NSX brakes - disable ABS or not?

[randalfo]

I have a 1991 NSX that was prepped for the track and has four pot Brembo brakes all around. I didn't put these brakes on the car and it does quite well most of the time hauling the car down from speed. However, many times the ABS system kicks in at times that seem unwarranted, and the sensation of losing braking power can be pretty unnerving.

Has anyone had any experience with running a track NSX after the ABS has been disabled, and secondly, does anyone know what the correct way to disable the ABS system is?

thanks

 

[stuntman]

I have a 1991 NSX that was prepped for the track and has four pot Brembo brakes all around. I didn't put these brakes on the car and it does quite well most of the time hauling the car down from speed. However, many times the ABS system kicks in at times that seem unwarranted, and the sensation of losing braking power can be pretty unnerving.

Has anyone had any experience with running a track NSX after the ABS has been disabled, and secondly, does anyone know what the correct way to disable the ABS system is?

thanks

I am going to assume you have the off-the-shelf Brembo Lotus caliper kit front and rear...

Also assuming you have the same brake pads front and rear you may find the car has a little more rear brake bias than stock - could be the reason for engaging ABS sooner than normal, because the rears are trying to lock a little earlier than they were set up to be stock. If you have this pre-engagement of ABS, it also could be attributed to going over a bumpy road, or a bump that when under braking, will trigger ABS even under light applications - huge problem with ABS in general and especially on older systems -like the NSX.

You can just pull a fuse (look it up in the manual) for the ABS pump and then you disabled abs (and traction control). I'd recommend playing with this on a track where you wont have a likelyhood of crashing your car or into another car/person. The more experience you have/from practice/-best comes from practice after learning what to practice from a good racing school (www.skipbarber.com) the better you'll be at braking w/o ABS - and when trained correctly you can brake better than ABS.

 

[nsxtasy]

You can also disable ABS by pulling the parking brake up one click. The warning light should go on. You will need to do this any time you start the car, as it gets reset when you turn it off.

In general, you shouldn't be engaging ABS on the track; you can maximize your braking performance by "threshold braking", i.e. braking just at the threshold of locking up the tires, but not past it - in which case, the ABS shouldn't be activating. However, if (as stuntman notes) your front/rear brake bias is too far off due to your aftermarket setup, you may be getting into ABS as a result; if so, I recommend installing a proportioning valve to adjust the bias, front vs rear.

 

[95EagleAWD]

I dunno, the whole point of ABS is so you can slam the pedal to the ground and let the system do the hard work for you.

Identical cars, one with ABS and one without, the one with ABS will ALWAYS stop sooner than the one without.

 

[thouchin]

I dunno, the whole point of ABS is so you can slam the pedal to the ground and let the system do the hard work for you.

Identical cars, one with ABS and one without, the one with ABS will ALWAYS stop sooner than the one without.

 

[L8apex32]

I dunno, the whole point of ABS is so you can slam the pedal to the ground and let the system do the hard work for you.

Identical cars, one with ABS and one without, the one with ABS will ALWAYS stop sooner than the one without.

Got any proof?

ABS was primarily built to assist drivers in maintaining (steering) control while in a panic-stop situation. Not all ABS units are high performance.

 

[Nihilation]

Unless you are a very skilled driver ABS will always allow you to brake in a shorter distance than a non-ABS equipped car simply because you're not loosing as much traction in the event that you do lock up several tires and skid. As a result of the ABS system working properly your tires stay nice and round. :biggrin:

Maybe it's better to think of ABS as an enhancement for threshold braking. Let's think about it. That's what using ABS on a track is, it's safely stepping over that line found between riding the limit of your tires under braking and well... an unplanned off course excursion.

 

[docjohn]

I played with disabling abs and power steering on my 96 for one track season,did'nt seem to make a significant difference in my enjoyment so I now now leave them on.Try it yourself and let us know how it feels to you.

 

[stuntman]

Identical cars, one with ABS and one without, the one with ABS will ALWAYS stop sooner than the one without.

100% false. Although modern ABS systems (NSX is not modern) are quite good, a skilled driver with enough practice and feel CAN stop sooner than ABS.

ABS should be renamed as the "Ability to Brake and Steer". The ABS pump pulsates causing the tire to very briefly lock, then unlock, then lock again. Although pretty efficient, their is still room left on the table. Whenever you lock a tire, even for a brief moment, you lose grip. By threshold braking, you are not upsetting or shocking the brake system and also keeping the tire right before lockup - which is the most effective way to slow the car down.

