Trail Braking.

[matespace]

As an owner of a performance car it?s safe to say that attending a track day is inevitable. Modding begins and parts like brakes, brake pads and tyres are usually the first to get upgraded in pursuit of achieving a personal best lap time and then you also have good old race craft, that doesn?t cost anything but practice, practice, practice.

What is Trail Braking?

Trail-Braking is a technique used by rally drivers to negotiate single corners at high speeds. Typically, the average driver negotiates a corner by first braking to regulate the speed, then releasing the brakes and steering the vehicle along the corner, and finally accelerating after the exit of the corner. Trail-Braking is used when the approach speed to the corner is high and the braking must continue even after the steering of the vehicle has started.



Consider for example a 90 deg left corner as in Fig. 1. Approaching the corner at high speed from the outer edge of the road, Trail-Braking begins by braking the vehicle without steering. The driver adjusts the brake pressure such that the maximum available friction is generated by the tire. This means that the maximum available deceleration is generated; subsequently, no friction is available for steering. As the vehicle approaches the corner, the driver starts steering. In Trail-Braking this is done by progressively releasing the brake (in order to allow cornering forces at the tires) and simultaneously?and progressively?increasing the steering angle. As the vehicle decelerates, the weight of the vehicle transfers from the rear to the front axle and thus, the front tires generate higher friction than the rear ones. The vehicle rotates about the vertical axis, counterclockwise. As the vehicle reaches the apex of the corner and its attitude is aligned with the exit of the corner, the driver accelerates and counter-steers (steers towards the opposite side of the corner) to stop the rotation of the vehicle and start the acceleration towards the exit of the corner. Acceleration causes weight transfer from the front axle to the rear. As a result, the rear tires generate more friction, resisting the counterclockwise rotation of the vehicle. Overall, TB involves high vehicle slip angles and yaw rates. This allows the vehicle to reach a controllable, straight line driving state as quickly as possible, and allow the driver to react to unexpected road condition changes ahead of the corner, which are typical in off-road rally racing.

Source : http://soliton.ae.gatech.edu/people/...ers/ecc07a.pdf

SO, who has tried it? How hard was it to learn? And how effective did you find it?

[Condor Man]

Not too diffficult at all.

Some corners you must always trail brake and other it is not necessary.

You must seriously get your head around the transfer of weight when braking and accelerating. Then consider that through braking the car has more turn in, as the nose is down, if you lift off the brake before turning in, the weight is transferred to the rear of the vehicle, therefore allowing less turn in.

I hope that this helps....

[allanuber]

To diffficult at all.

Some corners you must always trail brake and other it is not necessary.

You must seriously get your head around the transfer of weight when braking and accelerating. The consider that throw brake pressure the car has more turn in as the nose is down, if you lift the brake of before turning in, the weight is transferred to the rear of the veicle, therefore allow less turn in.

I that this helps....

C'mon man! Just because you actually drive on a track doesn't mean you should contradict a guy who has FORUMLAE.

I'm ignoring your wisdom. From now on, through every area where I need to retard progress, I wait untill I feel the front washing out and as soon as that understeer starts to kick in I am going to slam that brake pedal through the firewall.

[Condor Man]

C'mon man! Just because you actually drive on a track doesn't mean you should contradict a guy who has FORUMLAE.

I'm ignoring your wisdom. From now on, through every area where I need to retard progress, I wait untill I feel the front washing out and as soon as that understeer starts to kick in I am going to slam that brake pedal through the firewall.

That could work.

By the way, I just read my post and man typing on an ipad just turns out to be so difficult! I have since modified so that my comments now make sense.

[adam01]

.........

I just read my post and man typing on an ipad just turns out to be so difficult! I have since modified so that my comments now make sense.

ok, thought u might have been on the plonk

[Condor Man]

ok, thought u might have been on the plonk

LOL!!

No plonk...

Just an Ipad, I gotta get me a keyboard for that thing...

This trailer is breaking....

Attachment 63690

[MikeG]

Not too diffficult at all.

Some corners you must always trail brake and other it is not necessary.

You must seriously get your head around the transfer of weight when braking and accelerating. Then consider that through braking the car has more turn in, as the nose is down, if you lift off the brake before turning in, the weight is transferred to the rear of the vehicle, therefore allowing less turn in.

I hope that this helps....

First time I raced at Eastern Creek in anger was in a FWD in the pouring rain. I got to the high speed turn 1 after the first lap doing about 160 and got scared, and backed off (no brake). This was enough the get the weight on the front to an extent that the rear started to come out, and I had the presence of mind the feed in a little throttle, to maintain the drift / slide around the corner now at a mere 140km/h or so and then buried the throttle to straighten the car up again.

The guys on the flagpoint were jumping up and down with thumbs in the air, but I was happy not to have soiled my undies :S

As I developed my driving I found that I could go flat stick around that corner with the right suspension and tyre package, in excess of 200km/h so in a way my first stuff-up taught me a great deal about handing and weight transfer...

Trail breaking is really just a facet of threshold braking... Rally drivers are often sideways, so they can use left foot braking mid-corner to manage both weight transfer and corner speed.

M