PS - Congratulations to Nathan Weir TCS 2014 GT1 National Champ!!
Thursday, September 18, 2014
Continuing on with setup issues for the Tamiya track, one thing which I may have overlooked in the past was the tightness of the diff. I generally set my diff tight enough that it will not slip, but still has good diff action. I was told that the best way to run the diff is as tight as possible, but still having smooth action. This was something I never tried since I subscribed to a "1/12" theory of setting a diff, which is to have it just about as loose as it can be without slipping, and then leave it alone.
Well, I tried the tight diff, and I think that it's more an arrow to keep in the quiver when you need it than a hard and fast rule. What it seemed to do for my car was to make corner entry very stable. This came at the cost of mid corner rotation, and maybe some corner speed, at least for my setup. There is a 180* at the end of the big sweeper at the Tamiya track, and at that 180* with the tight diff the car gets into the corner with a lot of control and stability. The down side is that if you don't enter the right way, or have the brakes right, the car may push some here. I also felt like it was not quite as fast through the carousel type corners. It appears that locking up the rear end is creating stability. On my car, this may not have been the way to go for a couple reasons. I run a full size pack unlike most guys who run shorties. My car tends to be more stable in the first place, but with a short pack the car is a lot more lively especially in terms of the rear. I would imagine if you run a short pack, this would be something that would help calm the car down. The other issue is that I tend to like to drive the car on throttle as much as possible. I'm not much of a point a shoot driver, and having a car that will turn on power is key. Locking up the diff is going to make the car steer less on power, so it hindered my setup. There is a place for it as an adjustment, however. I do remember some of the guys from the UF1 MIDWEST series who had just clamped down their diffs. They ran on the ultra high bite Toledo track, and having a car that was not twitchy on corner entry would make a big difference. Their line of thinking makes a lot more sense now.
In the end, I was very happy with the car. It would drive very well over the whole run, and I felt like I could push it as much as I needed to without it wanting to spin or roast the rears off. A second place finish was not bad at all, and I felt good about that considering I get about 2 weekends at the Tamiya track to try to dial the car in versus the untold laps guys who live locally can get in. A few people told me I could have used some more motor, and that probably was true. I don't worry about motor most of the time, since I feel like you can't launch a cannon from a canoe, as the saying goes. Better to have a good car, motor is way easier to get a hold of in most instances. That being said, I am putting more time into making sure that I have a better motor program.
To sum it up:
-Make the car work in the heat of the day, over the whole run
-The car needs to be able to rotate in the 180* and carousel turns
-Your best results occur at any race when you are only making minimal adjustments...tire prep, adding or reducing a small shim, etc. Ripping the car down to the chassis is a last ditch effort.
(photos from Tamiya USA web site)
Monday, September 8, 2014
Now that I have had a little time to get back to normal and collect my thoughts about the 2014 TCS NAF, I'd like to review some of the themes that I thought emerged with car setup (F104W GP) and the track.
For the first time that I have been out there, I feel like I got the rhythm of the changes in the track. Most of the time in the past I have been chasing the setup so hard that I never was comfortable enough to just make the small changes like tire doping strategy and other slight adjustments between rounds. In the past, I was ripping the car apart trying to get something that would work. I attribute a lot of this to keeping much better notes on the runs I made in practice. Being able to refer back to previous days sessions made it a lot easier to see what I was missing or what I should keep.
The best way to attack the setup for the car is to get the car to work in the midday heat, from about 1pm to 3pm. We saw track temperatures of 140*F at this point and the track could get greasy. I found that a combination of Paragon FXII (white can) and a thick oily sauce like Tire Tweak or SXT 2.0 worked best overall. I would bake the FXII for 10-15 minutes @50*C and then put on the Tweak and bake the same way- rear tires only. The fronts were simply cleaned with Buggy Grip and then re sauced with Buggy Grip shortly before going to tech. The fronts were pretty sensitive to saucing, too soon and the car was edgy, too late/too little and the car pushed until the tires heated up. Generally, 5 minutes before tech was good. I also wiped the rears down with Buggy Grip before going to tech to ensure the car was ready to go without waiting for the tires to "come in".
Front tires were a hard choice to make. At home I had been trying a number of front tire setups, from kit front tires to TCS fronts (Pit 571). I had been able to get the car setup with enough rear traction that I eventually had to use the TCS front with a bead of glue on the sidewall. I had been ready to use the kit fronts, but even with the belt removed, I wasn't quite comfortable. TCS fronts with a large firm insert proved best for me, with the amount of track time available. Sometimes you just have to "pick a lane" so to speak and go with it. I think that with more time I would have gone with a kit front in some configuration. I think that the kit tire is more forgiving, and probably has a little wider setup window. At the same time, the TCS front offers more steering, and with the right insert is pretty consistent across a range of temperatures.
One other area I wanted to mention is front end droop. Normally, I have run quite a bit of droop, like 3mm+. This can be especially helpful on curb tracks so the car doesn't get upset and rides the curbs easily. It also helps the car keep steering if you want to run a low roll center on the front and a minimal amount of dynamic caster (high front ballstud / low rear ballstud for upper arm). This is good for a big track or a track with a lot of sweeping turns. Tamiya, however, has a couple 180's and some carousel turns where front end grip is needed to get cornering power. To get this type of steering, I used a tall ballstud on the rear of the arm. This generates more steering center of the corner, but also makes the car less stable on the brakes and on corner entry. During the morning practice on Sunday, I took 2 turns of droop out of the front end and suddenly the car was much better to drive with the amount of steering I was looking for. I wound up with 1-1.5mm of droop depending on how much steering I was looking for. Before this the car rolled across the front end too much at times, getting on the outside front. Along with the droop, a generous amount of Tamiya A/W grease on the kingpins settled the front end down. I checked the grease every other run at a minimum.
On the rear, I had been running a somewhat tight t bar and a lighter grease in the tube. I had both the large and small o ring on the center screw. I noticed the car did not have the rotation in the center of the corner I was looking for. Again, and my home track which is large and flowing, this was probably a better answer. to get the car to rotate, I was lowering the grease on the damper tube in the 20k-30K range. The car was still not what I wanted, and I was going back up on the damper tube to get a more stable feel. What did the trick was going to a single blue o ring (soft) and 100K in the tube along with a fairly loose center screw setting on the t bar. Now the car was able to articulate and pivot to generate the rotation I wanted with the proper dampening to create a stable feeling.
The center shock is also an area that provided strange results in terms of what I would normally expect. In trying to generate more on power steering, I kept upping the rate on the spring. On carpet I have gone very stiff, which can sort of lock up the car mid corner, especially on a link car. That actually seemed to work the same way here, with minimal effect on rear traction. What it did seem to do was cause the front end to overheat the tires or at least blow out the traction on the front of the car. Going super stiff made the front end lose traction as the race went on, and as I reduced the rate on the center spring, the longevity of the fronts increased. I had been about everywhere from the 9-10lb gold miatat spring all the way up to the purple super stiff spring. I wound up with the blue mini car spring.
I'll have to continue these thoughts in another post as this is all I have time for right now. I'll post again soon.
(photos from Tamiya USA web site)