Tuesday, May 24, 2011

Rambling about rubber...

This year so far, the tracks around here have been pretty green.  They have been preparing them, but there still a lot of grit and sand and junk out there, so it's been lower traction.  Most of my tuning has been to try to get the car to have grip enough to leave the corner better, and still steer.
I have been running the split upper deck sans damper plate, he car doesn't seem to miss the plate so far.  There really hasn't been enough traction to make the car roll hard just from the grip.  However, and this plays into the heavy pivot post's usefulness, as the car gets heavier, it may be worth while to try it.  The heavy pivot post is a nice part, especially for rubber tire since you save room on the chassis.  I have been adding an additional 1 oz. (28g) lead per side right behind the radio trays, so 2 oz. or 56g basically in the center of the car.  This is VERY helpful. in addition to that, I tried another 14g on each radio tray as a test, which i'm undecided about.  I also run 14g behind the servo flat on the chassis, and 7 to 14g on the wing right about even with the body mount for the nose.   This weekend I also added 14g (7 on each side) to the wing right in front of the camber plate.

 The nose weight depends on the track, and how much grip the car has.  Too much (usually more than 14g in the forward most position) and the car won't center up.  Too little and the car will push especially on power.

My car wound up as a tank with about 140g of lead spread around the chassis overall, not counting the additional weight of the heavy post over a plastic or aluminum piece.  The only bad thing was as I added the last 28g  to the car on the radio trays, it started to roll more and even wag the rear end a bit until the tires warmed up.  At this point I'm not sure if I just have too much weight, or if I need the damper plate back.  I tend to think maybe just a bit too much weight. I probably will try the damper plate just because it's worth knowing the effects.

I have found you can still use the camber settings (1.0, 1.5, 2.0, etc) to add overall steering without making the car totally bananas, if you reduce camber gain with a lowered,  flat upper arm.  I was able to go from 1.0 to 1.5 to get some more steering without overpowering the rear of the car.  I'd like to add even more just to see what will happen.  I know last year, adding camber always helped steering.  When the traction was really good, you could run 2* + and really get the car turning.

The other really important adjustment for rubber tires is shimming under the rear ball stud of the upper arm.  This controls the active caster effect, and is super critical for rubber tires since this car always wants to wash out the front end mid corner.  Adding shims under the ball stud will add mid corner grip.  I got up to 1.5mm in shims this weekend, had the extra steering, but it was still controllable. This is probably the most important adjustment for rubber tires, since it works very independently of the other front end changes.  You can maintain the fell you have and still add or reduce cornering power.

I recommend the split upper deck as well.  Right now I have it on, and I only have the screws in the pivot post securing the upper deck.  I'm using the FRP lower chassis, and I think letting the chassis flex front to back is letting my car get more forward bite.  It was able to launch pretty well out of the corner.  Usually, I would not think the front to back flex would help, but I think the funky T bar design needs all the help it can get putting the power down.


  1. Do you have pics showing the swimming of ballots and would this be something worth trying with the 3racing F109?

  2. Damn Autocorrect. That's shimming the ballstuds.

  3. You probably don't have enough room on the 109. Both the F103 and 3Racing car have smaller front rims, so there isn't as much room to shim the ballstuds. If you ran 104 front tires/rims and 104 kingpins, it would probably work. I'm not sure though.

    Look at this post for pics: