What to do when ABS becomes too intrusive?

[BuickGN]

I've had enough of this with my TL. ABS has always been very conservative. I've been able to beat it by over 10' at 60mph by pulling the fuse. Now it seems as though it's becoming inconsistant on the same stretch of street, same surface. It kicks in but the car just doesn't want to stop fast. It just keeps going and going and going. I now have the awesome Nitto NTO5 on it. Sometimes it feels like it's going to put me through the windshield and sometimes if feels as if I'm on ice. Just to see if I was going crazy, I pulled the fuse to the ABS and I have tons of stopping power. I haven't measured again but I guarantee it's a 30' or greater difference.

Where do I start with this? There is no ABS light on. The dealer can't diagnose anything without a code so that's out. I may go back to the thinner 5.1 fluid which seemed to provide better ABS braking.

I'm wondering if I should start by replacing all of the wheel sensors or if it would be better to start with the pump iteslf.

I even thought that maybe it had to "learn" the sticky tires so I did a few ABS stops but of course no difference.

This isn't a matter of a small difference due to different surfaces. This is a massive difference and it's as if I'm on ice. The ABS is not allowing any pressure to the brakes. It used to pulse fast. Now it pulses at maybe half the rate it used to which is why I'm leaning toward the pump/actuator.

I have the new Wilwoods sitting here but I'm not about to install them without correcting this problem first.

Any help or direction would be greatly appreciated.

 

[Audi Junkie]

Pulling the fuse is commonly done by the Audi guys. You could test the input voltage to the unit from the sensors and re-wire it to a steady source of the same voltage to trick it...just an idea, better then removing the whole unit.

 

[BuickGN]

Originally Posted By: Audi Junkie
Pulling the fuse is commonly done by the Audi guys. You could test the input voltage to the unit from the sensors and re-wire it to a steady source of the same voltage to trick it...just an idea, better then removing the whole unit.


Do you guys also see noticably better braking without the ABS?

 

[chevrofreak]

I removed the ABS fuse in my Crown Vic, and my braking is much nicer. I have locked the tires up a few times on a panic stop, which sure slows the car in a hurry, even though it creates flat spots. I do usually reinstall the fuse for winter.

My car has a traction assist that applies brake pressure to reduce wheel spin. The only way to override it is by stepping on the brakes. Removing the fuse was a much easier alternative.

 

[Colt45ws]

On CVN dRock has a writeup on howto disable the trac control on the Aero Vics. Essentially route +12V to the "brake on" wire via a locking relay and install a diode to prevent the feed getting to the rest of the circuit. A simple press of a momentary on button (that can be sourced from a newer ford for that factory look) locks the relay on so the trac control thinks the brake is on.
I do get annoyed when I am trying to stop and hit a bump and the ABS goes wacko.

 

[moribundman]

Originally Posted By: BuickGN
Originally Posted By: Audi Junkie
Pulling the fuse is commonly done by the Audi guys. You could test the input voltage to the unit from the sensors and re-wire it to a steady source of the same voltage to trick it...just an idea, better then removing the whole unit.


Do you guys also see noticably better braking without the ABS?


I used to drive (and still do frequently drive) plenty cars without ABS, so I have something to compare. The average driver with average attention and skills is better off with ABS in most situations. A competent driver can easily achieve shorter stopping distances, even during evasive maneuvers, than he can with ABS. ABS is however generally misunderstood. ABS is not about shorter stopping distances, it is about maintaining control and maneuverability of the vehicle, allowing accident avoidance.

On an unevenly slippery road, ABS seems safer to me in any case. On sand, ice, and mud, I do feel more confident without ABS. For general street driving, I prefer ABS, but don't mind driving a car that doesn't have it.

 

[Colt45ws]

Yeah, you are giving up some stopping distance to maintain some level of steering ability.

 

[d00df00d]

I would imagine that your tires would determine whether or not locking your brakes makes you stop shorter. Your tires' dynamic friction coefficient has to be bigger than their static coefficient of friction.

However, as moribundman said, the point of ABS is to let you steer the car under hard braking, and to prevent hydroplaning.

 

[moribundman]

Originally Posted By: BuickGN
Now it seems as though it's becoming inconsistant on the same stretch of street, same surface. It kicks in but the car just doesn't want to stop fast. It just keeps going and going and going. I now have the awesome Nitto NTO5 on it. Sometimes it feels like it's going to pu


Could it be that the shocks are not as good as they used to be and that the tires start bouncing and floating? You may not notice this as much if you disable the ABS.

 

[Colt45ws]

Pretty much the highest braking performance comes right at the edge of tire slippage. I recall reading a test of the new Taurus SHO and when they did the braking test they ended up with some tire smoke and it pulsed so fast as to be almost unnoticeable.. The ABS was keeping it right on the edge. It appears the latest ABS implementations may be very good.
I didnt think of mori's suggestion. I could see that. How old are the shocks?

 

[chevrofreak]

Originally Posted By: Onmo'Eegusee
On CVN dRock has a writeup on howto disable the trac control on the Aero Vics. Essentially route +12V to the "brake on" wire via a locking relay and install a diode to prevent the feed getting to the rest of the circuit. A simple press of a momentary on button (that can be sourced from a newer ford for that factory look) locks the relay on so the trac control thinks the brake is on.
I do get annoyed when I am trying to stop and hit a bump and the ABS goes wacko.


Somebody was working on something like that a couple years ago when I was still active on the board. I'll have to go take a look.

 

[BuickGN]

Originally Posted By: moribundman
Originally Posted By: BuickGN
Originally Posted By: Audi Junkie
Pulling the fuse is commonly done by the Audi guys. You could test the input voltage to the unit from the sensors and re-wire it to a steady source of the same voltage to trick it...just an idea, better then removing the whole unit.


