Cobra weight distributions?

[RET_COP]

Thanks Tom on that very informative link. This spring I'll get my car to my buddies scales.
How mush does your EM weigh?
Lou

[Tommy]

Lou,
With me and a half tank of gas in it, it weighs about 2450. BTW, I mispoke in my earlier post. My weight distribution is 48% front / 52 % rear.

[Dwight]

I have a 302 fuel injected motor in a Lone Star Cobra. I mounted my motor back in the car so my weight on the rear would be better.
I scaled mine at the local co-op on their drive on truck scale. I know it's not the best place to weight a car.

I drove the front wheels onto the scale, then the whole car and then the back half. Did the math and came up with 52% rear and 48% front with half tank of gas.

car 2315 lbs

with full tank and me 2660 Lbs

Dwight

[RET_COP]

Rick,Dwight thanks for the posts.
So three cobras
Front/Rear with driver
Tom 48/52
Rick 49/51
Dwight 48/52

Being that the driver sits behind the center of the car F[0"------90"]R dashboard is about the center 45" and driver butt is about 70" these cars are built about 50/50 without driver.
Is 50/50 optimal?
I think of a car like the GT40. with the mid engine, it must have been rear heavy yet I read where it cornered great
Lou

[scottj]

Originally Posted by RET_COP

Rick,Dwight thanks for the posts.
So three cobras
Front/Rear with driver
Tom 48/52
Rick 49/51
Dwight 48/52

Being that the driver sits behind the center of the car F[0"------90"]R dashboard is about the center 45" and driver butt is about 70" these cars are built about 50/50 without driver.
Is 50/50 optimal?
I think of a car like the GT40. with the mid engine, it must have been rear heavy yet I read where it cornered great
Lou

Mine is 45F/55R w/driver and 10 gallons of gas. I can get 57R with a full load of fuel. The driver accounted for +1% rear...

Scott

[Silverback51]

Originally Posted by RET_COP

......Is 50/50 optimal?
I think of a car like the GT40. with the mid engine, it must have been rear heavy yet I read where it cornered great
Lou

Is 50/50 optimal?

That is a yes/no question. There are so many factors in the equation that there is no one answer. The variables range from tire size and spring rates to the CG of the vehicle. For that matter tire pressure can have an influnce on how the vehicle handles.

Let's take the GT40 as an example. It is far from being 50/50 as it's a mid engined car. But then you look at the tire sizes. Much larger in the rear than the front. Not unlike a F1 or Indy car. Now look at a NASCAR (as much as I hate to refer to them) car. All four tires are the same size and I'm willing to bet the car is close to 50/50 weight distribution, with a side to side bias due to them only turning to the left.

Since a Cobra is not able to run same size tires front and rear (and by size I mean tread width) you would generally want a little more weight on the rear. The spring rates would be such that under acceleration you transfer the weight to the rear of the car for traction. The same is true under braking for a corner. The weight is transferred to the front to help in the braking and turn in at the beginning of the corner if you are trail braking.

Hope that helps a little, and didn't just confuse you more.

[scottj]

In steady-state cornering, such as a skidpad, the heavier end will lose traction first, everything else being equal. Road racing is more about transitions than steady state cornering. Since heavy braking transfers weight to the front tires, road race setups favor a static rear weight bias to counter weight transfer that would otherwise result in a turn-in push. Rear bias also helps forward bite off the corner. Being a short wheelbase car increases weight transfer.

[RET_COP]

Good stuff here guys, I'm taking notes.
Thats why the QA1 Proma Star double adjustable are $300.00 for one!!!
Its tough to set up for cruising with sometimes a passenger and then go autocrossing. Either its a compromise sacrificing on both ends or have two completely different setups.
I just set up for cruising, very neutral without a driver at this time. Next winter could be a different upgrade.

Two Cobra's would be the answer

Lou

[RICK LAKE]

RET_COP Lou every car company builds there own frame and body. The best thing I can let you is to start with the spring rates the company comes up with when they sell the kit. After everything is togeather, all the fluids full, half tank of fuel in the car, battery in the r/r corner of the trunk, get the car weighted with you in it. Have a wheel alignment done after ride height is set and weights are done both diagonally and front to back. If you are rally serious have the bumpsteer also done so that both front wheels are turning the same radius. After this you need time on the drives seat and take pictures of the car going around turns, right to left weight transfers, see how much the car leans around shape turns. Fromt here you go to stiffer springs about a 30% rate increase over the ones that came with the car, better shocks like QA1 with dual control for compression and rebound. Your street setup will not work well on the track. You will also take a beating running a track setup on the street. Getting your self a Kirkey road racing seat will help alot by not having to hold your weight in place when driving hard. If you are going to track the car, 2 important things to look into
#1 pay a 2 or 3 quart accusump and have it hooked into the oiling system. this will prevent lossing oil pressure around high "G" turns. Also work great as a preluber for starting the motor.
#2 add 1 extra quart of oil to the motor for the same problem of high speed turn and oil not going back into the oil pan fast enough having the pickup uncovered and have the oil pump sucking air. This will not do any damage to the motor. There are a couple of suspension books to look at. I good driving school is another thing to look into. IF you have any guys around where you live that are into dirt track racing, they have scales and know alot about seting up cars and suspension ideas. There is about a 50/50 about weather to go with higher rated springs and small sway bars and the other idea is larger sway bars and lite spring rates. The angle of the coil over springs has somnethings to deal with too. Rick L.