I have been working on braking issues in my 2004 MSM miata. It has an ABS system that proportions the rears without using a separate proportioning valve that is used on earlier systems.

The majority of my braking problems involved the rear brake bias trailing off toward the end of the braking zone. I would get initial bite, then less and less rear brake. I actually had a "crew" show up to the latest event who noticed that my rear distribution block was leaking when they were pressure bleeding. (as I was solo before, I had only used a vacuum bleeder and the leak went undetected).

So now I've got a firm nice predictable pedal... and I feel comfortable going with the BBK; however when I unplug my abs, the fronts will lock before the rears.

How am I going to be able to bias this thing? With bigger rotors/more rotor leverage on the fronts it would seem to exacerbate the front lock?... or will the "electronic bias system" do it all in it's "brain"?

 

prop valve

 

The prop valve can only turn the rear brakes down further...

 

Thought of mixing front and rear pad compounds to help make up for the bias/use? So many variables missing here though. What are you doign with the car? What suspension are you running? Tires? IMHO if you're running to the point of locking up regularly, such details make a difference when trying to help. Are you locking up both fronts in a straight line very easily? What compound pad are you running up there now?

 

Not if you replace the stock prop valve with an adjustable one.

"If your car has ABS but not the Sport brakes, or it has the Sport brakes but not ABS, you`re fine."

From FMs site.

Flyin' Miata : Chassis : Brakes : Complete adjustable brake proportioning kit


EDIT: I skipped the MSM part, so you have sport brakes, not sure how you handle that.

 

The fronts chirp in first, then the abs starts working. I've got willwoods up front, but not the 11.75 rotor kit. D-60 front/blues rear.

I wonder if a 11.75 front combined with a swap to a larger rear caliper like a willwood would be a fix?

 

I'll let one of the guys with more experience correct me, but if you are trying to get more rear bias without a prop valve, you'd want to leave the front piston diameter as is, and slightly increase the rear piston diameter.