Keith Code Talks Trail Braking--Interview

[Dylan Code]

This is an interview that Keith did with Misti Hurst who aside from coaching runs her own blog called "motomom" located here http://www.motomom.ca/

 

Keith Code- Interview on Trail braking

 

There is a lot of misunderstanding about the technique of trail braking; specifically people seem to be either for using trail braking all the time, or against it. Most often your name comes up as someone that is against using trail braking and that you advise getting all your braking done before you begin to turn the motorcycle.

 

Let’s start off first by defining trail braking. What exactly is trail braking?

 

Keith: It’s the tapering-off of brake lever pressure for controlling the bike’s rate of deceleration. That’s the most basic definition. Commonly, the term is used to reference the action of tapering-off brake lever pressure while leaning into a corner. Probably the easiest way to illustrate this is to get the idea of keeping the forks compressed roughly the same amount from braking through to leaning the bike into the turn. You would have to coordinate the release of brake pressure with the increase of leaning. The deceleration load on the forks diminishes while the cornering centrifugal force of the turn increases as the bike is leaned. That’s how I originally described and photographed it back in 1983.

 

Should new riders learn the technique of trail braking?

 

Keith: Every brake release should have some trailing off of lever pressure. Barring something like running off the road, there is no on-road or track cornering circumstance where an abrupt release of brake pressure is optimum.

 

Is trail braking a race and track only skill or should street riders use it as well?

 

Keith: As just mentioned, it's the correct way to release the lever for any corner entry situation. An abrupt release makes it quite difficult to accurately judge your final entry speed--if we call "entry speed" the speed that is left over right after the brake is released.

 

We also know that the bike will continue to slow until the gas is back on enough to accelerate it. That in itself is a very interesting subject which most people misunderstand. Most think that rolling the gas on 10 percent or so will maintain their speed but it won't, most bikes continue to slow. At race pace, the bike will be slowing an average of 8 mph per second between the brake release and throttle-on. Specifically, at Laguna Seca on a Supersport bike it requires from 12% to 43% throttle, depending on the corner, before the bike begins to slightly accelerate, up to then it is losing speed rapidly.

Do you teach trail braking at the California Superbike School?

 

Keith: It’s a key part of our RACE school drills. It also comes up on Level 3 during a drill called Attack Angles. It can be covered at any time during Level 4 classes for which we have specific drills. Otherwise it’s also covered on request at any other point. It's interesting that the very best riders who have trained with us don't ask about it, they've figured out where it applies.

Recently, trail-braking has become a topic. On-board footage of top racers clearly shows this technique in use. Riders intently study this footage trying to pick up wisdom that will make their riding better. Trail braking as a technique seems to have developed its own fan club. From some of its fans one could mistakenly get the idea that it is the "silver bullet" that will cure all your riding problems. Thinking that any one technique in our sport is senior to the others is like saying all a painter needs to be able to paint a masterpiece is to make sure the color “red” is included.

 

It's a multi-layered, multi-tasking, multi-sense oriented sport where there are no easy routes to achieving your riding goals.

Are there any new braking drills?

 

Keith: Recently, I've been researching all the aspects of braking, amongst other things. Right now my list contains 5 stages of braking control, each with its own on-track drills. There are half a dozen other important aspects to braking that we also use to train and coach our students.

When you coach high-level motorcycle racers like AMA Supersport winner Joe Roberts, British Superbike Champion Leon Camier, etc. do you encourage or teach trail braking?

 

Keith: It rarely comes up as a topic on its own. If a top level racer is having trouble with some aspect of his braking, often there is some underlying problem that when fixed, solves the whole thing. For that caliber of rider you are looking for the least time on the brakes and the earliest on with the gas. In all cases, they want to minimize the time on the brake and maximize the time on the throttle with no coasting.

 

On the track there are cornering situations that demand some extended trailing of the brakes, mainly places where you can't get the bike turned quickly to your knee. For example, nearly all decreasing radius turns require a longer tapering off of the brake because the steering into them is more gradual. Some double apex turns we will see riders trailing the brakes well past the first apex. Where it applies it applies.

