Brake Balance

[Sekred]

Fitted a BB kit recently left me wondering how I had changed the brake balance of my ST. Engineers are smart guys and I am sure Ford engineers are no different but here I was bolting on a bigger disc ( OEM : 278mm, KSport : 304mm) and changing the caliper to increase force on the pads and just hopping for the best, well sort off.
As well as increasing the front brake force I fitted a SiCo caliper bracket and the larger disc (OEM : 253mm, SiCo : 280mm) to try and compensate. Driving the vehicle and braking hard (ABS working), left me with the feeling that I have too much front brake.
I was wondering how other forum members with BB kits feel about their vehicles and the brake balance?.

I did find this useful brake torque calculator online. It is quite easy to use but you need to know caliper piston diameters. Below is the measurements I got for front brake percentage.

OEM : 73.2% front bias.

KSport front, 253mm rear disc : 79% front bias.

KSport front, 280mm rear disc : 75% front bias.

OEM front, 280mm rear disc : 68.5% front bias.

Piston diameters,

OEM front : 54mm (2.125").

OEM rear : 34mm (1.338").

I am going to experiment with disc pad compounds on the rear to change the CF (coefficient value) and see if I can notice a difference. This is the cheapest and easiest solution.

Sorry, forgot the link,

http://www.tceperformanceproducts.com/bias-calculator/

 

[Siestarider]

I found it takes some miles to get everything fully bedded and working together. That said, the WW front BBK is now obviously wagging the dog. So more rear brake is called for. I will be following this closely, good thread Sekred. Thanks.

 

[D-resonant]

Old tech paper from Stoptech still makes me leery of overkill 6-piston big-brake kits for the little FiST:

http://www.stoptech.com/technical-support/technical-white-papers/abs-and-big-brake-kits

Also brake balance and reduced rear bias:

http://www.stoptech.com/technical-support/technical-white-papers

 

[Joker328]

Not trying to be argumentative, but I'm curious what exactly makes you think the front bias is too much? What about the vehicle dynamics suggests brake bias is the issue? Are the fronts more quick to lock-up (i.e. activate ABS) than the rears? Is it heavily understeering or something? I'd just be careful trying to shift too much bias to the rear since the car (on stock suspension at least) shifts a lot of weight forward under heavy braking and locking up the rears too quickly after a weight shift could cause you to lose the rear suddenly (not to mention increasing stopping distance).

 

[Sekred]

Not trying to be argumentative, but I'm curious what exactly makes you think the front bias is too much? What about the vehicle dynamics suggests brake bias is the issue? Are the fronts more quick to lock-up (i.e. activate ABS) than the rears? Is it heavily understeering or something? I'd just be careful trying to shift too much bias to the rear since the car (on stock suspension at least) shifts a lot of weight forward under heavy braking and locking up the rears too quickly after a weight shift could cause you to lose the rear suddenly (not to mention increasing stopping distance).

My issue is that the ABS kicks in earlier than I feel it should and it feels like it is front related. If anything it will run wide if I am turning when the ABS is working. There is no hint of oversteer, the vehicle brakes straight as a arrow but the ESC is also working at this point so it is a little difficult to tell. Of course I try to avoid braking and turning at the same time and this is more of a issue if I find myself braking too late.
I am also comparing it too my MY WRX driven on the same roads. I could brake later in the Subaru, considerable later actually.
The other reason is well I have increased front bias and if anything manufactures tend to favor front bias over rear from what is absolutely idea IMO because understeer is easier to control.
Maybe I am expecting too much from the vehicle?. My Subie was a MY99 and ST 2013 but the Subie kills it in the braking department.
Anyway I fitted a set of EBC yellow stuff pads to the rear, Cf is around .6 and my front pads are Ferodo DS 2500s, CF around .42. Cf varies with temp so the difference is not that great.
The good thing is the ECS will look after me to a point.

 

[Siestarider]

I wondered what that yellow stuff looked like. Now we know, a steel backing plate and friction pad painted yellow.

 

[Nightcrew13]

Old tech paper from Stoptech still makes me leery of overkill 6-piston big-brake kits for the little FiST:

http://www.stoptech.com/technical-support/technical-white-papers/abs-and-big-brake-kits

^this, can someone please retrofit an RS 4 piston setup

 

[apex]

I've had same problem when I first got my ST. I found that the ABS intervened too early when braking hard in corners causing it to PLOW. However, I was able to reduce this by using HP street pads in the front Mountune pads in the rear. More importantly is to build heat in the brakes to reduce the early intervention of the ABS. Hope this helps.