BMW Brake Rotors - Which rotors are right for me?

Just like choosing brake pads, the answer to that question depends on the type of driving you do.

BMW brake rotors are excellent - vented and oversized for the application. When combined with a capable brake pad they provide superior braking performance even under mild track and autocross situations. The venting and sizing is key because brake rotors store heat (see below) and the added mass of oversized discs helps prevent 'warping'. In over twenty years of BMW racing and tuning we have never seen a warped BMW rotor.

The rotors we sell are from trusted and well-known brands. Depending on the application we sell Original BMW, OEM, and performance alternative rotors. We can use our experience as a BMW service shop, race team, tuner, and parts distributor to give you high quality rotors that we feel meet or exceed the factory standards. We don't want to offer you the lowest price brake parts - we want to offer the best BMW braking parts anywhere!

Brake Rotor Brands:

Rotor Types

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Standard OEM Direct Replacement

Perfect for a daily-driven street car as well as autocross, track, and race use (depending on pad)

Can be used with nearly any type of pad - street or track

Inexpensive

Will not contribute to pad wear

Typically uncoated so surface rust is likely to form

Centric Premium High Carbon Direct Replacement

Perfect for a daily-driven street car as well as autocross, track, and race use (depending on pad)

Black electro-coating covers the entire rotor for the best corrosion resistance

Can be used with nearly any type of pad - street or track

Inexpensive

Will not contribute to pad wear

Zimmerman Coated OEM Direct Replacement

Perfect for a daily-driven street car and commuting

Phosphate coating covers the entire rotor for excellent corrosion resistance

Can be used with nearly any type of pad - street or track

Inexpensive

Will not contribute to pad wear

Turner Motorsport cross-drilled performance

Perfect for a daily-driven street car and commuting (but the holes are just for looks)

Acceptable for autocross, track, and race use (some hole-to-hole cracking may occur)

Can be used with nearly any type of pad - street or track

Will not contribute to pad wear

Corrosion-resistant coating on the mounting hat and vanes to prevent rust

Turner Motorsport slotted performance/racing

Intended for autocross, track, and race use with an out-gassing brake pad
(still acceptable to use on the street but the slotting is just for looks)

Can be used with any type of pad - street or track

Corrosion-resistant coating on the mounting hat and vanes to prevent rust

Turner Motorsport cross-drilled and slotted performance

Ultra-aggressive appearance - shows off your brakes especially with open wheel designs

Recommended use only for street-driven cars (no track or autocross)

Can be used with nearly any type of pad - street or track

Corrosion-resistant coating on the mounting hat and vanes to prevent rust

M Sport, M Performance, or Euro (selected BMWs only)

Designed as street rotors by BMW and an upgrade for US-spec cars

Either blank rotor surface or cross-drilled, depending on the model

2-piece rotors with aluminum center hub for much-improved cooling, making them ideal for track use

Can be used with any type of pad - street or track

More Info (in very simplified terms...)

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It's a common misconception that simply changing brake rotors will improve your stopping performance. This will only prove true under extreme conditions - track events and racing - and only with rotors such as BMW's Euro and Performance parts. For the majority of us, the standard OEM replacement rotors will be more than sufficient for the type of driving that we do.

The brake rotor acts as a heat bank. Heat is stored in the cast iron of the rotor as the brake pads create friction. The central vanes of the rotor direct air through the casting, venting the rotor of the heat and also cooling it at the same time. A larger rotor has more capacity to store heat and can thus, provide better stopping performance for greater lengths of time.  This is one reason why racecars typically have big brakes. Too small of a rotor for the application will lead to the heat being trapped with the rotor and overheating the rest of the brake system.

This makes a difference in your rotor choice because a standard brake rotor has more mass and will act as a better heat bank than one that has been drilled and/or slotted. It has become necessary to drill or slot the rotors for other reasons - mainly to allow an exit for gases that build between the pad and the rotor. The gas needs an escape so that it does not block the application of the pad to the rotor. But newer technology has made these types of rotors nearly obsolete (although they look pretty cool on a street car). None of the street pads produce this gas and there are very few race pads that still do. One benefit to slotted or drilled rotors is that the edges of the holes and slots can graze the pad material, which will decrease pad life but help maintain heat in the pad (critical for track pads). Note that the Turner Motorsport rotors have their holes and slots chamfered to allow smooth transit of the pad over the rotor surface. One other thing to note: a drilled and slotted rotor will have less mass and less braking surface than any rotor - these are mainly for looks.

What does all of this mean to you?
On a street-driven car with street pads, the typical driver will see no benefit to using a cross-drilled, slotted, or two-piece Motorsport rotor over a standard OEM replacement rotor. There are small benefits to using one of these on a street car - looks/aesthetics, drainage for water, for instance. There's nothing wrong with using a different rotor on the street and we would not discourage that. But if you're looking for better braking on the street, first upgrade your pads and consider the rotor design to be an aesthetic choice.

For more in-depth and scientific explanations, see StopTech's excellent technical pages:

http://www.stoptech.com/tech_info/tech_white_papers.shtml