So the problem I had running the RX-7 or Volvo calipers up front was that the rear Ford Explorer calipers are just too powerful in terms of proportioning front to rear. So much so you can't really dial it out. Most road cars are setup so that the rear brake caliper clamping force is about 50% of the front. The rear Explorer caliper is about 80%. Since the Explorer is a near 2 tonne SUV, I needed something with roughly twice the clamping force of the rear, so I started looking around at suitable OEM options from vehicles weighing between 1800-2000kg.
I settled on calipers from the Lexus LS430. It weighs almost 2 tonne, so has similar clamping force front and rear as the Ford Explorer, even though the discs are bigger.
They are a pretty nice caliper. Radial mount, monobloc aluminium with 4 x 42mm pistons. I found a lot of Porsche guys use these with Cayenne 330mm rotors which is the same size as the S60R rotor I wanted to run. Plus they were only $400 for the pair from a local wrecker.
We then made the adapters. Took a couple of attempts as we relied on some dimensions online and messed up the dowel spacing.
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Here is the caliper bolted up. They fit up super nice being located on a dowel and radial mounted. It actually makes the adapter quite simple and the caliper easy to remove and refit etc.
Like much of the rest of this build, I wanted to use as many proven off the shelf OEM parts as much as possible. In figuring out how to adapt the metric flared brake hard lines to the Banjo style fitting on the Lexus caliper, I found this awesome Banjo-to-metric flare adapter sourced from a stock 1990 NA Mazda MX-5 master cylinder! Big thanks to the guys at ALLMAZ in Clayton who stripped two fittings off for me for just $10. Just made for this job! It's amazing how similar all cars are really when it comes down to it. Just a bunch of parts bolted together!
Bolted up:
The only issue then with all of this is the stock stepped-bore master cylinder. It's too small for this setup and results in a longer pedal travel than desired. I saw the guys in the States run Mustang master cylinders. I found that early RHD Ford Explorer (the diff donor), 1996-2000 vintage (UN to UP model) uses basically the same master, with a different plastic tank and the brake fittings on the correct side. It has a 27mm bore and more or less bolts on with only minor mods needed.
End result is a pretty awesome brake setup. It has very good feel and could really do with a more front tyre as I can lock the front up easily if I want to in a very hard stop, even with sticky 235 wide tyres. I have the proportioning valve setup about mid way at the moment, so can probably dial some more rear brake in. The valve is mounted just next to the brake booster.
Next up for the car is fitting a 23mm rear swaybar sourced from Mr. Iceton. Front/Rear roll balance at the moment is not great given the 27mm up front and the 19 in the rear. The 23mm bar is just over twice as stiff as the 19mm so will be interesting to see the results. The GAZ shocks sourced from Ash are proving to be terrific. Still fine tuning the adjustment on those, but they are doing a great job of controlling the rear end so far.
After all that is sorted I will be fitting a spare set of 17x8 and 17x9 alloys, R-compound semi-slick tyres and doing a track day at Sandown. Should be entertaining with these brown cloth seats! Might have to tape myself in!
