Inline Hydraulic Handbrake Setup on RX-8 Chassis (SR20DET Swapped) – Avoiding ABS Issues

Hello everyone,

I am currently working on a Mazda RX-8 with an SR20DET swap. I am planning to install an inline hydraulic handbrake 0.75 wilwood (using the stock rear calipers) and I need some technical advice on the brake line plumbing to avoid conflicts with the ABS module.

The Setup:

• Chassis: Mazda RX-8 (Series 1).

• Engine: SR20DET.

• Brakes: Stock RX-8 calipers and Master Cylinder.

• ABS: I intend to keep the ABS module functional for street driving, but I'm worried about "faulting" the pump when using the hydro.

• DSC: I don't have electric throttle so i don't care about dsc

• Planned Route: Intercept the rear brake line exiting the Master Cylinder, run it to the Hydro Inlet, and then from the Hydro Outlet back to the Rear (MC2) port of the ABS block.

• Materials: I am planning to use copper lines for the new sections of the handbrake circuit.

• ABS Conflict: I’ve read that pulling the hydro while the ABS is active (or while also pressing the foot brake) can cause the ABS pump to kick back, create a rock-hard pedal, or even damage the internal seals of the ABS block.

• Electronic Issues: Since the RX-8 ABS is linked to the ECU/CANBUS, will a sudden pressure spike from the hydro trigger a "limp mode" or constant ABS lights?

• Material Safety: Is copper piping reliable enough for the high-pressure spikes of a hydraulic handbrake in a drift environment, or is it prone to expanding and creating a "spongy" feel compared to braided/steel lines?

• Has anyone successfully run an inline hydro on an RX-8 ABS block without it failing?

• Should I install a one-way check valve (non-return valve) between the foot master cylinder and the hydro to protect the master cylinder?

• Is it mandatory to use a proportioning valve (limiteur) before the hydro to prevent the rear wheels from being too sensitive during normal braking?

I have attached an image of abs module with inlets and outlets marked. Also a pdf with a detailed brake system for rx8

Thanks in advance!

While I haven't personally done anything like this, I would say what you're trying to achieve here while keeping ABS is going to cause you some trouble. This is probably going to be harder/more time consuming and expensive than buying a dual calliper setup - but i'm happy to be proven wrong.

Don't use a non return valve between the hydro brake and the MC. The Hydro still needs to return otherwise it'll lock on.

Regardless I'd imagine this interference is going to cause faults and potential damage

A possible option is to put a line lock on the line to hydro, and then use a switch or pull the ABS fuse.

This way when you're at the track or plan to use the hydro you could switch the ABS off, and open the line lock to the hydro.

After you're done at the track you can lock out the hydro and then turn ABS back on.

I'd still probably try to plumb it in after the ABS module.

Finally, CuNi (Copper-nickel or Cunifer) lines are up to the task, just be sure to use a product designed specifically for brake lines.

ok thank you i will also ask some local friends that have tried something like that and i will come back with feedback