Brake Rotors

Brake rotors are one of the third major pillars of your braking system along with your brake calipers and your brake pads. The rotors are the friction discs that stop the overall movement of your wheels. Rotors are also wear-and-tear items that you should never neglect or ignore, and you certainly should never participate in a high-performance driving event if your rotors are warped, or showing any signs of wear. 

 

HOW DO I KNOW IF MY ROTORS ARE WORN OUT?

There are a few indicators. Vibration is one of them and this can be caused by a faulty caliper that causes uneven pressure on your brake pads which can cause uneven wear on your rotors. This will cause the balance to be off during rotation especially if there is more wear on one side of the rotor over the other. There will also be a substantial increase in vibration while braking. Physically while looking at rotors - at least steel rotors, they will be shiny, and this is just from the friction of the pad almost polishing the surface of the rotor. However, there are a few signs to look at while examining a bad rotor. The surface of good-condition rotors will be smooth. Worn rotors will have grooves dug into the surface as if the brake pads have trapped a piece of road debris and created damage. Another indicator to look for is when looking at the outside edge of the rotor, look for chips and wear to where there are no more shiny surfaces, and only rusted metal is exposed. But at this point, the inner edge of the rotor where it meets the hub will also show the same wear in terms of being so worn, that the inner edge no longer shows a shiny friction surface and only worn metal. 

Worn rotors will also have a major decline in performance. If you are coming to a stop and the vehicle keeps on moving that is an obvious problem you need to inspect. And if you need to come to an abrupt stop on the freeway or surface streets, you would have to apply a lot more pressure to the pedal just to get the car to stop. Fresh rotors provide a highly noticeable response as soon as you apply little pressure to the brake pedal while providing you with the feedback needed to drive comfortably on the road. Note that whenever you change your brake rotors, it is always a good idea to upgrade your brake pads at the same time because unevenly worn brake pads will create uneven wear on your rotors, and you will experience vibration soon enough. 

 

WHAT TYPES OF ROTORS ARE AVAILABLE?

Rotor technology continues to advance every year, but there are 3 main types of rotors that you can typically choose from to make for quality OEM replacements, or for a performance upgrade to improve the overall stopping performance. 

 

OEM-LIKE REPLACEMENTS: These will be rotor blanks. Meaning that in terms of design, they will look just like factory-issued rotors that are equipped in most vehicles. These will not have any slot designs or drilled holes, and provide comfort, safety, and performance for day-to-day activities. These types of rotors are not recommended for high-performance driving conditions as they will get hotter faster, as they do not have the drilled holes or slots to alleviate the heat. These will also be the most cost-effective when compared to performance rotor options. Listed below are some OEM-like brake rotor options available for popular Subaru models on the RallySport website.

• Centric Premium High Carbon Single Brake Rotor Front 25-217 Subaru STI
• Centric Premium High Carbon Single Brake Rotor Rear 28-217 Subaru STI
• Centric Premium High Carbon Single Brake Rotor Rear 22-25 Subaru WRX
• Centric Premium High Carbon Single Brake Rotor Front 22-28 Subaru WRX

 

CROSS-DRILLED ROTORS: Cross-drilled brake rotors feature drilled holes in a specific direction of the brake rotor. The purpose of the holes is to collect brake pad residue, and hot brake pad gases, and repel them through the vanes inside the brake rotor. This will keep the caliper, the brake pad, and the rotor temperatures lower during high-performance driving conditions. Typically the holes are drilled in the same direction as the vanes inside the rotor, and there will be some argument on which direction the drilled holes should face when mounted on the hub. Either way, the drilled holes also keep the contact surface between the pad and the rotor clean so that you can have optimal friction levels during braking. Now there are some problems with the cross-drilled design, and because the holes are drilled through the rotor, it affects the overall structural rigidity. On dedicated race cars, it is almost typical to see little stress cracks throughout the rotor, and this is because the rotor endures multiple heat cycles just like any brake rotor, but these will constantly go from glowing red hot then back to normal operating range. Now with cheaper cross-drilled rotor examples, these are also prone to cracking because of the cheap casting, and because they can be exposed to extremely cold conditions or with a harsh brake pad could subject these rotors to cracking. Cross-drilled brake rotors are ideal for those of you who participate in weekend track or autocross events, who like to do spirited canyon drives, or who have a fun weekend car that avoids bad weather. And of course, race cars certainly benefit from the cooling effects of cross-drilled rotors. Make sure you make a quality choice to deliver the performance results that you need. 

• Stoptech Drilled Rotor Single Front 218+ Subaru STI
• Stoptech Drilled Rotor Single Rear Right 28-214 WRX
• Stoptech Drilled Rotor Single Front Left 22-28 Subaru WRX
• Stoptech Drilled Rotor Single Rear Left 28-217 Subaru WRX

 

 

SLOTTED ROTORS: There will be a much larger variety with slotted rotors, and that is because there is now more variety in terms of slotted designs. Like cross-drilled rotors, the slots have been designed to wipe the contact surface between the pad and the rotor for optimal friction. Unlike cross-drilled rotors, the slots are grooved into the rotor, and the slots are positioned in such a way that they repel the excessive brake pad dust, residue, and gases away to promote better rotor cooling. Because the slots do not go through the rotor like most cross-drilled setups, the slot designs may differ depending on the manufacturer. There is a little give-and-take when compared to cross-drilled rotors. Slotted rotors are less prone to cracking when compared to cross-drilled because they have more structural rigidity, but cross-drilled rotors provide a little better cooling performance. It depends on your driving style, and if you're the type that has a daily driver that enjoys weekend driving events these are a great option. And they are strong enough to deliver the performance needed for dedicated race cars or rally cars. Check out some of the options we have, remember to enter your make, model, and year in the site filter to see if we have an option for you. 

