Need some guidance on master cylinder bore sizes

[2FAST4U]

Front brakes: 94 Mustang GT
Rear brakes: 94 Mustang Cobra
Pedals: Wilwood floor mount 6.25:1 ratio

From what I can determine with the information available, which isn't much, I come up with 5/8 bore for the front and 3/4 for the rear.

Any help is greatly appreciated

Bill

[mikeinatlanta]

I don't have direct knowledge of your setup, but 5/8 sounds a bit small. I'd suggest making sure that you can easily change whatever you go with.

[Railroad]

The larger bore master cyl usually feeds the larger piston caliper, front.
It is a volume thing. I have the same size master cylinders in my kit, MK IV Anniversary with the optional Wilwood brakes. The front calipers are 6 piston. The rear are 4, I think. I have not gotten them installed yet.

[edwardb]

Actually for brakes it's not volume but pressure. FF has been supplying 0.75" (3/4") MC for front brakes; 0.625" (5/8") MC for rear brakes for some time now, which helps to give more bias to the rear brakes. Needed in these cars. I have the Anniversary edition with the upgraded large Wilwood brakes. That's the combination that came with my kit.

[2FAST4U]

Thanks Edward

[Jacob McCrea]

Bill,

You may have seen this in the roaster manual, but if not, here is a page from my Gen 2 coupe manual, which gives suggested bore sizes, based on piston area, for dual MC/balance bar setups.

Master Cylinder Sizes.jpg

I have no experience with the suggest sizes. I am working on a "budget big brake" setup that uses 2012 GT500 rotors and 2015-16 Mustang GT 4 piston calipers, which are the size of a large pizza and a football, respectively. The chart suggests that a 7/10" master cylinder is correct for me as it instructs me not to count one side of the caliper if it has opposing pistons. This strikes me as odd but I'm not an automotive engineer, or any other type, for that matter. If anyone could comment on what they'd use for a 4-piston caliper with 1 5/8" pistons (manual brakes & Wilwood balance bar setup), I would really appreciate it.

[2FAST4U]

Thanks Jacob. That's perfect

[CraigS]

I have run exactly the brakes you have. As EdwardB says, using a 3/4 front and 5/8 rear is perfect. You may still want to use more aggressive pads on the rear even w/ those MC sizes. I did. I have run Hawk HPS and HPS 5.0 on the front and HP+ and Street/Race on the rear. I couldn't feel much difference between the HPS and HPS 5.0 (newer compound). I felt only a very slight increase in grip w/ the Street/Race (newer compound) and the HP+. The two rear compounds dust a lot but wow, do they grip.