Disc Brake Kits - #2

Disc Brake Kits: Early Rotor Design

I did, early on, look into manufacturing our own steel/cast rotors that attach to our hubs, but in the end I could not put together a manufacturing program that was, in my opinion, economical enough to pass on to customers. Also having replacement parts that are exclusive to us did not seem to make sense for the end user.

The variety, availability, and pricing of OEM rotors is mind boggling from a manufacturing stand point. 

However, finding a readily available OEM rotor to design from turned out to be harder than expected. The first priority was to find a suitable diameter and thickness as I wanted the first design to be backwards compatible with current available calipers and caliper mounts including stock ghia and super beetle mounts for the Varga calipers.

Stock 4 bolt Ghia, Super Beetle, and Type 3 rotors measure:

278mm / 10.94" Diameter

9.5mm / .374" Thick

I ended up settling on a rotor used on 06-12 Ford Fusions and 03-15 Mazda Miatas link that measures:

279.5mm / 11" Diameter

10mm / .393" Thick

The nice part about using the Mitata rotors is they are available in a ton of different configurations from coated to lightened/drilled for racing applications, plus being used on the Fords makes them very economical as well for stock applications. The only down side being the 4.5" (vs a 100mm) bolt circle for the lugs which interferes with the VW 4x130mm slightly. But the the larger 4.5" bolt circle is necessary to accommodated a larger through hole in the center of the rotor for the design of the hub. The slight thickness and diameter difference doesn't interfere with stock Varga style calipers and can easily be machined for applications requiring the most weight savings.

 

Here is the Miata rotor next to a stock 4 x 130mm VW Rotor

 

Notice the larger 1.5mm / .060" diameter difference of the Miata rotor.

 

So now the intent was to design an aluminum hub that will hold the Miata rotor while being mindful of manufacturing costs to keep the final price as reasonable as possible. 

The hardest part of designing something like this is material costs. Every bit of material removed has to be passed on to the consumer. So it makes sense to make a multiple piece design to waste the least amount of material. The multiple parts/setups does add cost on the manufacturing side, but is easily worked around with a quality manufacturing plan.

The 2 part design also adds the benefit of being modular. Parts can easily be changed as wheels/bolt patterns change or users change to different cars/spindles

 So, designing around that thought helps understand the 2 piece hub design I arrived on vs a 1 piece design.

 

Here you can see how any bolt pattern can be configured on the "outer Hub" (5 x 205mm and 4 x 130mm stock VW patterns shown). And the "inner hub" can be configured for any spindle (ball joint / link pin), vehicle (bug, bus, ghia, etc), or location (front / rear).