It’s all about the brakes…

Brakes are one of the most important – yet often overlooked – part of any car. Good brakes will often make a bigger difference in your lap times than a similarly priced horsepower increase. The brake system consist of many parts and it’s important to at least basically understand how they work, so your upgrade choices will have desired effect.

Lack of informed approach might result in buying parts which will hardly make any difference. For example only changing your standard brake rotors to an expensive slotted or drilled rotors will make no improvement to your car’s braking performance. We hope this article will help you choose your next braking upgrade wisely and will help you achieve your goal.

Main brake components

The brakes on Mazda MX-5 Miata consists of:

• brake pads
• brake rotors
• brake lines (both hard and flexible)
• brake calipers and carriers
• brake master cylinder
• proportioning valve
• brake fluid reservoir
• ABS module (on cars with ABS)
• and the brake fluid you have in the system.

We won’t go into technical details on each part in this article, but we’ll help you identify the weak points and improve your braking system.

Braking explained

The brakes converts your car’s kinetic energy into heat by brake pads pushing against the brake rotors, where the mutual friction creates heat and slows your car down. This means the main factors influencing your braking performance are the pads and rotors – and rotors are basically a piece of steel designed to dissipate heat, so the pad compound should be the primary focus in any brake upgrade. Alternatively you can get bigger rotors with greater heat capacity, but this is usually quite expensive as it would require changing the brake carriers and possibly calipers too. You’ll also need to make sure the brake fluid is in good condition as it absorbs moisture and degrades over time. Boiling the brake fluid means you have lost most of your brakes regardless of your setup.

Upgrading the brakes on your MX-5

Step 1: Braking technique

We’ll keep it simple – the shorter the braking is, the more time the pads and rotors have to cool down. You should always brake as firmly as safely possible in any kind of sport or competitive driving. The greatest enemy for heat dissipation and brake parts lifespan in general is a gentle application of brakes while gradually coming to a stop.

Step 2: Brake pads

Using brake pads designed to suit your car’s purpose is the most basic and most effective brake system upgrade you can get. There are regular street, performance street and various racing compounds available. If you have limited budget (who doesn’t?), we recommend to spend only necessary amount on solid rotors from an established brand and use most of the budget on performance pads. For MX-5s used both on street and track we had the best experience with Hawk HP+ and Ferodo DS2500 pads, both outperformed other brands we used before. The disadvantage is a more brake dust and often noisy braking. If you’re looking for a less aggressive pad for spirited country roads driving without track use, we can recommend for example TRW, Mintex or ATE pads.

Safety tip: brake dust is dangerous to breathe in and can damage your health. You should never “dust off” or blow off the brake dust – always use wet procedure, like washing it with water and detergent mix or with a brake cleaner fluid.

Step 3: Brake fluid

Once you get performance pads, you’ll be able to brake harder and more often – putting much more heat into the brakes than before. Hence we’d recommend to replace your standard DOT 4.1 brake fluid with a 5.1, which has almost 20% higher boiling point. This is a very cheap upgrade and has no disadvantages, so we highly recommend it. If you see track regularly or you’ve seen bubbles in your brake fluid after driving on track, it might be worth getting a performance fliud (e.g. Motul RBF 600, Castrol React SRF Racing).

Step 4: Performance rotors

There are several types of rotors – plain, drilled, slotted and a combination of drilled and slotted. While all of them have their advantages and disadvantages, we’d recommend to use plain or slotted rotors, which are less likely to develop cracks (usually microscopic and hard to see) than drilled rotors. Rotors can also vary in the inner veins design, which force the air to flow through the channels once the brake disc is rotating. Besides standard one-piece rotors there are also two-piece available, but for a much higher price and are an overkill for a street-legal car. These cosist of outer steel disc bolted into lightweight aluminium alloy centre section (which is not used for braking), thus reducing the rotating unsprung mass in the car and usually also providing slightly better cooling performance. Except for race application (long track use) we were never let down by normal one-piece rotors from established brands.

Step 5: Bigger brakes

If you drive or race with forced induction and slick tyres on fast tracks, it’s probably the brakes that limit your performance. Bigger brakes not only have increased heat capacity, but using multiple pistons they can also improve the braking force and control. The disadvantage is higher rotational and unsprung mass, so it’s as always about finding the right balance. There are many aftermarket kits available and if you’re on a budgetr, you can use 270 / 276 mm brakes from Mk2.5 (NBFL) Sport models.

Brake myths and misconceptions

Myth 1: My brake rotors are warped!

First, let’s state the most important fact: brake discs don’t warp. What makes the brake discs shudder and vibrate is uneven surface, which can be measured as increased lateral runout. It’s usually caused by uneven wear or uneven brake pad material distribution on the disc. There are many good articles available online on this subject, so we’ll just list them:

• Overheated pad material unevenly covered brake disc surface. This happens quite often with “OEM replacement” pads, which are not capable to withstand repeated excessive braking. Solution: get better pads (with good pads we never experienced brake shudder).
• Uneven wheel hub surface caused the brake disc to be off-axis when installed. The use of brakes will then amplify the effect, causing the brakes to vibrate more and more. Solution is to thoroughly clean the hub before the rotors are installed.
• Surface rust caused uneven wear, which is again amplified more and more by further use. This happens because rust will eat away disc surface, while the area under the brake pad remains untouched. Once the rust is removed by braking, this part of the disc will stand higher than the rest where the rust was. Solution: use the car at least once a week or when you notice the rust is building up. Remove the rust by braking harder several times (70-80% braking is enough) and park the car so the brake pads cover different part of the rotor than before.

Myth 2: Drilled rotors are better cooled because of the holes

Drilling the holes was designed to let out gasses created from the brake pad material during braking and also water if driving in the rain. Most current brake pads do not have these outgassing problems, so there’s little benefit to drilled rotors on a street car. While they would perform better in the wet, holes in the rotor weaken it’s structure and increase the possiblity of cracks during repeated heat cycles. Because with drilled holes you also reduce the mass of the rotor (thus it’s thermal capacity), depending on your setup the brakes might overheat sooner than with a solid rotors. From our experience, we’d recommend to use solid (or slotted) rotors instead.

TL;DR or improving the brakes in five steps:

1. Get pads made from high performance compound
2. Use a brake fluid with higher boiling point (DOT 5.1 or a racing-spec 4.1)
3. Install performance rotors (it’s not about whether they are drilled/slotted, but rather about their cooling efficiency)
4. Get bigger brakes (e.g. from Sportive models or an aftermarket kit)
5. Last but not least, using proper braking technique will help significantly

Do you have any thoughts or comments you’d like to share? Please let us know!