Here's a report I wrote to a friend shortly after the EMRA event at Lime Rock in November:
We had a great day on Friday at Lime Rock. Everything went smoothly (for a change!) and we didn't get into any accidents or have anything fall off the car. <grin>
The car was handling much better than it ever has before, and we both went considerably faster than we had previously. We both managed 1:06.5's, but Nate did his in the time trial, while I did mine in practice. I only managed a 1:06.7 in the time trial.
Nate took 3rd and I took 4th, out of about 16 cars in our class. It's the first time since NERC last year that we both took home trophies! Also it's the first time Nate has beaten me when I didn't have a problem.
Did I mention that we re-measured the rear motion ratio the weekend before? Both Doug and I thought (from watching the video I posted on my site) that the rear looked rather too softly sprung. Also Jim Schenck calculated a lower motion ratio for the rear than what we had originally measured (we had it at .56 vs. .32 for the front).
So after Nate and I put the 1000 lb springs in the front, and replaced the .188 wall front bar with the .125 bar we used at first, we measured the rear motion ratio. This time we got it at .32, same as the front.
After thinking about this, we decided to put the 800 lb springs we'd just taken out of the front into the rear. Doug agreed that this was the right thing to do.
This gives wheel rates fairly close to what Doug originally recommended, and in the same proportion (somewhat higher at the front). What we had before was much too soft in the rear, which is probably why the car understeered with power on.
It worked great! The car feels much more balanced now, and seems to have much better grip too. Also, it hardly rolls at all. It doesn't understeer as much; it just gets more stable when you get on the power. Also it didn't bottom anywhere at Lime Rock that I could tell.
It's not bad at all on corner entry. I found I need to use quite a bit less steering input on turn in; instead of tossing the car as I did before, I more or less ease the car into the corners.
I think we now have a bit too much rear brake, because the car tends to get loose if I turn in while braking, so I quit trail braking. Doug suggested we try using harder pads on the rear until we get a chance to make the balance adjustable, but he also pointed out that trail braking isn't necessarily the best technique for all cars.
The car does ride a little less comfortably now. Nate mentioned that now it's starting to feel like a sports car. In my opinion, it's still ok on the street, although for a purely street car I'd probably run springs a little softer (maybe 800 front, 600 or 650 rear).
We'll probably wind up getting the rear shocks re-valved to be stiffer, so as to get the damping rates at the wheel that Doug originally intended.
Also Doug recommended replacing the urethane bushings in the suspension with spherical bearings (aka mono balls). We'll have to check to see if the urethane bushings are allowing the suspension arms to move freely; if not, Doug feels this is a very important change to make (more important than a brake upgrade). He said those suspension arms should "move like butter". Any binding interferes with both the springing and damping behavior of the suspension.
Anyway, both Nate and I had a great time on Friday. It's always satisfying when you make changes that make the car feel better and also when you go faster!
We both felt that there was more time in the car, too. Doug said 1:06's are a very good time, and he thought that once we get the car (and ourselves) really dialed in, we should be into the 1:02's or 1:03's.