by Ross Bentley
SPEED SECRET
A shift should be made gently and with finesse.
UPSHIFTS
Simply place the shifter into gear as smoothly as you can. A shift should never be felt. You may be surprised at just how slowly and relaxed the world’s top drivers shift.
DOWNSHIFTS
Downshifting is one of the most misunderstood and misused techniques in driving. And it is a must for extracting the full potential of your car. It’s not always easy—it requires timing, skill, and practice—but when mastered, it will help you drive at the limit.
What is the real reason for downshifting? Many drivers think it’s to use the engine to help slow the car down. Wrong again! The engine is meant to increase your speed, not decrease it. In fact, by using the engine to slow the car you can actually hinder accurate brake modulation and balance. Race drivers, and good street drivers, downshift during the approach to a corner simply to be in the proper gear at the optimum engine rpm range and to allow maximum acceleration out of the corner.
Again, the reason for downshifting is not to slow the car. I can’t emphasize this enough. That’s what brakes are for. Too many drivers try to use the engine compression braking effect to slow the car. All they really achieve is upsetting the balance of the car, the braking effectiveness (if the brakes are right at the limit before locking up, and then you add engine braking to the rear wheels, you will probably lock up the rear brakes) and more wear and tear on the engine. So brake first, then downshift.
SPEED SECRET
Brake first, then downshift.
HEEL-TOE
To complicate things a bit, in racing you must downshift to a lower gear while maintaining maximum braking. This must be done smoothly, without upsetting the balance of the car. But if you simply dropped a gear and let out the clutch while braking heavily, the car would nose-dive, upsetting the balance, and try to lock the driving wheels because of the extra engine compression braking effect.
The smoothest downshift occurs when the engine revs are increased by briefly applying, or stabbing, the gas pedal with your right foot. This is called “blipping” the throttle. This matches the engine rpm with the driving wheels’ rpm.
The tricky part is continuing maximum braking while blipping the throttle at the same time. This requires a technique called “heel-and-toe” downshifting. To get a basic feel for this technique, practice it while the engine is turned off (see Illustration 3-1). Then you can begin to practice it on the road or racetrack.
ILLUSTRATION 3-1 Here is a step-by-step explanation of how to heel-and-toe downshift:
1. Begin braking, using the ball of your right foot on the brake pedal while keeping a small portion of the right side of your foot covering the gas pedal but not pushing it yet.
2. Depress the clutch pedal with your left foot, while maintaining braking.
3. Move the shift lever into the next-lower gear (from fourth to third in the illustration), while maintaining braking.
4. While continuing braking and with the clutch pedal still depressed, pivot or roll your right foot at the ankle, quickly pushing or “blipping” the throttle (revving the engine).
5. Quickly ease out the clutch, while maintaining braking.
6. Place your left foot back on the dead pedal, while continuing braking, now in the lower gear.
It’s important to apply consistent brake pressure all the way through this maneuver. You are simply pivoting the right foot to blip the throttle while braking at the same time.
This blipping of the throttle is one of the most important aspects. You want to match the speed of the engine with the speed of the gear you are selecting, and you can’t watch the tachometer. Your eyes must be looking ahead. So, correct blipping of the throttle and matching of revs depends on practice and input from the ears and the forces on the body. If you don’t blip enough, the driving wheels will lock up when the clutch is reengaged. That’ll cause big problems. If you blip too much, the car will attempt to accelerate when you are supposed to be slowing down.
The best way is to rev up the engine slightly higher than required, select the required gear, and quickly engage the clutch as the revs drop. It’s going to take practice, constant practice. It may seem like a lot to do all at once, but once you get the hang of it, it will become second nature.
To heel-and-toe properly your pedals must be set up correctly. When the brake pedal is fully depressed, it should still be slightly higher and directly beside the gas pedal. In a purpose-built race car, take the time to adjust the pedals to fit. If racing a production-based car, you may have to bend or add an extension to the throttle to suit you. Do not modify the brake pedal by bending or adding to the pedal. This will weaken it.
There isn’t a successful race driver in the world who doesn’t heel-and-toe on every downshift. And, again, it can be practiced every day on the street. In fact, that’s the only way to drive all the time.
TIMING
Now that we’ve talked about how to shift, what about when to shift? First, downshifting. Remember: “Brake first, then downshift.” If you don’t follow this rule, you will end up badly over-revving the engine. Think about it. If you are at maximum rpm in fourth gear and you downshift to third without slowing the car, you’ll over-rev the engine. And remember again, downshifting is not a means of slowing the car, unless you have no brakes.
Make sure you always complete your downshifts before you turn into a corner. One of the most common errors I’ve seen drivers make is trying to finish the downshift while turning into a corner. As the driver lets out the clutch (usually, without a smooth heel-and-toe downshift), the driving wheels begin to lock up momentarily, and the car starts to spin. Time your downshift so that you have completed it, with your left foot off the clutch and over onto the dead pedal area, before you ever start to turn the steering wheel into the corner.
