Trail Braking

[Primate]

Hey folks, I wanted to alert you to a great thread on Keith Code's new message board. This particular discussion relates to braking (straight line and trail braking), and is very thought provoking. After we started the thread we spent a couple of days at Laguna and I had the opportunity to experiment in various corners with different braking techniques. It is well worth the read! Check it out.

Steve

http://www.superbikeschool.com/bbs/

 

[theSteveCo]

I was checking that out the other day... great stuff. I will have to look over your findings from Laguna.

Me? I trail brake about 1/3 to 1/2 of the time - it really depends on the corner. I think that it is a great tool for passing, but ultimate lap times may not require (much) trailbraking.


[btw]Then again - I'm a MAJOR rookie in comparison to the audience in this forum![/btw]

 

[luke]

I've heard people suggest that if your not brakeing into the corner then you didnt carry enough speed into it. I trail break alot but it might be insecurity or uncertainty prompting me to do so.

 

[MrCrash]

Lots of good info there. Here's a direct link:

http://www.superbikeschool.com/bbs/index.php?act=ST&f=4&t=11&hl=trail braking&st=40

I trailbrake everywhere. Helps me get the bike turned. In many cases, it's a light touch on the brakes that I'm tapering off of as I add lean angle at the entrance of turns. I think many people automatically associate the term with heavy, aggressive deep braking - that's not the case.

Every turn at Thunderhill, I'm trailing in to some extent. 1, 2, 3, 5, 6, 8, 9, 10, 11, and 14.

A bike falls into a corner when the throttle is off, stands up when the throttle is on, and holds a constant lean angle when the throttle is just cracked open. Thinking about it, if a closed throttle shifts the weight of the bike forward and compresses it, a very light touch on the front brake works in the same way, carrying the technique a bit further. Done correctly, the bike is able to turn into a corner in less time and distance, with less handlebar pressure.

It'll make you faster on the racetrack, and save your ass on the street by allowing you to make adjustments all the way through the corner if the unexpected arises.

 

[balistic]

Lots of good info there. Here's a direct link:

http://www.superbikeschool.com/bbs/index.php?act=ST&f=4&t=11&hl=trail braking&st=40

I trailbrake everywhere. Helps me get the bike turned. In many cases, it's a light touch on the brakes that I'm tapering off of as I add lean angle at the entrance of turns. I think many people automatically associate the term with heavy, aggressive deep braking - that's not the case.

Every turn at Thunderhill, I'm trailing in to some extent. 1, 2, 3, 5, 6, 8, 9, 10, 11, and 14.

A bike falls into a corner when the throttle is off, stands up when the throttle is on, and holds a constant lean angle when the throttle is just cracked open. Thinking about it, if a closed throttle shifts the weight of the bike forward and compresses it, a very light touch on the front brake works in the same way, carrying the technique a bit further. Done correctly, the bike is able to turn into a corner in less time and distance, with less handlebar pressure.

It'll make you faster on the racetrack, and save your ass on the street by allowing you to make adjustments all the way through the corner if the unexpected arises.

I see one problem with what you say. As you turn the bike and the contact patch moves off center to the inside of the tire it will pull the steering to the inside(with the brakes on). this will stand the bike up unless you increase the steering input as you turn which makes it harder to turn not easier with the brakes on.
Will

 

[JeffKoch]

I see one problem with what you say. As you turn the bike and the contact patch moves off center to the inside of the tire it will pull the steering to the inside(with the brakes on). this will stand the bike up unless you increase the steering input as you turn which makes it harder to turn not easier with the brakes on.
Will

Not necessarily, it depends on the trail and the tire profile, as well as on how hard you brake - there's actually a mathematical formula for this effect that includes these parameters, and the result can be positive (stands up) or negative (falls in). I put a lot of effort into setting up my 748 so that it does *not* stand up while trailbraking, mostly by playing with the geometry and front compression damping - but if you brake hard enough while turning, then I think any bike will eventually want to stand up. The trick is to not brake that hard. Also, remember that as you brake you are slowing down, which at constant lean angle means you're turning more sharply even at constant brake pressure.

 

[JeffKoch]

kinda off topic but...

are there any drills i can practice to get over the fear of braking and leaning?

I have a huge problem trusting the front tire under even light braking while leaned. This basically puts me in a postion where I need to do 100% of my braking before I even enter the turn.

If im going in too hot Its really hard for me to adjust my speed and sometimes I end up standing the bike up and really parking it.

