[ZDan]

Originally Posted by Transport3r

How? Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488
Power output is not dependent on gearing. Effective wheel torque is.

Yeah, but what is *important* is how much wheel torque you have *at a given speed*. With torque only, you don't know that. With power, you have a good idea.

Power = thrust at the wheels * road speed
Torque = you know nothing without having all the gear ratios

In the end, power is what tells you about acceleration. When you adjust engine torque with gear ratios, you're basically calculating power. With no other knowledge than engine power, you can have a good idea of acceleration performance. With only engine torque, you know nothing about performance potential. Power is more "complete" info.

I could only find published data that says 53/47. I’m sure that’s with both seats all the way back and all that, but every manufacturer will play with those numbers.

Measured numbers >>> manufacturer numbers. See my link: https://drive.google.com/file/d/0B78...uXfT1q4d2rUvGA
55.2F/44.8R.
I weigh my car every track event to verify I'm OK for my classification. Stock with me in it and a full or nearly-full tank is indeed 55/45 and not 53/47.

The miata’s power to weight is 0.076, the BRZs is 0.072. Add to that that the Miata has less inertia to get off the line with the 400lbs missing and that it comes with much better tires, and I’m not surprised.

Have to include driver weight in there, I get 0.072 hp/lb (13.9 lb/hp) Miata and 0.070 hp/lb (14.3 lb/hp) for BRZ with 165-lb driver. They're comparable, with the BRZ's greater *peak* power/weight somewhat made up for by the Miata's "fatter" power curve.

The MIata's "less inertia to get off the line" is entirely accounted for in "power/weight". It's REAL advantage is *much better weight distribution*.

I’m sure some of it is marketing, but the principle holds true. Nobody cares about the exact weight distribution when launching, you just want as much as possible over the drive wheels.

Yeah, and 10% difference in load on the drive wheels is *significant*.

You care about the exact figure during cornering, during which the weight transfer is in the single digit %s. That’s how you figure out your tire stagger.

Which is why I was considering running 255 fronts with 235 rears... Static weight distribution is so piss-poor on the BRZ that with square setup the fronts are overworked and the rears underutilized...

55/45 should be a lot worse under *braking* as well (all other things equal), as again the fronts are way more overworked, and the rears contributing even less.

It’s also a fairly steady state condition once you’re settled so you don’t square the difference. You could argue that 53/47 is enough to warrant a 235/215 F/R stagger, but I think it’s entirely reasonable to assume 53:47 is close enough to 50:50 that you can account for that with alignment.

And more importantly front/rear roll stiffness distribution. Just installed adjustable (two-hole) Eibach sways front and rear, set to soft setting front, stiff setting rear. Looking forward to track days coming up this weekend!