Roll Centers on the MR-03

Well, it's been almost a month since my last post. I promised set-ups from the Tekin Race, but I just was not satisfied with them after I ran my car at the local track. The ILR track is funky and the grip is weird, so set-ups from there are very different from anywhere else I run at. I have edited the previous post with my old set-ups.

This post though, is about moving forward and fine tuning the new MR-03 front parts, that are getting rave reviews from customers all over the world.

Let me give you a run-down of what has happened at the track since the Tekin Race:

Last week, I raced for the first time at my local track with the new parts. Grip was a bit different, and everyone was running a bit slower than usual at the track (especially me). My car was about 2 tenths slower on fast lap from what I had done the previous time, but so was everyone else. Marcus (Mantis) was the only one that was going a bit quicker than before, but he was just starting to get his 03 figured out. Still I was the quickest in qualifying by about a lap over Jacob, but the consistency was not there.

In the first qual, I ran a 96mm set-up, while it was super easy to drive, I was not able to go any faster than a 7.36, which was about 2 tenths off of my quickest previous lap. Marcus actually ended up with the quickest lap with a 8.31 and Jacob had like an 8.4 or 8.5, so I knew I needed to pick up the pace.

For the second qual, I went back to 94mm and the F430. I instantly picked up a tenth and re-set fast lap at 7.22, but the car was not there yet. Consistency lacked, due to the fact that the car lacked rear grip. I was running the medium 94 FRP plate, so for the 3rd qual I went to the soft one. With the soft one I gained the rear grip I was looking for, but I also gained a lot of turn in, so the car became real nervous. I was running white low down springs, and they seemed a bit too soft. My feeling was right, as I traction rolled my 03 for the very first time ever in the carousel at the end of the straight.

So for the main, I went with yellows, the car became much more balanced, and much easier to drive. I was able to push down my fast lap to a 7.16, which was essentially the fastest I had run during a race. The only problem was that the dreaded traction roll had come back! :o This traction roll cost me nearly a lap and I even lost the lead for about half of the race to Jacob. I also had to drive conservatively at the end of the straight to prevent the car from rolling off the track again. In the end, I still took the win by like 5 or 6 seconds, but I knew that the traction rolling was a big issue that I had to deal with.

Having that in mind, I went home and I stared at the car for a while. I knew the problem was with the front end. At the moment I had lowered the front by putting 3 shims underneath the knuckle. This created an extreme angle with the upper arm which creates a really low roll center, which I was guessing was the culprit to my troubles. Whenever you have an angle that steep, you make the front act very soft and the only thing you can do is add a stiffer spring to fix this. I don't like runnign very stiff springs on my cars though, because I feel like it does not absorb imperfections as well.

I had a couple of options to raise the roll center. The first was running a smaller diameter front tire. This can be achieved with either a really small tire, or the smaller Mantis front wheels, or the combination of both. The problem, is that I hate to have to true down my tires too much and this is a waste of rubber. By running a smaller diameter front wheel and or tire, the front sits lower, so I can take some of the knuckle shims out.

The other option was the one that I actually went with. This was installing the PN Lowering knuckles for the 03. By raising the axle 1mm up, the car achieves a higher roll center, while keeping the ride height lower and the upper arm angle pretty much parallel to the ground. This achieves a little bit higher roll stiffness (think in between spring rates) with each spring. So now, the PN whites would actually work as a little bit stiffer spring. More importantly, the roll center being a bit higher, the car would not want to roll as violently in the corners, which in theory I thought, should eliminate my traction rolling.

Well, fast forward to tonight. Tonight was not looking like we were going to race. We had a very small turnout, so I had set my mind at working on my car's set-up. I wanted to test to see if my theory on racing the roll center would make a difference and I also wanted to try a couple of different bodies.

