utkinpol

exactly what i expected to hear, thanks. thanks to Larry too.

i always prefer to ask about stupid stuff than to try it in a car. works a bit better this way.

M758

Nope. This why you need to learn to heel and toe. In some corner you must brake hard, turn and down shift all at the same time.

So you must master heel and toe downshift as that allows you do the downshift as you are braking. This a fundamental skill.

Once mastered you can throw turn while braking in the mix as well.

When you execute the down change depends on RPM. If youi have long corner entry you will find the need to brake during corner entry and also be downshift as well.

One classic corner we have at a local track goes like this.

Entry is down the main straight. 115 mph in 944 spec or maybe 140 in fast high hp car.

For the 944 we wait till the last moment get on the brakes hard in straight line downshift then turn in while still braking. Downshift to 4th while still braking down to the apex. Then once slow down eniugh at near the apex downshift again to 3rd and get right back on the gas. Done right we will be turning 5000+ rpm in 3rd and full throttle all the way out of the corner. Of course we are al the limit of grip all the way around corner entry. I would guess 10% of speed reduction is done in straight line. The rest is all after turn in with a significant cornering load on the chassis.

If we were just braking in straight line we would have probabyl 7-8 car lengths of neutral throttle at 4500 rpm in 3rd and maybe 65 mph. And of couse be passed like we a standing still as turn in speed is probaby right about 95 or 100 mph by using trail braking. Min apex speed is probably 70 mph.

The other cool thing about trail braking is done well you can run a faster apex speeds since you can use the weight transfer off the rearend to make the car turn. It sort of feels like a controlled spin in the way you can get the back end ot rotate.


Trail braking is very powerfull skill and really seperates the men from the boys in track driving. Winning races and getting fast laps does not occur on straight aways, or corner exit. Those areas to pretty easy for any one to master. Even mid corner is not too hard. However braking and corner entry are hard to do and that makes then the place races are won and lost. Even with pros most drivers make a mistake not on corner exit, but at corner entry. Even if they go off on corner exit it was because of a mistake going into the corner.

That said you cannot let corner entry speed degrade corner exit speed. Slow in fast out is good for DE. However in race you need fast in and fast out. The challenge is that fast in done wrong means slow out. Getting it right is a very delicate balance.

M758

Jim,
Turn 1 at firebird main and Turn 2 at PIR. Same for turn 1 at miller. All require the downshift after turn in. Else you will be slow. If you try to downshift to the right gear going straight you will either overrev the motor or be just plain slow.

Granted changing gears in corner is not ideal, but there are many place it is just required. That is on reason sequental boxes that blip the throttle are so handy. It make the downshift easier and more precise.

J richard

Joe,

Absolutely agree, but this thread is trailbraking 101, thats more of a 201 course...

I'm trying to break it down to minimize the confusion between straightline braking downshift/heel/toe/trailbrake/move my braking zone/oh **** i'm out of track... for folks just moving from straightline braking into trailbraking they need to understand the basic principal, then you build on that...

See you saturday, going to be an early one....

utkinpol

I see (or I hope i do).
Down shifting to 4th gets done as at no time you should be in a turn with constantly depressed clutch, is it correct? I just got a feel from that section you never go on gas while on 4th gear, correct?
Very interesting read, thanks. It will probably take ages before I will be able to work clutch in a corner without upsetting the car, for now it is not in any plans at all. I had a constant struggle at NHMS trying to understand just on mental level where exactly in those 1-2b corners up and down shifting supposedly should be done, as even with not doing any of it there and flowing steadily through on 3rd gear it was obvious that car will fly aside easily if any mistake is done there. Not all the corners are same obviously, but, still, thanks for the explanation.

M758

Yeah early. I plan to be there at 5am. Leaving the house at 4am. DAMN!

utkinpol

what do you think of PDK cars on a track? i have heard somebody saying that in some cases PDK does not really downshift exactly when button is pressed.
It wsa quite interesting to read W.Roehl interview stating that he did run around ring with PDK in fully automatic mode and it resulted nearly close to his time with manual shifting - so, is it really something close to reality and people are actually able to run around track using advanced techniques with PDK in fully automatic mode? Not if I would ever had car with it, but, who knows.
Essentially - can PDK efficiently downshift in a corner without upsetting the car?

Larry Herman

That's just too early to go racing. Wake me up at 9.

J richard

naw its easy, I'm asleep at the wheel, ask anyone I've been on the track with...

M758

We enter the turn in 5th gear and must exit in 3rd gear. So we have to go through 4th. You can skip 4th and go directly to 3rd. However it can be harder to rev match for 3rd and not overrev the motor by putting the car in too low a gear for the road speed you are traveling. The key is timing it all just right. It take lots of practice to get perfect downsifts in straight line. Doing while cornering is even harder as you also need to keep brake pressure where you need it. Then throw into the mix that you may be side by side with another car making a racing pass is just one level. To be proficent at both downshifting and trail braking you need to do it without thinking. This means you are not metally focused on the gear changes or braking. This gives you the metal capacity to work on racing.

Now clearly if are only going to DE you don't need to get to this level, but it is the level every solid racer needs to be at.

As for the clutch it should always been engaged unles your are actually moving from one gear to th next. Never hold it down for anything more than a second or so. The except is a spin where you want to go both feet in. Of course when do to that you are not trying to be fast, but just limit the damage.

Heel and toe took me about a year to learn. Most drivng on the street and thinking about each down shift and getting it perfect. The best place to practice is when you are making a right turn with a green light. Slow the car in straight line and just before you turn and before you get off the brakes heel and toe to 2nd gear. Then turn floor it. Ok becareful flooring it, but you get the ideal. You will make mistakes so just leave room for this. Heel and toe on street is harder than the track also. This because the brake is proabbly too high to hit the gas smoothly. On the track you are braking harder so the pedals line up better. Same thing for the blip. On the street you don't enter a corner at 4500 rpm so giving it enough throttle can be hard. Still you can pracitce heel and toe multiple times a day every day. You just can't do that on track. Once you get the hang if it start on the track and just make sure you leave room to get ti down and room incease you mess up and miss the corner.

In any event a down change should be so smooth a passenger would not feel it occuring. If their head jerks forward it still too rough. So practice practice practice. It takes time.

M758

I have never driven one. The two shafts should make for fast downshifts. I do know that F1 boxes chagne gear very quck and that allows them to do 5-6 downshifts in a corner if needed. Very trick stuff. The PDK has the potential to be very good, but it all comes down it being street progamming first. Good on the street does not equal good on the track. Just like early ABS which was most slower on the track than good manual sytem. However as ABS advanced most performance street cars will brake better even on the track with ABS.

M758

We will be headed home at 9am. BTW.. when it is 80F at 6am , 100F at 10am and 110 at 3pm getting it done early just seems like the only sane way.

Larry Herman

The PDK makes lightning upshifts because it pre-selects the next gear up, and only has to switch clutches. The downshifts are a good bit slower, but still acceptable as compared to a manual. It will delay the downshift if your revs are too high for the next lower gear.

Larry Herman

Yeah, but it's a dry heat.

M758

not in a racing suit it is not!