[Fot] Paging Tom Krieger re: rear springs

[Bill Babcock]

I'm sure it does. I bet it needs to be locked down so it doesn't move at all.
I took one look at the IRS of the TR4 and TR6 and thought "no thanks". Hard to
see why they designed it that way. I would point out that I DID say "unless
you can't get the suspension to work". I don't have any idea how that monkey
motion stock suspension could be made to work.

I think the biggest advantage of soft springing is compliance of the car to
the track surface--you want the wheels to do their own thing but keep as big a
contact patch as possible in the corners and over the rough stuff, and
probably be on the edges of the tires down the straights. When I ran a lot of
roll/bumps in simulation software for Peyote I found a stiff spring for a
given wheel load overcomes the shock damping so the wheel winds up bouncing on
rebound. If you increase the damping it moves the bounce to compression and
the shock pumps down. With an ideal suspension setup the best spring weight is
what is required to hold the fully loaded car off the ground at the required
ride height with the suspension more or less centered in it's travel. At least
that's the case in software.

In the real world, I increased the stiffness of the springing in my Radical to
accommodate my fat ass because I was grinding the splitter away and bottoming
the rear suspension in some bumps.  Lost about four seconds around PIR. FOUR
fricking seconds, went from 1:22:yada with the chicane to 1:26:sumpthin.
Played with tire pressures, shock tuning, roll bars and got about two seconds
back, sort of. sometimes. You know how that goes. Put everything back to stock
and got my four seconds back. Went to a lower downforce splitter and dialed
most of the wing off, ground off half of the wing wickerbill, and it stopped
bottoming and I got another two-three seconds. Wahoo. Went from thirds and
fourths to firsts and seconds.

Of course guys like Garmey can run you down in a Corvette with suspension from
a Conestoga wagon and pass you with his wheels bouncing up and down like
superballs. But he's F&$%ing nuts.

On Mar 22, 2010, at 4:07 PM, Kas Kastner wrote:

> Well, it might be true for a lot of cars, but the IRS Triumph needs some
umph in the rear end.  Anything around 600 pounds is a disaster and SLOW. I am
talking about the stock suspension not the SCCA version. Like beer, try it
you'll like it.
> ---- Bill Babcock <Billb at bnj.com> wrote:
>
> =============
> I don't think much of stiff springs either unless you can't get the
> suspension to work
>
> Sent from my iPhone