Track driving - ABS
02-26-2023, 12:05 PM
#46
Rennlist Member
Quote by GT3Laguna…’ That said, if you're in an emergency situation where say you have to stop as fast as possible on the freeway to avoid an accident, then yes, smash the pedal all the way down and use the **** out of ABS. none of the benefits of non abs braking exist in that scenario.
From my understanding, (and I could be very wrong) ABS braking in an emergency situation, is designed to allow the most inexperienced driver to keep control of the car and brake in the shortest possible time. Key words here are “allow the most inexperienced driver to keep control of the car”. Personally I feel I can stop/slow down a car faster without getting in to the ABS. I don’t like the way the pedal feels, I don’t like the way car feels when ABS is activated.
https://speedsecrets.com/ask-ross/sh...-on-the-track/
I copied this link from another thread. Looks like we all have our opinions and that’s “ok’ speaking for myself, I try to learn something new every time I’m on the track and use what works best for me.
From my understanding, (and I could be very wrong) ABS braking in an emergency situation, is designed to allow the most inexperienced driver to keep control of the car and brake in the shortest possible time. Key words here are “allow the most inexperienced driver to keep control of the car”. Personally I feel I can stop/slow down a car faster without getting in to the ABS. I don’t like the way the pedal feels, I don’t like the way car feels when ABS is activated.
https://speedsecrets.com/ask-ross/sh...-on-the-track/
I copied this link from another thread. Looks like we all have our opinions and that’s “ok’ speaking for myself, I try to learn something new every time I’m on the track and use what works best for me.
it takes a lot of seat time to be at near max deceleration and also stay out of ABS…seat time and experience you normally do not aquire via street driving - even decades…
Last edited by daveo4porsche; 02-26-2023 at 12:06 PM.
02-28-2023, 10:38 AM
#47
Rennlist Member
With RWS TC and SC (I never turned it off) its not critical, but there is a lot of lap time in true full on braking (pedal to the floor) where the track allows straight line braking (Work up to it and stay a bit extra away from the edge of the track), just take two 0.1Secs to get to full application and off into the turn in part of the corner. There is no longer a lot of trail brake needed with RWS, so adjust depending on the corner. Its cheating but its faster.
11-04-2023, 03:43 PM
#48
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Not to brag but for credibility - I race in a very competitive amateur series and can turn in laps within 0.2s/minute of my pro coach, who is an active pro racer with numerous wins. I review data after practically every day of driving and log everything up to the individual wheel and tire temps and corner heights under load, and generally know what each metric means for car setup or driving technique.
Here is a summary of ABS on track based on everything I've learned so far (applies to the 991 or newer GT3 ABS - older ones were not as good).
1. In a straight line and steady state, ABS will stop the car faster than a human, even at threshold-braking. Getting into ABS during straight-line braking will be the most efficient way to brake. It's easy to prove by data. Even if you can perfectly put the pedal pressure at just before the lockup level (most people can't - they just brake too lightly so ABS does not engage), the problem is that grip changes and the balance of grip between axles changes over time, triggering ABS & EBD. So completely avoiding ABS reaction inevitably means that you are leaving braking force on the table. But there is a catch.
2. Engaging ABS has a cost - brake pads can wear faster or even crumble if worn/overheated due to vibration, and can also leave uneven deposits - many have seen multiple overlapping "stamp imprints" of a brake pad on a rotor - that's typically what a result of ABS action with overheated pad looks like. It may cause vibrations and uneven braking in the future.
3. You do not want to engage ABS during weight transfer. For example, if you slam the brakes so quickly the front wheels start to lock up before the weight transfers to them, ABS will engage prematurely and not allow full brake pressure to build up, which will reduce deceleration and delay the weight transfer, creating a kind of a negative feedback loop.
4. Always make sure you are out of ABS sufficiently before the turn-in point. The problem with ABS is that it prevents knowing exactly how far beyond the threshold you are - you could be pushing the pedal 1% stronger than threshold or 50% - it will feel the same. And when you start turning in and gradually releasing the brake, you need to index the brake release from the threshold. Let's say you know you need to be at 60-70% of the threshold the moment you start turning in. If you are in ABS, you will have no idea whether you need to reduce the pressure by 30% or by 60% because you cannot feel how far past the threshold you are pushing into the ABS zone. So it's important to be out of ABS and feeling the brakes before starting to blend braking and turning, and not get into ABS while turning (that usually just does not work well, too long to explain why).
5. Some anomalies of track surface can make ABS suboptimal even in the straight line - typically it happens when one wheel gets very unweighted or in the air, so it does not provide braking force, and that creates a force that rotates the car (on one side two wheels brake but on the otherside only one). ABS/EBD will try to compensate for this force to avoid rotation or spin, but that may be counter to the driver's intention. In such cases I would not go into ABS if possible or turn it off. But if that happens, you will know exactly where it happens - it's noticeable.
