Handling traits and charecteristics

[Sideways]

Wider rears will help a lot when you have as much torque as you do. The info on springs was just to show the different ranges and what stiff really is. My guess is your stiff ride has more to do with shocks than anything else. The wider rears will allow you to use more throttle while the car is turning without the car trying to step out on you. This will make a huge dent in your run times.

 

Cary

 

Always a perk being able to use more tire to lay down more power, just need to be careful, might find yourself out accelerating those front tires on the corner exit and pushing wide. But I guess that falls into the category of "balance".

 

Good read btw Tube. Falling into the topic of the thread, would you mind posting your opinions on the traits of your car and your setup (Assuming youve a Z or had one)

[tube80z]

So with that sort of weight orientated platform you have a basic setup? Tune it with ARB's? Its just that with a lot of HP to me the emphasis shifts to getting power down. Where wider rear tyres may or may not balance out the setup.

 

The setup is arrived at a completely different way really. What I now do is weigh the car ready to go to get the wheel loads and the front and rear percentages. Then I plug this into a spreadsheet that has the all the basic parameters to compute weight transfer (CG, RC, track width, camber, etc.) and use this to solve for front and rear roll angles as well as the percent of weight transfer at the front, which is referred to as a magic number.

 

I pick equal roll angles because I'm trying to keep from loading the chassis in torsion as much as possible, which is a trick you can use when you don't have a stiff car. Then I set the front load transfer (note the terminology change -- what I'm saying is the percent of load dealt with by the springs, bars, RC) to be around 3.8 percent of the total weight transfer. What this means is I've used a systematic way to split the front rear balance of load transfer I control on the car. It will transfer weight based on the CG height and track width and there's nothing you can do to change this. All you can control is the split front to rear.

 

You're probably wondering what's up with that number. It's biased towards understeer and the recommendation for a racing car is 3 to 5 percent front bias (understeer). If you try and setup a car with a negative front percent (oversteer) you'll quickly learn the car is impossible to drive. Even when we say we like a car loose we really have them setup front stiff to a certain degree. A car setup to oversteer will not put power down at all.

 

The magic number is driver, track, and car dependent. But once you have it will let you play with springs, bars, track width, etc. and Keep the car balanced. If you set the car up this way it will always respond as expected to setup changes. If you have weird setups you may get into positions where you have to do the opposite of what you expect.

 

With regards to the wider rear tires they are setup so that I can get max cornering and still get forward drive. This came from reading a number of Ortiz articles and a really long corner we have out our track. To maintain your speed on a constant arc you need forward drive. But if you've loaded the tire 100% laterally then you can't give it any drive or it will slide. In this scenario I really setup the rear tires to corner and have extra capacity for forward drive, which is the key to going faster. This works even on a 200 HP car (my old one) as well as the more powerful monsters.

 

Cary

[tube80z]

Good read btw Tube. Falling into the topic of the thread, would you mind posting your opinions on the traits of your car and your setup (Assuming youve a Z or had one)

 

My car is very neutral. I can set it up too neutral (note not loose) but I prefer to drive off the front end. It is really setup to change direction extremely quickly and this along with being able to put power down under cornering is why it was as fast as it was.

 

This setup does require experience and commitment. You've got to be very careful when the back steps out. I'd almost say you need to learn to simply drive through it because if you try and steer into the slide the car will often over correct and pitch you off.

 

Basic info.

 

class SCCA FP using GT-2 allowance (engine setback)

weight 200 pounds under class minimum with no ballast (ballasted to 2% rear heavy and almost perfect corner weights)

approximately 200 WHP

ride height at class rule minium

track at class rule max

tires: Formula atlantic front and rear (13 inch)

1.4 to 1.5 lateral Gs

1.1 to 1.2 under braking

Approximately 2.5 seconds faster than a ZO-6 vette on a 49 second course (Fall enduro in Medford)

 

Hope that helps,

Cary

[Sideways]

Damn those are some very impressive numbers

[260DET]

Gold, hard copy of this page going into my suspension Folder of Knowledge