It's been pretty quiet here on the F1.blog, but it's been busy. I've been trying to come to grips with a rubber tire setup for a TCS legal F104v2. So it's been a couple weeks of hiding in the under mountain secret lair/track trying to work it all out.
The big problem with this car being new, and a little unfamiliar, was that I did not have my "go to" adjustments figured out. Usually I have a few things that are sort of the big adjustments that will send your car in one direction or another and you know you've changed something. I had a bit of time where I felt like everything was vague and I was flailing a bit. I was trying to use both what I knew and the concepts I was learning from other people as well, and it was not meshing. So last weekend I decided to go back to the baseline to try to get my car working.
One thing I was pleased with was using a stiffer side spring. In the past I had run my Exotek car fairly stiff since it seemed to me the heavier rubber tires needed a stiffer car. I had recently began to try to make lighter springs work based on what I had seen with some of the on line setup sheets, and when the track was lower traction, it worked well. As soon as traction came up, it was not easy to drive, and in fact, somewhat unstable. It was still fast at times.
The problem with stiffer springs is that they can stabilize the car too much. The link car needs to roll a little to get around the corner, but there has to be a balance to be able to drive the car in a straight line. This is where the preload comes in. With the soft springs like Associated black or Tamiya pink/copper. you have to preload the spring a bit in a lot of cases to stabilize the car. With the softer springs, they really need to be set at just touching or even backed off the pod plate. This will dictate a lot on how the wraps the corner. With a really stiff spring, you can be backed of the pod plate so the car will rotate, but when the spring goes into compression, it will keep the car fairly flat. I think that a lot of the traction roll problems with these cars are generated from the rear of the car versus the front. This brings me to my next point, dampening.
I'm probably going to sound like a kook here, but I think that really heavy dampening is key. I had been up to 50,000 wt diff oil in the X1 damper tube, but I was wondering if maybe more could be better. After talking it over with one of my buddies who was endorsing massive amounts of dampening, I decided to go big. After some playing around, I settled on 120,000 wt Losi diff oil in the tube. This made the car much flatter, so much so that it would slide rather than traction roll. This again goes toward the theory that the much higher unsprung weight of the rubber tires requires the car to be a lot stiffer to control all that mass.
What really got the car working correctly with the higher dampening was a boatload of rear droop. I am now at 3mm over ride height. The droop seems to really give the car a lot of forward bite. I can get on the car pretty much where ever I want to. Previously, I was having to be a lot more careful with throttle inputs. Don't get me wrong, I find that smooth throttle input makes for very fast laps with F1 cars, but I feel a ton of confidence with the added bite.
At the same time, a minimal amount of front droop appears to better for me. I think it helps to keep the weight on the front tires under power to retain the on power steering. Steering feel is also less "floaty" and more direct. I had tried a lot of front droop, but I started migrating back to a minimal front droop setup, and I prefer it.
Another thing I had tried was a very horizontal shock. Usually this does produce a lot of on power steering at the expense of rear stability in my experience, but I'm not 100% sure about that now. I actually felt like the car was a little more stable, but more mid corner out. It still seemed to turn in. Oddly enough, I also tried some heavy rate springs with the shock in a more angled setting, which I usually run. The heavy springs also seemed to stabilize the car in certain corners, especially the sweeper. Returning to the usual Short Black spring set brought the steering back. I wonder if the stiff shock inhibits the cars ability to roll or at least, articulate the links? Chassis roll seems to be the key to cornering with the link cars.... At this point, I am running the shock with quite a bit of angle. That seems to be the best for my track conditions.
I should also add that I was encouraged to run my battery to the rear of the chassis. I had been running the short pack with the electronics behind it, but I moved the RX and ESC to the sides of the chassis and began to experiment with the battery. Full back seemed to cause to push in the sweeper, so I moved it forward a small amount at a time. What seemed to work for me was about 3/16 to 1/4" (4-6mm) off the back of the chassis. I'm finding it's easy to tune the car a little by moving the battery in small amounts.
So here is the setup sheet....for lower bite try gold side springs and a yellow center shock spring....
Thanks to The Passehls, T Marshall, RedBullFxx and Rocket Ron for the help.....