The Physics of Racing

With recent discussions on Mike's car, bringing this article back to the top. :)
 
I LOVE that article. Thanks for reminding me about it. I downloaded the PDF for my kindle so I wouldn't have to loose it again. It makes for some very interesting reading and very informative. Thanks Tim for bringing in back up.
 
Tim thanks for posting this!

Take a look ay Part 1 weight transfer.

His calculations:

"Lf = 1600 + 3200 / 5 = 2240 lbs, Lr = 1600 - 3200 / 5 = 960 lbs

Thus, by braking at one g in our example car, we add 640 pounds of load to the front tyres and take 640 pounds off the rears! This is very pronounced weight transfer."
_____________________________________________________________________________
My calculations:

Lf = 1600 + 3200 / 5 = 960 lbs, Lr = 1600 - 3200 / 5 = -320 lbs
so 960 + -320 = 640 lbs?????
_____________________________________________________________________________
So on my car:

Lf = 1080 + 2400 / 5 = 696 lbs, Lr = 1320 - 2400 / 5 = -216 lbs
so 696 + -216 = 480 lbs of weight transfer in my coupe if it had the same wheelbase and CG as the example which it does not.

That means my weights would then be 1560 front and 840 rear = 2400 total
Lf now is 1560 = .65% front
Lr now is 840 = .35% rear
_____________________________________________________________________________
So on a Mustang that these brakes were designed for:
a 1998 SVT Cobra has 1950 Front and 1425 rear = 3375 total

Lf = 1950 + 3375/5 = 1065, Lr = 1425 - 3375 / 5 = -390
so 1065 + -390 = 675 lbs of transfer

Lf now is 2625 lbs = .78% front
Lr now is 750 lbs = .22% rear

Now there are some things to consider. Our cars are more stiff and have a much lower CG than a stock Mustang. You must also take into account the larger rear tires we use which will have more friction thus more stopping power. But ignoring all that.

We are using a braking system engineered to be balanced and stop a car that has 4 times the weight on the front tires than the rear. We now take that same braking system and install it on a car that has less than 2 times the weight on the front than the rear. So after all this do we consider the braking on our cars to be as balanced as a mustang????

So now I have taken a braking system that appears to be at least 50% out of balance (using the laws of physics) and reduced the power of the front brakes by 57% via my proportioning valve. I have tested this system and verified that the system is in fact fairly well balanced.

Funny how all this math and physics can verify reality.:)
 
I lost you at "Tim thanks for posting this!" :D Will take me a while to do that math :rolleyes: Math and paper are just that, we must have a test. :D Not sure where. Anyone have an area where we can do 60-0 tests?
 
Let's make this clear too, anyone could/should participate. The more real data we have, the better. This isn't a competition between Mike and I, it's an exploration to determine what is better and what modifications could/should be made.
 
More Info

Mike and Tim
I have an Excel spreadsheet that calculates line pressures, clamp forces, etc for a braking system, if you'd like a copy.

Pretty comprehensive - it takes into consideration Co-efficient of friction of tires, pads, center of gravity, weight distribution, all the data that goes into a full blown braking calculator.

I used it to determine what size master cylinders I needed on my car - it was a rough calculator type tool, so when installed, I can then dial in the balance between front and rear and still be within the range of adjustability.

If you want a copy, send me your email addresses

Paul
 
You must log in or register to reply here.
Back
Top