 

Theoretically, you would be going the fastest if the tires were always just at the limit of traction, whether from acceleration, braking or cornering. In auto racing they commonly use circular graphic representation of G forces called the “traction circle”. It shows G forces in all directions while driving. The idea is to keep the meter as close to the edge of the circle (the theoretical limit of traction) as much as possible while going around a track. Trailing the brakes is required to accomplish this in most corners. However that style of riding/driving would not be recommended for a Sunday ride down your favorite road. In any case, you certainly wouldn't want to be thinking circles and numbers while riding at any sort of quick pace, you'd want to be feeling what the bike's tires were actually doing.

 

So, the winning rider's you've coached and trained do or don't trail-brake?

Keith: They do where it applies. You asked about Joe Roberts, who set the American racing community on its head last year by winning 5 out of 5 races he entered and who had never raced a 600 before; he doesn't like to trail-brake. His competition did like it and you could see the difference in their styles and the results. In the 8 years we've been training Joe I'd say we spoke of trail-braking 2 or 3 times.

 

There are so many other important fundamentals to master which put the bike under the rider's control and, frankly, give him more options in how to ride corners. Just as the painter must learn to draw well and understand contrast and perspective and form and a dozen other things to make that masterpiece so the rider must have the underpinnings to be able to make decisions on his handling of corners and to make them his own. It's the ART OF CORNERING not just the techniques.

 

Do all the top racers in AMA, World Superbike and Moto GP trail brake?

 

Keith: For the corners where it applies, for sure. Keen observers of the sport will notice that the deep trailing of the brakes that was so popular a few years ago has evolved somewhat. In only some corners will you see the brake still on at the apex. When you see a rider’s hand back on the gas before the apex, which you see more and more, you also have to realize that it takes 1/2 second to transition from brake to gas. At 60mph that 1/2 second is equal to 44 feet (about 6 bike lengths) earlier where the brake was actually released. You can find all sorts of exceptions and variations to technique. A rare example is the Moto3 riders going into turn one at Phillip Island, you see them turning in with the throttle wide open, then going to the brakes after the bike was well-pointed into the turn.

One of the reasons riders were deep-trailing the brakes is because they could. I mean that the newer race front tires allow very heavy, leaned over braking. One of our students who had won in Moto 3 and Moto 2 graduated to Moto GP and I'll never forget how enthusiastic he was about how amazing the Moto GP front tires were under braking.

I suspect James Toseland fell under the spell of this when he went from WSBK to Moto GP, he even mentioned it in some interviews. It clouded the issue of how to ride those bikes well. Remember that was the time when MotoGP went down to 800cc and all the top riders were talking about keeping up mid-corner speed versus a point-and-shoot style. Even in slow corners he was giving up so much by deep-trailing. Rossi, Stoner, Pedrosa were off the brakes 15 to 30 feet earlier and back to gas at, for example, turn #11 at Laguna Seca while he was possibly thinking how great the front tires were sticking under braking to the apex.

Seeing how deep-trailing has devolved reminds me of the era where nearly everyone was backing the bikes into corners. It was so much fun and so spectacular and the fans loved it. Where did it go? You see much less dramatic "backing in" compared to a few years ago. Now it’s more the chassis setup causing the bike to back in regardless of the rider’s intent, such as some of the Moto2 bikes. The riders did it because they could and then everyone realized it was huge fun but in most cases slower, especially for Superbikes and MotoGP bikes.

Can you compare trail braking in cars vs. trail braking on a motorcycle?

 

Keith: That's easy, you can't tuck the front wheel from over-braking while leaned over and you can’t fall off a car! But with cars you have a wide variation of how to use the brake and throttle depending on the car’s configuration: front-wheel drives require different technique than rear wheel drives, as do all-wheel drives; also if the car is front, rear or mid-engine. I’d say the application is more consistent regardless of the type of bike you ride. Of course trailing the brakes changes the bike’s geometry by compressing the forks, this changes fork rake, overall ride height, trail and wheelbase.

