Advise on Trail Braking

[kurquhart]

Question for a Steve or others?
This happened when I instructed a 996 driver at an AX.
It seemed if both the brake and throttle were applied on occasion the computer would override my open throttle request and return the engine to idle?
The owner warned me of this tendency before my left foot brake demonstration and during the lap it happened once maybe twice.
Later I was able to recreate the abrupt drop to idle while left foot braking in some tight 2nd gear circles.
Is this a common concern when left foot braking newer ABS equiped street cars?

On my 997, if I am on the throttle and apply the brakes at the same time then the throttle will close. Conversely, if I am on the brakes and apply the throttle then heel/toe works just fine.

I think it is more related to e-throttle than ABS; my 964 has ABS and it doesn't object if I apply both throttle and brakes at the same time.

[kurquhart]

Re "trail braking" does "Lrayner" have ABS?
I was just looking at some video from our POC races at Las Vegas this last weekend (the inside track)and watching as guys with ABS were killing me trail braking deep into the corners.
If Lrayner has ABS, trail braking is not a big deal and should be done.
JP

That's interesting: I was under the impression that a competent driver could stop faster w/o ABS. What generation cars (996?) were you watching? On my 964, if ABS kicks in then I have blown the corner; there is no way I would do it on purpose.

[Dan Chambers]

I was under the impression that a competent driver could stop faster w/o ABS. What generation cars (996?) were you watching? On my 964, if ABS kicks in then I have blown the corner; there is no way I would do it on purpose.

Kris, I think you're on to something here. It has been my observation that ABS tends to lenghten the stopping distance, and make braking less efficient while maintaining steering control (anti-skid?). So ... if you go into a braking zone really hot and ABS kicks in, do you wind up "extending" your braking zone/braking area while additionally extending you braking "time" on the pedal ... thus 'blowing' the corner?

As to ABS and "Trail-braking:" I can see in theory that ABS could be helpful in Trail-Braking since the rear-tires can get a bit squirrelly/loose in some cars when trail-braking. My '87 944 didn't have ABS or LSD (it was a TBD, and thus 'open' when braking) and trail-braking was a real trick. Jad/Kris/Mike/Steve: does ABS aid in trail-braking? Leigh, do you have ABS in your 944S?

[993Panzer]

I was under the impression that a competent driver could stop faster w/o ABS. What generation cars (996?) were you watching? On my 964, if ABS kicks in then I have blown the corner; there is no way I would do it on purpose.

Kris, I think you're on to something here. It has been my observation that ABS tends to lenghten the stopping distance, and make braking less efficient while maintaining steering control (anti-skid?). So ... if you go into a braking zone really hot and ABS kicks in, do you wind up "extending" your braking zone/braking area while additionally extending you braking "time" on the pedal ... thus 'blowing' the corner?

As to ABS and "Trail-braking:" I can see in theory that ABS could be helpful in Trail-Braking since the rear-tires can get a bit squirrelly/loose in some cars when trail-braking. My '87 944 didn't have ABS or LSD (it was a TBD, and thus 'open' when braking) and trail-braking was a real trick. Jad/Kris/Mike/Steve: does ABS aid in trail-braking? Leigh, do you have ABS in your 944S?

Guys,

ABS is there to stop you safer, not quicker. I try to get as close to engaging ABS as possible without engaging it to get maximum braking out of my car. If I hit the ABS I've blown the corner just like Kris stated. ABS keeps us from flat spotting tires. Yes you can turn with ABS engaged but I wouldn't recommend making a habit out of it.

[lrayner]

I deny having ABS or being competent. My 944 S doesn't have ABS and my "new" 924 S spec. or GP (?) car that I am bringing to Streets doesn't either.

Now I just want to be within earshot of all these technique talks at the track. I think, as Jad suggested earlier, trail braking into the curve of the corner is a natural progression. I just need to be more aware of the interplay of the throttle, brakes, speed etc. Finesse is not a natural part of my vocabulary and much of this dialog is focused on subtle adjustments that undoubtedly add up to seconds.
My new excuse for being slow is that I am focusing on some new techniques in my new car, rather than just on going fast Thanks for all your help... I think

[Jad]

From my research and experience, an expert driver in good conditions could outbrake ABS from the 80's early 90's. I do not believe anyone can outbrake modern ABS under any normal circumstances even in a straight line, let alone on a rough track while turning.

This is supported by the fact most races series, if they allow ABS, add at least 100 lbs to the car showing the value of ABS even amoung professional drivers.

Oh, and you save expensive tires while comfortably braking at the limit, something you can't do without ABS and thus very few non-ABS cars brake anywhere near their limit.

[Irksome]

Question for a Steve or others?
This happened when I instructed a 996 driver at an AX.
It seemed if both the brake and throttle were applied on occasion the computer would override my open throttle request and return the engine to idle?
The owner warned me of this tendency before my left foot brake demonstration and during the lap it happened once maybe twice.
Later I was able to recreate the abrupt drop to idle while left foot braking in some tight 2nd gear circles.
Is this a common concern when left foot braking newer ABS equiped street cars?

On my 997, if I am on the throttle and apply the brakes at the same time then the throttle will close. Conversely, if I am on the brakes and apply the throttle then heel/toe works just fine.

