WynnS123

^That's what I do. The pedals in the S were designed for you to do a "real" heel and toe unless you have Flintstone feet.

ZDan

No, the engine is acting to SLOW the car all the way through the brakings zone, it's NOT trying to turn the rear wheels forward. It's acting to SLOW the car, not drive it forward. The ABS doesn't care about this additional braking from the engine, it still senses impending lockup normally and will modulate the rear brakes accordingly whether there is engine braking (clutch engaged) or not.

ABS prevents the wheel from stopping. The only time the engine would "fight" against (act in opposition to) the brakes with the clutch engaged is if you brake all the way down below idle speed. Or step on the gas while braking.

you don't have to be looking at the TACHOMETER (do you call the speedometer the "mph gauge"?) to know what the engine's doing and have a very good idea of when the best time to downshift is. With the clutch disengaged and the engine idling all the way through the brake zone, you have very little idea (of course within a few laps you would, but a student learning will be changing/improving his entry speed all day long, so taking this info away is another reason your technique is a BAD IDEA.

I'm not confused about anything, I just know that "double-clutching" with any decent semi modern synchro gearbox is TOTALLY UNNECESSARY. It's not necessary in the S2000, it's not necessary in a 1971 240Z. If you have a non-synchro crash-box, yeah, you'll need to double-clutch.

Again, double-clutching isn't remotely necessary unless you have a non-synchro crash box.

Matching revs is of course required whether you leave the clutch engaged or disengaged, no improvement using your "clutch-disengaged-through-the-entire-braking-zone" technique.

Any book you can name on performance driving.
Dude, engine BRAKING you get leaving the car in gear SAVES the brakes, it doesn't use them more. The engine is acting to SLOW THE CAR DOWN.

I dont' care how fast your lap was, your technique is what I'd call "non-standard" at best, you certainly shouldn't be instructing students to use it!

Leave the clutch engaged except briefly while shifting. This will always reliably put you in the appropriate gear at the end of the braking zone even if you're totally unfamiliar with the track/road, and will do a better job of ensuring you're always in total control of the car.

The only time you should be on the clutch and on the brakes (other than briefly while downshifting) is if you are in a spin.

Sukeetoshyoo88

which one do you do?

robrob

Take a look at an ABS skidmark. Black lines broken up where the ABS releases brake pressure. Where there is skidmark the tires are not turning (watch some super slow motion of ABS braking). Your drivetrain is going from standstill in the skid--to rotating when ABS releases brake pressure.


Now you sound like a little girl.

I use a Sparco pedal on the accelerator pedal so I can roll the top of my foot to blip the throttle. Without the additional pedal I couldn't blip the throttle with my heel on the floor.

ZDan

ABS can leave stitched black marks without the wheels being locked, and anyway the drivetrain being engaged isn't negatively affecting ABS function or braking (if anything it's HELPING). Would like to see superslomo of ABS, I wouldn't think a modern system would react so slowly that the wheel actually locks...

You are doing it wrong. Ask any of your fellow competitors and instructors what *they* are doing with their clutch in the braking zones. Extremely poor form to have the clutch pedal to the floor through the braking zone.

robrob

In theory, but watch some video. Very few racers compete with cars with ABS. The books on high performance driving were written about cars without ABS. When the rear tires are in ABS there's very little engine braking going on because of the very low speed of tire rotation while in ABS. With the clutch engaged your entire driveline & engine are going from stopped during the ABS skid to moving again as the ABS releases brake pressure.

In a modern sedan based race car with ABS the rear tires will be in ABS if you're threshold braking the front tires due to the stock brake bias being designed for the street and street tires.

While instructing for Bill Scott Racing (BSR) we had a braking drill we'd have our tactical driving students perform to learn max braking in a turn. We'd turn ABS off and while in a moderate speed turn brake until the inside rear wheel locked up. Skidding the inside rear allowed more braking to the other three tires for a maximum performance stop. The key was to modulate between one locked tire and two. If the outside rear locked too you would loose directional control. It was a great way to teach brake modulation techniques. It's amazing how quickly a 65 year old female State Department employee can learn to threshold brake using this technique.

We also had a drill to threshold brake while driving at max speed in reverse (simulating reversing out of a terrorist attack). With normal front brake bias the front tires lock up much easier than you'd expect.

My point is I know braking and the S2000 brake system. I didn't pull my threshold braking technique out of my butt. Does your Z car even have ABS?

ZDan

Regardless of ABS or no, having the clutch disengaged throughout the braking zone is a bad habit for reasons mentioned above.

Of course the 240Z doesn't have ABS (neither does the S at the moment, actually). Makes no difference, the proper technique is to keep the drivetrain engaged, with or without ABS.

robrob

The original poster said he couldn't find any reference to the clutch in the Barber Racing book. I don't recall ever reading about clutch technique for threshold braking either. I'll review my textbooks when I get home and see if I can find anything. Maybe you should do the same.

WindingRoad

The factory brake bias on a production car has been very well developed for the last decade or so. However, these systems are designed without the "engine-brake" in mind. So, theoretically, if you were to leave the clutch engaged while in gear, you are adding to the brake torque done on the rear tires, making the complete system rear-biased. If your car can slow-down faster than the powertrain can reduce in speed, you are adding to the brake torque NEEDED to the rear tires, making the complete system front-biased.

What robrob outlines is a great way for novice to advanced drives focus on their braking ALONE and develop a good sense of modulation. Even at the competition level, I have seen drivers use this technique. Being in the right gear ALL THE TIME may not retrieve lost seconds, but being able to brake at 100% efficiency makes up seconds in racing.

But then again, in wheel-to-wheel racing, you never know when you might need to throttle out of a sticky situation.

ZDan

Says who? You can rest assured that the abs systems in modern cars ARE designed to operate normally when PROPER braking technique is used (clutch remaining engaged).

Only *slightly*. IN an ABS car, no effect at impending lockup. ABS will simply engage *slightly* sooner at the rear with clutch engaged than with it disengaged. In a non-ABS car, the bias is generally more front-biased to ensure front lockup prior to rear lockup during NORMAL and proper braking (clutch engaged).

*IF* is a mighty big word. The engine is going to want to slow down quicker than the car can decelerate. In practice, the engine will still be acting to slow the car even at maximum braking on R-comp tires.

I think it's a horrible habit to get into.

Suffice it to say, there are plenty of people "competing" who aren't necessarily using the best driving techniques.

I'm not saying you have to be in the right gear all the time, in fact I skip gears on the way down. If the course (or road) is unkown, of course being in the right gear all the time is an advantage. There is no advantage to threshold braking with the clutch disengaged vs. threshold braking with the clutch engaged. Either way, at some point you're going to have to blip the throttle to rev match, so being able to do that while maintaining threshold braking is an advantage either way.


I see zero advantage to the clutch-disengaged method, and at least a couple of potential pitfalls. I've never seen this method espoused at any instructor clinics or at any drivers school.