When upshifting, for absolute maximum acceleration, you need to know the engine’s torque and horsepower characteristics. Talk to your engine builder, or study the engine dyno torque and horsepower graphs to determine at what rpm you should be shifting. It makes a huge difference. With many engines you’re better off to shift before reaching the redline. You want to shift at an rpm that allows the engine to stay in the peak torque range.
Let’s look at an example using the Torque and Horsepower versus Engine rpm graph in Illustration 3-2. Assuming a 2,000-rpm split between gears (an upshift from one gear to another, dropping the engine speed by 2,000 rpm), if you shifted from first to second gear at 7,000 rpm, you would then be accelerating from 5,000 rpm back up to 7,000. As the graph shows, from 5,000 rpm the torque curve is on a decline. However, if you shifted at 6,000 rpm, the engine would be accelerating through the maximum torque range to maximum horsepower. In fact, an engine will operate most effectively—resulting in the maximum acceleration—when the rpm is maintained between the torque peak and horsepower peak.
ILLUSTRATION 3-2 Torque and horsepower versus engine rpm graph.
Notice I talk more about the engine torque than horsepower. As they say, “Horsepower sells cars; torque wins races.” Torque is what makes the car accelerate; horsepower maintains that.
When you are proficient at smooth, well-timed downshifts, try skipping gears when downshifting. Instead of running through all the gears (for example, from fifth to fourth, fourth to third and third to second) shift directly to the required gear (from fifth to second). Obviously, this takes the right timing, using the brakes to slow the car, then downshifting just before turning into the corner. You must slow down the car with the brakes even more before dropping the two gears.
This goes back to what I was getting at earlier: The less you do behind the wheel, the faster you will go. Every time you shift, there is a chance you may make a small error that will upset the balance of the car. So shift as little as possible. In fact, the less downshifting you do while approaching a corner, the less likely it is you will make a mistake. It will be easier to modulate the brakes smoothly.
Now, with some cars, it seems the gearbox doesn’t like it when you skip gears. Often, it is difficult to get a perfect match of the revs, therefore making it hard to get a good, clean downshift without “crunching” it into gear. Obviously, with this type of car, you’re better off not skipping gears.
DOUBLE-CLUTCHING
What about double-clutching? I believe double-clutching is unnecessary in any modern production car (anything built in the last 20 to 30 years or so), but may be useful in some real race cars with racing gearboxes.
What is double-clutching? Basically, you depress and release the clutch twice for each shift. The routine goes like this for a downshift: You are traveling along in fourth gear and begin to slow down for a corner. You then depress the clutch pedal, move the shifter into neutral, release the clutch, rev the engine (blipping the throttle using the heel-and-toe method), depress the clutch again, move the shifter into third gear, and release the clutch. Your downshift is now complete.
The reason for double-clutching is to help evenly match the rpm of the gear you are selecting with that of the engine to allow a smoother meshing of the gears. In a non-synchromesh transmission, such as a racing gearbox, it may make gear changing easier. And that’s why I say it may be unnecessary to double-clutch in production-based race cars with their synchromesh transmissions. But, if the synchros in your car’s transmission are beginning to wear out, double-clutching can extend their life a little longer and make it easier to get it into gear.
You may be able to go racing for many years and never have to double-clutch. But a complete race driver knows how and is proficient at it. In endurance races, a driver may want to double-clutch to save wear and tear on the gearbox. At other times it is more a matter of driver preference.
CLUTCHLESS SHIFTING
Another option with a pure racing gearbox is not to use the clutch at all when shifting. This takes practice, as it is more critical that the engine and gearbox revs are matched perfectly when downshifting. The advantage to not using the clutch is that it may save a fraction of a second on each shift. The disadvantage is that it usually causes a little extra strain on the gearbox, perhaps wearing it out a little sooner or risking a mechanical failure in the race. Also, there may be more chance for you to make an error this way. Again, I think it’s important for a driver to know how to drive without the clutch. You never know when you’re going to have a clutch problem and be forced not to use it.
More and more race cars are being built with sequential shifters. This is much like a motorcycle shifter, in that the shift lever is always in the same position. You simply click it back to shift up and forward to shift down. With this type of shifter it is impossible to skip gears on a downshift. You have to go through all the gears. Also, it may work better if you do not use the clutch. On an upshift, you just ease up on the throttle (as you would with a normal gearbox) and click the shifter back into the next gear. On a downshift, it works the same way only you heel-and-toe blip the throttle as you click it down a gear.
Throughout my career, with most cars, I have usually used the clutch when shifting. I’ve found it puts less wear and tear on the gearbox. But when I started driving cars with sequential gearboxes, I found they shifted much quicker and easier without using the clutch. It took a few laps to get used to not using it—and to not being able to skip gears on downshifts—but once comfortable with it, I realized it was the only way to go with the sequential shifter. With a regular gearbox, though, I still prefer to use the clutch.
