Early Booster And Hilux 4-Pot Calipers

[wildy55]

Hi

Is anyone running the smaller (70-71) brake booster with Hilux S12+8 calipers up front? Just about to reco my booster but want to be sure it'll handle the bigger Calipers (running std drums rear) first.

Cheers

[Agno]

The booster will be fine but I would suggest upgrading to a 15/16" master cylinder.

[dat2kman]

It'll be fine.

The total square mm of the original two piston units, vs the toyota four piston is not a big difference.

[Cozza]

I’ve done some numbers on this in the past, I think it depends on which Hilux calipers you have.

 

For reference, standard 240z brakes use 2x54mm dia. pistons = 4580mm2 surface area

 

I have some S12W’s in the shed and they have 4x43mm dia. pistons = 5808mm2. Which is about 27% larger than standard.

 

But, I think some Hilux S12+8 calipers have 2x43mm dia. + 2x33.8mm dia. pistons = 4699mm2 which is only about 3% larger than standard

 

The standard 240z 7/8” master is 388mm2

 

The 15/16” master is 445mm2, about 15% larger than standard

 

The 1” master is 507mm2, about 31% larger than standard

 

 

Anyway, I’d confirm your caliper piston diameters to determine your master cylinder.

 

As a side note,

I’ve read MK63’s use 4x41.3mm dia. pistons = 5358mm2 which is about 17% larger than standard.

I wonder what size master the factory recommended when they supplied the MK63 calipers? I’m guessing a 15/16”

[dat2kman]

Cozza, well done for looking that up!

I used to do all those sorts of calcs,,,,,

Factory, when fitting the mk63's also redrilled the pushrod clevis pin hole on the brake pedal, to alter the leverage ratio.

Edited November 30, 2017 by dat2kman

[Cozza]

Thanks dat2kman.

That’s interesting. Yes, there are many peices to the puzzle of getting a good brake pedal. I’d be interested to see a complete Mk63 setup.

On the front of my car would be even better ?