Kendall_Jones New Reader
July 26, 2009 1:24 p.m.

Looking at a 2001+ Sport Brakes Miata....

Aside from one extra brake line port on the Non ABS Master (ABS has 2, non ABS has 3), is there any other difference?

Front & Rear bores are the same correct? 15/16" or something.

Does it matter which circuit (front / rear) goes where on the master cylinder?

Reason I ask, on the non ABS master there are 2 brake ports on the end of the master (furthest from pedal) & one near the booster (3 total). Mazda diagrams say the 2 at the end are for the front brakes & the 3rd for the rear brakes.

I then see the targa miata blog click for pic shows the front brakes splitting off the rear port. (The master on the targa car is the 2 port abs unit)

If the ports are all the same bore, then it doesnt matter correct?


Keith SuperDork
July 26, 2009 1:36 p.m.

The Sport Brakes with ABS don't have a proportioning valve, they rely on the ABS for proportioning. The bores are the same in both the front and rear chambers (is that the correct terminology? probably not, but I'm going to use it) in the master - dual bore masters are actually pretty unusual. The Sport master is a 15/16". Tip for all Miata builders - the size of the master is cast into the body of the cylinder.

Obviously I don't think it matters which port is used for the front brakes if you only have two I would try to keep the front brakes on the same chamber and the rear on the other, given the choice. Otherwise, if you have the rear brakes and one front brake running off one chamber and something goes wrong with that circuit, you've just lost your brakes on three wheels.

Kendall_Jones New Reader
July 26, 2009 1:47 p.m.

Thats what I thought, thanks! Probably should have emailed you directly :)


Kendall_Jones New Reader
July 27, 2009 11:08 a.m.

What about Vacuum Boosters? Any "real" difference between units?

I see different PN's for Sport, Non Sport Brakes, ABS, Non- ABS, and W/ Turbo....


Keith SuperDork
July 27, 2009 11:57 a.m.

The Sport brakes do use a different booster than the previous cars. I'm not sure technically how they vary. The only external difference is the angle and location of the vacuum port - otherwise they're interchangeable.

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