The drills they do at Freddie Spencer's school are great, they basically have you come into a turn and *STOP* at the apex. It's amazing when you first try it and realize that you can use your brakes anywhere, not just straight up and down. This is hard to safely arrange on the street or at a track day, but you might try just staying on the brakes next time you go into a turn on your favorite road (maybe starting at a mellow pace), and getting a feel for what happens when you brake and turn. Just gradually release the brakes as you turn, rather than getting off them first, and as you get used to it try going in a bit faster and braking a bit more. That's what I'd do, anyway, in the absence of a school with proper drills.

I just got back from one of Freddie's schools, and it was really clear once again, from discussions and on-track experience, how important it is to be able to ride the brakes into the turns and to use them to help you turn and adjust your entry speed. For track riding, I personally do it a lot in certain circumstances and I think most racers do too, but it can really be a life saver on the street if you have to slow down in a turn to avoid, say, rear-ending the pickup that turned into the road just around the next blind curve and putzed along at 25 mph.

 

[balistic]

Not necessarily, it depends on the trail and the tire profile, as well as on how hard you brake - there's actually a mathematical formula for this effect that includes these parameters, and the result can be positive (stands up) or negative (falls in). I put a lot of effort into setting up my 748 so that it does *not* stand up while trailbraking, mostly by playing with the geometry and front compression damping - but if you brake hard enough while turning, then I think any bike will eventually want to stand up. The trick is to not brake that hard. Also, remember that as you brake you are slowing down, which at constant lean angle means you're turning more sharply even at constant brake pressure.

I didn't mean to ambiguous. ALL BIKES WILL WANT TO TURN IN WITH THE FRONT BRAKE ON, STANDING THE BIKE UP UNLESS THE RIDER CONTINUES TO PUSH ON THE BARS TO OVERCOME IT. The amount of effort may vary depending on the geometry of the bike but the effect will remain and must be dealt with either by pushing the bars or letting the bike stand up.
On another note wouldn't it be great if you could develop a sense of speed sensitive enough that you simply knew you had the speed correct and could turn and get on the gas? How much faster would that be?
Will

 

[JeffKoch]

I didn't mean to ambiguous. ALL BIKES WILL WANT TO TURN IN WITH THE FRONT BRAKE ON, STANDING THE BIKE UP UNLESS THE RIDER CONTINUES TO PUSH ON THE BARS TO OVERCOME IT. The amount of effort may vary depending on the geometry of the bike but the effect will remain and must be dealt with either by pushing the bars or letting the bike stand up.
On another note wouldn't it be great if you could develop a sense of speed sensitive enough that you simply knew you had the speed correct and could turn and get on the gas? How much faster would that be?
Will

Will, the front wheel always wants to aim inwards when you're turning - whether brake torque makes the bike want to stand up or turn in more depends on a lot of factors, including how much brake torque you apply (and how quickly you apply it), the geometry of the bike, and the tire profile - that's my personal experience, anyway, and my understanding of the dynamics from Robinson's and Foale's books. In fact if you're leaned way over and want to turn even more sharply without going to the brakes, you can deliberately turn the bars in like on a dirt bike and tighten your line (counter-counter-steering) - I do this often on my duc, but you have to do it gently.

But sure, some bikes just don't want to turn with the front brake on - my BMW is an example - and any brake pressure at all starts a big fight with the bars to keep the bike from going straight. In that case, taking the example of the slow-moving truck around the next bend taking up the whole road, you gotta either fight the bars while braking, run off-road and hope for the best, or rear-end the truck....

Ya, a perfect sense of speed and timing would be great, but I sure don't have it.

 

[winders]

In fact if you're leaned way over and want to turn even more sharply without going to the brakes, you can deliberately turn the bars in like on a dirt bike and tighten your line (counter-counter-steering) - I do this often on my duc, but you have to do it gently.

Jeff,

Are you are saying that you can be leaned way over in a left hander and turn the bars to the left and you will turn in even more?

If that is what you are saying, you are incorrect. As soon as you turn the bars to the left, the bike will start to stand up.

Scott

 

[JeffKoch]

Jeff,

Are you are saying that you can be leaned way over in a left hander and turn the bars to the left and you will turn in even more?

If that is what you are saying, you are incorrect. As soon as you turn the bars to the left, the bike will start to stand up.

Scott

Scott, you understood correctly, and that is what I'm doing, same as you can do with a dirt bike. Try it, very gently - if you turn too abruptly you'll get the opposite reaction. I was talking to Spencer about this in Vegas, and he does this too sometimes - so does Ben Bostrom, among others. Which doesn't necessarily mean it's a fantastic technique, but it does work and people use it. I only use it when I'm leaned way over, can't hang off any more, and don't want to risk upsetting the front tire but want to tighten my line.