From the first run on the track with my Stock car was pretty good. The car was balanced, but a bit loose, this led me to bring the car into the pits where I experimented a little with lube on my DDS and the front knuckles. I found that a good combo was Kyosho 5000wt in the front and Atomic 500wt on the DDS, this gave me a car that was fairly aggressive and very planted. At the time I was running PN White springs in the front and I had the chassis slightly lower in the front than in the rear. After trying different pre-load combinations and springs, I found that this was the best and quickest setting, so I did not mess with it any more. It is important to note that the MR-03 is very sensitive to ride height and suspension stroke (how much the suspension compresses) adjustments, so don't be afraid to try them out!

In the spirit of experimentation I tried the Lexus SC430 body on my car. This is the body I won the World Cup in '07 with and also a very popular choice out with the Norcal guys. Instantly, the car felt really good. The grip was very neutral and the car seemed easier to drive than with the F430, remaining flatter through the corners and acting a little bit less aggressive. I really liked the body. Soon after, we all decided that it might be a good idea to run a couple of qualifiers and a main.

At the start of the first qualifier I jumped into the lead. I was able to stretch it out fairly well, the car felt good, but for somereason, I was not able to go any faster than a 7.2 second lap. Given that my fastest lap was a 7.16, it was not far off base, but I felt like the car had more to give.

After the run, I went into the pits and switched back over to the F430GT. Typically the F430 generates a bit more grip and it allows me to hug corners a little bit better than the SC430. The SC430 feels smoother and faster, but what came to light, was certainly enlightening. From the beginning of the run I started dropping consisten 7.1's and 7.2's, whereas before it was 7.3's. On lap like 10, I dropped a 7.03, a couple of laps later, a 7.06! This was what I knew the car was capable of doing. The scariest part was that it was a less powerful battery pack than what I had saved up for the main. Coming off the track Marcus even said "I guess that body works better!" I agreed...

Right before the main, I put the car on the track and took it for a lap. The car was a ROCKET!!! I thought for sure I was going to crack a 6.9 second lap. Off the start I jumped out into the lead and started getting into the groove. Unfortunately some sort of debris got into the commutator of the car and the car slowed down severely. It even left a little smoke trail going around the track, looked almost like a real car blowing an engine. Whatever it was, if burned off quickly though and the car got back up to about 85-90% of the speed it was going to. I knew this was not going to be enough power to do a 6.9, but I thought maybe I could do a 7 flat if I worked hard. Honestly, the 7.0 was probably a little bit of a stretch with how slow the car was, but somehow, I still managed to get 7.13. After the 10 minute main was over, I realized I had just shattered the previous stock class record of 80 laps in 10:06, not only that, but the Modified track record of 81 laps in 10:06 had also gone down, since I had ended up with 81 laps in 10:04. If I had only had a better motor, I know an extra lap would not have been out of question either...

After the dust settled I was really happy. This was the 3rd track day with the new Reflex MR-03 parts and I am still finding tenths of a second each time out! That to me, is VERY exciting. There is nothing like going faster than before after installing your very own option parts. Specially because the dreaded traction roll never made an appearance during the whole night.


THE SET UP:

Front:
-Reflex Extra Long King Pins and Delrin Balls
-PN Racing Lowdown White Springs
-PN Racing Lowdown Knuckles- 0.3mm shim underneath
-Spring Pre-load neutral (no slack when off the ground)
-4mm Spring Cup
-0 offset wheels
-Kyosho 30 slick, trued to a flat carcass
-Kyosho 5000wt grease on kingpin
-0 degree toe rod

Rear
-Reflex 94mm G10 Soft Plate
-PN 70 turn stock
-51/12 gear ratio
-Kyosho F1 Shock with greenspring
-Atomic 500wt oil on DDS
-Axle at 2nd highest ride height pos. On PN 94-98 Mount
-Kyosho 30 deg Rear Radial, tread gone
-Atomic Green DDS sprigns
-+1 Rear Offset Wheel
-QteQ Rear Diff Parts


Body: Ferrari F430
Battery: R1 Wurks 750