So what made you decide to switch? What are the advantages and when is it advantageous to do it?
Or, is this more of a test to just see the difference? Very very curious about your "testing" results one you get it on track. Possibly notice anything on the street with it? Did you have to remove or add an inch of bumpsteer shims to correct bumpsteer?
PLEASE PLEASE PLEASE report back after you have a chance to put it on track.
I removed about an inch of spacer stack. I say "about" an inch because I forgot to record exactly how high my rack was mounted before I took it down, so I re-measured and re-adjusted the bumpsteer for the location its in now. Assuming nothing changes, you can remove exactly an inch of spacer stack. Interestingly, the resulting stack is shorter than the shortest tapered spacer MM provides.
As for why I changed it, I've been chasing a rather persistent understeer condition for a long time. I have the rear where I want it with 500-lb springs and an Eibach bar. Meanwhile I've also been chasing uneven tire wear in the front. No matter what, I wear out the edges of the tires long before the rest of the tire is gone.
Jack Hidley once had this to say about the location of the arms:
Lowering the FCA in the k-member increases the distance from the roll center to the CG. This results in less roll stiffness at the front. Less roll stiffness means less load transfer, AT THAT END OF THE CAR (FRONT). This means each of the front tires is more equally loaded and therefore can provide more total grip.
This is pretty basic, and it's always made me wonder if I was sacrificing grip for a better camber curve. Meanwhile:
Another advantage is this. The higher the roll center, the greater the jacking forces created from cornering forces. The jacking force actually causes the sprung mass to lift. Tire scrub tends to hold it up. Higher sprung mass cg, increases the total weight transfer of the car, which reduces total cornering grip. This is why fairly low roll centers are important.
Hmmm...jacking forces, tire scrub, reduced grip...it's been getting me thinking. Furthermore:
One of the local guys that runs AI with our parts dropped his FCAs in the k-member, added 30% more spring rate to increase the roll stiffness and dropped his lap times about 1.5 seconds due to the decreased understeer.
Sold. Except I'm not increasing the front spring rate beyond the 425's I'm already running, so this should be educational. Unfortunately I'm not a consistent enough driver to nail it down to lap times (I took 3 seconds off my best lap time on Arizona Motorports Park last time I was there, with NO changes to the car), and I'll be running different tires next time anyway. So my report back will likely come down to how it feels
and how tire wear nets out.
- '92 5-sp LX coupe, TKO, 3.55s, pulleys, Al DS, 1-5/8 shorties, Magnaflow spun metallic cats, 2.5 Dynomax VT's, Pro5.0 w/ Steeda Comfort Pro
- GT40Y's, E cam, Cobra intake, tmoss ported lower, FRPP 65mm TB, BBK 75mm MAF, 155 lph pump, FRPP oil cooler, Al rad, 130amp alt, Energy mounts
- Autopower 4-point bar, 5-pt harnesses, MM weld-in subs and STB
- MM K-member/A-arms/Coilovers, 425# springs, MM cc plates, Koni Yellow DA's
- MM adj rear LCA's/torque arm/panhard bar, 500# rear springs, Eibach swaybar, Koni Yellow SA's
- SN95 Cobra brakes, FR500 17x9 wheels, Raybestos ST47 pads
- 3400 lbs with me and 1/2 tank of gas
- Regional autocross champ 99-02, 10,100 miles on 17 tracks