[Mgs] lowering rubber bumper car

[Larry Colen]

> On Jan 31, 2024, at 9:32 AM, Jim Ray <jimray at 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 at red4est.com  sent from ret13est