You have an NF Fairlane Master Cylinder and Rear Brakes with Jaguar XJ Series I Front Brakes
I expect those Brakes are dangerous - Too easy to lock the Front Brakes and can't lock the Rears
Especially in low grip conditions I expect you might have a choice between very poor brakes and steering - Not Both - Touch the Brakes and the vehicle ploughs straight ahead
As the Professor would say - Why is it so ? - You have 77% more Front Brake Piston Area than the Ford - That is the Problem that should be Fixed.
I assume that your vehicle has similar total weight and front to rear weight balance as an NF Fairlane
Ford (and other vehicle manufacturers) have spent HUGE Person Hours and Dollars getting Brakes to where they are now
Engineers like systems that have been proven to work and using like systems usually results in less total costs
IF it was my vehicle I would look at fitting Jaguar Series II-III vented front discs - 285mm OD compared to 287mm for NF Fairlane
- Same stud pattern and I expect an easy fit - Hub Hole Diameter may need to be increased from 82mm to 82.5mm - Check how much wheel stud showing on SI and SII-III
Then adapt NF Fairlane type Front Calipers with single 60.3mm bore pistons with the matching Ford Brake Pads and you have duplicated the Ford arrangement
- The 24mm New Disc Thickness is within the 25-22mm Ford range.
https://www.vmaxbrakes.com.au/fits-jagu ... disc~38632
https://www.vmaxbrakes.com.au/rtype-slo ... gJjY_D_BwE
https://www.ebay.com.au/itm/13327545948 ... SwGIVd-Wfk
https://www.bestbrakes.com.au/EA-EB-ED- ... UILD-KIT-2 - Indicates that these all use the same calipers
I suggest talking to who will approve the vehicle and I expect that doing the above would result in good brakes for less than you will spend - and rotors and calipers can be sold if required
As a separate issue pedal position should be considered based on modern vehicles - Many have hit the wrong pedal with disastrous results
But remember - I know nothing ! But Vented and Not Vented Discs are on my kitchen bench, Adaptors are on my desk and at the front door with 4 front calipers.
Greg N Smith wrote:Warning - Brakes (and Steering) are Very Important and I'm called Schultz (from Hogan's Heroes) - I know nothing !
A look on the internet and it appears that -
Jag XJ S1 Front Calipers have 1 x 57mm and 2 x 40mm Pistons - Total Area 7.85 square inches per side - Does yours have 3 Pistons ?
NF Fairlane Front Calipers have 1 x 60.3mm Piston - Total Area 4.43 square inches per side -
Your Jag XJ S1 has 1.77 times more front piston area per side than the NF Fairlane
The real difference is in the total area of all front pistons - a large Difference which I expect would change braking pressures and front to rear brake balance.
Jag XJ S1 Rear Calipers have 2 x 43mm Pistons - Total Area 4.50 square inches per side
NF Fairlane Rear Calipers have 1 x 40.4mm Piston (from Falcon AU size) - Total Area 1.99 square inches per side
Jag XJ S1 Master Cylinder has 15/16" (23.81mm) Bore - Total Area 0.69 square inches per side
NF Fairlane Master Cylinder has 1 x 15/16" (23.81mm) Bore - Area 0.69 square inches AND 1 x 1 1/4" (31.75mm) Bore - Area 1.23 square inches
Some big differences there ... I don't know whether that combination is suitable.
In a safe area with plenty of run-off I would check that you can lock all wheels from moderate speed with someone watching from a safe distance without being an "on-off" switch
In an area with plenty of run-off on loose gravel or wet surface what happens when you brake from moderate speed with a bit of turn - do you lock the fronts and plough straight ahead or do you lock the rears and spin out ?
Please check the booster and all measurements and calculations and let us know how you go.