Master/Caliper brake combinations and ratio changes

[240260280z]

Hi All,

I decided to compare master cylinder area to total caliper piston areas for common Z part combinations and apply hydraulic principals.

Note: The total caliper area is the area summation for all pistons in both calipers.

From the data, it is clear to the Sumitomo 4 pot (Toyota S12-8) caliper upgrade has minimal area change from stock (2%) thus there is no significant change in required pedal pressure nor pedal travel.

With reference to the table, the common upgrade to a 15/16" master and S12-8 calipers will increase pedal pressure by 11% but reduce pedal travel by 11%. For a 240z or 260z, this will reduce pedal travel from 140mm to 126mm (which is what an 82 280zx's stock travel is)

Stock brake pedal strokes

• 72 240z: 140mm
  
• 74 260z: 140mm
  
• 75-78 280z: 123mm
  
• 82 280zx: 125mm
  

Pedal height from floor is 203mm

Examples:

adding a S12-8 calipers to a 72 240z will increase pedal travel from 140mm to 143mm

adding a S12-8 calipers and 3/4" master to a 72 240z will increase pedal travel from 140mm to 195mm (not good as maximum travel is 203mm)

Data:

• Stock Datsun 240z to 280z caliper has two 53.98mm pistons (I could only find 72-78 data)
  
• S12-8 caliper has two 42.82mm & two 33.93mm pistons
  
• S12-W caliper has four 42.82mm pistons
  

I hope this is useful

Edited March 9, 2013 by Blue

[Diseazd]

Blue....All but one of my Z's run Willwoods with vented rotors on the front. The green 72 runs Willwoods front and rear. I use the stock M/C on all 5.......works perfect. Regards. Guy

[Travel'n Man]

Guy - did you add the prop. valve to your setup? Brakes are my next target and trying to figure out what I want to do.............

[Diseazd]

Mitchell.....Just on the 72 with front and rear Willwoods. I think most of your stopping is done with the front brakes.....If I were you Mitch I'd just go with fronts......see how you like 'em......Heck of a lot easier than the rears. The Willwoods are really nice looking and they work good, but I rebuilt the stock fronts on the 73 and replaced the rotors and they work pretty good too.

Edited March 9, 2013 by Diseazd

[240260280z]

How many pistons in a Willwood caliper and what diameter? I'll update the table. I also noticed a 5/8" master in my heap so I'll add that.

[Travel'n Man]

Guy -

you did not change your your MC - I already have a 15/16ths in storage - just don't want to lock anything up............on down the road

[Diseazd]

Blue ......4 piston Willwoods (no idea what diameter...Arizona Z could tell you). Mitchell...yes I used the stock Datsun M/C and booster....it works perfect. I know people recommend the 15/16 M/C, but stock works great for me.

Edited March 9, 2013 by Diseazd

[240260280z]

Looks like the pistons could range from 1.12" to 1.88" Wilwood Forged Superlite Internal 4 Piston Aluminum Brake Calipers - JEGS

Can't find any more details on arizonaz or other retail sites.

[Oiluj]

I have the 13/16" master and Toyota 4x4 fronts, larger 1973 master vac and an adjustable proportioning valve.

I really like the pedal feel and she stops fine. Probably not required for a street car, and it may not stop any shorter, but I like the pedal feel better than the stock brakes.

[240260280z]

Thanks Julio, that sounds like a nice mix. What did the 13/16" come from.

[Nigel]

Mitchell.....Just on the 72 with front and rear Willwoods. I think most of your stopping is done with the front brakes.....If I were you Mitch I'd just go with fronts......see how you like 'em......Heck of a lot easier than the rears. The Willwoods are really nice looking and they work good, but I rebuilt the stock fronts on the 73 and replaced the rotors and they work pretty good too.

FYI, significantly increasing the brake torque on the front wheels without a proportional increase in the brake torque on the rear wheels can actually result in longer stopping distances, which defeats the purpose. You need the maximum combination of front AND rear brake torque to generate the load transfer onto the front wheels for the bigger front brakes to take advantage of the additional traction. Otherwise, additional front brake torque will just overpower the traction of the front tires more easily, and a sliding tire takes a longer distance to stop the car.

Also, the AZC Wilwood calipers come with four 1.75" diameter pistons.

Nigel