05-30-2004, 08:15 AM
Join Date: Apr 2004
Location: SF Bay Area
Originally posted by AMGRacer
I am new to 12th scale racing and I wonder if the experts could answer some questions for me.
It seems to me that under acceleration in a 12th scale there is little weight transfer to the rear unlike in a touring car. Am I right? It does appear that the rear pod will flex downwards some, but the middle shock (I have a rc12l3) appears to control the rear wheels contact with the ground due to bumps in the track more so than affecting rearwards weight transfer under acceleration?
Also what is an "average" ride height setting for a 1/12th scale?
In gas sedan racing you usually want your foam tires to be as low profile (side wall) as possible. Is it similar in 12th scale where you use smaller sidewall tires on higher grip surfaces?
Lastly, is there any good online reference material for 1/12th scale tuning?
1/12th scale car setup depends on the surface you are racing on. General rule of thumb is that the less traction the racing surface is providing, the higher the center of gravity (CG) and or the roll center (RC) needs to be. If you are racing on carpet, which provides the optimum in traction, the lower the CR and RC needs to be. This prevents traction rolling. As you move to racing outdoors or on asphalt, then you need to start raising your CG and RC to provide better traction on less than optimum surfaces. The RC can be and most often should be, different from the front of the car to the rear of the car. Changing the RC on a pan car can be difficult due to a lack of adjustability of the suspension but there are ways to improve mechanical grip.
EXAMPLE: If you have an over steer condition under acceleration, which is most often the case on 1/12th cars, you need to increase the RC on the rear of the car or decrease the RC on the front of the car. As I mentioned, due to the minimal ability to adjust the suspension on the rear of a pan car, there are several things you can do.
1. Use a softer compound (durometer) rear tire.
2. Increase the diameter of the rear tire. This in effect raises the rear CG.
3. Use a firmer compound front tire.
4. Decrease the diameter of the front tire. This lowers the front CG.
5. Decrease the thickness of the T bar if you are running a T bar style car.
6. Add cut outs or holes in the T bar to increase flexibility. (Be careful! The T bar is the most fragile part of the pan car suspension.)
7. Remove the center bolt from the middle of the T bar where it attaches to the motor plate.
8. Use lighter weight oil in the center shock.
9. Use a lighter spring on the center shock.
10. Use a stiffer spring on the front kingpins.
11. Increase the toe in on the front of the car.
12. Apply a traction additive to the rear tires but not the front tires.
All of these things or a combination of these things will increase the mechanical grip on the rear of a pan car which will help to eliminate an over steer condition. Joel Johnson grew up racing at our local tracks in the San Francisco Bay Area. I remember one time when the track conditions were so bad that after trying just about everything to increase the traction on the rear of his 1/12th car, he ended up putting layers of tape over the battery slots so the batteries would not set down in the slots. This raised the CG on his car providing more weight transfer which increased his rear grip! Battery slots in pan car chassis were added to lower the CG for carpet racing.
As it turns out, there are many options to increase the grip on a pan car. Not like there is on a touring car, but enough to make a pan car a most enjoyable and satisfying class. Go over and talk to the person who is putting in the fasted lap times and ask him or her what set up they are using remembering that their set up may only get you close. The same holds true for any setup you get off of the internet. Understanding your driving style/abilities and the track conditions is paramount in setting up your any car, scale racing or 1:1 racing.
The key thing to remember is – it must be fun!!
Thanks heaps guys.