Good insight on bump steer Larry. And thanks for the cool photos!
Charley
> On Jan 31, 2024, at 2:46 PM, Larry Colen <lrc@red4est.com> wrote:
>
>
>
>> 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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