The "Ability to Brake and Steer" should be the acronym because the primary goal of ABS is to allow you to slam on the brakes while trying to avoid an obstacle. In most panic situations, the driver will tend to attempt to avoid a crash while slamming on the brakes. Without ABS, this input will cause the tires to lock, you don't slow down quickly, and you understeer straight into the object you were trying to avoid. ABS allows you to change the direction of the car (turn/steer) while slamming on the brakes. Although very inefficient, the ABS pump is trying to allow the tire to have enough grip to brake and turn at the same time (keep in mind a tire can only do 100% of one thing).

Unless you are a very skilled driver ABS will always allow you to brake in a shorter distance than a non-ABS equipped car simply because you're not loosing as much traction in the event that you do lock up several tires and skid. As a result of the ABS system working properly your tires stay nice and round. :biggrin:

Maybe it's better to think of ABS as an enhancement for threshold braking. Let's think about it. That's what using ABS on a track is, it's safely stepping over that line found between riding the limit of your tires under braking and well... an unplanned off course excursion.

Skip Barber teaches you how to stop in a shorter distance than ABS, and most of my students are able to do this after the exercise. Does that mean they are better off w/o ABS? -no, but they were ABLE to stop sooner.

 

[nsxtasy]

100% false. Although modern ABS systems (NSX is not modern) are quite good, a skilled driver with enough practice and feel CAN stop sooner than ABS.

ABS should be renamed as the "Ability to Brake and Steer". The ABS pump pulsates causing the tire to very briefly lock, then unlock, then lock again. Although pretty efficient, their is still room left on the table. Whenever you lock a tire, even for a brief moment, you lose grip. By threshold braking, you are not upsetting or shocking the brake system and also keeping the tire right before lockup - which is the most effective way to slow the car down.

The "Ability to Brake and Steer" should be the acronym because the primary goal of ABS is to allow you to slam on the brakes while trying to avoid an obstacle. In most panic situations, the driver will tend to attempt to avoid a crash while slamming on the brakes. Without ABS, this input will cause the tires to lock, you don't slow down quickly, and you understeer straight into the object you were trying to avoid. ABS allows you to change the direction of the car (turn/steer) while slamming on the brakes. Although very inefficient, the ABS pump is trying to allow the tire to have enough grip to brake and turn at the same time (keep in mind a tire can only do 100% of one thing).

That's an excellent description.

In addition to the situation of slamming on the brakes in a panic stop - the typical situation and response for accident avoidance - it's also worth noting that ABS is also particularly effective for maintaining the ability to steer while braking on slick surfaces, such as roads covered with rain, snow, or ice. As difficult as it is to achieve true threshold braking without ABS on dry pavement, it's that much more difficult to do so on wet/slippery surfaces. (I bet most of us have unintentionally activated the ABS in rain, sometimes without even slamming on the brakes.)

 

[Tanto2]

Some very good posts, thank you all! I'd still like to hear from those track only folks (at least those that are running tire sizes that allow). Are you guys using it? My experience that has REALLY colored me: Back when my car was a baby, I was speeding a bit and hit the brakes at about 80 coming up to an intersection on a road that had been repaved a week earlier. Two or more of the wheels did not take for I'd guess 25-30 feet and I went into the intersection and was just lucky no one else was in that space. Scared the hell out of me. It happened a 1/2 mile from my house, so I walked over and inspected the road. It was extremely clean with just a very few 1/4" asphalt pebbles here and there. If the ABS would have been off, I might have a pebble or two stuck in my tires, but I would have stopped in time.(disclaimer-I'm not suggesting anyone disable-just my one very strong experience). In 14 years I have not repeated that, but what if you live in the country with gravely roads? Scares me. So for me it's either disable or try the late model unit? My search did not show anyone saying the late unit is significantly better. Comments? TIA

 

[nsxtasy]

I'd still like to hear from those track only folks (at least those that are running tire sizes that allow). Are you guys using it?

My car is extensively tracked, but still streetable, and I drive it to and from the track (over 12K actual track miles out of 70K total). I leave my ABS connected at all times; I use the dash button to switch off the TCS while on the track. (I don't drive on the track in the rain.) I rarely engage the ABS, either on the street or on the track, other than once in a while intentionally to prevent the ABS solenoids from sticking from lack of use. Every once in a great while, either on the street or on the track, ABS activates, and usually it's a good reminder to me that I am using too much brake and causing the tires to lose traction. Every once in an even greater while, I will face a "panic stop" (sudden stop) situation, and if I engage the ABS, I am usually grateful for the ability to steer.

