Saturday, April 30, 2011

Front end setup how-to

Ok, I'm not sure I have ever laid this out 100%, so I will just do a little how-to on the front end.  I will add the pictures once my camera charges :>  Part numbers are referenced from the F104 pro instructions.

The first thing to do is remove the upper arms (part F8) from the front suspension, and remove the camber plate and the spacers underneath it (F1 and F5).  This is not necessary, but if you are running your servo in the manual suggested position, you may want to change it to the output shaft forward---pic:

You will need to add 2mm spacers to the underside of the servo saver to properly space the ballstuds down.

Now, the camber plate (F1) mounts directly on top of the lower arms (F10).  The camber plate spacers (F5) can also be put on top of the camber plate, and secured by non flanged nyloc nuts (BA7) upside down.  You don't have to use the spacers, but they can be retained if you need to keep all the original parts on the car (as you might for TCS races).  Otherwise, just use the nuts as provided by the instructions.

I like the aluminum camber plate over the plastic one simply because it locks down the upper arm ball studs harder and it won't wallow out.  It's not necessary, but it is worth buying.

Anyway, you can set up the camber plate per instructions with a button head screw from the bottom, but I prefer to use a long grub screw.  The long grub screw will allow you to remove the upper arm for changes without popping the upper arm off, thus prolonging it's life.  12mm is a good size to start with, but the length sort of depends how many spacers you use for the ball stud.  After a lot of fooling around, I find that 4mm under the ballstud is a good place to start.  I also like to set the camber plate to the 1.0 position.  That will yield around .5* camber with the front end set as I recommend.  Adding and subtracting spacers will change the camber, so the plate will not be accurate.  You may need to change plate settings to get the camber where you want it to be if you are changing settings.

At the kingpin on the front knuckle, you can remove F2, F3 and F4, the steering knuckle spacers.  These spacers can be used, or you may use .5 or 1mm spacers instead.  The spacers are 2.5mm, 1.5mm and 1mm, for a total of 5mm.  I use 2x 1mm and 6 x.5mm so I can adjust in .5mm increments.  This is important if you race foams, since the car will respond to that small of a change.  For both foam and rubber I recommend starting with no spacers under the knuckle (BB14), and 2.5mm on top.  Then the remaining spacers on top of the arm (F8).   If you use the plastic spacers, just put the big one (F2) on top of the knuckle, and the rest op top of the arm.  For carpet, this will lower the to about 3mm with the correct size front tire (around 54mm) and for rubber it will raise the front end to start with a bias to rear traction.

The rear ball stud on the upper arm should be set up with no spacers to start.

The steering should be either set to 0* or 1* toe out.  You may need to run toe out on lower traction surfaces to get the car to turn in at all if you have it biased to a lot of rear traction.  That will be a car to car and track to track thing.  I hope that my front end setup will allow you to dial more steering in without being too twitchy/hard to drive/abrupt.  I have found this setup makes the car very smooth steering and linear, like a 1/12 car.  The stock setup seems very sensitive off the center and darty.

Note, this setup also tends to provide more caster:

My basic directions are like this:

The more level the arm, the more linear the steering feel

Raising the overall height of the arm, without altering angle, makes the front end dig in more, like it wants to screw itself into the ground.

Lower the overall height of the arm lowers tendency to dig in and makes the car more linear through the turn.

Raising the angle of the upper arm increases steering, but also increases twitchiness/sensitivity off center.

Increasing the height of the arm at the kingpin (outer end) is a bigger change than lowering on the camber plate (inside)

Raising the rear ball stud on the upper arm without changing anything else, increases bite in the center of the turn.  This is important for rubber tire or low traction tracks.

Use camber to get more or less "gross" amounts of steering- this is more of a macro adjustment.

The whole reason for these modifications is to reduce the sensitivity of the front end overall.  Stock the car is like a volume knob that is ON FULL BLAST or OFF.  My way is more of a 1 through 10 selector knob, which you can use several variables to tune in...tire dope, camber, arm height/angle, etc.  Better that you can dope the whole front tire and have the ability to reduce it than be forced to run a 1/16 tire sliver or none at all.