Antidive, how to adjust it... Options

[Mike T]

I am somewhat familiar with antidive characteristics with a double a-arm type suspension but was surprised today when I read on the Pelican board a discussion of increasing antidive on a 911 front suspension(similar to our 914) by shimming the front torsion bar mount down.

Has anyone played with that at all? What was your result? How much of a shim would be needed?

Mike T

[groot]

The benefits are certainly debatable. The downside is impact harshness and the inability for the suspension to keep the tire on the ground when facing a sharp bump (transition to concrete for example).

[Mike T]

The benefits are certainly debatable. The downside is impact harshness and the inability for the suspension to keep the tire on the ground when facing a sharp bump (transition to concrete for example).

Maybe that's why Staniforth says it goes in and out of fashion in the racing world. There are tradeoffs.

I have a V8 autocross car and I am fighting rear end looseness on hard braking. When I stop with the steering dead straight there is no problem but add any steering input and the rear tends to want to slew around.

I have adjusted rear Koni firmness and it seems to help with a firmer setting but then in transitions such as a high speed slalom the back gets looser.

The front bites well with no understeer.

This week I am evaluating the car. Alignment settings, bushing condition, etc.

Car Specs;

weight 2215 with driver
58% weight on rear
52% weight on drivers side
Koni reds front and rear
250lb rear springs
22mm torsion bars
22mm Welt front swaybar set about 1/2
no rear swaybar
-1° camber front
3/16" toe out front
?° camber rear
0 toe rear
23.5x12-15 Hoosier R25a rear on 14" wide wheels
22.5x9-15 Hoosier R25a front on 10" wheels
Weltmeister Polygraphite bushings front and rear(8 years old)
camberball upper strut mounts
turbo tie rods
welt bumpsteer spacers
lowered with front control arms and rear semi trailing arms parallel to ground

Mike T