 

Do those changes in geometry help or hinder the rider?

 

Keith: It's a bit of a Devil's tradeoff; the steepened rake will make the bike turn easier as does the slightly shortened wheelbase help that, but, the increase in trail is what makes the bars feel heavy and somewhat unresponsive under brake trailing. Because the braking expands the contact patch area to the inside of the bike's center line, it counter-steers the bike upward, a little or a lot.

 

You can do a simple experiment to feel a light version of this by getting the bike leaned over in the corner, go back to gas and then off the gas. When the weight transfers forward, off gas, the bike's first response is to stand up some. That same effect is amplified if brakes are used while leaned over. To counter that "stand up" action the rider must apply some bar pressure to hold his lean. Rider's learn to do this almost unconsciously.

 

It's quite similar to the false perception that the bike stands up on corner exits from acceleration, which it does not. Riders unconsciously steer the bike up as they add gas.

 

The big negative is that the fork's are restricted in their ability to rotate side to side that slight amount that you feel when cornering. That slight oscillation is necessary for the bike's stability, which I covered in A Twist of the Wrist, Vol II.

 

These forces are in conflict with one another and the forks become less compliant, less able to follow the road's surface changes, under those conditions. The tire then begins to "dance" over the ripples and bumps. This, I'm convinced, contributes greatly in even the top riders losing the front and low-siding while trail-braking.

 

How high a priority should trail braking be given to riders that are just getting involved in the sport?

 

Keith: That depends on how you approach their training. You certainly wouldn't start a new rider off training him to trail brakes before he had some idea of how he should take a corner to begin with. You'd want to give him a solid grounding in several other basics like that before launching into that technique.

Back to the controversy about trail braking, people believe that you either do it all the time in all corners or you don’t do it at all. What are your thoughts on this?

 

Keith: It is irrelevant whether you are finishing off your braking straight up or leaned over, you always trail off the brakes. The logical approach is to train someone to do that straight up first. Later you could take up trailing them leaned over.

Is there a hard fast rule that braking should be done BEFORE you tip the bike into the turn?

 

Keith: There are 27 references to trailing brakes and why in my three books on riding. They were released in 1983, 1986 and 1993, way before there was any controversy on the subject. Interestingly, those books were the first time anyone had approached trail-braking in writing and photographed the advantages and uses of the technique for motorcycles. No one can argue with that, it is the first written history of trail-braking for motorcycles.

 

These days, from how some riders talk about it you'd think that trail-braking was some new innovation, just invented. It’s probably due to me describing it as “braking while leaned” or “letting of the brakes while leaning in” instead of calling it “trail braking” which had previously been an exclusively car racing term.

What is the difference between trail braking into the turn, and braking in the middle of a corner?

 

Keith: Trailing in is for speed and line setting. Braking in the corner is an emergency situation, they are totally different. One is calculated the other is out of necessity and often panic.

Would carrying some brake pressure into the corner help you if you had to brake suddenly in the middle of the turn because the brake pads are already touching the rotors?

 

Keith: Keeping a finger or two resting on the lever helps reduce reaction time, but you don’t have to have the brakes slightly engaged whenever cornering “just in case”.

You can apply the brake as fast as lightning provided you do so lightly. It's the pressure at the end of the brake pull that is critical not how fast you pull it in.

 

A quick on-track braking action takes as little as 2/10ths of a second to get to full brake pressure for some turns. If you snapped the brakes on to a very light pressure you could get into the brakes even at a good lean. It wouldn't feel very stable but you can do it. Our Panic Brake Bike fitted with outriggers allows riders to practice rapidly going to the right amount of pressure without overstepping the boundaries. Five minutes on that bike is better than five hours of talking about braking.

