Visit The Dirt Forum for More Information

Author Topic:   attn: jammin
Dirt Roller

Total posts: 21
posted July 28, 2002 10:39 PM

i currently race a 79 camaro with lf-900, rf-1100, lr-200, rr-175 springs and 51 rear, 53 left, 51 cross and the car is good with 75 to 100 left rear. i work in a race shop and have seen the owner set up many coil spring cars(metric) and i have a few questions. a few weeks ago he set up a 1st year drivers metric car, the percentges were the same as mine but he installed lf-800, rf-900, lr-350, rr-300 springs. the ride height was about 2 inches higher in the rear with the weight and fuel cell high on the left rear to get the car to roll over. he said he likes the rear springs to compres 1 in when installed. this rookie went out and dominated the heat and feature. he made many mistakes like most rookies and was still fast enough to win by half a straight away. i am currently building a metric car for next year. explain why these high spring rates worked so well. also, the track ran late models this weekend and was very slick, the metric cars that he set up with the weight high didn't do very well. i can understand this because when a metric car rolls over on the right rear on a tacky track the rr will roll over on its edge and bite but on a slick track it over loades the rr and is loose. i also think when the track slicks over the rear frame heights should only be an inch higher than the front to control some of the roll.when i build my car should i make a weight rack on the left rear where i can move the weight high for tacky and below the frame for slick. and will i still have enough weight up high to make the car roll if i mount the fuel cell low in the car. every metric my boss builds has the cell high and to the left. my car ran good this weekend when it was slick with 120 left rear and the left rear kicked out 3in from the left front. so please somebody explain the spring rates and how you need to control how the car rolls over. i don't want to be lost next year when i roll out my new car on the local 3/8 med banked clay track.
thanks, tim

Dirt Administrator

Total posts: 5556
posted July 29, 2002 01:22 PM UIN: 16262997
First of all....with the fuel cell high, the car will transfer weight better in the turns an help set the car. With the cell to the left, the car will actually gain crossweight when the fuel burns off which will tighten the car up some to minimize the effects of fuel burnoff. I would say that he did a good job setting the car and knows what works on the track is why the rookie did well. As far as the springs go....on compression, the are going to reach a point to which they compress. You put a 350 lb spring in, it may compress 2 inches to 600 lbs of pressure. If you use the same height spring and just increase the rate to a 400 lb spring, it may only compress 1.5 inches to reach that same 600 lb rate. Rate will be the same.....the ride height wont be.
When you go into the turn, centrifigal force moves the car onto the springs....say the Right rear....just to throw a number up....say you have 1000 lbs of weight on the RR when you are in the turns....A spring rate such as a 250 lb spring will have to compress much farther to reach that 1000 lb point than the 350 lb spring will. This is what makes the weight move in the car and the angles change.

Transferring weight.....heavier on left or lighter on right sides of the car will help in any situation....will always promote more roll. I hope this helps a little.


[This message has been edited by jammin (edited July 29, 2002).]

Back to the Archives