McLaren Inverted Brake Caliper Brackets

This project was part of an experimental brake configuration for the electric McLaren MP4-12C platform that I got the chance to work on while at Orbis Electric. The unique brake orientation is part of the Orbis EcoWave architecture, which reorients the caliper to the inside of a large 'ring' rotor, allowing allowing for more versatility with hub motor packaging. This configuration also allows for equal stopping power from smaller calipers by increasing the moment-arm of their

clamping force.

When I started this conversion, the McLaren had a fully stock front end, with knuckle-mounted calipers. Since the original twin-turbo V8 had been replaced with our hub motors, so had the conventional vacuum powered brake-booster. This meant the McLaren had significant difficulty locking the front brakes with an un-boosted master cylinder, and stock brakes. If this project were to be successful, the McLaren would need to be able to lock it's front brakes from a range of speeds, with driver input force alone.

I will address some of the design challenges I was faced with, and how I successfully executed the conversion in a short, high pressure timeframe.

The basic parameter was to remove the original McLaren brake calipers, and create a series of brackets and spacers to install new OTS calipers in an outward facing orientation to interface with an existing custom rotor system.

This required careful FEA analysis of loads involved in braking, while staying inside the tight space constraints of a rotating wheel. All of this had to be executed without modifying any of the original wheel offsets.

The first part of the challenge was the new caliper itself (black). This was an OTS part from the motorcycle industry, which we already had in house, and accommodated a much narrower rotor than the stock caliper (orange).

To address this, I needed to make spacers to stand-off the two halves of the calipers, which is common practice for custom motorsport parts. There was a significant added challenge to this, since these fixed, 2-part calipers had an internal brake fluid passthrough between them. This meant I had to incorporate pressure sealed hydraulic passages into my spacers. To achieve this, I exactly copied the O-ring seats in the castings onto my billet spacers, simply adding a set of

O-rings to one side, and essentially extending the hydraulic pass-through.

In order to shape the spacers appropriately, and design my bracket, I created complete 3D scans of the caliper using EINSTAR equipment, and simplified the mesh to include it directly into my CAD file for fitment checks. I also 3D scanned the knuckle of the McLaren, and the internal profile of it's wheel, to create a complete assembly.

After completing this assembly and consulting several times with our machinist, these are the brackets I designed, along with the billet caliper spacers.

One of the design challenges of this bracket was that it had to be a chiral shape, to accommodate a left and right version, while interfacing with identical, non-mirrored calipers. This affected features like bleeder clearances, and required me to develop a special bleeding procedure for left and right sides.

This image shows the caliper fully assembled with spacers, and mounted to the McLaren knuckle using original hardware specifications.

This image shows the test fit with the EcoWave rotor mounted to the hub, and interfacing with the new caliper. For the brakes to function correctly, there had to be no more than 1mm clearance between the pads and rotor, without making contact throughout the entire rotation.

After bleeding the system, installing the wheels, and torquing to spec, the new braking configuration met these requirements on the very first test fit. I performed the first test drive, and was able to easily lock up the front brakes unassisted, marking a significant performance improvement. Later analysis of pad wear showed acceptable parallelism and rigidity

from the brackets.