Understanding chassis and suspension adjustments and what they mean to you as a driver is a critical part of your job. There are many good books that deal with race car dynamics in great detail. At the back of this book I’ve listed the ones I think are mandatory reading for any driver. If you don’t understand something, go back to these books or ask someone to explain it. If you want to win, you must know this information.
I don’t intend to go into great detail, but the following is a brief overview of some of the key areas of chassis and suspension adjustments that you have to know to reach any level of success. I hope this piques your interest to go out and learn more.
CAMBER
Camber angle is the inclination of the wheels looking from the front or rear of the car. A wheel inclined inward at the top is said to have “negative camber”; a wheel inclined outward at the top has “positive camber.” The angle is measured in degrees.
It is important to keep the entire tread width of a tire, which is generally very wide and flat, in complete contact with the track surface as much as possible. When a tire leans over, part of the tread is no longer in contact with the track, drastically reducing traction. Therefore, the suspension must be designed and adjusted to keep the tire flat on the track surface during suspension movement.
Understand that as a car is driven through a corner, it leans toward the outside of the turn. This causes the outside tire to lean outward, creating more positive camber, while the inside wheel tends toward more negative camber. Therefore, to keep the outside tire (as it’s the one that is generating most of the cornering force) as flat on the road surface as possible, generally the suspension is adjusted to measure negative camber when at rest or driving down a straightaway.
ILLUSTRATION 4-1 Camber is the angle of inclination of the wheels when viewed from the front or rear. This shows negative camber.
Your goal in adjusting the camber angle is to maximize cornering grip by having the tire close to 0-degree camber during hard cornering. This can take a fair bit of adjusting and testing to come to the best static setting that will result in the optimum dynamic camber angle.
CASTER
Caster angle provides the self-centering effect of the steering (the tendency for the car to steer straight ahead without holding the steering wheel). It is the inclination angle of the kingpin, or upright, looking from the side. Positive caster is when the top of the kingpin or upright is inclined to the rear. Negative caster is never used.
ILLUSTRATION 4-2 Caster is the angle of the inclination of the suspension upright.
The more positive caster, the more the steering will self-center, which, generally, is a desirable effect. However, the more positive caster, the more effort it takes to turn the steering against this caster. There has to be a compromise between easy self-centering and heavy steering.
Caster also affects the camber when the steering is turned. The more positive caster, the more negative camber on the outside tire during cornering. This must be kept in mind when adjusting for the optimum camber setting. Perhaps, instead of dialing in more static camber, you may be better off adjusting in more caster. Remember, this will result in more negative camber on the outside tire during cornering. This can be an important factor. Learn and understand caster.
TOE
Toe can be either “toe-in” or “toe-out.” It is the angle of either the two front or two rear tires looking at them from above. Toe-in is when the front of the tires are closer together than the rear; toe-out is the opposite. The front of the tires are farther apart than the rear. Toe can always be adjusted at the front and can be adjusted at the rear on cars with independent rear suspension.
ILLUSTRATION 4-3 Toe is the angle of the wheels looking from above; in this case, toe-in.
Toe plays an important role in the car’s straight-line stability, as well as its transient handling characteristics (how quickly the car responds to the initial turn into the corner). Generally, front-wheel toe-in results in an initial understeer; toe-out results in an initial oversteer (more about understeer and oversteer in the next chapter).
Rear wheel toe-out must be avoided. It causes instability and unpredictable oversteer.
ACKERMAN STEERING
The inside wheel of a vehicle driving through a corner travels on a tighter radius than the outside wheel. Therefore, the inside front wheel must be turned sharper to avoid it scrubbing. The geometry of the front suspension is designed to achieve this. This is called Ackerman st
eering.
Some race cars have been designed or modified to have anti–Ackerman steering. This means the inside tire is actually turned less than the outside tire. The reasoning is that the inside tire has so little of the cornering load that some tire scrub will not hurt. Other cars have increased Ackerman geometry to the point where the inside wheel is turned more than would be necessary to track the inside radius. Both of these variations are designed to help the car’s initial “turn-in” characteristics.
BUMP STEER
Bump steer should be avoided. This is when the front or rear wheels begin to either toe-in or toe-out during the vertical suspension movements caused by a bump or from body roll (sometimes called “roll steer”). Although it has been used to help “Band-Aid” a handling problem, generally bump steer makes a vehicle very unstable, particularly on the rear wheels.
ANTI-DIVE
When you apply the brakes, the front end of the car has a tendency to dive. The suspension geometry is designed in such a way as to reduce this tendency. Generally, this is something designed into the car and requires—or even allows—little or no adjustment.
ANTI-SQUAT
When a car accelerates, the rear tends to “squat” down. As with anti-dive, the suspension geometry is designed to limit this. And again, little adjustment is required or available.
