Curmudgeon wrote: Porsche put lead weights inside early 912 bumpers to help with weight distribution, so don't be afraid to add if needed. It may very well be that the weight bias correction done by adding 100 lbs in the front of the car
I thought it was the early SWB 911s that had the weights.. the 912s were better balanced with the shorter and lighter 4
Ok guys after many setbacks and delays in almost done.
Current question, I have a beefy front sway bar on, and right now the rear one isn't installed, should I try that first or install the rear as well? Next Friday ill get it corner weighed
Try the car first, the lack of a rear bar will help with traction. Bring it to a skid pad and try to loose the back end and work from there.
Also do you have a brake proportioning valve? Most rear-engined cars are tuned so the front wheels lock up before the rears. Very helpful in an emergency situation.
I have a valve, don't know how it's set yet but that's tips on the list of things to figure out once its moving
As mr2peak suggested, a skid pad would be the way to find out how the car handles
Full throttle, steady speed, closed throttle can all be explored.
The Corvair had vastly different tire pressures front and rear.
All things that need to be explored before driving in anger.
Having built a mid-engine Mini and "Seven:"
First thing, take it to the autocross. There you don't have to worry about balling up the car should you find the limit. Throw it around in order to become familiar with your new creation so you two can learn to trust each other.
As others have said, put wider tires on the back. If you proportion tire width front/rear to match your weight distribution front/rear, it'll go a long way to undoing whatever oversteer tendency there is.
"In general", the faster you go the more the rear weight bias becomes an issue - it's as if the center of gravity moves rearward with speed. It doesn't of course but that's how it felt in my old Datsun 1200, where I needed a large rear bar at the autocross to help the car rotate, but on a road course that same bar wanted to put me in a ditch. No rear bar for high-speed stuff.
The rear weight bias causes accidents because drivers don't know how to properly exploit the car's capabilities. It's like hearing "this knife makes a terrible screwdriver." Yeah, but it's an awesome knife when used as one. Having the rear come out and getting off the gas is the worst thing you can do. The weight comes off the rear, lessening traction, moving to the front where it improves traction, and getting off the gas also causes the engine to essentially put the brakes on slightly. When the back end comes out, stay on the gas. A high-power mid-engine car can be driven very well by someone who understands that the gas pedal essentially steers the back tires.
With the weight at the back you're going to have a ton of traction and gobs of braking ability. Couple that with the light weight and small size and it should do well at autocross.
mad_machine wrote: I thought it was the early SWB 911s that had the weights.. the 912s were better balanced with the shorter and lighter 4
It was.
I always wondered if part of that wasn't for weight distribution, and part was to increase the polar inertia so the cars would be less likely to snap. Maybe.
My guess is, it just made things worse...
Karts won't teach you the balance of a car with the engine hanging past the rear axle, they'll teach you the balance of a short mid-lateral layout car like an AW11 or Elise/Exige...which is much easier to drive.
Truth be told, I can't see where this car should be overly weight biased towards the rear.
With the size of b*lls that are going to be required to drive it, center of mass should work out fine
I don't think it will be as scary as everyone seems to be implying. Just don't put super-high grip tires on it for the first outing, start with something hard so you can feel it begin to let go before it's gone.
Might help to decide on final tire sizes after you have the cross weight #'s, then find a stock car that shares the bias and borrow the sizing.
Very cool project!
NOHOME wrote: Truth be told, I can't see where this car should be overly weight biased towards the rear. With the size of b*lls that are going to be required to drive it, center of mass should work out fine
I laughed and sent this to my wife. her reply is if it was true it would be offset by the total lack of brain material.
You'll need to log in to post.
