A Guide to Setting Up Your Autocross Car
This is a very basic starter set-up guide. You may like some cross weight in your car if there are more right hand or left hand turns...
Start by disconnecting your swaybars, having your steering box at the center of travel and roughly setting your ride heights to where you want them. Now you can square the rear end. We used to use a long string tied to jack stands and run it the length of the car. Then you’d bump it up against rear tire, then measure to your frame. Now I have a laser ‘string’ I can use to measure to the frame. Measure at two points along the length of the straight portion of the frame. Adjust your lower control arms until the two dimensions are equal. Move everything over to the other side as a double check. The dimension from the string should be the same dimension as the first side which tells you that your rear end is centered within the frame.
After the rear end is square, you can now set the front end toe. Measure from the ‘string’ to the rear of the front tire and then to the front of the tire. Adjust your tie rods in or out to make these dimensions equal. One side is now done, now move back to the other side and set the toe.
Disconect sway bars
https://i.imgur.com/mzVJnk9.jpg
Using the Laser String
https://i.imgur.com/2HO3ZCa.jpg https://i.imgur.com/VUNbiG9.jpg
After squaring the rear and the front end, you are ready to set your corner weights.
First thing you do is check the ride heights again and adjust as necessary. Everything should be close….
https://i.imgur.com/mzofcOT.jpg https://i.imgur.com/23qwqR7.jpg
I have double adjustable coil over shocks. To adjust ride height to make the rear or front equal, measure both front, or rear shocks and adjust the nut accordingly. Make sure to mark the adjusting nut so you know how many turns you want. Each turn on my Penske shocks is 1/16”, so ¼” ride height change is 4 turns, but start out by only turning half the number you think you need because there are four springs working to hold the car up. Once you get the ride heights set, zero out your scales roll the car on and see what you have.
https://i.imgur.com/Iknpg9f.jpg https://i.imgur.com/HOQ5eCW.jpg
https://i.imgur.com/w7CvpOG.jpg https://i.imgur.com/6YcYLde.jpg
When scaling the car you cannot change the right to left or front to back weights. The only weights you can change is the cross weight, or left rear to right front or vice-versa.
As you can see on my first attempt, my LR to RF cross is 52.42% or 85# more than the RR to LF weights. Everyone’s first question is how do we fix this. You fix it by adjusting the spring adjusting nut on the shock. If you change just one adjuster, you would need about 10 or 12 turns on any one shock to fix this. Then all of your ride heights are jacked up. But, to keep ride heights the same, in my case, I need to loosen both the LR and RF spring adjusters and tighten the RR and LF spring adjusters.
https://i.imgur.com/vPFatXi.jpg https://i.imgur.com/EZr4Eqn.jpg
By experience, I started by loosening the LR by 3 turns and RF by 2 turns. Then I tightened the RR by 3 turns and LF by 2 turns. That brought me to about 14# difference. So, I did 1 more turn at each corner and this is where I ended up at. As you can see, the percentage is at 50%, but there is still 3 pounds difference, but you’ll never see that on the course.
At this point double check your ride heights and you may need to adjust them a bit, but don’t let the weights get away from you. Anything within 1/8” is good…
https://i.imgur.com/EakJaxM.jpg
Now you can go onto finalizing caster and camber…
My camber and caster started out at almost 3 degrees each. 3 degrees neg camber is good for the track, but not for the street. I want between 4 and 5 degrees pos caster and something less than 1 degree for camber and tire wear.
Camber is a direct readout from the gauge.
https://i.imgur.com/lF2Zpsm.jpg
To check caster, you turn the wheel 20 degrees out, zero and level the gauge as indicated in the picture. This is the drivers side of the car.
https://i.imgur.com/7x08YVy.jpg https://i.imgur.com/5NHaVgS.jpg
Turn the wheel 20 degrees towards the inside and read the caster. Here is a little under 3 degrees. The bubble is hard to see, but it is there.
https://i.imgur.com/cOXpJS2.jpg https://i.imgur.com/GJH74Ll.jpg
I have heim ends to adjust my caster/camber. This isn’t the easiest to adjust, but it works fine. Since I had too much camber for the street, I wanted to lengthen the heims, but to gain positive caster, I wanted to lengthen the front one a bit more.
https://i.imgur.com/fenqhhU.jpg https://i.imgur.com/ylRDYQg.jpg
After two tries, I got everything to work out. I initially used 6 turns on the front heim and 4 on the rear one, but it still wasn’t quite enough caster and just a little too much camber, so I extended the front heim 2 more turns and left the rear one alone. As you can see that gave me about ½ degree camber and 4-1/2 degrees caster, which is what I was looking for.
https://i.imgur.com/BWsXXot.jpg https://i.imgur.com/8HGf9Ai.jpg
