ABS Activity ater brake upgrade ?

blksc

Registered User
First: the mark 8 upgrade is awesome! but i've noticed that i've gotten alot more abs activity out of the system when i do short stops, is this because the bigger brakes are grabbing more and causing the abs to "pump" the pedal ?
 
I would think so.....Those bigger brakes dont need as much brake pedal pressure as before to lock the wheels.
 
I have been contimplating this upgrade myself for sometime. I assume you got the parts from a junk yard? Was it a direct bolt on? Any problems with the brake line? Big difference in braking? Sorry if I am hijacking your thread :)
 
HI
The install was real straight forward. No problems with the brake line at all. I've noticed a big difference in stopping. I wouldnt get the semi metallic pads though, go ceramic. less dust and they grab better, but they are more harsh on the rotor
 
Most likey you have upset the brake bias front to back with the upgrade making the front brakes more prone to try and lock up on hard braking. The ABS system can't tell why a tire is trying to start to slide....just that it is and tries to correct for the percieved problem by actuating.
 
Does it sound logical by getting better tires and suspension, before getting a better set of brakes and rotors, to reduce ABS activity and/or lockup? Afterall, doesn't ABS activity and lockup occur, when the tires can't accomodate adequate friction or traction to the road vs. braking force applied?
 
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Now a days ceramic pads are pretty cheap. I got mine from pep boys for 59.99

Isnt the bias set as a fixed amount of fluid pressure between the front and back system ?
 
I would agree there is a bias issue. But I would check the rear brakes first to make sure they are actuating. If you haven't changed the pads back there in a while, the lower slide pin for the caliper can seize causing the rear brakes to hardly even function.

The main reason why many upgrade to the bigger brakes is to reduce brake fade and to reduce rotor warpage. Thus no need to worry about tires or suspension due to that.

This is the first time I've heard of anyone upgrading to the Mark brakes that has noticed an issue with increased ABS actuation. I guess I'm wondering if blksc's rear brakes are functioning at all.
 
On the SC brake bias is done via the proportioning valve. There is a 1 : 1 relationship into and out of the valve until you reach a setpoint pressure. Then only a percentage of the applied presssure from the ABS Hydraulic Actuator (master cylinder) is actually "fed" to the rear brakes. The bias is created by the point chosen as the setpoint where the percentage kicks in. If the brakes are upgraded on the front compared to the rear either the percentage at the split point needs to be changed and/or the actual value (pressure) at the setpoint needs to be changed to remain correct. That value is determined by the weight of the car and the relative effectiveness of the front compared to rear brakes. The proportioning valve is non-adjustable and also houses the pressure switch that actuates the ARC above 400 PSI brake line pressure. Don't have the actual setpoint where I am right now but it is in the Helms Manual.

I did the Cobra Brake upgrade front and rear using stock SC caliper in the rear. I do not have an issue as both ends of the car where effectively upgraded. By using the larger rotor in the rear and relocating the caliper to accomodate the rotor the effective moment arm is longer resulting in more braking action plus there is a larger swept area for the pads.
 
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