[F32Fleet]

Not sure if posted before but here you go. Interesting that the sweep area on the front rotors is the same for the 4/335i regardless of the brake pkg. The front brake pads are interchangeable.

http://www.turnermotorsport.com/t-br...fferences.aspx

http://www.turnermotorsport.com/t-br...fferences.aspx

[613Bimmer]

Great find, that'll definitely answer some of the never-ending questions that occur in this sub-forum. Maybe it should even get sticky-ed.

[ronanz]

+1 Definitely needs to be Sticky'd!!

[DTP1980]

Excellent. Please sticky. Also applies for 35d models and various others too. Portefield RS4 pads need adding in too though.
AP1656
AP1609

[DrifterX]

Originally Posted by F32Fleet

Not sure if posted before but here you go. Interesting that the sweep area on the front rotors is the same for the 4/335i regardless of the brake pkg. The front brake pads are interchangeable.

http://www.turnermotorsport.com/t-br...fferences.aspx

Here's the link for 28i models
http://www.turnermotorsport.com/t-br...fferences.aspx

[therealm3]

Props to TMS for putting this together. great resource.

One thing to note for 335 cars. while the "swept area" is the same size due to the pads being the same shape across base/m sport/ m perf; this does not mean all is equal. with the larger 370mm rotors you end up with more area of rotor surface that moves under the pad with each rotation of the wheel. this in theory would lead to better stopping power and cooling given the same pad compound. On the street, could one tell the difference 340 vs. 370 with the same pad compound and tires? probably not. But I am sure an experienced driver on track could.

[shivaswrath]

Originally Posted by F32Fleet

Not sure if posted before but here you go. Interesting that the sweep area on the front rotors is the same for the 4/335i regardless of the brake pkg. The front brake pads are interchangeable.

http://www.turnermotorsport.com/t-br...fferences.aspx

http://www.turnermotorsport.com/t-br...fferences.aspx

We need to make this a sticky

[spuntyb]

Please sticky

[RPM90]

Originally Posted by therealm3

Props to TMS for putting this together. great resource.

One thing to note for 335 cars. while the "swept area" is the same size due to the pads being the same shape across base/m sport/ m perf; this does not mean all is equal. with the larger 370mm rotors you end up with more area of rotor surface that moves under the pad with each rotation of the wheel. this in theory would lead to better stopping power and cooling given the same pad compound. On the street, could one tell the difference 340 vs. 370 with the same pad compound and tires? probably not. But I am sure an experienced driver on track could.

The "swept area" takes into account the circumference for the rotor.
A larger rotor has the potential to have a greater sweep area, but that depends on the brake size, and where the pad is located from the center of the rotor.
The 2 brakes in question use the same pad size, so that factor doesn't change.
If the pad is located at the same distance from the center of the rotor on both the 340mm and 370mm rotor's, then the swept area is still the same for both rotors.

For the 370mm rotor to get more rotor under the pad, it's pad needs to be located farther away from it's center.
Is that true for the 370mm rotor compared to the 340mm rotor?
IIRC, both brakes use the same calipers, brake pads, caliper mounting points. If that is true, then swept area would remain the same between the 2 rotors.

If the pad is located at the same distance from the center of the rotor for both rotor sizes, then the larger rotor will simply have more surface area that will not be touched by the pad.
A larger rotor does have a larger overall surface area that can help dissipate heat better. So on the track that can help keep the rotor color potentially leading to less brake fade.

[therealm3]

Originally Posted by RPM90

The "swept area" takes into account the circumference for the rotor.
A larger rotor has the potential to have a greater sweep area, but that depends on the brake size, and where the pad is located from the center of the rotor.
The 2 brakes in question use the same pad size, so that factor doesn't change.
If the pad is located at the same distance from the center of the rotor on both the 340mm and 370mm rotor's, then the swept area is still the same for both rotors.

For the 370mm rotor to get more rotor under the pad, it's pad needs to be located farther away from it's center.
Is that true for the 370mm rotor compared to the 340mm rotor?
IIRC, both brakes use the same calipers, brake pads, caliper mounting points. If that is true, then swept area would remain the same between the 2 rotors.

If the pad is located at the same distance from the center of the rotor for both rotor sizes, then the larger rotor will simply have more surface area that will not be touched by the pad.
A larger rotor does have a larger overall surface area that can help dissipate heat better. So on the track that can help keep the rotor color potentially leading to less brake fade.

Agreed. Unfortunately, something is different because my car with the 370mm rotors does not have unused rotor surface area. So, my guess is when you get the M Sport (Or M Performance) calipers and rotors, the caliper mounts push it slighter further from center if the pads are truly the same. Which I think they are based on talking with Porterfield when I ordered my pads.

Just for giggles I wanted to roughly see how much extra area my $600 for the M Sports got me on the front:

area of a circle = pi r squared
my crude measure of swept area is ~75mm

so ((370 / 2 ) sq * 3.14)) - (((370 - 75) / 2 ) sq * 3.14) = ~39,151 sq mm
vs.
((340 / 2 ) sq * 3.14)) - (((340 - 75) / 2 ) sq * 3.14) = ~35,619 sq mm

so 3531 sq mm more swept area on the 370 mm rotor set up.

[DrifterX]

Originally Posted by RPM90

For the 370mm rotor to get more rotor under the pad, it's pad needs to be located farther away from it's center.
Is that true for the 370mm rotor compared to the 340mm rotor?
IIRC, both brakes use the same calipers, brake pads, caliper mounting points. If that is true, then swept area would remain the same between the 2 rotors.

The caliper is not the same between 340mm rotor and 370mm rotor equipped cars even though they look identical. The part numbers are different and have a different sweeping position (from the same mounting point on the knuckle); the calipers for 370mm rotors are located further away from the center of the hub which would give them the greater sweeping area. You can see that the rotor contact surface is further out from the center by comparing the pictures below as well; the 370mm rotor has a larger "hat".

340mm x 30mm


370mm x 30mm


Part Numbers for Reference:
340mm equipped F30: http://www.realoem.com/bmw/enUS/show...diagId=34_2312
370mm equipped F30: http://www.realoem.com/bmw/enUS/show...diagId=34_2312