When you upgrade your braking system, you may wonder if you should increase the size of your rotors. Are bigger brake rotors better? It depends on several different things, including:
- The purpose of your vehicle (performance car, towing vehicle, daily driver, etc.)
- Your vehicle’s overall design
Bigger rotors aren’t a “blanket solution” to better braking. They can improve your braking in certain situations. Yet, they can make your vehicle’s braking performance worse in other situations.
Let’s talk about how bigger rotors are better in certain situations, and how they’re worse in other situations.
Increasing The Size Of Your Rotors Improves Heat Dissipation
The biggest benefit of increasing the size of your rotors is improved heat dissipation. When you use your brake rotors and pads hard (for example, at the track), they heat up faster. As a result, these parts will have a hard time cooling down. This is a problem because:
- The excessive heat can cause the rotors to warp.
- When brake pads overheat, the friction material creates a thin layer of gasses between the pad and rotor. This reduces friction, which increases your vehicle’s stopping distance.
- When your brakes overheat, the brake fluid is likely overheated, too. When that happens, air can form in the fluid. This greatly reduces your vehicle’s braking performance.
Do Bigger Rotors Stop Better?
Technically, yes. But it doesn’t always mean that you should upgrade to bigger rotors.
If you have a daily driver, it’s more than likely that your brake pads and rotors are well suited for stopping your car. Do you need performance or towing brakes? You would need brake pads and rotors designed for these purposes. That doesn’t necessarily mean you have to upgrade to bigger rotors.
The question you should be asking is how much faster do you want your vehicle to stop. Having bigger rotors means better heat transfer and better performance stopping. Yet, there’s an important factor to take into consideration: the added weight of bigger rotors.
The Drawbacks Of Using Bigger Brake Rotors
Using bigger rotors on your brakes can give you better stopping power than those that are smaller. But this can have several drawbacks. The biggest drawback is that bigger rotors add more weight to your braking system. This can be a problem for two reasons:
1. The Added Weight Can Affect Your Vehicle’s Braking Performance
Every automaker designs their braking systems based on two important factors:
- The vehicle overall design
- The type of use the vehicle is intended for
Each braking system is designed to operate within a prescribed temperature range. Upgrading to larger rotors can be detrimental. The extra weight, or mass, in the rotor allows it to absorb more heat. A larger rotor also takes longer to heat up. These factors can bring your vehicle’s braking system temperatures below their optimal range. Your brake pads and rotors need some heat to perform well. When you apply your brake pads to big rotors, the rotors can dissipate too much heat and remain too cool. That will affect your vehicle’s braking performance.
For illustrative purposes, lets look at a couple of situations on each end of the spectrum:
- Take a mid-seventies American muscle car for example. Any of them are relatively heavy, and weren’t built with great brakes from the factory. This is a type of vehicle that can benefit from a bigger rotor. There’s plenty of weight available to heat up a bigger rotor, and plenty of power to get them moving. Larger rotors are made easier by putting slightly larger than stock wheels on the car.
- On the other hand, a Miata is a very lightweight sports car. It was designed with more than adequate brakes for most situations. If the brakes aren’t quite up to how the car is being driven, bigger rotors probably aren’t the answer. Different brake pads and higher performance rotors are most likely all that is needed.
2. The Added Weight Can Reduce Your Vehicle’s Stopping Power
Decreasing the weight of the vehicle is one of the best ways to enhance its performance. Adding bigger rotors achieves the opposite. It adds more weight to your vehicle’s braking system. The extra weight may affect the way your car accelerates and stops.
Heavier rotors take more power to get spinning, and take more energy to stop. As a rule of thumb, adding one pound of rotating mass is equivalent to adding two pounds of static mass. So adding weight to the rotors has a bigger impact than just the weight added. If we revisit the examples we used above:
- A seventies muscle car probably makes more than enough torque to get the wheels moving, and the extra weight of bigger rotors will most likely be unnoticeable.
- Someone driving a Miata, with much less torque available, might find the car slower off the line with larger rotors.
So, before upgrading to bigger rotors, it’s wise to consider carefully the nature of the vehicle they will be used on.
Upgrade Your Entire Braking System Instead
It makes sense to get bigger rotors in several situations. For instance:
- If you have a vehicle that tows a lot
- If you often drive downhill with a heavy load
- If you have a racing vehicle, or a vehicle with performance mods
Yet, you should never only upgrade to bigger rotors. You should also upgrade your brake pads and calipers. A bigger rotor has more surface area for the pad to rub against. Using the original pad would be wasting some of the rotor surface. And, bigger pads need bigger calipers. The bigger rotor is really only one third of the solution. Bigger pads and calipers provide the other two thirds of the increase in braking performance.
If you want to upgrade your vehicle’s braking system to improve its stopping power, consider getting a big brake kit. This article explains how big brake kits stack up against stock brakes.