OVERVIEW: ENDLESS Racing Discs

Written by Mike Cullingford.

 

ENDLESS is best known in the racing community for their racing brake pads, but they also make an amazing quality disc. Cast, machined, finished and heat treated in Japan - ENDLESS means business when it comes to brake disc rotors. ENDLESS produces both one piece and two piece discs, for both road and racing use. I'm going to talk about their two piece racing discs and looking at the processes of manufacture, design and usage.

Almost everything nowadays starts with computer design and analysis. Discs can be put through FEA analysis to ensure there are no stress/strength flaws before discs are made. From here machine programming can be derived from the drawings for manufacture.

ENDLESS has a range of castings that they produce their racing discs from. Their smallest disc is 262mm and their largest a massive 430mm. Castings have a minimum "eye" inner diameter and a maximum outer diameter. All discs have to be built around these limitations and this is why ENDLESS has a range of different sized and configuration castings. 

When designing a disc, the correct casting must be chosen for the application. Each casting has a unique airgap and vane count which must be taken into account for each application. This airgap and vane count will determine the cooling capacity of the disc which is important for racing applications. The cheeks need to be thick enough to give the correct disc mass and disc life. If the discs are too lightweight for the application they will crack easily because the temperature fluctuation is too high.

These are all cast in Japan to the highest quality. The casting quality is really important for overall strength, performance and safety. ENDLESS has spent a lot of time getting the recipe for the material correct for racing applications. 

ENDLESS Engineers designing a racing disc on CAD software. Critical dimensions are measurements displayed on the right hand screen for the machining department.

 

A raw ENDLESS disc casting being machined in the first operation. Every manufacturer has their own methods to ensure the machining on a disc is successful - it's not as easy as just "pushing a button".

 

 

Slotting being added after the disc has been fully machined. Slotting pattern will determine the level of bite and friction the disc offers. This example is 12x curved slots per face. The slots run right to the disc edge to eject any brake dust and debris.

 

Surface grinding to get the disc perfectly flat. This eliminates the chance of any thickness variation. Coolant is added to keep the temperature down and contain the dust.

 

This is how ENDLESS checks their disc thickness variation. Note there is a laser on the top and bottom surface. DTI gauges are difficult to use with slots on the discs - so lasers simplify the process.

 

Disc balancing - ENDLESS applies spring clips to get the balancing just right. This allows discs to be balanced quickly without requiring more machining work done to the disc.

 

Discs that have completed manufacture, waiting to be packaged and shipped. Note the thermal paint applied to the outer diameter - and also the different casting configurations (vane count and airgap).

 

Assembly - this is an ENDLESS technician installing a disc onto an aluminium bell using their own bobbin design. Bolts have loctite applied and torqued to a specific value to ensure their locking function.

 

Finished product - once the discs have been fully machined and finished, they are sent off for heat treatment. This ensures the material stays stable during the extreme conditions of racing. This is what gives the discs their colour. Each disc size and weight will have a slightly different colour due to the difference in the change of temperature of the material.

 

This disc is a replacement unit for the new Subaru Impreza WRX with 6POT brakes. 340mm diameter and 32mm thickness. Better quality than the factory Subaru discs and cheaper - what more could you ask for?

 

This really shows the curved vane design. This particular disc uses an 18mm airgap with 84 curved vanes. This high vane count offers excellent cooling potential - teams can block off the brake ducting if the disc is running too cold.

 

Let's go racing!

So now that we've gone to all that effort to produce a beautiful disc, they get fitted onto racing cars to get consumed. Brakes are just like any other consumable item and must be replaced at the correct intervals to ensure best performance and safety. How long does a disc last? This all comes down to application, pad compound and braking conditions. Bedding in the discs and pads correctly will also get the optimal life out of your discs.

 

This is an ENDLESS RacingMONO4 kit with a 345x32mm disc fitted to a Honda Civic FD2 endurance car. The compound is MA45B endurance. This picture was taken after the first session of running. The brake pad has applied a layer/film onto the disc which is critical for optimum performance and life.

 

NISMO R35 GTR GT3 prepping for racing. The team is going through their checks, and the pads and discs have just been through a bed-in process. ENDLESS worked directly with NISSAN to have their discs and pads homologated for these GT3 cars.

 

Serious brakes for a seriously fast car. If my memory serves me correctly, these are a 390x36mm front disc. They could be 380x36mm. The ENDLESS discs feature a 12 E-Slot pattern for maximum friction/bite. The "tooth" design of the hat to the hub allows discs to be changed without removing the caliper. This was designed for endurance races where discs and pads will be changed together - generally longer than 12-hours.

 

Racing Prep - Bedding in pads and discs correctly is important. These discs were fresh off a GT3 level car after a run-in session for the brakes. Once this was done the old brakes were put back onto the car for testing. Doing this early in a race weekend allows teams to plan accordingly for their test schedule and driver training.

 

This setup is from a BMW M6 GT3 car. ENDLESS worked with the BMW engineers to get the perfect setup for this car. The disc design is very different to the NISMO R35 GTR GT3 car. Less slotting means less friction and bite levels, but it also means less pad wear. Moving to six plain slots was done for tuning the pad life of the system for 24-hour racing.

 

Brake temperatures - the disc is hot but the cooling is doing its job. You can see how the friction material of the brake pads acts like an insulator. The green paint changes white at 430ºC and the red paint changes to white at 620ºC. The disc cheeks are more than 620ºC but the cooling vanes are less than that. For a GT3 car with heavy braking conditions, I would consider this the sweet spot. This disc setup is a 21mm airgap with 97 curved vanes for maximum cooling.

 

So that takes us from design and manufacturing, right through to being used on some of the fastest cars on the planet. ENDLESS produces an excellent quality disc with high performance to boot. ENDLESS can produce custom discs for Prosport Auto, I just send them a design outline of what I want and they will produce it for us. Custom discs have an initial minimum order of 4x pieces. It's not common to get this kind of service from a company at this level!

Get in touch with me at mike@prosportauto.co.nz if you're needing a better quality disc for your setup. Or if you just need something that other companies can't offer.