Originally Posted by
erchn
Any progress? I've been thinking of trying two different directions. Given that the car feels good but lacks mid-corner I'd like to try getting more roll in rear of the car. I've already run all the way in on the tower for the rear shock and that didn't seem to do it, so thought of trying a two hole rear arm, running on the inner hole of the arm to get things a bit softer. My concern is that it's already close to being loose on exiting the turn, so it might cause the rear to dump too hard to the outside tire on corner exit.
So I tried a few things with good results this weekend: I normally like running antidive in the lowest roll center position in the front, but like you said, with the reds all around there just wasn't enough mid-corner rotation. The car was super easy to drive, but still off by about .2s.
Ended up dropping the roll center to the bottom in the FR position eliminating the antidive completely. I threw on the 4deg blocks and voila! the car had a good deal more mid-corner rotation. In fact it had a bit too much. To compensate for the additional 'noseyness' of the car I went down to a green rear spring and equal ride-height all around. Gained the .2s I was looking for. Broke the track record on the current layout that Haynes and Schreff laid down two weeks prior. Comfortably still need another .1s - .2s though. I have a feeling what's remaining is simply me continuing to adjust to mod.
In response to your first point: I'm always nervous about the whole aggressively roll-over-on-the-outside-rear-tire-to-get-it-to-rotate-style setup. I find cars like that do not fit my driving style. I seem to prefer stiff, edgier setups to generate rotation rather than soft, divey ones if that makes sense. To each their own I suppose.
Another couple ideas (in different and opposite directions) were either lower the front roll center (arm holders) .4mm or raising the rear a similar amount to see if either the front just isn't working as well needed, or taking a bit of rear traction away will get that rotation.
Did the first one--was awesome!
Your second point was also a passing thought for me, but since Jackson is not a particularly high-bite track (and neither are the spec tires we use for that matter) I felt the right course of action was to increase bite in the front of the car rather than take it away from the rear.
I'm interesting in your findings.
I'd be happy to hear what your findings are as well. I've really enjoyed using the RSD springs this past season. I know some folks I run with don't care for progressives, but I love them particularly on asphalt. By the way here's what my current setup looks like:
XRAY T4 Setup - Jon Williams