Nova Dirt Setup Questions
I really enjoy reading your articles on suspension, however being new to this on my own car I have a few basic questions. I run a ‘77 Nova, 3,400 pounds, on Towel City retread (recapped Hoosier 890 ashphalt carcass). Now I have a RF 1,200, LF 1,000, RR 225, LR 200 springs with standard Bilstein shocks, factory A-arms upper and lower, new bushings, and more running on a 3/8-mile semi-banked dry, sometimes rough track.
My questions are: 1) When the lower control arms are level, is that your ride height for the front? Should it be level or down any on either side? 2) Where do you measure the ride height, center of the A-arm bolt to the ground or frame to ground? 3) Where do my upper A-arms need to be and at what angle should they be? 4) Where do I measure the ride height for the rear, center of the forward shackle mount? 5) Can I measure front and rear heights at the factory pinch welds on the bottom of the car? 6) Does adding lowering blocks add bite; does it do anything with the chassis height in the rear? 7) Does moving shackle height adjust rear ride height? 8) What would a start for ride heights be? +1 around, ie: F+1, RR+1LR+1 ? 9) What kind of tire pressure would be close on a dry sometimes rough track? I’m LF 20, LR 22, RR 24, RF 26.
I’m sorry this was so long winded, I’m new at this part of racing, just want to make sure I’m right where I need to be initially so I can apply more as I go and learn. Thanks for your time helping us racers!
You are long winded, but that’s OK. Some of this is common sense so we’ll talk overall about your questions. You can get a lot of basic information by just talking to your fellow racers at your track. If you’re new, most teams will be glad to help since you won’t be a threat to win for a while anyhow. Hopefully, it won’t take long to get up to speed.
On dirt, we generally want to keep a high center of gravity, so you can keep your ride height more towards the normal cars ride height. That being said, we need angle in our upper control arms in order to have a good moment center location, and lowering the car helps do that.
The Camaros have the longer spindles and therefore are easier to get upper control arm angles. A lot of Monte Carlo teams look for and install Camaro spindles just for that reason. I think they are 91/4 inch and the MC’s are only 73/4 inch. Check your spindle height to see if it is the long ones or short. It’s possible that the same spindles were used on the Novas and Camaros.
Most teams measure ride height from the bottom of the framerail to the floor in the front and rear. Since you run leaf spring in the rear, your rear ride height will be controlled by the mounting height of the leafs.
Placing blocks between the axle tube and the leaf springs will lower the car in the rear and running longer or shorter shackles will alter the height also. Since leaf spring suspensions have a wide spring base, you might need to either run even rear spring rates or reverse the springs you have installed now in order to get any bite on the slick track.
With the rear spring rates you now have, the car would be great for a high banked and tacky track. As for tire pressures, ask around and see what others are running. Those pressures seem high for dirt track application, but I don’t know your track like the teams who run there do.
Calculating Rear Bite?
I’ve been trying to find a formula to calculate rear bite in my stock car. Is there a formula? If so, where might I find it?
No, there is no formula for rear bite. There are formulas and software programs to find rear steer, antisquat, pull bar loading, and so on, but they don’t translate into finding the amount of rear bite.
A g-force meter would measure how many g’s the car is experiencing during acceleration and you could make changes and see if the g’s increase or not. A stop watch tells us a lot about acceleration and bite too. Just record the time it takes to get from the point of throttle application to the flag stand or other point about midway down the straight.
Bite is a product of several things. We have rear tire loading as well as load distribution between the two rear tires (the more equally loaded they are, the more grip the rear will have), rear steer, throttle modulation (sometimes you just can’t mash the gas), track surface conditions, tire compliance and softness of the rubber, and more.
Contrary to what you might have heard and read, third link angle and pinion angle do not enhance rear bite, but they do have an effect on the car. The greater the third link angle, the more anti-squat there is which transfers more load onto the link and off of the rear springs.
A High Speed Crash Wearing A H&N Restraint
I am a longtime subscriber to CT. I subscribe to many of the car mags, and I picked up a CT subscription many years ago because of your in-depth articles. I now run Open Road Races (ORR) and of course turn in both directions, but I find much of the info in CT very helpful since I do all of my own work (except machine work).
I just wanted to respond to your “Flying Lessons” article in the Feb. issue. I run toward the top of the grid in ORR seeing speeds above 200 at times. I would like to add my little story to your push to have more racers use a head and neck restraint.
In ’04 the ORR organizations did not require an H-N-R for the faster classes but it was recommended. They now require them. It just so happened that for the ’04 season I upgraded to a Kirkey aluminum seat and a Simpson H-N-R, mostly at the urging of my wife.
During the last event of the season (Silver State Classic Challenge, NV highway 318, a 90 mile run), I experienced a right front tire failure at about 165 mph. It occurred in a left curve and when the tire failed, the car ceased turning left and began to turn right. In no time I was off in the dirt.
I hit a small depression, the nose dug in and I was off on a pretty spectacular end-over-end. As the car flipped, it hit several times right on the nose. Those hits were extremely violent. I had absolutely no control over my head. Due to my well constructed cage, tight fitting racing seat, tight harness, and my H-N-R, I pretty much walked away.
I did crack vertebrae in my neck and had bruises showing up all over my body for weeks afterwards. There is no doubt in my mind that minus that well fitted safety equipment, particularly the H-N-R, I certainly would not have walked away and may not even be here today. I would urge anyone involved in just about any kind of racing to please acquire a H-N-R and always wear it making sure that it is properly fitted.
One of the things that I love about ORR is that the only rules for the vehicle are safety oriented. They don’t care what your car weighs, what kind of engine you run or what size it is, and so on. As long as it is a four wheeled car (or truck) and it can pass the safety inspection for the class that you want to run, you are good to go.
Thanks for your very helpful magazine. Much of the info can be applied to any form of racing.
—Charlie Friend; Alamogordo, NM
I did see the photos of the crash and you are indeed lucky to be still with us. Your chosen form of racing is probably the most dangerous I can think of. Although Cup cars reach upwards of 200 mph, they have soft walls now to soften the impact. You have dirt and rocks and trees.
Impacts with dirt can cause the front end to dig in and produce a lot of G-forces from the sudden deceleration. In your case, the G spike could have been way up there from 70 to 100, well into the danger range.
Your car hit a shallow dirt depression, dug in, and flipped up over several times. That first hit was probably the hardest, but subsequent impacts would have increased the damage to your neck if you had not had a restraint devise on. Good choice my friend, no pun intended.