Originally Posted by Korey Harbke
Sometimes this is a little weird to explain, but I'll give it my best shot. I think of the shims under the camber link and the shims under the suspension blocks as two totally different things. It makes it a lot easier to understand, apply, and see the results on the track.
Shims under the camber link do change roll center, but it's a much finer adjustment of roll center. Personally, I don't think you are feeling this change. When you change the shims under the camber link, most people feel the change in the camber gain characteristics. On the cyclone, more shims under the pivot (flatter link) reduces camber change, so the camber setting stays mostly the same as the car rolls, but it gives a slightly lower roll center. Generally more shims will create slightly more initial grip (especially at high speed) and produce less overall grip through the middle and exit of the corner. Fewer shims (more angled link) does the opposite, and have more camber change (more negative camber as the suspension is compressed), but also gives a slightly higher roll center. Generally a more angled camber link will have less initial grip entering the corner, but more in the middle and exit.
Now for the suspension blocks. The suspension blocks do change roll center and camber change characteristics much like the camber link shims do... but the shims under the suspension blocks have a much greater effect on roll center than it does on the camber change characteristics. More shims under the suspension blocks raises the roll center. This gives more initial grip, less roll, but less overall grip in the middle and exit of the corner. Think of it as if the car feels... stiffer. Fewer shims will lower the roll center. The result is a car that rolls more and has more overall grip in the middle and exit of the corner. It does smooth out the car entering the corner though.
I hope that wasn't too confusing. Sometimes these adjustments can have varied effects depending on the track conditions and the rest of your setup. But it is a good guideline to work from. Hope this helped!
Thanks for the feedback.
What I have not been considering is the camber change (gain). I have been looking at the change purely from an RC perspective and assuming that a 0.5mm change on the upper arm shims is about the same as a 0.5mm change on the pivot block shims (noting that kit setting uses 2mm shims as default for pivot block shims and upper arm shims).
In the past, just as an experiment, I have tried zero and 3mm shims on the rear upper arm shims, and the handling does what one might expect from an RC perspective.
Heres one problem and solution, that I may need to rethink based on your new feedback.
My car was pushing in a high speed sweeper and being very taily in the tight technical sections of the track. A single change, which fixed both problems, was to make the rear camber LESS THAN (more upright than) the front camber. Settings were as follows:
-- Pivot Block Front Shims = Pivot Block Rear Shims = 1.5mm all round.
-- Front Upper Arm Shim = 0.75mm
-- Rear Upper Arm Shim = 2.0mm
-- Front Camber = 2.0 degs (BEFORE front = 1.0 degs)
-- Rear Camber = 1.0 degs (BEFORE rear = 1.5 degs)
The logic goes something like the following BEFORE the change. Too much rear tire touching track on high speed sweeper (as tire rolls under), and not enough tire touching track on slower technical section (tire camber too angled and not enough of tire contacting track). Solution was to reduce rear camber (more upright) and increase front camber (more angled) just for luck. Seemed to work, but maybe there is a better setup solution.
One of the very top drivers (who also runs a TC) mentioned that he uses zero shims under the rear pivot blocks, but I am unsure about his other settings.
Track is outdoor, asphalt, low grip, 1000' length, on side of hill.
An off camber corner.
Using Sorex 32 rubbers.
I'll need to take some time to think about this more.
Any comments appreciated.
PS: I have attached my complete setup in tabular form.