> On Jan 31, 2024, at 9:32 AM, Jim Ray <jimray@hartcom.net> wrote:
>
> Guys, I think you are over thinking this.
> When I lowered my 1980 MGB I used springs and lowering blocks from Moss
> (264-399). The only problem was bump steer which was corrected with shortened
> bump stops (266-590). I have never had any issues with steering behavior.
> This was about 10 years ago.
Interesting, you've read some different books than I have on suspension design
and modification (Fred Puhn's "how to make your car handle" and Carroll Smith's
"Tune etc. to win" books.
My understanding is that the job of a bump stop is to smooth out the
non-linearity when the suspension bottoms out. Rather than suddenly going from
a lot of compliance, to zero compliance, when it touches the rubber bumpstop it
gradually transitions from "soft" springs to "very stiff" springs.
Bump, and roll, steer is caused by the arm from the steering rack changing
angle differently than the suspension arm causing the wheel to turn as the
wheel rises, or falls in relation to the chassis. Bump steer has nothing to do
with the bump stops, unless you're leaned over so hard that you are on the bump
stops, so that the suspension angle then changes very little.
Many years ago, I had a 1980ish Corolla that I had bought for something like
$400. Since it was effectively impossible for me to do more than $400 worth of
damage to it, It was my track car for when I was teaching.
http://www.red4est.com/lrc/racer_html/schoolpix.html
I put some "take offs" from the Cortina I was racing on it and beat the snot
out of it. Most of the Toyotas that I've driven have egregiously bad roll
steer, and this one also had worn out springs, and well I called them shock
observers, because all they seemed to do was notice that the car was bouncing
up and down. My technique when driving that car was to take a very had and
aggressive turndown so that the car very quickly went from softly sprung on the
straights, to using the bump stops as my suspension (anybody remember formula
440?). Once it was on the bump stops, roll steer wasn't a problem because the
lean angle, and thus the steering, didn't change much.
--
Larry Colen
lrc@red4est.com sent from ret13est
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