Do you guys also see noticably better braking without the ABS?


I used to drive (and still do frequently drive) plenty cars without ABS, so I have something to compare. The average driver with average attention and skills is better off with ABS in most situations. A competent driver can easily achieve shorter stopping distances, even during evasive maneuvers, than he can with ABS. ABS is however generally misunderstood. ABS is not about shorter stopping distances, it is about maintaining control and maneuverability of the vehicle, allowing accident avoidance.

On an unevenly slippery road, ABS seems safer to me in any case. On sand, ice, and mud, I do feel more confident without ABS. For general street driving, I prefer ABS, but don't mind driving a car that doesn't have it.


Same here. I drove a non-ABS equipped car from 16 to 29 years old and in some ways I prefer it. I'm great at modulating the brakes though I agree with you that ABS is good when traction is uneven from one wheel to another.

This is a problem with the car, not the concept of ABS. We're talking about a 25% or greater increase in stopping distance with the ABS functioning.

My shocks are practically new. I recently softened the rebound adjustment, I guess it couldn't hurt to stiffen it up and try again. I've gone into ABS with my window down next to a wall to see if I could "hear" any issues with tire hop and such.

 

[PeteTheFarmer]

Originally Posted By: d00df00d
Your tires' dynamic friction coefficient has to be bigger than their static coefficient of friction.


I think you've got that backwards.

 

[JHZR2]

Honda quality, eh?

Let's take a step back... you have 5.1 fluid in there? You sure there is not 5.0 fluid in there, which is a different chemistry?

As I recall, the car has had "work" done on it. How sure are you that an ABS harness was never cut, compromised, etc? You never know...

Are all the sensors clean? Perhaps there is metallic fouling, which isnt enough to trip a light, but is enough to change the magnetic field and effect readings? Could the pump have marginal issues?

ABS can be tricked, especially with unloadrd pickups and on vehicles in certain situations.

I personally think you may have too many variables in play, and one may be factoring in to the situation.

 

[BuickGN]

Originally Posted By: JHZR2
Honda quality, eh?

Let's take a step back... you have 5.1 fluid in there? You sure there is not 5.0 fluid in there, which is a different chemistry?

As I recall, the car has had "work" done on it. How sure are you that an ABS harness was never cut, compromised, etc? You never know...

Are all the sensors clean? Perhaps there is metallic fouling, which isnt enough to trip a light, but is enough to change the magnetic field and effect readings? Could the pump have marginal issues?

ABS can be tricked, especially with unloadrd pickups and on vehicles in certain situations.

I personally think you may have too many variables in play, and one may be factoring in to the situation.


I had 5.1. When I had the subframe replaced I specifically told them I wanted 5.1 in there. When I got it back, the invoice said DOT3. I likely have a mixture right now so I'm going to take care of that this weekend.

It does feel like it's being tricked. If you've every tried to stop on a washboard surface with ABS, you'll know what mine is doing.

I'll check the sensors for anything metallic stuck to them. I remember about 40,000 miles ago wiping them off due to small metal shavings stuck to them.

Suspension consists of factory sport springs, good shocks, and aftermarket front and rear sway bars. Part of the reason I went with the factory sport springs was to eliminate any suspension issues from going too low. I didn't want to change geometry beyond what was offered from the factory.

I'm really leaning toward an electrical problem just because it's so inconsistant. There are times it stops very well and other times on the same surface it just keeps going and going.

 

[d00df00d]

Originally Posted By: PeteTheFarmer
Originally Posted By: d00df00d
Your tires' dynamic friction coefficient has to be bigger than their static coefficient of friction.


I think you've got that backwards.

When the tire is locked up, the contact patch is sliding along the ground. That's when the dynamic cf is dominant.

When the tire is rolling, the contact patch is not sliding. At any given moment, it is static in relation to the ground under it. That's when the static cf is dominant.

For stopping distances to be shorter with locked wheels than with rolling wheels, the dynamic cf must be greater than the static cf.

 

[PeteTheFarmer]

Originally Posted By: d00df00d
For stopping distances to be shorter with locked wheels than with rolling wheels, the dynamic cf must be greater than the static cf.


Assuming those rolling wheels are at maximum braking force, i.e. threshold braking, then yes.

For most materials, static friction is greater than dynamic friction, and I would certainly want that from tires on dry pavement. The converse would suggest that I could never exploit the cornering potential of my tires.

 

[IndyIan]

How is the ABS working when you try to threshold brake with the fuse in? Does the ABS cut in too soon? My buddies 97 Odyssey was doing that and he had some sensors replaced which seemed to solve the problem.
I also wonder with your sticky tires, if the ABS is calibrated to only accept a maximum deceleration rate, you might be trying to exceeded it and the ABS doesn't allow for it, or maybe it goes into a safe mode or something... You could try braking on a gravel road and see if it works normally there.

 

[d00df00d]

Originally Posted By: PeteTheFarmer
Assuming those rolling wheels are at maximum braking force, i.e. threshold braking, then yes.

For most materials, static friction is greater than dynamic friction, and I would certainly want that from tires on dry pavement. The converse would suggest that I could never exploit the cornering potential of my tires.

Agreed. I was just talking about what would be required for locked wheels to stop better than rolling wheels. What's real or optimal is another story.

 

[Tosh]

I just flipped through my Acura CL Helms service manual, and one thing that stands out is there is a 'detection item' for 'different tire diameter' (as the ABS bases its actions on relations between wheel rotational speeds and vehicle speed. But you haven't changed the tire OD, right?