MWP":37kx2jcb said:
Yeah ok, but will you see/feel that difference (seat of pants, or lap times)?
I very much doubt it.
How many of us care that much about tire weight and distribution of mass?
Drag racers may see a difference , but they don't care about stopping so much, so big brakes aren't on the must have list.
Well, yes you should. You are constantly decelerating and accelerating on a track. Force(accel)=Force(stop). Therefore, lighter rotating components will effect your braking. I'm not trying to fight you guys on this but the math doesn't lie. It's very often overlooked and is a situation to consider. In FormulaSAE this was a very big concern and we did a lot to avoid the issue(Diffs with most mass near the center, smallest brakes we could get away with(rear was mounted on the diff) aluminum axle carriers). In a 4wd car you take a big hit in the area but you regain in reduced wheel slip (for acceleration).
A little guesstimated arithmetic:
Al flywheel = 10 lbs loss
Large vs Very Large rotor delta (4 corners) = 8 lbs loss
Carbon Driveshaft = 20 lbs loss
Wheel/Tires (4 corners) = 25 lbs loss
63 x 1.5 = 94.5 lbs of effective mass lost
The real objective of my concern is just don't think throwing the biggest brakes you can on a car is going to make it perform at its best. If the thermal mass (which the AllTrac completely lacks) is correct and the proper clamping force is determined, there should no need to put 18" rotors on your car because you WILL effect your lap times and handling. Other things like pads, fluids, and ducting will make the additional performance push you need.
MWP":37kx2jcb said:
Oh, and almost none of these are performance items due to lower inertia that helps with acceleration.
Sure they might have a slight positive effect in that regard, but its not why they exist.
lightweight flywheels & clutches - light to help with high rpm gearshifting (drop revs quicker on disengaging clutch). multiplate is for power handling.
carbon driveshafts - because steel is heavy (car weight), and they reduce unsprung weight in live axle applications.
Yup they help those as well, but you better tell ACPT they have they're selling points all wrong:
Independent testing by a leading automotive magazine (Turbo, October, 1996) showed rear wheel horsepower gains of more than 5% with the simple switch to an ACPT carbon fiber driveshaft. This significant increase is primarily due to lower rotational mass of the driveshaft.
http://www.acpt.com/Products/Composite-Driveshafts.aspx
Low engine rotating inertia is essential as, in the lower gears especially, it adds significantly to the overall mass of the car that has to be accelerated.
Source:
http://www.grandprix.com/ft/ftpw005.html