I think it is more related to e-throttle than ABS; my 964 has ABS and it doesn't object if I apply both throttle and brakes at the same time.

On my 2003 996 I definitely have this behavior. It freaked me out when I drove around the block to dry out my brakes after working on cleaning my wheels, and I wanted to hold the brakes on (gently) and compensate with the gas, and learned that it can't be done! I've tried at various speeds, and I'm pretty sure that my car makes it impossible to be on the gas while braking. You can stomp that pedal down as far as you want, you're still getting idle.

Since it happens at conditions where ABS is not engaged, I assume it is not related to ABS. It also is unaffected by turning off PSM. I suspect it is purely an egas thing. I bet I could fake it out by removing the brake sensor (keep it permanently off), but I think that might also mess with ABS and/or PSM, so I'll just live without the two-foot technique.

[gulf911]

From my research and experience, an expert driver in good conditions could outbrake ABS from the 80's early 90's. I do not believe anyone can outbrake modern ABS under any normal circumstances even in a straight line, let alone on a rough track while turning.

This is supported by the fact most races series, if they allow ABS, add at least 100 lbs to the car showing the value of ABS even amoung professional drivers.

Oh, and you save expensive tires while comfortably braking at the limit, something you can't do without ABS and thus very few non-ABS cars brake anywhere near their limit.

Jad is correct... ... after watching many video's of POC races, I beleive it was Greg Franz car, he would blow by cars without ABS before the corner because he could brake so much later by standing on the brakes. It wasn't trail braking , but just able to brake much later. I also saw a race with a 997cup vs 996cup , the 997cup did not have ABS and the 996 car would reel him in at every corner.

[Jad]

Jad is correct...

There is a quote I never expected from you!

You going to Streets next weekend to get beat?

[kurquhart]

Jad is correct... ... after watching many video's of POC races, I beleive it was Greg Franz car, he would blow by cars without ABS before the corner because he could brake so much later by standing on the brakes. It wasn't trail braking , but just able to brake much later. I also saw a race with a 997cup vs 996cup , the 997cup did not have ABS and the 996 car would reel him in at every corner.

I am sure that ABS technology has advanced since the 964 (which doesn't even differentiate between the two rear wheels).

[gulf911]

Jad is correct...

There is a quote I never expected from you!

You going to Streets next weekend to get beat?

I haven't even got my free tires yet... Still waiting to see if Kumho releases the new size that was supposed to arrive in january..

For now I'll have to have you try and beat my practice time of 1:29 a few years ago, before I installed the new gears , suspension, wing or 710's....

[Dan Chambers]

I haven't even got my free tires yet... Still waiting to see if Kumho releases the new size that was supposed to arrive in january..

For now I'll have to have you try and beat my practice time of 1:29 a few years ago, before I installed the new gears , suspension, wing or 710's....

Dan A.: Tisk Tisk. You should have been more conservative with my tires at the DE day (yeah ... your avatar speaks volumes). One less lap "smokin' someone else's tires" would have granted you another set of freebies for Streets .... at least for practice laps. Don't get me wrong; the avatar picture is nice.... I think the laps on someone else's tires at Streets would have been even better.

We'll miss you.

[bibbetson]

From my research and experience, an expert driver in good conditions could outbrake ABS from the 80's early 90's. I do not believe anyone can outbrake modern ABS under any normal circumstances even in a straight line, let alone on a rough track while turning.

As you stated previously Jad, I trail brake a LOT, probably more than I should and I have been trying to break the habit a bit because I was slowing the car more than I really needed to. That said, I've experimented with the ABS on my car many times and there is no doubt that if the ABS kicks in under hard braking, I'm screwed as the braking distances are much longer with ABS engaged. I've noticed this much more in the past year with good race pads but it could be that my threshold braking has improved. Whatever the reason, as others have said, if ABS kicks in, the corner is blown.

My comments should not be confused with using ABS in trail braking. There it's a godsend and saves lots of tire money.

[Jad]

A very common problem with ABS, is also driver error. ABS is not an on/off thing as many people treat it. With ABS you often have 1 tire locking up and you feel the ABS pulse and decide you are at the limit. This is not true, it just means THAT tire is at the limit and pushing the brakes harder will provide additional braking power at the other wheels. This is especially true or evident in spins where the rear brakes may become the front and vice versa. The front brakes (now in back) lock much earlier and the ABS activates on those wheels well before the rears (now in front) lock, so if you don't press even harder on the brakes, you will not stop very fast.

This is not to imply older cars don't take a lot further to stop once the ABS kicks in. My old 964 was terrible once the ABS kicked in, but in the turbo and the 996's I have not experienced it.

[pdy]

ABS is there to balance the braking forces between wheels, and prevent lockup of one wheel (the one with the least traction). Period.

I suspect that if one activates ABS immediately when initiating braking, it indicates being less than smooth with the pedal. Jabbing the brake pedal will
cause the car to become unsettled and lead to a large difference in grip ability (traction) between the four tires. The ABS is compensationg for this
difference due to the unsettled attitude the driver has induced.

OTOH, after initial application of the brakes, activating the ABS might not be all bad. If the car has already hunkered down and is firmly planted
and stable, the ABS is merely fine-tuning the slight traction differences between the four tires (and their local road surfaces). The ABS activation at
this (stable) point may actually indicate that the optimum (or close) braking force has been realized.