Unsprung Weight -- Brembo Brakes

I've been informed that the Brembo brake kit for the 996TT reduces unsprung weight by 14-18 pounds per corner (one tuner told me it was 14 lbs -- another said it was 18 lbs). Thats a lot of unsprung weight. However, the brake kit is not cheap (over $5k). My question is this: How much difference/improvement in performance will be experienced by reducing unsprung weight by 14-18 lbs per corner? Will it be appreciable? Will it improve acceleration noticeably? I've seen formulas for comparing normal weight reduction to increased hp (e.g., reducing the weight by X lbs has approximately the same effect as increasing hp by Y). Obviously, the impact of reducing unsprung weight is much more significant. Is there any similar formula for comparing reduced unsprung weight to hp? From my perspective, the increased braking capabilities of the Brembo kit, while nice, would not justify the expenditure alone, absent other appreciable performance improvements. Thanks for the input. Craig (L.A.)

Craig: I think you're thinking in the right direction. Someone a year or so ago posted a claim that 1# reduction in ugly unsprung rotating mass was equal to 10# of plain ole sprung non-rotating mass, but I think that's highly exaggerated. I've heard others say somewhere around 4#, which sounds much more reasonable. Let's say it's 4#, and that the Brembos save 14# per corner (even that figure surprizes me). That would work out to approximate a loss of 224# of ugly sprung non-rotating passenger, for example. Would that be significant for your hp and tq? Several years ago I got lighter-weight wheels and shaved 9# per corner from my NA car with 260hp and could not tell one iota of difference. I also don't think I could tell that I had lost 144# of sprung weight (e.g., a puny passenger). Maybe the stop watch could tell though. What do people mean when they say that losing a certain number of pounds is like getting a certain number of hp/tq? If they were talking only about drag racing, I think I could understand the equivalency. To get there faster, produce more power or move less weight. But it's not quite like that on a road course (except under straight line acceleration, of course). Under heavy braking your engine's power is meaningless, but your car's weight is very important. There are also corners and transitions where weight and nimbleness are more important for speed than is power. It's been said that $100 for each honest and reliable hp increase is a fair price. If you subscribed to that principle, you'd want the Brembos to give the equivalent in weight loss of a 50 hp increase. I don't think they'd do that. But wait; they're supposed to improve braking too.

I spoke with Barry at Race Technology (Brembo Rep) -- he is a real straight forward guy -- no unnecessary hype. He provided me with some accurate information. The 14 in, four piston, two piece (floating hat/rotor assembly) Brembo kit for the 996TT weights 24.6 lbs per corner. OEM is 31 lbs. Thus, 6.4 lb savings per corner. Barry advised that nine out of ten customers use this kit on the front, but only a larger caliper on the back (the larger caliper on the back is needed to counter balance the increased breaking strength on the front and prevent nose dive during breaking). The larger rear caliper (with everything else OEM) increases the rear weight slightly. It is possible to put the full two piece kit on rear as well, and save 6.4 lbs per corner in the back, but it is costly. The GT2 steel six piston 15 in. brakes weigh 38 lbs per corner. Thus, they add seven lbs per corner of unsprung weight. Barry advised that every pound of reduced unsprung weight translates to three pounds of regular weight. Craig (L.A.)

Yes, Barry sounds like a very straight shooter. So it seems you should get Brembos only for their braking. According to Barry's figures (which seem very reasonable), if you got Brembos all around, you'd save 25.6# of ugly unsprung rotating mass (uurm), equivalent to about 77# of regular mass. I don't think you could notice that by seat-of-pants. If you got Brembos in front and larger calipers in back, it's just about a wash weight wise. You know, Porsche makes those new light-weight brakes that cost about as much as a Ford Focus.

"I spoke with Barry at Race Technology (Brembo Rep) -- he is a real straight forward guy -- no unnecessary hype. He provided me with some accurate information. The 14 in, four piston, two piece (floating hat/rotor assembly) Brembo kit for the 996TT weights 24.6 lbs per corner. OEM is 31 lbs. Thus, 6.4 lb savings per corner." My OEM 13" TT brakes came from Barry and weighed 34.5 lbs per corner! I should check with him to see if he has the 13" floating hat/rotor assembly rotors which would even further reduce the weight of what I have.