Originally Posted by IndyRC_Racer
(FYI: I don't glue the outside of my VTA tires - I made the A-main in VTA at Harbor Hobbies - my car was on the edge of rolling but I was careful how I drove it).
During all of the tire discussion, I have seen anyone explain why a VTA car might roll and why to mechanically adjust the car to prevent rolling. IMHO gluing the sidewall is masking a setup problem.
Can someone take some time to explain why traction rolls happen (other than the obvious too much grip) and which setup changes (other than gluing the sidewall) help prevent rolling? This is an opportunity for someone to help everyone have more fun in this class.
Thanks in advance for helping newer VTA racers (as well as older racers like me who always struggle on high bite tracks).
Adding glue isnt really masking a setup issue. Its really more of tuning aid. Most cars are their fastest just as they are about to traction roll. If adding some glue to the tires helps eliminate this risk then its worth it. If you add the glue and your still traction rolling then you have a setup issue.
Your car traction rolls because your roll centers are too low and your car is actually rolling into the carpet or track. If you raise your roll center then your car will just roll but will not have as much traction.
General rules of Thumb to help with traction roll.
Raise your inner camber link locations
Shorten your camber links ~ longer links more traction shorter links less traction.
General rule is adding to the inner links less traction and raising the outer end of the link more traction.
Raise your arm mounts on the chassis the lower they are the more traction you have.
Less castor will help but effects many more parts of the car but is another thing to look at.
Sway bars help when done and set properly.
More camber and camber gain can help.
Originally Posted by AlGio
As you stated, the reason for traction roll is too much grip and the way to correct this is to lower your roll center. High roll center has more grip than a low roll center. The way to do this is to either raise the inside of the rear link or lower the outside. However you should never go beyond it being parallel to the lower arm. Try it you will notice the difference.
This is a misleading statement what your saying is correct about the raising the inner link location but you are raising the roll center. So that contradicts with your statement about a high roll center has more grip which I have never seen this ever be the case. When your roll center is low or too low then your car will have more traction than when its higher. Also depending on the car and its arm and link length you might have to go past parallel with the link.