 

[balistic]

Will, the front wheel always wants to aim inwards when you're turning - whether brake torque makes the bike want to stand up or turn in more depends on a lot of factors, including how much brake torque you apply (and how quickly you apply it), the geometry of the bike, and the tire profile - that's my personal experience, anyway, and my understanding of the dynamics from Robinson's and Foale's books. In fact if you're leaned way over and want to turn even more sharply without going to the brakes, you can deliberately turn the bars in like on a dirt bike and tighten your line (counter-counter-steering) - I do this often on my duc, but you have to do it gently.

HI Jeff
A couple more questions for you.
It sounds like you are to some degree stipulating that the braking force will turn the front in, Yes.
So can you release the bars once turned? if so what happens, does the bike stay turned, fall in , or stand up?
The idea im working towards here is that the front will always try to find the rear unless otherwise directed by the rider. If you are on the front brake and turning you are locking the steering up and making the bike unstable for a longer period of time than you would if you did all your braking and turned quick.
The bike can be turned in one or two tenths of a second and then the rider can release the bars and front end can do it's job and hunt for the rear. If trail braking is used into the corner, I will assume to the apex then the instability will remain for many seconds. This dramatically increasing the time for a costly mistake.
I have noticed what you said about turning the bike in and tightening the line but I don't agree with the perception being the reality of it. I believe this is a function of the geometry in action. If you change the load on the front in a turn the fork will go up or down the rear will go up or down opposite. This will cause the rake and trail to change which in turn will move the contact patch forward or rearward on the front tire and will steer the front to some degree. this steering can be noticed as the bars turn. More load on the front and the patch moves forward and the bars turn in. So it's true that the bars turn in and the line tightens but it's secondary not primary.
Will

 

[winders]

Scott, you understood correctly, and that is what I'm doing, same as you can do with a dirt bike. Try it, very gently - if you turn too abruptly you'll get the opposite reaction. I was talking to Spencer about this in Vegas, and he does this too sometimes - so does Ben Bostrom, among others. Which doesn't necessarily mean it's a fantastic technique, but it does work and people use it. I only use it when I'm leaned way over, can't hang off any more, and don't want to risk upsetting the front tire but want to tighten my line.

Jeff,

Physics dictates that what you suggest is impossible. As soon as you start to turn the tire into the turn, no matter how slowly, the bike will start to stand up. Lean angle has no bearing on how the physics works. You must have misunderstood what Spencer said.

This is a simple thing to prove right or wrong. At 50 MPH push the handle bar to the to the right or the left very slowly. The bike will start to turn the direction you push the bar. The physics does not change while leaned over and the same thing will happen.

Scott

 

[balistic]

I am not a trial braker and have a biased opinion towards quick turn for sure but I haven't seen the pro's or con's so I will give mine.

Quick turn:

Pro's
making the turn as big an ark as possible ( giving the most potential turn speed.

having good turn speed, good exit speed.

picking a turn point close to the turn gives you a very deep brake point.

You can get on the gas very soon and get weight off the front allowing a higher entry speed.

The bike is stable sooner giving the rider more confidence in the turn

once you have certainty you can make the bike turn when you want, the ability to run any line into the turn. Making passing easier than being confined by how much you can turn with the brake on.

Con's
It's scary to learn

Trail Braking

Pro's
Stuffing it under someone on the turn entry (lowlineing)

Slowing down in the turn?

Con's

turning slow because the brake is on.

having to stay tight on the bars well into the turn, locking the steering up with your arms and making the bike unstable.

lessening the ark in the turn and slowing your mid turn and exit speed.

increasing the risk of crashing, overloading the front and it locking. you loose the gyro and very few can recover from this.
Will

 

[JeffKoch]

HI Jeff
A couple more questions for you.
It sounds like you are to some degree stipulating that the braking force will turn the front in, Yes.
So can you release the bars once turned? if so what happens, does the bike stay turned, fall in , or stand up?
The idea im working towards here is that the front will always try to find the rear unless otherwise directed by the rider. If you are on the front brake and turning you are locking the steering up and making the bike unstable for a longer period of time than you would if you did all your braking and turned quick.
The bike can be turned in one or two tenths of a second and then the rider can release the bars and front end can do it's job and hunt for the rear. If trail braking is used into the corner, I will assume to the apex then the instability will remain for many seconds. This dramatically increasing the time for a costly mistake.
I have noticed what you said about turning the bike in and tightening the line but I don't agree with the perception being the reality of it. I believe this is a function of the geometry in action. If you change the load on the front in a turn the fork will go up or down the rear will go up or down opposite. This will cause the rake and trail to change which in turn will move the contact patch forward or rearward on the front tire and will steer the front to some degree. this steering can be noticed as the bars turn. More load on the front and the patch moves forward and the bars turn in. So it's true that the bars turn in and the line tightens but it's secondary not primary.
Will

