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[Fot] GT6 Alignment and suspension set-up

To: Bobby Whitehead <igofaster@att.net>
Subject: [Fot] GT6 Alignment and suspension set-up
From: Scott Janzen <sjanzen@me.com>
Date: Tue, 24 Jan 2012 10:11:03 -0500
Bobby, I'll share how my suspension is set up, describe the handling, and pose 
a question of the group - what would optimize the handling/reduce understeer on 
corner entry?

Car weight roughly 2100 lb w/ fuel, 200 lb driver/gear, corner weighted to 
optimize, but LF is still heaviest
Tires 205/60-13 on 6" wheels, R888 Toyo Proxes, 21 psi front, 19 rear
Front Susp 550 lb springs, 1.5 degrees negative camber.  Tried 2.5 negative on 
last outing, and got more even tire wear (less wear on outer 25%) but more 
twitchy steering and no reduction in understeer.  Front bar 1" OD, solid, with 
about 13.5" lever arm. 1/16-1/8" toe out.  All plastic bushings.
Rear Susp: stock spring(I think), with spacer on diff to lower about 3/4", 1 
degree negative camber, 1/16" toe-in, 5/8" OD anti-roll bar with 9" lever arm.  
Welded diff.  Every connection on "stock" rear susp elements is a rod end 
except for the lower a-arm connections to the upright, full IRS w/ rotoflex 
replaced by ujoints.

The car understeers on corner entry, more as I go faster, and more on tighter 
turns (welded diff).  Jason tells me it's my driving style - I carry a lot of 
speed into the corners, trail braking, and the car pushes going in, can hear 
the front tires protesting. At the apex, when I get on the gas, the balance 
shifts rearward, the front tires get quiet, the backs start making noise and 
the car points where I want it to go.
I'd like to reduce the understeer on turn-in.  Have increased the rear bar 
stiffness, which did not reduce understeer but made the transition to oversteer 
more dramatic!  Adjusting tire pressures up and down has not made a material 
difference.
So, anything else I should try adjusting?  Or, just acknowledge the nose heavy 
nature of the car and get my braking done in a straight line, go slow on entry 
and get on the gas early?
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