I have a few questions about the E46 M3 rotors.
1. Why does the European E46 M3 have cross-drilled rotors and the US
M3 have plain rotors?
2. Will cross-drilled rotors provide improved braking?
3. Will the European cross-drilled rotors fit on the US M3?
4. Will I need to replace any additional parts or hardware other than
pads if I get the cross-drilled rotors?
I think they're the same fitment but check on m3forum.net I can
only imagine that it's for cost cutting because they see the US as
being the market for looks over performance.
If that was the case, drilled and slotted rotors look Way Cool, and USA
models would all have them at any cost.
I bought slotted and drilled rotors for an E36, and the extra machine work
was only $20 over plain rotors. That works out to $5 per rotor, hardly a
number that would keep them out of the market.
Thanks for pointing me to m3forum.net.
One poster there said the following about the rotor differences
between Europe and US:
1) Fear of how easy it is to sue a manufacturer here for product
liability. BMW's lawyers were nervous about possible liability
concerns. They were worried that some owners would use the
cross-drilled rotors too long (well past their wear thickness rating)
increasing the possibility of the rotor cracking between the holes.
That could potentially lead to the very remote possibility of
catastrophic brake failure. (and the subsequent lawsuits blaming BMW
for this) The poor maintenance reputation we have in the U.S. (at not
being diligent about performing routine inspections on our cars) is
something I heard before from other manufacturers as well. It seems we
are somewhat 'marked' in that regard.
2) Cost - Euro-spec rotors have a two-piece 'floating' construction
that is more expensive to manufacture. The aluminum hat (instead of
CAST IRON) uses steel pins to mate to the outer cast iron friction
ring. This type of rotor effectively doubles the manufacturing cost
per rotor, so a cheaper but still effective alternative was selected.
(100% CAST IRON solid rotor) Also, U.S.-spec M3's had the lowest base
price point of any E46 M3 in the world. Our U.S.-spec E46 M3's are at
least $10,000USD cheaper than any other world market. That
significantly reduces the profit margins on those cars. Volume sales
only cover a part of that deficit. You have to remove some standard
equipment (making them optional), and manipulate a few other things in
order to make the much cheaper base price financially feasible.
3) Noise - The cross drilled rotors make a distinct noise as the air
passes through the cooling vanes and the cross drilled holes at lower
speeds. They also create a sound based on how the edges of the brake
pads interact with the edges of the drilled holes. This noise is very
irritating to some individuals, and it was determined that the solid
rotors would not produce this noise problem.
What was said in item 1 & 3 seems reasonable. What was said in item 2
about cost is anybody's guess.
On Tue, 12 Feb 2008 16:45:29 GMT, "Jeff Strickland"
I did not point you anywhere.
I do not know the validity of any of the three points you made, except that
Point # 3 is 100% true, the slots and drill holes make lots of noise -- they
click under light braking at low to moderate speeds. They could make noise
at other times too, but I have them mounted on a convertible that has lots
of other noise that drowns out the brakes. I do not find the clicking to be
annoying or harmful, but it is noticible noise.
Just that euro M3 rotors aren't slotted - only drilled. I don't
notice any brake noise other than when completely standing on the
brakes and then the noise is usually "whaaaaaaaa!"
I think list price of euro rotors is in excess of $300 each.
Have you ever had brake fade? If you have had issues with brake fade,
cross-drilling will provide improved cooling that will reduce the problems.
I have never encountered brake fade on any modern car. If you are driving
on a racetrack, or regularly do high speed mountain driving, though, brake
fade could be a problem for you.
I believe so. There are also plenty of third-party racing rotors that
No. However, you should know that there are rotors out here that are
optimized for long life, and there are rotors that are optimized for low
fade under racing conditions. In addition, some rotors are much quieter
than others. In general (and I don't know if this is the case for the BMW
OEM ones), long life and high performance don't go together. You can buy
plenty of third-party rotors from the racing equipment suppliers, some of
which have better cooling than any of the stock ones, at the expense of
If you have never encountered brake fade and never had to pull over and
see your rotors glowing, there is no reason to use anything but the OEM
On the other hand, a stock Plymouth Valiant in San Francisco will suffer
from brake fade just in normal driving...
"C'est un Nagra. C'est suisse, et tres, tres precis."
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