ABS deactivation?

My 03 Murci is not the easiest car to stop...  It already has the upgraded discs and calipers but it is still not as good at braking as I thought it could be. 

One thing I have noticed is that the ABS, like the TCS, cuts in really early and feels like it is fighting the stopping.  So if I could disable the ABS, on a switch for example, I could really explore the limits of the braking.  Any ideas on how to do this, e.g. is there an ABS fuse?

How old are your tires?

ABS doesn’t come on unless there are wheels skidding. Mine certainly doesn’t Maybe your tires are tired from age. They start to lose it after 5 years from date of manufacture.

So many factors of age/wear/etc that can cause brake systems to be blamed for stinking. Age of/quality of/air bubble in brake fluid, flexible brake likes collapsing from age, pad condition and type, sliding brake parts not lubed, brake discs worn unevenly and/or too much, tires tired, etc. 

Maybe it's because mine is an 03 and the ABS software is different.  On a modern car, you can feel the traction loss just as the ABS cuts in - on mine it is far too early.  To generate traction, braking, accel and turning, the tyres need to slip an amount to generate the grip.  If this amount is say 10%, it feels like the ABS is cutting in at 3%.

So, I want to turn it off to see what the real braking potential is.

Tyres are near new. Pads and discs are near new and brake fluid is new.

3 hours ago, V12noise said:

Maybe it's because mine is an 03 and the ABS software is different.  On a modern car, you can feel the traction loss just as the ABS cuts in - on mine it is far too early.  To generate traction, braking, accel and turning, the tyres need to slip an amount to generate the grip.  If this amount is say 10%, it feels like the ABS is cutting in at 3%.

So, I want to turn it off to see what the real braking potential is.

Tyres are near new. Pads and discs are near new and brake fluid is new.

Hopefully someone knows.

Do you have stock wheels on the car, or aftermarket?

I borrowed a set of 19/20's while mine were being refinished, and I did notice the ABS cutting in surprisingly when it normally never does while I had those wheels on.

Hmmm.....  they are LP640 wheels that were needed to fit over the larger brakes.  Std tyre sizes though.... 

5 hours ago, V12noise said:

Hmmm.....  they are LP640 wheels that were needed to fit over the larger brakes.  Std tyre sizes though.... 

I wouldn't think the Hermera of Hurcules wheels would be a problem. I have my Speedlines in the attic and Hercules wheels on my car, and I don't have the ABS coming on like I did with the larger aftermarket wheels.

The ABS system is fairly self contained in the main unit below the brake master, it connects to the sensors at each wheel as well it has a connection to the CAN line for dash information as well as a few other things (TCS etc) you can technically unplug the central harness from the ABS head and deactivate it, you will throw codes and alarms and such but nothing detrimental, if you just want to see what it’s like with out the anti lock system functioning.

my first thoughts would be your fluid but you say it’s new, then my thoughts would point to the one way valve before the accumulator (blue tribulb plastic) in the rear if it’s leaking then you wouldn’t be getting the same response as you would with full vacuum

The new calipers may be too effective while the original rears act accordingly, this would cause a drag on the fronts but not the rears causing premature response from the ABS system.

there has been lengthy debates on the brake system which in the end was certified as a safe and reliable system at the time of manufacture, if you have changed parts of the mechanics of the oem brake system, then to expect it to perform normally would be questionable, as I will assume you now have 6 piston calipers and far more fluid required to motivate them from a master that was designed for smaller calipers and a control unit looking for a response from the original components.

it’s possible if you adjust your pedal height it may also create a response favourable or otherwise, by reducing or increasing pressure,  testing on a closed circuit of course.

just my thoughts there, I will see if I can find anything else that may be of actual use to you

 

 

Thanks Digibeam.  Just one question, where exactly is this one way valve - behind the ABS unit or in the rear of the car? 

It’s in the rear of the car, I believe the right rear, usually a dual coloured plastic valve. Inline with a “T” fitting that also leads directly to the blue accumulator,

It prevents the accumulator from bleeding vacuum back into the engine leaving it specifically for the master assist. Also look at the seal around the blue bottle as it can dry out and have a loose fit

and as a note, one may suppose a leak there would produce a vacuum error, but the valve stops the engine from having any notice or affect

I ran with ABS disconnected (fuse) on my '02 and the rears really liked to lock up. I don't suggest it and my daily driver Viper doesn't have ABS. 

What brakes do you have up front?

380mm discs with Brembo GT calipers - I posted the pictures on the other forum a few months back.

On 2/28/2019 at 8:36 AM, Digibeam said:

It’s in the rear of the car, I believe the right rear, usually a dual coloured plastic valve. Inline with a “T” fitting that also leads directly to the blue accumulator,

It prevents the accumulator from bleeding vacuum back into the engine leaving it specifically for the master assist. Also look at the seal around the blue bottle as it can dry out and have a loose fit

and as a note, one may suppose a leak there would produce a vacuum error, but the valve stops the engine from having any notice or affect

What's a good test for checking the vacuum works - pulling the line to the exhaust valve solenoid and seeing there's vacuum after the engine is switched off?  How long does the vacuum last for?