Doesnt change my opinion. Nor is there data to support both being superior... do you have data that says the AMG design is better? Or is this a presumptive, "if AMG does it, it MUST be better" conclusion?

like 20" rims on a 'race car' with plenty of room between the caliper and barrel... why?

Simple, marketing demands it - not engineers.



I see you bought the slotted/drilled... must stop just like the AMG now.

AMG AG would not have done it without doing its own testing and seeing a definite benefit. This would be like stating parts designed/tested by ///M group for BMW have no gains/use.

Never claimed It would stop like an AMG, just pointing out that in fact, tuning arms of major manufacturers (who extensively test different designs) do in fact drill/slot rotors. A fact you state there's no gain in doing.

Even Lockheed/AP Racing has a race application for drilled and slotted rotors. Lockheed/AP Racing has been engineering ultra-high performance brake systems for almost 100 years, was purchased by Brembo in '99.

These are without any doubt the 2 largest brake technology companies on the planet. You should contact them and let them know they got it all wrong! :dunno:

I've seen these on the ALMS GT2 BMW ///M3 prior to the 12hrs of Sebring race. Contact Rahal Letterman Racing too.

You know why tuners drill & slot rotors? Because drilled/slotted perceived as 'performance', 'upgrade' and 'sport', just like red (or yellow) calipers, stripes, stickers and huge spoilers. Between solid rotors & unpainted calipers and cool looking brake kit - which one majority would choose and will be more willing to spend $$$? Exactly.

Think about it: what is better, more or less friction surface? And why they use slicks - if allowed - on dry pavement?

LOL at the claim that AMG don't sell style accessories. Mercedes even refers to the AMG Style Package on their website. They sell whatever people will buy.

Friction force depends on the normal force and the coefficient of friction. Area doesn't enter into it. OK, it can spread the heat out, but it doesn't create more braking force. Clamp harder, change coefficient of friction, or have a larger diameter rotor (better lever). The latter is heavier, so drilling helps reduce unsprung weight with a larger rotor. Drilling the same size rotor just weakens it.

Slicks allow the use of softer rubber compounds. Tire traction for acceleration doesn't depend on tire width.

The common theme here is that racers use certain features because they allow other features which themselves have benefits. People have adopted those features because they look like the ones the racers use. Drilling stock diameter rotors is like installing a hood scoop that doesn't actually penetrate the hood. But the racers have them! Yes, but the racers design them to do something.

Agree with you completely on the marketing decisions.

Well duh, everyone who didn't skip school knows that.

Got a chance to drive these for over 1 hr on the Hwy last night, heavy rain/cool weather. The instant bite when wet brakes are applied is one of the things I was hoping for and they don't dissappoint. The 1 or 2 seconds of pad hydroplane/no braking force is totally gone (BMW operation manual states drivers should lightly depress brake pedal regularly to keep rotors warm/dry while driving in rain, who does that?). Inital bite/pedal pressure/modulation are identical hot or cold.

2 cycles of 12 near ABS activation back to back stops from 50 and 60mph down to 10mph resulted in ZERO fade or required additional pedal pressure to keep near ABS intervention (actually saw smoke from the pad binder mat'l burning off). No OE BMW system I've driven has been able to do that.

JCL, please provide link that states AMG defines SRS GT drilled/slotted rotors are for appearance. I searched this AM and could not find it.

Race on Sunday, Sell on Monday!

I put Bosch Quiet Cast rotors on the rear, which has "made in Germany" stamped on it and it has been fine and they were $60-70 a pop. This is a X5, my family hauler. As long as the car stops, that's all I care for. As long as the rotors don't warp, I'm good....

For pads, I was going to get Akebono, but ended up getting Pagid's becuase they were a little chepaer and were sold by the place I bought the Zimmerman's. Textar's I believe are OE for most BMW's but they tend to leave a lot of dust so I shy away from them if needed.

Glad they work for you. :thumbup:

I didn't state those specific rotors are only for appearance. You stated that AMG only made things that gave better performance, or they wouldn't sell them. I countered that by pointing out that they also sell style accessories. Accessories that are just for appearance. QED.

Those particular rotors may be of a larger diameter, I don't know. It would be a reasonable assumption. If they were larger, they could certainly give better performance. If as a result of being larger, they were too heavy, they could also be drilled, and actually optimized to be drilled when the cooling fins were designed, in terms of layout, thickness, thermal fatigue, etc.

But that is completely different than taking a stock sized rotor with a standard vane design and drilling it. Even if you then put an AMG badge on it.

AMG sells steering wheels. Do those steering wheels make their cars corner better?

Ok, I see what you're saying.

AMG worked over/track tested different MB models into vehicles like the E55 Hammer back in the late 80s. MB and AMG were seperate (like RUF is to Porsche to this day). MB purchased AMG about 25 yrs ago and cashed in on AMGs hardcore "form follows function" credo by putting AMG logos on almost every dress up item in their catalog. AMG is still a separate arm of MB and extensivly tests items going on the top of the MB line vehicles (the SRS GT AMG for 1). With MB buying AMG and diluting the name by AMG logoing dress up kits and steering wheels, this does not mean that AMG design/development of items such as brake rotors for the SRS GT AMG are dress-up only.

BMW puts the ///M logo on steering wheels too, by your logic this means ///M division is "dress-up" only with no added performance on the ///M developed/tested vehicles.