I’m trying to get a better understanding of bump steer.
Adjustments pretty much just move the curve along y-axis.
Makes sense since I’m not altering any suspension component length, but rather just moving the steering rack attachment point vertically.
The idea (may be terribly wrong) was to minimise toe out in bump and allow toe out in droop. See curve below.
Or does it make more sense to set it symmetrical?
Whatever adjustment you make on the track rod, you need to do the opposite at the rack, hub or split between both to maintain the correct toe setting.
Essentially what you are doing is altering the distance between the pivot centres of the track rod geometry so both inner and outer coincide with the lines through the inner and outer suspension arm axes.
Dave Minter explains what’s going on. ‘The Elise had
too much grip at the front originally,’ he says of the
prototypes, 'and in the wet it could spin suddenly.We
had to fit an anti-roll bar and make the front wheels
toe-out over bumps, to add understeer and have some
chance of the rear gripping. That’s why the steering
writhes. It’s very “un-engineering” but we had to do it."
Well I agree, it certainly is unstable to have increasing toe out under heavy braking. Surely that makes it undesirable. Perhaps the quirkes of the Elise chassis mean that other positives outway the draw backs…