:. Racing .:. 2005/07/29 - Autocross
Results: None
Eureka!
Ha!
After nearly a full season of trying to figure out the understeer that is apparently inherent in this Radical, I finally figured out why I, among other Radical owners, have been having such a huge problem with push. The reason? Bad Info.
A few months back, I asked Radical what the motion ratios were on the suspension. They answered that it was 1.1:1 front and rear. Weeeell, that's not entirely true. I'm guessing that it's true for the newer Radicals, which are Nik-Link front and rear, but such is not the case for the older Radical with the traditional rear swaybar. I measured my rear motion ratio at somewhere between .70 and .75 or so. That means that the rear springrates need to be a LOT stiffer than they were to help balance the car out!
So, after having run 300/400, I swapped the night before to 350/450. The increase in front rate was to help with transitions in the slaloms, since I remembered just how difficult it had been with the 250 fronts. Even the 300# front still seemed to take some "set time", so the 350# I thought would feel pretty darn good. And, it did.
The 450# rear was a bit of a hedge against being too stiff, but with a day to test, I was thinking we might raise to 500# or 550# if necessary.
Lastly, based on tire wear and some help from R. Pare, I took a bit of camber out of the alignment, since it looks like the inners were getting too much wear, and a bit too much heat.
Impressions
Jeff and I ran the test course several times, and did our best to see how the car felt. As before, it was a little twitchy on cold tires, so you had to be very careful on turn-in, or the car would want to slide. After the tires warmed up, the car was MUCH more neutral than ever before, and the steady-state mid-corner understeer was much reduced from previously. As well, the car was less sensitive to lift-throttle, and generally more predictable. Quite positive overall.
At the end of the test course was a relatively tight slalom. With the car handling better, we could really attack the slalom, and it felt like the car was still responding just a bit too slowly - when the front *really* dug in, it felt like the car could use still more roll stiffness.
Changes for Next Time
Based on both of our impressions, Jeff and I decided that there is still a hint of understeer, and that the front can stand some more spring without getting "slidy". So, we will go to stiffer springrates for Saturday and see what we get.
However, this is the best the car's ever been, and with the correct numbers in hand, changes can progress, and make sense too!
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