There haven’t been many two-seater roadsters as popular as the Mazda MX-5. In fact, this is the best-selling small sportscar in motoring history. It has repeatedly ousted more traditional (and reasonable) sedans, hatchbacks, and SUVs in the running for “Best Car of the Year” awards across the world. The fourth-generation car was even voted “World Car of the Year” for 2016.
Many of the awards and accolades are owed to the sheer fun factor the car has. Even early models stripped of all of today’s tech were exhilarating to throw around a track or rev hard down the street. The brilliant handling and ride, pushed along by small but energetic 4-cylinder engines, was nevertheless assisted with a few additions rarely found in the day. Late editions of the first MK1 (or NA) Miata had standard ABS sitting on discs all around. Something even luxury cars missed out on.
The Braking Performance of the MX-5
Braking hard and fast is not only about bringing the car to a stop. Yes, safety is the primary role of brakes. But it’s also about maintaining speed longer in the straights, before bends begin. This helps lighter cars like the Miata even more. They won’t be burdened by the extra weight, and with a stiffer chassis, can maintain better driving lines.
Central to that stopping power is having a good MX5 brake caliper, along with pads with decent bite. The MK1 cars were fitted with smaller rotors and slightly smaller brake assemblies than the following models. As engine power rose, so did overall brake size and braking force. The rims got bigger too. 14-inch steel wheels were replaced with bigger alloys in each subsequent model.
Brake Calipers in the MX-5
Disc brakes were somewhat of a novelty when the MX-5 was introduced in 1989. Or at least an expensive alternative to drums. Brake calipers are what runs the show. They allow the MX-5 safer or more intense braking (aided with the anti-lock system), depending on how you drive and the conditions on the road.
If you suspect that the brakes on your Miata aren’t up to scratch, replacing the pads and calipers is the first point of action. The stock rotors wear quicker than you’d think, even in cars that have been driven with more enthusiasm. To remove all doubt, let’s delve deeper.
Calipers are clamp-like assemblies mounted along the steering knuckle. They consist of several parts, each with a vital role in bringing your Miata to a stop. This includes the caliper body and mount, the pads and pistons as the main parts. Smaller, but still crucial parts are the mounting clips and locking bolts (or a mounting bracket), the piston seal and dust cover, as well as slide pins. A bleeder screw, often located on the top of the caliper, is used to bleed excess air out of the system.
When you press the brake pedal, hydraulic braking fluid is fed to the caliper from the master cylinder by way of a flexible brake fluid hose and banjo fitting. The resulting pressure pushes on the piston and the inside brake pad. As this happens the caliper moves along the slide pins to engage the outer brake pad. When the pedal is depressed, and pressure decreases, the pistons pull back the pads, and the caliper resumes its initial position. This is in floating (or sliding) callipers, and the ones you’d find on the MX5.
To avoid contamination from liquids, dust, and road debris, the pistons are sealed with rubber seals and housed in a dust cover.
Symptoms of Bad Brake Calipers
You’ll definitely notice when the brake pads and calipers aren’t performing their best. Older Miatas with higher mileage need to be checked for brake pad and rotor wear and damage to the caliper components, especially the pistons and slide pins. Different driving habits and conditions, like road debris, moisture, and constant hard braking will likely cause more wear.
The first sign of wear and damage to an MX5 brake caliper is increased braking distances and loss of brake feel. This can be from inadequate pressure in the brake line caused by leaks, or jammed pistons that fail to push on the pads. In addition, calipers can fail to engage because of issues with the slide pins. In floating calipers, the slide pins may stick due to a loss of lubrication or advanced rust.
Related to this is vehicle or brake pull. If one of the (front) calipers seizes or fails to engage, then the wheels spin at different speeds and pull to the affected side. The calipers in this case can be affected by pistons that don’t pull back, or are too corroded to act on the pads. Another reason for this is that pads in different wheels have uneven wear.
More obvious and audible are weird noises from the wheels. A piston that has seized will cause the pad to rub against the rotor, even without the brake pedal pressed down. If the sound is more of a thump, then there might be damage to the mounting bracket or the clips and locking bolts. This, if left unchecked, can cause more damage to other parts quite soon.
If seals are worn out, there’ll be low pressure or brake fluid leaks. A simple inspection will confirm the extent of a leak, which can also include a torn brake fluid line. Of course, the most obvious indication of worn brakes is when the brake warning light lights up in the dash. Any of the issues above require immediate attention. If damage is extensive, then it is advised to replace the whole caliper assembly.
Improving the Braking Performance in the MX-5
In order to provide efficient and effective braking, brake force needs to be equally distributed between the front left and right calipers, and 60% of overall braking power going to the front axle and 40 to the rear. If there is wear or damage to one of the front calipers, this can be repaired, or both calipers can be swapped out. Each brake then needs to be bled.
If the existing rotors and calipers are fine, you can improve braking performance by changing to higher performance brake fluid to engage pistons with more force, and have the fluid fed through braided brake lines that swell less than stock rubber hoses. In addition, changing to better spec pads will reduce braking times, with surfaces that grip better to the rotors, while also staying cooler. Look for packaged performance kits, with better spec pistons, pads, and calipers, as well as braided brake lines. These are sold for most Miata variants, including rare early models.
Mazda has restarted to supply OEM parts for older vehicles, especially for the Miata, due to high demand. Rebuilt callipers, with the original look, are way more expensive than newer aftermarket designs. So, it makes sense to go for aftermarket MX5 calipers. If you’re swapping out for bigger rotors and matching calipers, also have in mind the rim size.