So, unless there are special circumstances, I would drive an ABS car like this:
- Quick but gradual brake application, making sure ABS does not engage before the weight transfer completes (it is very quick, though in the 992 generation and especially in the RS)
- During straight-line braking, feel free to (gently) dip into ABS for best performance (unless brakes are starting to get greasy due to pads overheating). If anything, it's a good way to understand where the threshold is - otherwise, how will you know? In non-abs cars, racers slightly lock up wheels during warm-up to know, for example. In ABS cars, you dip into ABS.
- Before turn-in point, make sure to release brakes enough to not be activating ABS, and releases brakes during trail-braking quickly enough so that ABS does not kick in then either.
- If there is a specific place where ABS engages unusually early, try the threshold braking there and see if it's better.
Some other caveats:
- Stability control sometimes vibrates the brake pedal too, so vibration can be not ABS but stability control. You do not want that type of vibration.
- Long ABS engagement feels like brake fluid overheating - pedal becoming soft and going toward the floor. That's ABS reducing pressure rather than fluid overheating, although it feels very similar. ABS does not put more heat into pads or rotors but can have a similar negative effect on brake feel when overused.
Here is a summary of ABS on track based on everything I've learned so far (applies to the 991 or newer GT3 ABS - older ones were not as good).
1. In a straight line and steady state, ABS will stop the car faster than a human, even at threshold-braking. Getting into ABS during straight-line braking will be the most efficient way to brake. It's easy to prove by data. Even if you can perfectly put the pedal pressure at just before the lockup level (most people can't - they just brake too lightly so ABS does not engage), the problem is that grip changes and the balance of grip between axles changes over time, triggering ABS & EBD. So completely avoiding ABS reaction inevitably means that you are leaving braking force on the table. But there is a catch.
2. Engaging ABS has a cost - brake pads can wear faster or even crumble if worn/overheated due to vibration, and can also leave uneven deposits - many have seen multiple overlapping "stamp imprints" of a brake pad on a rotor - that's typically what a result of ABS action with overheated pad looks like. It may cause vibrations and uneven braking in the future.
3. You do not want to engage ABS during weight transfer. For example, if you slam the brakes so quickly the front wheels start to lock up before the weight transfers to them, ABS will engage prematurely and not allow full brake pressure to build up, which will reduce deceleration and delay the weight transfer, creating a kind of a negative feedback loop.
4. Always make sure you are out of ABS sufficiently before the turn-in point. The problem with ABS is that it prevents knowing exactly how far beyond the threshold you are - you could be pushing the pedal 1% stronger than threshold or 50% - it will feel the same. And when you start turning in and gradually releasing the brake, you need to index the brake release from the threshold. Let's say you know you need to be at 60-70% of the threshold the moment you start turning in. If you are in ABS, you will have no idea whether you need to reduce the pressure by 30% or by 60% because you cannot feel how far past the threshold you are pushing into the ABS zone. So it's important to be out of ABS and feeling the brakes before starting to blend braking and turning, and not get into ABS while turning (that usually just does not work well, too long to explain why).
5. Some anomalies of track surface can make ABS suboptimal even in the straight line - typically it happens when one wheel gets very unweighted or in the air, so it does not provide braking force, and that creates a force that rotates the car (on one side two wheels brake but on the otherside only one). ABS/EBD will try to compensate for this force to avoid rotation or spin, but that may be counter to the driver's intention. In such cases I would not go into ABS if possible or turn it off. But if that happens, you will know exactly where it happens - it's noticeable.
So, unless there are special circumstances, I would drive an ABS car like this:
- Quick but gradual brake application, making sure ABS does not engage before the weight transfer completes (it is very quick, though in the 992 generation and especially in the RS)
- During straight-line braking, feel free to (gently) dip into ABS for best performance (unless brakes are starting to get greasy due to pads overheating). If anything, it's a good way to understand where the threshold is - otherwise, how will you know? In non-abs cars, racers slightly lock up wheels during warm-up to know, for example. In ABS cars, you dip into ABS.
- Before turn-in point, make sure to release brakes enough to not be activating ABS, and releases brakes during trail-braking quickly enough so that ABS does not kick in then either.
- If there is a specific place where ABS engages unusually early, try the threshold braking there and see if it's better.
Some other caveats:
- Stability control sometimes vibrates the brake pedal too, so vibration can be not ABS but stability control. You do not want that type of vibration.
- Long ABS engagement feels like brake fluid overheating - pedal becoming soft and going toward the floor. That's ABS reducing pressure rather than fluid overheating, although it feels very similar. ABS does not put more heat into pads or rotors but can have a similar negative effect on brake feel when overused.
By wheel speed analysis or is there something more straight forward?
11-04-2023, 08:45 PM
#49
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You should be able to feel it in real time - it pulsates the pedal. On the data, I don't remember already what GT3 allows to log - in some cars there is ABS channel, but more often it's pressure per calliper or wheel speed. Pressure per calliper is also great for seeing ESC/TC interventions.
11-04-2023, 09:01 PM
#50
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You should be able to feel it in real time - it pulsates the pedal. On the data, I don't remember already what GT3 allows to log - in some cars there is ABS channel, but more often it's pressure per calliper or wheel speed. Pressure per calliper is also great for seeing ESC/TC interventions.