SouthernSon

A point was brought up about braking/downshifting in another thread and, not wanting to high jack the tread since it was more about engine reliability, I want to get input on a couple of points;

Is it not true that no matter what input, brake pad or driveshaft drag, the vehicle will only allow decelleration to the level allowed by the contact efficiency of the tire and pavement?

Also, is it not true that one would want to downshift only at lower RPM's, at the point of getting ready to accelerate out of turn, in order to save wear and tear on tranny?

If what I understand about this braking is correct, one would only want to use engine braking in cases of something being deficient in the braking system as in bad pads, cracked rotor, air in lines ..etc....

Independent1

Your ability to brake is limited by traction as is your ability to accelerate and corner.

The point of downshifting is to be in the proper gear to go through a corner and accelerate out of it. You should be in the correct gear before entering the turn. If you shift while cornering you will upset the balance of the car and if you are near or at the limit you will lose control of the car.

If you have a problem with your brakes you can use you engine braking to slow down your car. If you are not in a real race, I would hope if you encounter the kind of braking problems you mentioned that you would get off the track. There is no sense in endangering yourself and others without having your brakes.

If you are interested in learning more about race driving, I suggest you look into some books written by Ross Bentley and also Caroll Smith (Drive to Win). They are excellent and you will learn a lot.

yellow01

I think the other thread had some confusion regarding definitions, at least I was and I think I straighted it out...

If you are on the brakes as hard as you should be, even when you downshift and the engine revs down, it will supply little to the actual braking effort (at least per my limited experience can ascertain). But, you still downshift and the engine does still rev-down, so this could be termed "engine braking" (higher revs with a closed throttle). Obviously if you only use the engine you'd be decelerating much more slowly.

You're right in that you are ultimately limited by traction for any and ALL maneuvers - going, stopping, changing direction etc...

For me personally, where I downshift may vary a little by corner, but I do not do it just as I'm ready to accelerate out as you suggest. By the time my foot starts releasing pressure from the brake pedal I'm in the gear I want to be in, clutch is already engaged and I'm rolling from brake to throttle.

AU N EGL

This is part of the heel-n-toe downshifting technique. Reving the engines rpms just enough to match the drive shafts rotation speed to downshift a gear, just prior to turn in on the corner.

It is not waiting for the rpms to drop then shift. It is waiting for the rpms to drop, then blipping the thottle to match the gearing then downshift.

Here is a little video demo. It not a vette, but a great video. Even with a little double clutching action.

Click here to see Video

Driving is a highly multi-tasking envoinrment.

Braking into a fast brake zone is Brake HARD AT FIRST. Stomp on that brake peddle and get into ABS, then ease off as needed. Not like street braking where one eases into the brakes and brakes hard when needed.

VetteDrmr

I downshift before I enter the turn, mainly because I'm concentrating on trying to turn while in the turn, and don't want to expend any additional brainpower to a downshift. (did that make sense? )

I do downshift late in the braking portion, at a low rpm, as I'm coming off the brake. That requires only a tap on the accelerator to get the revs matched up decently and set up for the corner entry.

Note also that I'm a top-third driver in our autocross group, both in class and overall. So, a Danny Popp I'm not

Here's a video from one of our recent autocrosses that I had a lot of shifting in. If you listen carefully (still working on the microphone noise) you can hear the downshifts.

http://www.youtube.com/watch?v=7QowaUEaL_A

HTH, and have a good one,
Mike

Aardwolf

If I had a braking problem I would go for the E-brake.

Tintin

To add - you are waiting for the revs to drop so that you will not be beyond the redline of the engine when you select the lower gear. You will note that as the car is geared up or down that in the two minutes of the video , the clutch pedal is depressed only about 8 seconds in total. This speaks to my engine reliability thread - if you downshift, even though it may seem a short time - you are causing the engine to decelerate with the throttle closed as the brakes are used. In the Nissan I raced for the factory, this caused a similar problem as described about the Z06, i.e. Ka-Boom . We did not use engine braking for any longer than the video, but the cars couldn't take it without having engine failure. There is one point in the video where you hear the engine winding down for maybe 5 seconds. At 5-7 thousand RPM a lot of up and down is happening in the cylinders. If there is a problem with design , that is way long enough to find it..