Hi Will, when you release the bars in a turn, you can stand up, fall over, or stay tracking on the same radius - it depends on whether or not the steering is "neutral" at that lean angle, which in turn depends on the tires and geometry. If camber thrust is sufficient to maintain a constant turning radius, the steering is neutral - if not, you have to turn the bars either inwards (pushing on the outside bar) or outwards (pushing on the inside bar), adding or subtracting a slip angle, to maintain your arc. Tony Foale's very excellent book has plots of the bar force necessary to hold a constant line through a turn for various parameter values, and it varies a lot - and because it's a function of lean angle, a bike can go from "neutral" to "tippy" (or, alternatively, "resists turning") as you lean more. I'm not sure what you mean by "find the rear".

As to the race-track value of trailbraking vs. braking and then turning, that's a debate for the pros that I don't want to get into , but it sounds like you're a Code-style rider and use his wording to describe turning on the brakes (making the bike unstable) - that's fine. I think it's safe to say that most if not all the top riders do trailbrake in some turns, at least, so if it were universally a bad idea then I suspect no one would do it. For street riding, though, it's absolutely a lifesaving technique - it most definitely saved my arse on at least one occasion, when a truck pulled a U-turn around the next bend and started going in my direction headed down 84 towards La Honda. If I hadn't been comfortable riding the brakes *hard* while continuing to turn I'd have either rear-ended him, run off into oncoming traffic, or run inside over an embankment and into the trees.

Jeff,

Physics dictates that what you suggest is impossible. As soon as you start to turn the tire into the turn, no matter how slowly, the bike will start to stand up. Lean angle has no bearing on how the physics works. You must have misunderstood what Spencer said.

This is a simple thing to prove right or wrong. At 50 MPH push the handle bar to the to the right or the left very slowly. The bike will start to turn the direction you push the bar. The physics does not change while leaned over and the same thing will happen.

Scott

Really, Scott, try it. I didn't misunderstand Freddie, we were discussing it at some length as a semi-sketchy technique that can work well but requires care. Lean angle does have a bearing here, because when you're tracking an arc the front tire is turning inwards. When you're tracking a tighter radius, the bars will need to turn in even more. It's more obvious on a dirt bike, but it works the same way on my Ducati.

 

[winders]

Really, Scott, try it. I didn't misunderstand Freddie, we were discussing it at some length as a semi-sketchy technique that can work well but requires care. Lean angle does have a bearing here, because when you're tracking an arc the front tire is turning inwards. When you're tracking a tighter radius, the bars will need to turn in even more. It's more obvious on a dirt bike, but it works the same way on my Ducati.

Jeff,

Lean angle does not have a bearing on this other than how far the front tire is turned into the turn. The more lean angle the more it is turned.

Since the bike is at an equallibrium when in a turn, turning the bars into the turn will change that equallibrium in the same way. The speed of the turn in changes the magnitude of the change, not the direction.

If you you are leaned over in a left hand turn and you push the right hand bar, the contact patch will come in under the cg and cause the bike to stand up. It does not matter how slow you do this are how far you are leaned over. The bike will start to stand up.

Counsteering works all the time as expected at any speed and any lean angle you will see while road racing.

Scott

 

[aintgotnoride]

Jeff,

Physics dictates that what you suggest is impossible. As soon as you start to turn the tire into the turn, no matter how slowly, the bike will start to stand up. Lean angle has no bearing on how the physics works. You must have misunderstood what Spencer said.

This is a simple thing to prove right or wrong. At 50 MPH push the handle bar to the to the right or the left very slowly. The bike will start to turn the direction you push the bar. The physics does not change while leaned over and the same thing will happen.

Scott

Why don't you try it before you blurt out that it's impossible!? apparently you're not much of a physics guru, because if you were, you'd know that the results of equations of equilibrium always differ from what you see in the real world.

From reading your past posts, the only constant is that you're a tool. Have a nice day!

 

[JeffKoch]

Jeff,

If you you are leaned over in a left hand turn and you push the right hand bar, the contact patch will come in under the cg and cause the bike to stand up. It does not matter how slow you do this are how far you are leaned over. The bike will start to stand up.

