Does anyone have vertical CG data or estimates for their car?

[DMXF]

I'm doing some brake system optimization work and it requires a CG value. Please include your ride height and other pertinent car details with any CG number you may have. Thanks

[strictlypersonl]

Originally Posted by Dcmgt

I'm doing some brake system optimization work and it requires a CG value. Please include your ride height and other pertinent car details with any CG number you may have. Thanks

A simple site search for center of gravity turned up this. Just a couple of weeks ago. Last thread

[DMXF]

Bob - I don't see ride height referenced there, which can be significant with some people running their cars 2" or more lower than others. I assume the reference to the FFR spec racer, however, would mean that car is probably running pretty low. So maybe a lighter weight aluminum body and absence of all the spaceship rollcage would lower the CG to a max of 16"?

[strictlypersonl]

My figures are predicated on 5"-5.5" ground clearance so you can extrapolate from there.

[DMXF]

Bob or anyone, what is the maximum expected deceleration in g's that one of these cars is likely to develop? Thanks

[strictlypersonl]

Anywhere from 0.8G for mediocre street tires to 1.6+G for race tires.

[DMXF]

Thanks Bob. Am I correct in that it is desireable to have the front wheels lock up just a tad before the rears? I'm putting comp brakes on my car and just going through the calculations because Shelby American offered several bore size masters back in the day to optimize the braking. I have input from guys who have set these up before, but unfortunately it's not clear cut with their choices varying (and some people complaining).

[strictlypersonl]

Yes, the fronts should lock a bit before the rears, mostly to prevent doing donuts when you trail-brake into a corner.

[Jerry Clayton]

And then you can run/slide straight off the track because your front wheels are no longer turning

[Larry Spillman]

Contact Shelby Racing they have all this info from as far back as 1962 up to todays new series of Cobras dont forget the new tires out perform anything from the 60s and 80s era.

[RICK LAKE]

Dcmgt Don't know if it helps but run my car at 4 1/2" off ground. I have the 12" rotors and dual piston caliper setup from ERA. Car is 2705lbs with 1/2 tank of fuel in it. I have gone up 35% in spring rate to stop the nose diving when going into turns and hard braking. From 15" tires to 17" with better rubber made a huge differents in the cars handling. Adding the power steering has made the control of the car better also. The problem is the old driver is loosing his quickness and the car has gotten away from him. No damage or problems to hurt either. Would have been nice to have the car 25 years ago when yellow line on back was smaller and bigger B@!!s. QA1 shocks are also working out with more adjustments over the stock ones.
There are Gauges out there for checking the pressures of the calipers. The unit goes between the pads and you press the brake pedal It's gives a pressure reading within 10psi of real number. With having this, weight of car, getting a tech 1 for "g" force you might be able to come up with balancing the brake system the way you want. I know that if I pound my brake pedal, I can go through the windshield. All four wheels do lock up. I have not adjusted my balance bar in my car since it came from ERA. They have the setup right. Rick L.

[DMXF]

One issue with brake setup for these cars is you can never get ideal braking distribution for all regimes without a proportioning valve or similar device. You usually have to just optimize for heavy braking lockup type conditions, which is most critical.

Bringing up tires is an interesting subject. I am very skeptical of modern tires being that much better in all out handling/stick than the best bias ply you can run on these cars. Most of the time people are not comparing to the best bias ply tires, which I believe are the D2672 and D2772 Goodyear "Stock Car Special" slicks, with tread cut in them for street use. These tires have substantially more sidewall stiffening than any other bias ply race tire you can readily run on a Cobra (far better than the Goodyear "Cobra" tires), which is like simulating a slightly larger diameter wheel. The front to rear height ratio with these also seems more optimal than some others. Bill Murray smokes new production Corvette and Porsche laps times at the tracks he goes to with the vintage Goodyear "Sports Car Special" 6.00 & 8.00x15 tires on CSX3032 and those tires are reportedly notably inferior to the D2672 & D2772 I mentioned. I remember when radials were coming into widespread use that I didn't like he feel going to them... more jittery, the bias plys felt more stable. Even when NASCAR stock cars went from bis ply to radials around 1990 I remember their laps times weren't really any different and some of the drivers complained. Yes, I know the real wide bias ply tires on a Cobra helpes make it more sensitive to low speed groove tracking on the streets, but I'm referring here to all out handling.