Earlier today the issue of traction rolling 12th scales came up on RC Tech. Being a victim of this lately, led me to write a long post on some of the techniques that I have learned setting up my car in order to eliminate them from my race nights. I thought this would make a good blog article for the week and it would help keep building on the pan car information base located here on the site.
Often, all it takes is removing camber and/or camber gain from your car. However this can lead to severe coning on the outside of the tires which makes tire life shorter than it should be. So in an effort to make the car wear tires flat in the front, these are my go to moves:
2. Softer side springs, linear springs being preferred as they cause less lifting. This allows the pod to react a little bit slower. In low traction conditions can make the car feel lazy, but we are talking about high bite here and it does not seem to affect response too much as the car already has too much.
3. Wider Track Width: Both front and rear. The wider the car, the less lateral weight transfer and the less traction rolling you will have. In High bite conditions, you want to run wider. An added benefit of the wider rear is that it will put more leverage on the side springs making them act softer.
4. More Forward shock position: This is big. I am happy I can do this with our car. It slows down the transfer of weight to the front tires and I can run a stiffer center spring which controls the lateral roll on the car to keep it from rolling. It's sort of like reducing droop on a sedan. Increases response and limits lifting, to a point. Go to stiff and the car just turns too much on entry.
5. Longer side links. This is also big, this allows the car to roll at a further forward position on the chassis and it decreases leverage on the front end from the rear pod. Makes the car flatte.
6. Longer upper arm: The longer the upper arm, the slower the reaction time of the front end as well as a tid bit less camber gain. This makes the car less aggressive in the middle of the corner.
7. Less Static: Reduces camber gain in the middle of the corner. Makes the car turn in harder at the beginning of the corner, but mellows middle.
8. More Reactive Caster: More reactive caster actually reduces caster in the middle of the corner as the car rolls more. This is big because it actually reduces some initial entry corner response and then does it further in the middle of the corner. It is a good adjustment to use.
9. Longer wheelbase: with our car, it moves the pivot further forward, which again gives the rear less leverage over the front to lift it, sort of like a longer link as well.
10. Run battery in line: Keeps more weight at the front of the chassis which makes it harder for the car to lift.
11. Softer front springs. The harder springs put more pressure on the carpet which creates a bigger "wrinkle" where the tire is contacting the carpet on the track. This slows down reaction and allows the car to roll instead of "dig in" to the carpet. Put a stiff spring in the front of your car at our place and watch it do some somersaults.
12. Lighter tube fluid, again, this is sort of like softening up the pod springs, it just allows the car to dump over and roll. I always try to get away with the lightest fluid I can get away with without my car becoming unpredictable on our bumpy tracks.
13. Less tire sauce in the front: I am not sure if saucing less time is particularly effective past 5 or so minutes, however how much you sauce is big. Using less additive in the front can dramatically decrease your rolling over.
14. Softer front tire: A harder tire digs into the carpet harder which causes more rolling over. The opposite is the case with a softer tire.
Like everything there is a curve to all settings. I think if the grip is lower, the settings seem like they have the counter effect, this is due to the relationship of grip and reaction forced on the car. When the grip is lower, you want to increase response and weight transfer to dial in the car, to a point.
On a lower grip track a soft spring can both increase steering and decrease steering, depending on the part of the corner you are looking at tuning. Early in the corner and it turns harder, but later in the corner it makes it push. Opposite is of a stiff spring.
When I think about it, when you are tuning on high grip vs low grip you are tuning a different part of the corner. On lower bite, you want the mid corner response to be higher as cars tend to be on top of the track and need a quick response suspension to come back to center quickly and get around the corner fast. On high bite you are trying to tame down than middle corner response to keep the car on all 4 wheels.
Just my 2 cents. At my place, when the grip comes up and everyone is flipping off the track, I keep on trucking and I take the approach above.