Quote:
Originally Posted by j.lecram
Any chance Essex's going to put together an AP Racing ENDURANCE kit for our E9x M3s, as you did for the C6 Corvette?
With the weight of our cars, it seems the current COMPETITION kit available is more akin to the C6 SPRINT kit. If we could get the kit with rotors in the 368-378mm range, we should still be able to fit it under many 18" wheels but have the added benefit the larger rotors would offer. It would look a bit like the AP Racing setup on the M3 GT4. Now that would be nice!
|
What exactly do you plan to do with your car that would make you think the discs in our kit aren't adequately large enough? Also, what are you basing your assessment of the disc size on? Are you simply assuming that because the M3 GT4 has larger discs, our kit isn't large enough? I'm not trying to be confrontational, I just want to understand your perspective.
All real world data, including professional racing experience on a wide array of cars, and feedback from actual customers on both platforms suggests that our discs are indeed very appropriately sized to provide a long service life for these platforms while removing the maximum amount of unsprung weight.
A C6 Z06 weighs approximately 3200 lbs., has about 500hp and tq., and typically would be running a 305 width front tire on track. It's also arguably easier to achieve superior aero on a C6 Vette.
An e92 M3 weighs 3400-3500 lbs., has 100 less hp and far less tq., running a considerably narrower front tire, and likely won't be as slippery.
Despite the 200-300 weight difference, the vette is going to be far harder on the brakes. All else equal, it's going to be going a lot faster at the end of the straight. More speed = more kinetic energy transferred into heat. I addressed this issue on the first page of my post...not sure if you caught this or not. It mentions weight vs. speed, and the impact on brakes (see below).
As another example, did you know that the biggest discs we sell to NASCAR Sprint Cup teams are only 328mm in diameter? Those cars weigh about the same as an e90 M3, have about 900 hp, and run fat slicks hitting 200mph. At a road course like Watkins Glen, they are absolutely devastating on brakes!
Therefore, I believe our Endurance Kit for the M3 is every bit as much an Endurance Kit for these cars as it is for Corvettes. We have yet to see anything to the contrary.
Huge discs look pretty, but come with significant penalties. Our design philosophy with these kits is essentially, anything more than is required is too much. Why drag around an extra 5 lbs. per corner of dead weight if it's not needed? Now if you told me you were going to run a 24 hour race, then I'd say, "Sure, you could probably go a little bigger." That's why the GT4 has larger diameter front discs, but that's not something most of our customers plan to do however. Also, please note that they're only running 355mm discs on the back of that car, despite running 24 hr. races.
Hopefully that all makes sense.
Quote:
Q: Why aren't the discs bigger?
A: Short answer: Because they don't need to be! Long answer: Our systems are built from a racing mentality. In the pro racing world, teams scrap and scream to remove ounces of weight from the cars. Anything that is larger than necessary to get the job done is simply dead weight to drag around. That is how we approach our design. If you want to go faster and a 14" disc will work, a 15" disc will simply add weight, increase the moment of inertia, and hinder wheel fitment. Sure it will look pretty behind 20" wheels, but that's not what this product line is about.
The 14" AP Racing CP5773 Heavy Duty J Hook discs we are using are the exact same discs that won the championship last year on the Action Express Corvette Daytona Prototypes. These discs are being tortured in endurance racing events every weekend at the hands of some of the top drivers in the world. Yes those cars are significantly lighter, but they're also significantly more powerful, and far faster. To give you an idea of the boundaries they're pushing, one recently hit 223 mph in testing! :O If you think you'll give these discs a harder workout in your 20 minute DE session than these guys will when running 24 Hours of Daytona...no offense, but you're probably wrong. Keep in mind that the amount of energy transfer (changing kinetic spinning energy from the disc into heat) in a braking event is most greatly impacted by speed....more so than by weight. I'm going to get a bit technical here, so feel free to skip ahead if you feel your eyes glazing over! The core formula for kinetic energy is:
kinetic energy = vehicle weight x vehicle speed2
Take note of that little superscript at the end. If you look at the equation above, you'll note that doubling the vehicle's weight would double the kinetic energy, but doubling the vehicle speed would increase the kinetic energy by a factor of four! So in plain English, that means a stop from 220mph on a lighter car is going to be tougher on the brakes than a stop from 140mph on a substantially heavier car.
When comparing discs, you can't simply look at the diameter and decide that one will be more effective than another. The number of vanes, air gap, wall thickness, vane shape, metallurgy, hat attachment design, etc. all have to be taken into account.
To give you another example, our small four piston C6 Corvette Kit has found its way onto quite a few C6 Z06's pushing 600hp at the track. That kit features a 325x32mm disc. The OEM front disc on a C6 Z06 is 355x32mm. With a disc that is 30mm smaller in diameter than stock, many of our customers are seeing huge increases in pad and fluid fade resistance, less disc cracking, longer disc life, pads that wear longer, etc. Again, it's not just disc size that matters. It's all about design and optimization.
Wheel fitment is also of critical importance in our design process. As mentioned above, most of our customers run the smallest, lightest wheels available for the platform. I won't go into all of the merits of doing so, but obviously unsprung weight, lower rotational mass, cheaper tires, etc. all factor in. Our systems are packaged tightly to allow for a wide range of wheel fitment. Using an extremely large diameter disc kills wheel fitment, and the utility of a track-optimized brake system.
Okay...I've beaten that one to death.
|