• Stoptech Slotted Right Front Rotor 24 Subaru STI
• DBA 4 Series T-Slot Slotted Rotor Single Rear 28+ Subaru WRX
• Faction Fab Swept Slot Bi-Directional Rotor Rear 26-27 Subaru WRX
• Wave Spec Black Line Front Rotor 215-22 Subaru WRX
• DBA 5 Series T-Slot Slotted Rotor Single Front 22-214 Subaru WRX
• Wave Spec Silver Line Front Rotor 215+ Subaru WRX

 

 

DRILLED AND SLOTTED ROTORS: Now these are going to provide you with the most optimal performance in terms of cooling and stopping power during high-performance driving conditions. The surface of the rotor will have cross-drilled holes, as well as slots to promote cooling and clean surface contact. These are ideal for those of you with a dedicated race car, but they can also deliver the performance and comfort needed for daily driving purposes. Are they extreme for the commute to work or while getting groceries? Sure, but they will deliver the braking performance needed especially for road course events whether they be Time-Attack style of driving or HPDE events. Like cross-drilled or slotted rotors, these will also help optimize the type of brake pad you are using to avoid overheating the compound you have and to also cool the brake pad faster. This also means that you are reducing the chances of brake fade. Here are some examples of drilled and slotted designs we offer:

• DBA 4 Series Drilled/Slotted Rotor Pair Front 24-217 Subaru STI
• Hawk Talon Cross Drilled and Slotted Rotor Pair Front 25-217 Subaru STI
• Stoptech C-Tek Sport Drilled and Slotted Rear Rotors Pair 28-214 Subaru WRX
• DBA 4 Series XS Cross Drilled and Slotted Rear Rotor 217-221 Subaru STI

 

 

DIMPLED ROTOR EXAMPLES: Dimpled rotors will have that cross-drilled design, and there are some pros and cons. Since we carry a few examples we will take a moment to discuss dimpled rotors. The dimples will help clean the friction surface between the rotor and the pad for optimal stopping performance. However, when compared to cross-drilled they won't cool as effectively. However again, they will have more structural rigidity when compared to a cross-drilled setup and will perform much like a slotted design. We have dimpled and slotted examples, and we also carry drilled and dimpled examples.

• DBA 4 Series XD Drilled and Dimpled Front Rotor 217-221 Subaru STI
• EBC Brakes 3GD Series Sport Dimpled/Slotted Front Brake Rotors 22-27 Subaru WRX

 

 

2-PIECE ROTORS: Also referred to as "floating" rotors, this is a 2-piece design. You have the rotor hat which attaches to your hub, then you have the rotor blank that bolts onto the rotor hat. These are typically lighter than your one-piece rotor, however, they are not available like 1-piece rotors are because they are usually a larger size. These are found standard on R35 Nissan GT-R models as they come from the factory with a larger brake setup, and 2-piece rotors are common on aftermarket 6-piston big brake kits. These can be a little more difficult to service in terms of finding the right place that carries rotor blanks when your exiting rotors wear out. Luckily, we do carry some replacement blanks, and we also carry fully assembled rotors. Here are a few examples:

• DBA 5 Series T-Slot Slotted Rotor Pair Front 22-214 Subaru WRX
• DBA 5 Series Drilled/Slotted Rotor Pair Front 24-217 Subaru STI
• Stoptech Aerorotor 38x34 Slotted Pair Front Nissan GT-R 29+ 
• DBA 5 Series T-Slot Slotted Rotor pair Front 24-217 Subaru STI

 

 

IMPORTANT NOTE ABOUT THE CORRELATION OF PERFORMANCE AND WHAT TYPE OF ROTORS YOU USE:

Note that the faster your Subaru, or whatever vehicle you have, the more important it is to have a performance rotor. For example, if you have an 5 STI and you have an intake, cat-back exhaust, and a COBB Accessport you may be making anywhere between 3-35 wheel HP depending on how healthy your engine is, elevation, and other variables. Your stock rotors or OEM-like rotors should be fine for weekend autocross events and even driver's education events. You just need to choose the right brake pad to sustain the heat levels. However, if you have a Subaru with a rotated turbo kit, or an Evo making 4 wheel and above horsepower levels and you're running down cars, and entering 14+ MPH speeds just before braking while coming towards the end of the straightaway at your local track, you are going to generate much more heat than a standard bolt-on car. More speed will create more heat with your rotors, so if you are making big power, and you go to local track days where you are making more power to compensate for the weight of your vehicle, you will need a cross-drilled, slotted, or drilled/slotted rotors with the right compound of brake pad to avoid fading issues.