Fine, Scott, I'm wrong, and so is Freddie Spencer and Ben Bostrom. I'm not sure precisely what is physically happening in this situation since I've never ridden an instrumented bike, but the effect from the rider's seat is: "I want to tighten my line to the right, and if I turn the bars in by gently pushing with constant force on the left and gently pulling with constant force on the right, I turn in more sharply." Countersteering is a transient effect, you push on the inside bar and release pressure as the bike leans in (your initial state has the wheel turned in, the final state must have the wheel turned in even more, and in between you force the wheel to turn in less) - what I'm describing isn't a transient effect.

I agree, generally if you push on the outside bar you stand up, but I can also imagine an "adiabatic" sort of path between the two equilibria that allows you to turn in by moving the bars from the former turned-in state to the new turned-in-more state without standing the bike up. That's how as a physicist I can rationalize what my brain is perceiving in this situation. I also have only tried it at big elbow-dragging sorts of lean angles, where the geometry is quite different than it is closer to vertical.

But in any case, try it and see what you think. I use it, for example, in T7 at Sears.

 

[winders]

Jeff,

Let's look at this from a physics stand point.

What happens when you in a left hand turn and the you push on the right clip-on? The front tire steers to the left. Since the contact patch is below the center of mass of the bike, the bike MUST rotate to the right. There is no way to mitigate this effect as long as the center of mass is above the contact patch. For your position to have merit, you must be able to argue successfully how the bike will rotate the wrong way.

I have raced for years and have used countersteering to control the lean angle of my bike to a very fine degree. I have NEVER had my bike lean in more when I applied extremely light pressure to the outside clip-on. If that had happened I would have crashed many more times than I did.

I fairly confident that I carry more cornerspeed than you do so my lean angles are at least as severe. So my experience in control should be useful to this conversation.

Scott

 

[balistic]

Hi Will, when you release the bars in a turn, you can stand up, fall over, or stay tracking on the same radius - it depends on whether or not the steering is "neutral" at that lean angle, which in turn depends on the tires and geometry. If camber thrust is sufficient to maintain a constant turning radius, the steering is neutral - if not, you have to turn the bars either inwards (pushing on the outside bar) or outwards (pushing on the inside bar), adding or subtracting a slip angle, to maintain your arc. Tony Foale's very excellent book has plots of the bar force necessary to hold a constant line through a turn for various parameter values, and it varies a lot - and because it's a function of lean angle, a bike can go from "neutral" to "tippy" (or, alternatively, "resists turning") as you lean more. I'm not sure what you mean by "find the rear".

As to the race-track value of trailbraking vs. braking and then turning, that's a debate for the pros that I don't want to get into , but it sounds like you're a Code-style rider and use his wording to describe turning on the brakes (making the bike unstable) - that's fine. I think it's safe to say that most if not all the top riders do trailbrake in some turns, at least, so if it were universally a bad idea then I suspect no one would do it. For street riding, though, it's absolutely a lifesaving technique - it most definitely saved my arse on at least one occasion, when a truck pulled a U-turn around the next bend and started going in my direction headed down 84 towards La Honda. If I hadn't been comfortable riding the brakes *hard* while continuing to turn I'd have either rear-ended him, run off into oncoming traffic, or run inside over an embankment and into the trees.

HI Jeff
I am not talking theoretically or mathematically, Im talking about the bikes I ride and have ridden. A KZ1000, ZX9R, Concourse, 636, R1, R6, FZR600, ZX600, KZ750, GPZ750, EX500, EX250, VFR750, ST1100, MILLE, 996,998, FZR1000, V65 Magna, V45 Saber just to name a few. All these bike I could let go of the bars after turning and they were neutral. Some of these were on the track some on the street, but they all worked the same way.
What I mean by finding the rear is that a function of trail is the steering being self centering, on what? The rear. So if you whack the bars one way and let go the bike will settle in a lean and the front will hunt around as it hits bumps and irregularities to find center which is the rear wheel. The front of the bike is live and when you hold the bars it will be suppressed but not denied, this is the source of most wobble. It’s the rider inducing it by suppressing the bikes tendency to self center, causing the forces to escalate until the riders input is overcome. This is the reason a rider can be flung off in a wobble and then the bike stabilizes and continues on without him.
I never said trail braking wasn’t a useful skill. I did try to point out that it has a down side that must be weighed against the benefits. I do use the brakes while leaned over, I just try not to use them while I turn the bars. You get the difference?
I don’t know what a Code style rider is, but I am a Code trained rider. The words I use are my own I assure you.
Will