, push the bars, stick the knee out and sweetness prevails. 3/4 through the turn is Squid 99. Taking the WRONG line, you see him cutting into your line and you have to either brake or lean more and take a different line. This is all assuming you have Superbike throttle control and you are either +-5% of the traction circle on /off the gas as you carry momentum though the turn. This leaves roughly %90 of your tire's grip left for leaning/lateracceleration. Squid 99 leans into your line and you grab a bit of front brake since your brain computes that gas won't work to avoid him. You apply %20 brake. You now have %70 left for cornering BUT you went in so hot that you were using %80 already for lateral grip. Many things can happen now, you will wash the front (understeer some call it) and go wide but right into Squid 99 or you will lose rear traction and get seriously sideways for a moment until traction is balance to the natural %100. This can be a highside. It appdepends on the situation though, seat position, condition of tires, What brake you used etc.

Don't forget that all roads are not flat. The traction circle is greatly affected by inclines, declines and road conditions. But a tire's traction never exceeds %100. That %100 and how much force it can withstand is in constant flux.

In order to ride as fast as possible while taking it smooth, then the limits must not be broken but instead the bike is ridden to its highest performance limit

2.

3. Are these your words, or is this copied from somewhere else?

4. It's heavy edit of a poorly written web page from years ago,

I posted it once in it's "car form" and no one really understood it because they though bike tires were obeying different laws of physics from some fantasy part of the universe.

http://www.teammatrix.com.my/Driving/traction.html

I learned about this years ago in my karting days. The traction circle in a kart can be manipulated for about .03 of a second before you spin.

5. trail braking *is* in fashion :P
why use your muscle to steer when you can let the brakes do it for you

a good read as always j7

6. Originally posted by cosworth
I posted it once in it's "car form" and no one really understood it because they though bike tires were obeying different laws of physics from some fantasy part of the universe.
Probably because average bike tires are way stickier than average car tires!

I remember reading how most people think bikes have some magical handling advantage when in truth it's because bikers pay \$200 for tires with half as much material as \$60 car tires.

7. Very cool. Thanks for the post.

8. shut it bastard! i bet you didnt even read the thing!

9. Originally posted by G-slide
shut it bastard! i bet you didnt even read the thing!
Are you being sarcastic? I hope you are.

10. Blow me gurp.
You, of all people, should be proud of me for being able to read this thread. You know as well as I do that it was only last week that you let me borrow your "hooked on phoenix" books.

11. Originally posted by baldbastard
Blow me gurp.
You, of all people, should be proud of me for being able to read this thread. You know as well as I do that it was only last week that you let me borrow your "hooked on phoenix" books.
Shouldn't that be hooked on phonics? Ebonics? Tonics? Colonics?

12. Originally posted by Jayson
trail braking *is* in fashion :P
why use your muscle to steer when you can let the brakes do it for you

a good read as always j7
how 'bout if you don't actually have to slow down for the corner? or even if you can go in faster than the speed you are before you enter the corner?

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