Caliper upgrade lim...
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Caliper upgrade limits

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Joined: 6 years ago
Posts: 1
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I am working on a 1964 ISO Rivolta and want to upgrade the front calipers

The ISO currently uses early  Dunlop calipers and an ATE master cylinder (60's Benz), later versions used the 3 piston Girling (2-small and one big) calipers with the same MC

I want to use 70's Jag 4 piston calipers but am worried about fluid capacity in the MC. I don't want the pedal to go to the floor.       

I calculated the clamp area in square inches as Dunlop = 3.54  Girling avg 4.44 and the Jag = 5.62  

Do you think this is enough of a size difference to worry about?     Before I start making caliper brackets I want to answer this question, Plan B is a Wilwood 120-7327 which is 3.53 sq in. but might look too modern. This upgrade will also include a change to a vented rotor.  I will not be changing anything in the rear.

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Joined: 15 years ago
Posts: 35

My experience with the Jag 4 piston is limited to the 57 Olds I did a few years ago. 

On that one, I had an underfloor hydroboost and adapted the same 78ish Jag master cylinder. Brakes on that car feel amazing. 

Increasing the pad surface area can give you a firmer feel, if you don't want that,  this may have to be a bit of trial and error. Maybe even playing with pedal ratio could solve an issue if it arises.


The books show the Jaguar master cylinder with a 15/16 bore, which is pretty close to the standard 1" bore stuff common in hot rodding prior to the Low Drag calipers everyone started using, then consequently having to use the 1 1/8" bore stuff to compensate for the extra retraction of the caliper pistons.