 

[L8apex32]

I have many track miles in my NSX. At frist, I'd always disable it by pulling the parking brake up one click (until the light comes on), then driving for 20 seconds or so, which then disables the ABS and activates a light, then unsetting the parking brake (to 0 clicks).

And, this was fine. But, recently I had not been on the track in a while (in an NSX anyway) and thought that since I had new pads and new tires I didn't want to flat spot, that I'd leave the ABS on.

That was 4 events ago. Even though I brake hard, I still don't often get lock up and, when I do, I'm ok with the stock ABS peformance in this situation.

If I had rear heavy brake bias, perhaps due to a brake "upgrade", I'd sure as heck leave the ABS on. Rear lock up is normally worse than front lock up and I'd choose to avoid it. (And, as NSXTASY said, if you have rear brake bias because of an "upgrade", the "upgrade" should have come with brake bias control.)

 

[Tanto2]

[QUOTEIf I had rear heavy brake bias, )[/QUOTE]

I do understand your comments, but this begs a couple of other academic question I've been wondering about the stock configuration: Does the NSX HAVE a slight front bias ?(perhaps for safety) because the NSX fronts seem to take more braking burden than other mid engine cars I've owned. It's real hard to get the rears to lock. The other question nagging me is: If you were comparing a driver with poor abilities (or any of us say on a bad day) stomping and staying at say 130 plus (and of course you wouldn't WANT to do this), would the abs NSX or the non version stay straighter and thus safer. 100% of magazine articles and I'm sure the designers will tell us that that is exactly where abs would shine. But, I've never read anyone who has actually tried it, and since we've all probably experienced considerable and ripid when back or forth motions when different wheels are catching, I've always thought "gee-I don't think I'd want to do that at high speed? Anyone have those big ones and tried it? Thanks

 

[stuntman]

If you were comparing a driver with poor abilities (or any of us say on a bad day) stomping and staying at say 130 plus (and of course you wouldn't WANT to do this), would the abs NSX or the non version stay straighter and thus safer. 100% of magazine articles and I'm sure the designers will tell us that that is exactly where abs would shine. But, I've never read anyone who has actually tried it, and since we've all probably experienced considerable and ripid when back or forth motions when different wheels are catching, I've always thought "gee-I don't think I'd want to do that at high speed? Anyone have those big ones and tried it? Thanks

No matter how hard you hit the brakes at 130, ABS or not, you will not lock a tire, unless you have something seriously wrong (100% bias going to the rear). ABS only engages when you are on the verge of/locking your wheels, which wont happen at those speeds.

As you slow down into the 70mph and below speeds, thats where you would start to see lockup.

 

[thouchin]

No matter how hard you hit the brakes at 130, ABS or not, you will not lock a tire, unless you have something seriously wrong (100% bias going to the rear).

I understand this completely when you are driving a car with downforce. With a street car, however, you generally have lift at that speed (or possibly a slight amount of downforce). The normal force on the tire is the not much difference than at 70mph. So the only thing that could not allow lockup is the friction of the brakes being less. I didnt realise this had much variance with speed....

Please explain.

T.J.

 

[stuntman]

I understand this completely when you are driving a car with downforce. With a street car, however, you generally have lift at that speed (or possibly a slight amount of downforce). The normal force on the tire is the not much difference than at 70mph. So the only thing that could not allow lockup is the friction of the brakes being less. I didnt realise this had much variance with speed....

Please explain.

T.J.

A lot of cars I drive don't have downforce. The little orange fireball dosn't have ANY aero :wink:

Simple. It is harder to stop a moving/spinning object the faster it is going. The higher the speed, the harder it is to lock/stop anything.

ex.) Take the wheel/tire off your car, roll it down the driveway and stop it (5-10mph). Now roll it down the street (20-30mph) and try to stop it. -It takes more energy/force to stop the wheel/tire the faster it is going.

Mathematically: With all things constant, if it requires 500psi if brake pressure to lock a tire while traveling 40mph, 500psi at 140 is not going to slow you down much. Brake pressures of over 1,500psi will not lock a tire at 140mph, but at 40 it would easily.

The faster you are going, their is more resistance and the harder it is to lock a tire.

