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Professional Motorsport Data Analysis: Braking Technique

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Braking Technique

07.59

00:00 - Your car might have all the braking power in the world but without good technique from the driver, it'll be a waste of time and money.
00:07 Thankfully we're able to analyse this technique and clearly show where and when improvement is needed.
00:15 The first thing we need to do is identify the different areas of the brake pressure trace.
00:20 Here we've got an example which is for a big stop going down several gears going from a long straight down into a slow corner.
00:29 You can see that I have the throttle and brake plotted over top of each other.
00:34 This is just my preference because it allows both to be plotted at a larger scale than if they were shown one above the other which helps to see the details.
00:43 Also, because of their nature, hopefully only one of them is going to be active at a time so they tend not to overlap too much which makes it easier to read.
00:52 The first area we need to identify is the gap between the throttle being released and the first brake application.
00:59 This gap depends both on the skill level and technique.
01:03 Obviously the larger the gap is the more time is being lost as we want to minimise any coasting time here.
01:10 The skill part comes from how well the driver can coordinate their feet and the technique depends on whether they're a left or a right foot braker.
01:19 The choice of being a left or right foot brake is sometimes made for you by the type of car being used.
01:25 If a manual clutch needs to be used on the downshifts then right foot braking is going to be the only option.
01:32 Even though a right foot braker will lose some time shifting their foot from the accelerator to the brake, this time lost, in most cases, is less significant than having poor braking feel and pressure modulation by forcing yourself to use a different foot for braking than you're used to.
01:49 My point is that for an amateur driver, even if your car allows you to left foot brake, unless you've grown up left foot braking in karting or single seaters, you're probably still going to be faster as a right foot braker due to having better brake feel.
02:04 So don't feel like it's a requirement to suddenly learn to left foot brake.
02:08 As a side note, there have been many extremely successful right foot brakers that have operated at the highest levels of motorsport.
02:16 So left foot braking is certainly not mandatory.
02:20 The next area of the braking phase is the pressure buildup.
02:22 Sometimes also referred to as the brake aggression.
02:26 Ultimately the rate of pressure input needs to be relatively high as the quicker we build brake pressure, the quicker we can get the tyres to peak slip ratio.
02:35 With that said, the optimum rate of pressure buildup is different for each car and tyre combination and is dependent on the stiffness and damping level of the suspension and tyres, the dynamics of the chassis and the braking stability margin you have in that area of the track.
02:51 The point of peak pressure should ideally flow on roughly to be aligned with the rate of the pressure increase which in this case looks quite good.
02:59 The peak pressure should generally occur at the beginning of the stop and will generally steadily bleed off from there.
03:05 It's quite common for amateur drivers to apply peak pressure, realise they brake too early and release, followed by another increase in brake pressure as they get closer to the turn in point.
03:15 This is something we need to avoid.
03:17 The peak pressure should always occur at the start of the stop and the release be smooth after that.
03:23 The way the pressure bleed should look will depend on the type of car we're running and the speed we approach the braking zone at.
03:30 In a car with a lot of downforce, it will be possible to use a lot of brake pressure initially while the car is still travelling fast.
03:38 However as the speed reduces, the downforce will also reduce quickly, meaning the proportion of vertical load on the tyres coming from the downforce will be dropping off.
03:47 This will require a consistent drop in pedal pressure to maintain peak slip ratio and avoid locking a tyre.
03:54 In a car with little or no downforce, the shape of the brake trace may have much more of a plateau to it with the initial peak pressure staying on for the initial part of the stop.
04:04 With the car still travelling straight, the brake pressure doesn't need to be varied through the braking zone just because of different downforce levels.
04:12 The optimum slip ratio is also changing with rotational speed of the tyre.
04:17 The bulk of the braking and speed reduction is generally happening with the steering wheel held straight.
04:22 This is simply due to the tyre being able to provide a lot more longitudinal force when the force is purely longitudinal.
04:29 However when the point comes to start turning into the corner, this requires a second type of pressure bleed off that is distinct form the initial bleed.
04:38 This is the area of the braking zone people refer to as trail braking.
04:42 Referring back to a generic friction ellipse for a tyre, when we look at the maximum force the tyre is capable of producing, it's clear that if we want to start producing lateral force we need to reduce the longitudinal force first.
04:57 As a rough guide for how we'd want to reduce the brake pressure in response to steering angle, think of it simply as we need to reduce the brake pressure in proportion to the steering input.
05:07 So looking at this braking event we can identify a second distinct gradient where the driver is reducing brake pressure approximately linearly with steering input which is the target we want to aim for.
05:19 Another way to visualise this is by plotting steering angle vs brake pressure on an XY plot.
05:25 We can see in this case that from the point steering input occurs, the change in brake pressure is roughly linear with increased steering angle.
05:35 If this plot had data that followed this line then too much pressure is being held on with steering.
05:41 However if it followed this line, there wasn't enough pressure.
05:45 In an ideal situation, the brake pressure is steadily and linearly reduced as the car approaches the apex in the point of maximum steering input.
05:54 So in summary, we can separate the analysis of braking out into the following areas.
05:58 The gap between the throttle lift and the first brake application.
06:03 The rate of building pressure.
06:06 The timing and magnitude of the peak pressure.
06:08 The initial pressure bleed from peak pressure.
06:11 Trail braking and the point of final release.
06:15 The braking example we've discussed so far in this section was for a large braking event.
06:18 Say slowing for a tight corner at the end of a long straight.
06:23 A different type of braking event is one that often happens between corners and is small enough that no downshift in gears is required.
06:31 In these situations, the brake application should be much smoother and more gradual.
06:36 This is because in areas of the track where multiple corners of a similar speed are close together, you're often carrying significant lateral load through the car at all times.
06:46 This means the braking events need to be more gentle which allows the car to remain more settled.
06:52 In situations like this, you don't want to be changing the pitch or attitude of the car quickly as this will often create an imbalance.
07:00 This is an example of the style of brake application we should be aiming for in that situation.
07:06 Notice that the form of the brake trace is quite symmetrical and smooth compared to the heavy stop we looked at previously.
07:13 In this case, the inputs should be gentle as we're trying to keep the car as settled as possible.
07:19 Regardless of the type of braking zone we're in, our goal in every braking event is for each input to be as smooth as possible because tyres work best when loads are applied smoothly and consistently.
07:30 In reality, this is never the case because of things like downshifts and bumps in the racetrack.
07:37 But it should always be our goal.
07:38 When overlaying different data sets to compare both braking points and technique, it's important to remember to check the data alignment like we discussed earlier in the course.