Disc Brake Conversion (2)

Red Caliper Drilled Rotor
Car brakes, red caliper

What Do Floating and Non-Floating Calipers Mean?

You’ve decided that your hot rod, muscle car, or antique truck needs disc brakes, and you’re looking through a selection of caliper options, which include single piston and multi-piston calipers. In both manufacturing and retrofit disc brake packages, the single piston caliper is the most common caliper. When brake fluid pressure is supplied to the single internal piston, the single piston caliper uses a floating design, in which the caliper is mounted on a pair of guide pins and moves on these pins. The two disc brake pads press down on the disc brake rotor with this movement.

It’s a straightforward but effective design. The floating caliper mounting system, however, is not without flaws. Dirt, brake dust, and other debris can clog the guide pins, causing the caliper to stick. The pins can rust and corrode to the point where they seize the caliper in place, preventing full braking application. Furthermore, the floating design has a lot of intrinsic flex, which reduces brake rotor gripping force. A single piston floating caliper disc brake conversion can suffice for a cruiser-style build or a low-cost build, but if you want the best braking and performance, you’ll need a non-floating caliper arrangement.

Non-floating, or fixed, calipers normally have four pistons, although some have as many as six, evenly distributed on either side of the caliper assembly. A four-piston caliper has two pistons on the inboard side and two pistons on the outboard side, and the braking fluid is delivered to all four caliper pistons at the same time via an internal or external fluid crossover. Although the pistons are of the same size, some calipers have different caliper piston diameters to help with clamping force for a given brake rotor rotation.

Because of the thicker mounting bracket and more robust caliper assembly, the fixed caliper is chosen in a performance brake package. This drastically decreases caliper flex, especially in radial mount setups, and the pistons clamping on both sides of the rotor, as opposed to one side in the floating caliper setup, offers significantly better clamping force. If the non-floating caliper has a disadvantage, it is that the bigger caliper body necessary for the outboard caliper pistons can be taller than the brake rotor hat dimension, necessitating precise wheel measurement to ensure they will clear the brake caliper.

Can You Use Disc Brakes with Your Original Drum Brake Master Cylinder?

The “jelly jar” configuration of many original drum brake master cylinders has a single reservoir that feeds all four drum brake components. If the hydraulic fluid circuit fails, such as when a brake line or fitting fails, all four brakes are affected, and once the reservoir is empty, you will have no pedal and no method to stop your automobile. This is a very dangerous situation, and even if you plan to keep your four-wheel drum brakes, we strongly advise you to switch to a split circuit front/rear master cylinder on your car.

A disc brake conversion will not be compatible with a drum brake arrangement that has a split reservoir. For starters, the two brake systems operate at different fluid pressures and with different master cylinder bore sizes. Drum brakes require about 400 psi to apply, but disc brakes require 900 psi or more. The bore size and capacity of the drum/drum split master cylinder will be insufficient for the disc brake fluid volume. Furthermore, because the drum/drum master cylinder is designed to provide the same brake fluid pressure to all four wheels, you will not have enough pressure when upgrading to disc brakes in the front, necessitating multiple pumps of the brake pedal to get any sort of brake application from your discs. As a result, it’s vital to use the correct disc/drum master cylinder with any change or a specific disc/disc master cylinder if your ride is equipped with 4-wheel disc brakes.

Finally, most drum brake master cylinders include a built-in residual pressure valve in the master cylinder’s outlet fitting(s), which in the case of drum brake application is a 10 psi valve. A 2 psi valve is used in disc brakes, but only if the master cylinder is below the calipers’ level (such as a hot rod under floor frame mount setup like our illustration examples below). Attempting to use such a master cylinder will apply 10 psi of line pressure to your disc brakes even if the brake pedal is not depressed, causing brake drag, overheated brakes, and finally brake lockup due to the heat. In this Toolbox guide, we go over residual pressure valves, proportioning valves, and combination valves.

What Does a Disc Brake Conversion Cost?

We’re all aware that moving quickly costs money. Stopping quickly has the same effect. You can either pay for convenience or pay for time, as the case may be. You can either take the time to piece together your disc brake conversion kit from individual parts, potentially saving a few dollars, or you can pay for the convenience of an all-inclusive disc brake conversion kit that includes everything you need, right down to the brake hoses and fasteners, to get your conversion done quickly and without hassle. In all honesty, our kits rarely cost more than putting your brake package together piece by piece, and for the most common applications, our buying power and in-house manufacture mean our disc brake conversion kits will often save you money (and time) over shopping for individual parts. However, prices will vary based on the contents of the kit. Basic front disc brake conversion kits for Mustang II spindles cost under $200, whereas GM muscle car front disc brake conversion kits cost $600-$800. Brakes with aluminum non-floating four piston calipers, drilled rotors, and other high-end front brake packages typically cost around $1,300. These prices may fluctuate, but they are accurate as of the date we released this buyer’s guide.

You won’t find more disc brake conversion kit options anywhere else, from street to race, with tons of outstanding features and all-inclusive pricing. We also provide pedal kits, brake master cylinders and boosters, and other parts to help you switch to power disc brakes.

Enjoy the ride in your hot rod, muscle vehicle, or classic truck while making it safer.

Disc Brake Conversion (2)