 

[john@johnhudakracing]

Now roll it down the street (20-30mph) and try to stop it.

Ok Billy, now my neighbor at the end my cul-de-sac is seriously pissed. :smile: :biggrin:

 

[NSXDreamer2]

I've been driving my miata with no ABS in all weather. So it's not like I had no experience on threashold braking, but I'm no expert either. I had also driven many miles of my nsx with ABS on track.

What would you guys suggest of "trying" to drive without ABS?? I always wanted to try that but then I do think of myself engaging ABS more than couple times that actually saved me...

 

[thouchin]

A lot of cars I drive don't have downforce. The little orange fireball dosn't have ANY aero :wink:

Simple. It is harder to stop a moving/spinning object the faster it is going. The higher the speed, the harder it is to lock/stop anything.

Angular momentum. damn, I feel really stupid now. For some reason I have never considered this. Thanks for the insight.

T.J.

 

[thouchin]

If the anti lock is not coming on, then it doesn't matter if you disable it or not. Its only when it activates and you become curious wether you could have stopped faster without it that you should even consider turning it off.

T.J.

 

[stuntman]

Ok Billy, now my neighbor at the end my cul-de-sac is seriously pissed. :smile: :biggrin:

See! It's harder to stop :tongue:

I've been driving my miata with no ABS in all weather. So it's not like I had no experience on threashold braking, but I'm no expert either. I had also driven many miles of my nsx with ABS on track.

What would you guys suggest of "trying" to drive without ABS?? I always wanted to try that but then I do think of myself engaging ABS more than couple times that actually saved me...

Why not track your miata - great track cars, and you'll also be able to see the pressure differences it takes to lock a tire with greater speeds. When you first apply the brakes at the end of a long straight (90-110mph in a miata), no matter how hard you initially apply the brakes, they wont lock, but if you keep that pressure, as you slow down, they'll become easier to lock. Which is why your initial stab/application you spike with a lot of brake pressure, then slowly relieve pressure as the car slows down (keeping the tires on the verge of lockup). =as you slow down, you have to relieve pressure, you cannot have the same pressure at 50mph as you do at 150mph.

If the anti lock is not coming on, then it doesn't matter if you disable it or not. Its only when it activates and you become curious wether you could have stopped faster without it that you should even consider turning it off.

T.J.

It is possible to out-brake ABS systems, especially the NSXs archaic system. Newer systems (like the S2000) are much better, are less intrusive and easier to drive around (and I'd actually prefer them over nothing). Not so much for the NSX...

 

[Tanto2]

Thanks stuntman and all, great input. I guess if you did tromp at 130, at some point, say 70 or so, my query might become relevant. After more thought though, I think my inherent predudice is that the idea of any UNEXPECTED YAW messes badly with the man/machine connection that we use to tell us how much traction(or sideforces to deal with) we have at any moment. The NSX is SOOO good at that, and then along comes that pesky computer messing with it. At 70 though I CAN see abs being an aid if it cycled faster(therefore a little less yaw). At 90 it sounds scary.

 

[stuntman]

Does the NSX HAVE a slight front bias ?(perhaps for safety) because the NSX fronts seem to take more braking burden than other mid engine cars I've owned. It's real hard to get the rears to lock. The other question nagging me is: If you were comparing a driver with poor abilities (or any of us say on a bad day) stomping and staying at say 130 plus (and of course you wouldn't WANT to do this), would the abs NSX or the non version stay straighter and thus safer. 100% of magazine articles and I'm sure the designers will tell us that that is exactly where abs would shine. But, I've never read anyone who has actually tried it, and since we've all probably experienced considerable and ripid when back or forth motions when different wheels are catching, I've always thought "gee-I don't think I'd want to do that at high speed? Anyone have those big ones and tried it? Thanks

Yes it has more front bias as all street cars do. It's much closer to even than most cars, but still retains the front-bias -all cars are set up to understeer/abs makes the car understeer, cars are designed with crumple-zones in the front and they want you to hit something head-first, not sideways.

The NSX with too much rear bias w/o ABS is not really a fun thing... If you upgrade to a BBK front and rear, a proportioning valve is recommended and also recommended someone who knows how to tune it, set it up for you. Regardless for street/racing use, it's better to have the fronts lock up slightly earlier than the rear, but the NSX can take advantage of more rear bias than a FR layout car...

 

[liftnot]

does anyone know or has anyone removed the abs system on the NSX? is it very involved?