If you watch the video, you will see that there is a lot of engine braking in concert with the brakes... No offence to the autocross crowd but did you count the number of shifts per minute in the video? I have seen autocross and most of it seems to be in maybe two gears at low speeds. I think you will find that at high speeds , using 5 or 6 gears that it is far more critical to get this right and to do it seamlessly. You don't hit cones on a mistake. Don't take it the wrong way, ok? If there were 40 other cars on the autocross all trying to be first at the same time as you are there you might find it more difficult to concentrate on your apexes...

Heel and toe (or in my case foot rotation) is one of the most critical skills to learn in motorsport, IMHO. In the other thread , there were those who felt it was hard on the car, it is if you don't know how to do it..

wtknght1

The easiest thing to remember is that pads are cheap, drive-lines are not. Don't use the tranny/diff/engine to slow you down.

SouthernSon

Actually, your explanation is more in sync with what I meant. I stated it very badly. I must have had a very tight switchback in my mind!

The Spark

I had a hard time with heel-toe until I bought the heel-toe gas pedal from Elite Engineering. It is almost effortless now. Plus it looks great wiht the metal brake and clutch pedals.

AU N EGL

Now let me understand this. You downshift BEFORE you make the corner. at which time you rolling on the throttle.

Not dowshifting AFTER the corner, just prior too rolling your foot on the throttle.

petefias

I normally complete a downshift during braking before beginning a turn. There are exceptions. If a sweeping turn is followed by a short straight, followed by a sharp turn I make the sweeping turn in the high gear and downshift on the short straight while braking and before beginning the next turn.

Is there a better way? Can't see how.

AU N EGL

I am asking for more of a hard braking zone then corner, not a highspeed decreasing radius turn of which you down shift in the corner itself.

Tintin

Did it come with all of those girls?

If your pedals are too far apart, which is common in US cars, you can rivet an aluminum plate to your throttle pedal. I have done this in every car I take to the track as I prefer my pedals to be less than an inch apart. That being said, many people have trouble driving my cars as they tend to open the throttle whilst braking, not a good thing. I am used to it and typically brake only with my big toe and rotate the rest of my foot to the throttle.. it is personal preference. You must learn the downshift technique or you will never be quick at the track, period. Cars that you take to the track have expendable parts, if you worry about them then you can't afford to race...

Herr Golden Adler, why is this so hard for everyone?

yellow01

If I understand what you're asking - yes.

To confirm - in the scenario of end of straight into a corner, I begin braking hard (straight line), blip & downshift while still braking as hard as I can - still going straight forward - now I'm in the gear I need and I roll over from brake to throttle through the turn.

Where I go from brake to throttle depends on the corner and if there's trail braking involved or not but I've completed the downshift before ever turning the wheel and under hard braking.


I think what I phrased wrong/weird was when I said "where I downshift depends on the corner". What I meant was it is always as described above, but depending on the braking zone and the straight leading up to it (and associated speed/rpm/gear choice), I may downshift earlier or later, but still straight line and still under braking as above. After rereading what I wrote, I realize it was worded poorly.

Mojave

When you get to the apex of the corner, you want to be on the throttle (most of the time). Not necessarily at full throttle, but on the throttle. Not always, but that is a good rule of thumb. You shouldn't be braking when you get to the apex. If you don't want to be shifting and turning, that means downshifting during the braking before entering the corner.

Slow in, fast out! Being fast out involves getting on the throttle ASAP (at least by the apex!), and that means the downshift needs to be done before entry.

Tintin

I prefer to do all my braking before I turn the wheel and then use an even pedal to the apex. I have found that if you do this, it is easier to balance the car through the corner. It involves only braking hard enough to slow to a speed that is the maximum the car will do without flying off and then moving the weight back for balance with the even throttle to overcome any bumps or irregularities in the surface. Worked for me, I had 2 T1 track records attained during my SCCA days from California tracks.... They have been surpassed with the rule changes and car improvements I expect ,but the theory is the same...

0Randy@DRM

Driving a race car is the easiest thing in the world
Drive in hard
brake late
depress clutch (still on brake)
put in exit corner gear only-blip gas(lower RPM is better)
let out clutch
roll on gas during turn in
apex hard on gas

And repeat

A pro golfer is trained to only think about one thing standing over the ball. Don't get too caught up on everything going into a corner. Do what is feels right and produces the faster lap times.
Randy
I am not good at any of these things

C6400hp

AU N EGL

Repeat untill end of race.

Put car on trailer
take back to shop
rebuld for next race

and repeat