Ultimate MCP 650 Guide

This document will outline all the information I have found on the MCP 650EP caliper through my online research and calls with Brad (the goat) from MCP. Yahoo We will be using this caliper for MS15.5 and hopefully for MS16! The specification sheets are not available on the internet and were passed on to me from MCP, I don’t think it's a problem but be wary of sharing this information publicly online.

Background:

The MCP650EP is a hydraulic active-retract floating caliper. This caliper was created and is commonly used on racing go-karts and dragster vehicles. However, it has found a niche in solar car racing due to its strong braking performance while having a very small form factor. Moreover, it uses a simple 1/8” steel sheet metal plate to mount.

The main selling point for this caliper, and the reason why we want to use it, is because of its active-retract functionality. As the name implies these calipers retract the brake pads away from the disc after braking which denies any passive rubbing of brake pads onto the rotor and improves the efficiency of the car. The MCP 650 does this by leveraging springs on the piston side of the caliper that will extend when active (brake pushed) and compress back to neutral position when not active.

Here is a cool video that MCP sent me showing the calipers in action. A few things to note in these videos: in this experiment instead of hydraulics pressurized air was used to actuate the brake pads, and the distance between the pads and rotor is very large for viewing purposes. The first video is an explanation, second video is a demonstration.

Caliper Specifications:

1 Inch piston bore
1/8-27 FNPT nozzle for fitting
Works standard with 1/8” rotor thickness
- DOES work with larger rotor thicknesses given you add shims between the piston and anvil components of the brake caliper. MCP sells ots shims that work with the caliper (part no. 668)
Brake pads are included with purchase, as well as a 1.75” mounting bracket
The different variations of the 650 caliper refer to the hydraulic fluid that it is compatible with. The 650EP works with dot 3,4,5 fluids. The 650 base model uses dot 5 if I recall correctly (might be wrong)
Bolts on caliper are standard imperial thread
Important notes:
- Must use Teflon paste NOT TAPE to seal valve fittings into caliper
- Parts to consider for purchase: extra bleed nipples (no. 1382), bleed bottle (no. 912)
- With the MCP 650 you have the option to either float the caliper or float the rotor (not both just one)
- Reputable Suppliers https://www.bmikarts.com/MCP-Big-Bore-Front-Hydraulic-Caliper_p_551.html https://cometkartsales.com/products/mcp-650-black-front-caliper-assembly-with-bracket

Caliper Diagrams:

Side View:

Front View:

The spring is located within the counterbored thought hole on the piston side of the caliper encased in a metal sleeve. As shown in the (really blurry sorry) image below when the caliper is extended:

Mounting:

As previously mentioned, the MCP 650ep is mounted with a 1/8” steel sheet metal plate that attaches between the brake pad and piston side of the caliper. This means that the bolts used to fasten the sheet metal plate are the same bolts that thread into the brake pads (5/16-18 button heads). The brake caliper comes stock with a 1.75” sheet metal plate, however, this plate can be, as is often, custom-made. The people at MCP have laser-cut custom sheet metal pieces for specific applications, as shown in the photo below, we can make our own using waterjet. The alloy of steel used for this plate can be any low-carbon steel, 1018 or 1080 will suffice. The photo below is an example of a custom sheet metal mounting plate that MCP manufactured:

You may be wondering why we must use a steel plate for mounting, rather then a lighter, aluminum piece. This is because using steel we can keep the thickness of the plate at 1/8". If we choose an aluminum alloy the mounting plate would have to be thicker which is a major problem with where the mounting plate is located. Since the plate is located between the brake pads on the piston side of the caliper it means it is in direct contact with the springs that perform the active retract component of the caliper. So, by increasing the thickness of the plate we are applying a pre-load to the springs which can effect the retract mechanism.

Technically, there are ways around this by playing around with brake pad distance by repeatedly adjusting caliper location and such BUT in my opinion this is not worth the effort, time and overcomplicates a simple mounting procedure. It is also unlikely that the plate will fail under our loading conditions because these calipers are used to stop go-karts of greater weights going at faster speeds (of course we will have to run our own FEA still).

When choosing a mounting location for the MCP 650 we have to weary about the location of the caliper bleed nipple. The bleed nipple of the caliper must always be at the caliper's highest point for the bleeding of the brakes to go smoothly. There are two 1/8-27 FNPT nozzles in the caliper and the bleed nipple can go on either one.

Another constraint when mounting this caliper is that we need to mount it such that the entirety of the brake pads are in 100% contact with the rotor of the vehicle. Luckily MCP was kind enough to give a mounting reference drawing (shown below).

Mechanical