I was changing my car over to the long wheelbase setting, and it just occurred to me there are some interesting aspects of the front end which might not be readily apparent.
Owing to the fact that there are two positions for the steering arm post, you can actually get quite a bit of adjustment in the Ackermann for the front end. Setting the car to the long wheelbase and leaving the post in the short wheelbase position will make the steering rods much straighter. This should promote more corner speed, but be less aggressive entering the corner. Likewise, the short wheelbase with the post forward would put quite a bit of angle into the rods, which would be pretty aggressive on corner entry.
Long wheelbase with steering post back (short w.b. position)
One other aspect to think about is the caster link on the upper arm. This is something that may or may not make a hug difference. Theoretically, a shorter link would have more change in caster as it moves through it's travel than a long link. This really only comes into play if there is a big difference in the heights of the inside of the camber link and the height of the caster link at it's rear - essentially the dynamic caster effect.
These are just a few things to think about or try on your car. If I have time I'm going to see what they do myself next time at the track.
After getting the car together, I brought it out to the club parking lot race not far from my house. The lot the race is held at is pretty bumpy, though traction is good due to a generous application of grape soda pop. This is actually a perfect test for the car. The rear suspension is designed for exactly this sort of less than perfect surface.
My thinking was to take the tires directly off my TRF 103, as it has been fantastic everwhere I take it. The last race I used it at was at a very small but smooth track in central Illinois. Traction was excellent, and we raced a night, so conditions were relatively cool.
We did not have enough cars for an F1 class, so I was running the car in practice and between rounds. Time was a little limited to get too much done as far as setting the car.
I had Pit Shimizu 575 rears and 571 fronts on the TRF car. As it turns out, the 575 rears may have been a little too soft for the hot conditions on the day, though not horrible. 571 was too aggressive in hindsight. The car would sort of wander on the straight, and was really sensitive to corrections. I had the same problem with the TRF 103 when I visited the small track downstate, and reduced droop via shortening the center shock. Figuring that might help here, I shortened the shock on the F1Ultra.
That change seemed to help some, but now the car was getting on the nose going into the corner. That was a little strange considering shortening the shock tends to take away entry steering in my experience. The other problem was now the car occasionally wanted to snap the rear end in the middle of the sweeper if I got overly aggressive with the wheel. At this point, I changed the fronts to F104 kit fronts, which are less aggressive. The F104 front is reliable for most parking lot situations to balance the car to stability.
Unfortunately, there really didn't seem to be much difference between the two tires. I was having virtually the same problems. At this point, I just put a bunch of droop back into the car, not knowing exactly what to do, and running out of track time. That did make things better, but not by a huge margin.
The whole experience made me think I had done something wrong setting the droop on the car. It's a little different that the cars I have run in the past, so I thought my normal tricks might not be what were needed. I contacted Mike from Exotek to get some advice.
Mike recommended that I run the droop as noted in the manual, and ensure that the ride heights were correct. He also suggested that I look to tire selection, as he felt I was on the wrong rear and had too aggressive of a front tire. I took Mike's suggestions and went over the chassis to ensure everything was correct (this is also where I developed my alternative micro shock droop check).
As an aside, here are Mike's tire recommendations for asphalt:
"Personally I'm really liking the Volantefronttires due to the different compound choices. I tend to have the softest spring settings all around and just tune the balance of the car by changing the front tire;
Medium Soft for more steering
Medium for medium steering
Medium Hard if the car/track is loose
For rear tires I use;
Volante white dots if the track is fast or grippy
Shimizu 72 if the track is small or low grip
Yokomo Soft rears (looks like Shimizu) if it's a bit cold outside."
My qualifier starts at 1:29, it's the white car (Brawn livery)
The next time at the track we had a group of 10 F1 cars (!). This worked out great, since I was just able to concentrate on working on the F1 car all day. After getting the info from Mike, and also consulting his setup sheet for asphalt I made a few changes. Foremost was putting Pardus fronts and Pit Shimizu 572 rears on the car. I wasn't able to find the recommended Volantes quick enough, but I knew that the Pardus tires were a hard compound. I also know that 3x UF1 champ Lee Passehl used them extensively in the past, so I thought it would be a good choice.
Beyond that, I also noted in the setup sheet that the shorter of the two camber link positions was used. I had initially built the car with the link long, so that was changed as well. I also widened the rear end at the axle. The wheelbase remained the same, short.
The changes were apparently the right ones, as the car was now excellent straight off the setup board. The only things I really looked at changing were the front tires and the upper links on the front end.
I did try a pair of Pit 573 fronts in a practice run, just to see what they might do. They are a harder compound, but even so, they were a little to much in the steering department. The Pardus tires were actually perfect for the track. This car develops a lot of steering in the short wheelbase setting, and the Pardus fronts were fine. In case you are wondering, Pardus tires are discontinued. You might be able to find them somewhere online new, or even used since they last forever. Tamiya F104 option hard fronts (54198) would be the closest thing that is available. Otherwise, I would just follow Mike's suggestions and buy some Volantes.
Changing the upper link did give me some insight to why my car was hard to drive the week before. While the tire was a big part of my troubles, the long upper link did not help anything. Once I changed from a short link to a long link, the car began stepping the rear end out in the sweeper again. The car rolls the front end so hard it whips the rear out when it bites. So, that was at least a good bit of information even if it was a bad change.
I had changed the upper link looking for just a bit more steering in the center of the corner. Plan B was to dial in some more caster, which was the correct option. I made the caster link's gap about 0.75 mm smaller, winding up with a 7.5 mm gap. Since the last time I raced, Mike has published a new asphalt setup recommending 12* caster (I think his link gap was 6.6 mm!). I have the car short right now, but I think for the next race I'll take a stab at the long wheelbase to see what that is like.
In closing, I think the main points are correct tire selection is critical (duh), and you may have to look at how you tune an F1 in a new light since this car is a little different. Once I got things straightened out, the car did the fast lap of the day, TQ and I won the first main. We had a second main, but my battery connector pulled out in an incident, so I lost too much time, but I was leading at that point. The car works. One guy said it looked like a slot car, so it can't be all bad. You can drive it easy, and it will do super fast laps. It was pretty composed in most of the rough parts of the track as well. Not bad, since it helped me get on the throttle a little earlier than most.
