Found my old weight to hp formula I had from autocrossing days. Might be of some interest.

Reducing unsprung weight by 1 lb. is equal to reducing total weight by 4 lb.

Reducing total weight by 11 lb. is equal to 1 rwhp. increase.

Lighter wheels and tires = more responsiveness.

 

very cool formula

 

time to go on a diet

 

What do you mean by "unsprung weight?" Weight not on the suspension?

 

^^anh...dont ask questions. just stop eating. its free horsepower. not only do you not have to pay for food but you gain power too!

 

If those are true I gained ~18.9 whp by changing my wheels from the last set of 20's.

Fronts are now 12lbs lighter (each)
Rears are now 14lbs lighter (each)

12+12+14+14 = 52
52*4= 208
208/11 = 18.909

Wow...

 

why do you think i'm going to the gym, Calvin?

 

hahahahahahahahhaha

 

That's why I'll be using 18's. Go ahead, flame away. I know they look like sh*t compared to 19's or 20's, but just can't go against the numbers.
Big diff in tire weights if you look (050's +4 over PS2). We always pulled spare and everything out of car

 

I agree, if you are more into performance than looks go forged 18's all the way.

 

That's my plan, just haven't decided which wheel yet.

 

So... I'm considering replacing OEM Bridgestone Turanza's @ 26 lbs ea with Kumho Ecsta ASX @ 28.4 lbs ea... Do I understand your formula correctly to say I will be losing the equivalent of approx 1hp? Or is it possibly more due to rotational mass?

 

9.6 additional unsprung x 4 = 38.4 lb
11 lb. = 1 hp. so 38.4 divided by 11 = 3.49 hp

Handling will be most affected, not really on the street as much as a track or other road course. In fact, the car may seem to ride and drive better on the street.

Don't go crazy with this formula as for most of what we do and the way we drive it's no big deal. Rotational mass will affect straight line racing.

 

If you like formulas, here's one from Road & Track Tech to figure bhp from 1/4 mile ET.

"There is no formula to derive horsepower from gearing and rpm, but there is an estimate using quarter-mile times and vehicle weight:

bhp = weight
(ET/5.825)3

You did not give your Camaro's weight, but we'll guess it scaled 3350 lb. with driver (everything was lighter in those days!). Plugging in the numbers, we get 383 bhp with an elapsed time of 12.5 seconds. That doesn't sound like a lot of power, we know, and our guess is the formula assumes a somewhat prepped chassis and thus good traction. You'll have to plug in the real vehicle weight, if known, and make your own hunches relative to your old Camaro's traction, but in any case the power would seem to be in the 400-bhp neighborhood, which is definitely capable of mid-12 sec. times with good traction in a production-based sports car.

Another formula uses quarter-mile mph to solve for bhp:

bhp = (mph/234)3 x weight

Tickling the calculator with your 110-mph figure and our 3350-lb. guesstimate, we get 348 bhp. Again, not a huge power number, but enough to do the job at 3350 lb. If you and your Camaro weighed 3650 lb., then our Casio says you had 390 bhp.

There are plenty of assumptions concerning traction and wind resistance, etc., in these horseback equations, so you can fudge the numbers any way that makes sense. Of the two, we prefer the mph-based equation because traction and driver technique spread ETs all over the map, while mph remains surprisingly constant."

 

Thanks for the response... I figured a much - however I wasn't sure about the term "unsprung"... I guess I'll be sacrificing 3.49hp as I do not autocross but do occasionally drag... Maybe some light weight rims in the future to counter the added tire weight.