 

[YellowDuck]

Nice. One point I am confused about though. I thought the main physical reason that a cornering bike tends to stand up under braking is that the extra compression of the front suspension brings the center of gravity lower and to the outside of the corner. It is like the rider suddenly started hanging off less, bringing his weight inwards towards the bike. This article mentions a completely different effect (which I don't totally understand) about the effect of braking on the tire contact patch. Is my preconception wrong, or are there two different things gong on here? And how exactly does the one mentioned in this article work?

[Dylan Code]

Nice. One point I am confused about though. I thought the main physical reason that a cornering bike tends to stand up under braking is that the extra compression of the front suspension brings the center of gravity lower and to the outside of the corner. It is like the rider suddenly started hanging off less, bringing his weight inwards towards the bike. This article mentions a completely different effect (which I don't totally understand) about the effect of braking on the tire contact patch. Is my preconception wrong, or are there two different things gong on here? And how exactly does the one mentioned in this article work?

 

I think any person would be biting off a big chunk of physics and mechanics to adequately confirm or disprove what you are saying. However what I know to be correct from what I have studied and tried in practice, your impression is at least partially wrong. Go through a longer corner with a constant throttle reach forward and gently apply the brake. In most instances, if not all, the bike will stand up. Ok we already agree on this. Applying the brake pulls the contact patch in more, pro-steering the bike up. "Pro-steer" means to rotate the bars further into the turn. When actively doing this, the bike stands up. Applying the brake when leaned seems to have this effect.

 

There are without doubt other physics and mechanics that come into play but the simplest and largest influencing factor that I am aware of is stated above.

 

This is one topic where empirical observations are the most important and then an explanation helps to complete the understanding.

 

What I am happy about is that Keith mentions some aspects of trail braking that have not been broadly spoken about and sheds some light on the subject for everyone.

[faffi]

Thanks for posting that interview

[ktk_ace]

the G circle mention helps alot on how to trail brake correctly

imho a rider is only as skilled as his weakest skill ; filling in and correcting weakness makes one a better overall rider imho

[rchase]

Very good article. There's a lot of hype out there about trail braking. As always Keith is able to provide clarity with science.

[YellowDuck]

 

Nice. One point I am confused about though. I thought the main physical reason that a cornering bike tends to stand up under braking is that the extra compression of the front suspension brings the center of gravity lower and to the outside of the corner. It is like the rider suddenly started hanging off less, bringing his weight inwards towards the bike. This article mentions a completely different effect (which I don't totally understand) about the effect of braking on the tire contact patch. Is my preconception wrong, or are there two different things gong on here? And how exactly does the one mentioned in this article work?

 

I think any person would be biting off a big chunk of physics and mechanics to adequately confirm or disprove what you are saying. However what I know to be correct from what I have studied and tried in practice, your impression is at least partially wrong. Go through a longer corner with a constant throttle reach forward and gently apply the brake. In most instances, if not all, the bike will stand up. Ok we already agree on this. Applying the brake pulls the contact patch in more, pro-steering the bike up. "Pro-steer" means to rotate the bars further into the turn. When actively doing this, the bike stands up. Applying the brake when leaned seems to have this effect.

 

 

 

Thanks for this explanation. I think I almost get it, just one more question....what do you mean "pulls the contact patch in more"? Which way is "in" in this case? Towards the inside of the corner, or backwards towards the bike in a longitudinal direction? I expect the former but want to be sure I get it.

[Dylan Code]

When I say "pulls the contact patch in" I am referring to being leaned, arcing through a turn, then putting resistance at the front contact patch by means of applying the front brake. Now, aside from the forks compressing, the bars tend to turn further into the turn. That's the action I am referring to and is very slight, but this has an effect of steering the bike up out of the turn (from subtle to marked depending on attendant factors).

[Hotfoot]

This article mentions a completely different effect (which I don't totally understand) about the effect of braking on the tire contact patch.

 

The best and clearest explanation I have ever seen of this is on the recent Twist of the Wrist II DVD, there is a GREAT computer animated graphic that shows what happens - in my opinion, that little clip alone is worth the price of the DVD.

[Dylan Code]

Here's a video showing CSS student trail braking at Laguna Seca.