With the more conventional setups, the dive and roll actions tend to cancel each other out
The rebound settings in both front shocks will need to be increased with the LF rebound needing the most increase. Some teams feel the need to run very high rebound rates at the LF corner. We don't agree with that concept and this trend has caused a lot of cars to develop a mid-corner push that can't be corrected with crossweight adjustment.
The amount of increase and decrease in rebound and compression varies as to the track size. Long, smooth, and flatter tracks can use much more rebound control than on shorter tracks that might be rough. Rough tracks also have a negative effect on the RR when using a very stiff spring. The car tends to bounce at that corner instead of negotiating the bumps smoothly. A reduction in the RR spring rate along with changes to the crossweight percent to bring the car back to neutral handling is necessary.
Most of the high-end racing shock companies make shocks that are double adjustable. We've been using the hlins double adjustable shocks on our Late Model project cars with a lot of success. We can make changes to the overall spring stiffness and still have enough range of adjustment to make each work.
Yes, there have been a lot of problems associated with trying to run the BBSS setups, usually because of incorrect application. There are other areas where we need to make changes to accommodate the BBSS setups. The front geometry must be redesigned in order to properly gain the advantages of the BBSS setups. Moment center location is still very important, and camber change characteristics are totally different with these setups.
The BBSS setups have very little roll and a large amount of dive associated with them. Her
The BBSS car will dive more and roll less. That means our camber changes at the front are entirely different than what we saw with the conventional setups. Both front tires will loose lots of camber due to the high dive numbers, 3 to 4 inches in most cases and low roll angles that normally would counter camber loss in more conventional setups.
The bottom line is that the upper control arm angles will need to be reduced. If you had say 18 to 24 degrees of upper control arm angle with your conventional setup, you will now need to reduce those to 10 to 14 degrees, all the while maintaining a decent moment center location.
The static cambers themselves must be altered with the transition. The RF must be reduced from the normal (-) 3.5 to (-) 4.0 degrees to under (-) 1.5 degrees or less in most cases depending on the type of tire you run.
The LF tire camber must be increased from a normal 2.5 to 3.0 degrees positive to 5.0 degrees or more. This tire will loose around 4 degrees of camber in the turns.
Ackermann effect is very detrimental to the BBSS setups. If you are used to using some amount of Ackermann in your conventional setups, you can't run it with the BBSS setups. The reasoning is this, with the BBSS setup, the LF corner is forced down and a lot of the front load is carried by that tire. Since it is doing a lot of work, it will compete with the RF tire.
These two tires must track along their proper arcs, tangent to the curve and perpendicular to the radius. We have computed and proven that a car running on a short 1/4-mile track only needs around 0.100 inch of added toe, or about 0.2 (1/5) degree of additional steering angle in the LF wheel. On half-mile tracks, that number goes down to 0.040 inch of added toe or less than 0.10 (1/10) degree of increased LF steering angle.