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.

Tamiya Tire Test 2011!

Leisure Hours Hobbies opened the outdoor asphalt track for the first time this year, today.  I took advantage as this is one of the best permanent facilities in the US.

Video of Leisure's track






Anyway, it was in the 60's all day, and the track had been prepared for the first time all year, so it was a bit green.   Actually, I felt it was a great time to test tires just because the ability to make grip would be highlighted.

I only used the option soft rear and kit front tire, as they had been the best all around choice for most tracks last year.  The hard fronts may also be worth a try as well, since it might allow a more aggressive front end setup, but that will have to wait for now.

What I wanted to highlight was tire preparation.  This is to me is overlooked at times, but it is really critical with rubber tires.  You can look at race reports from big sedan races highlighting what small changes in tire prep can do for a car's performance. Last year I approached the tires from a sedan-centric viewpoint.  I more or less copied what i was doing with sedan tires.  I would clean the tires with SXT 1.0, apply Paragon FXII for a bit and then bake in SXT 2.0 or possibly Tire Tweak with warmers.  This seemed to be fine for tracks that had a lot of traction, but I'm not sure if it was the best thing overall. At the TCS Nats, only myself and one other guy were using warmers.  He did a lot better than I did, and I'm not sure of his routine, but my car was not all that great.  Most people seemed to be cleaning the tires or not using anything at all.  So in that vein, I went with a less aggressive regimen.

I tried a few different things, including Trinity Red Dot, PB Blaster, Simple Green, and Sticky Kicks Blanco.  I either cleaned with SXT 1.0 or the product itself.  Red Dot was ok, but I was not 100% satisfied with it.  The problem may have been that it made the tires too sticky, and it would up picking up junk off the track.  Either that or the tires were somehow greasing off.  PB Blaster made the tires softer, and even a bit sticky, but the greasy effect came into play here as well.  I think that these two, along with the other oil type additives (Tire Tweak, SXT 2.0, Paragon) may make the tires greasy or  prone to overheat somehow.   That was part of my problem last year.

I moved on to Sticky Kicks Blanco, which is more of an off road tire product, like Buggy Grip, but less aggressive.  I used a rag to wipe it on, since it is a spray.    This actually turned out to be the best overall for me.  It left the tire feeling soft and sticky, but not greasy.  The run I made with SK was really good, and the grip held up for the whole run.  Sticky Kicks makes three different sauces, and Blanco is the middle in terms of aggressiveness, so I will be testing the other varieties to see how they will work in different situations.

Straight Simple Green was next.  Simple Green is a cleaner more often than not, but I let it set on the tire a few minutes.  Much like Sticky Kicks Blanco, it got the tire clean and sticky again, but I don't think it penetrated the rubber as much.  I went out to the track thinking this would be as good or better than the SK.
My car was definitely hooked up at the beginning of the run, but it tended to break away in some corners as the run went on.  I think Simple Green works well, but may not work as well into the run as the SK.  This might not be as noticeable if the track temp is high, as the tires might heat up enough to develop more grip.

So maybe Sticky Kicks or something similar like Buggy Grip or Ragu may be the way to go.  I think that Simple Green may even be better than the Sticky Kicks as we move into the warmer months to prevent the tires from overheating due to too much softening.  I also like the way the tires don't "grease" over with the buggy style additives.