[Bill Verburg]

Originally Posted by phunt

The only way to properly lower a car is to raise the spindles.

that depends on how much lower the car is going to be, there is no point where below you have to do one thing and above another

if you want to go down 10mm then likely the screw adjusters will be adequate and certainly a 10mm rack spacer to compensate for the drop in rack height while lowering.

certainly, if going down 20mm raising the spindles is the way to go, here a rack spacer of 11mm w/ a 9mm drop in knuckle height compensates

Originally Posted by phunt

Any other way changes the geometry. You have to live with whatever comes from it. Good or bad.

any change in ride height b, changes both roll center geometry and steering geometry., you do want to live w/ RC geometry change as that is good, you do not have to live w/ the bad roll steer geometry, unless you want to. To correct it just change the steering knuckle height.

Originally Posted by phunt

With upper and lower A arms you can get away with a lot more. My car only has a lower A arm so it matters what you do a little more.

arguably double A arm has better bump and drop curves. Either needs similar corrections to complement any given change

Originally Posted by phunt

What does the T-bars have to do with anything? The only thing they do , besides act as a spring, is give the lower A arm a pivot point. It is fixed in the car and can not be changed. Just like the upper perch where the top of the strut mounts. Unalterable besides the small adjustments for caster and camber it is fixed.

correct, both are the only fixed reference points to describe any given geometry that is implemented. You need these as reference points for the rack, spindle and knuckle heights. You don't change reference points they just give perspective and define consequences.

Originally Posted by phunt

That is why the location of the ball joint matters.

the only way the ball joint matters is that it clears the wheel. Other than that it's only significance is as the outer end of the A-arm where is determines the A-arm angle and hence determines the line to the instant center. You do want it to be low enough that the IC line goes as high as possible. The only way to change the ball joint height is by changing the spindle or axle height.

Originally Posted by phunt

Even to the amount of travel you get on the shocks. Which is what I am worried about. If you lower the car by raising the position of the ball joint in reference to the pivot point/t-bor you will have adverse effects on geometry.

Most of us want to lower our cars but a Safari car has the opposite goal, they would raise the spindle height which raises the ball joint which changes the A-arm angle which changes the IC etc. on a safari car the steering compensation would be to raise the knuckle

Bilsteins at stock height only have ~3.5" of travel, lowering the car via t-bar adjusters removes 1 " of travel per 1" of lowering

which is why raising the spindles is such a good idea, raise the spindle 1" and the compression travel remains the same. AND you improve RC height as a freebie

The issue is that when the spindle is raised 1" the steering knuckle is also raised 1", This causes the roll steer geometry to get far worse, which is why you also need to lower the knuckle and or raise the rack to correct it.

Originally Posted by phunt

That is why the 108 “c” measure is so important. In a strut system like on my car when the ball joint is below the pivot as the suspension compresses under load, as in a turn, the the A arm will swing up relative the pivot. So as the ball joint swings up it will also move out away from the pivot or center of the car. As it does this it will move the bottom of the strut out away from center line adding negative camber. As the inside tire of the turn will become less loaded the A arm will swing down pulling the bottom of the strut in towards the pivot adding positive camber. So additional negative camber on the outside wheel and positive camber on the inside well. Yep that’s a good thing. When you lower the car by raising the ball compared to the pivot like straight out or worse slight angled up. When the wheel compresses in a turn it will pull the bottom of the strut in adding positive camber. Yep that’s a bad thing. That is why that lower control when video the front of the car has the droop below the pivot point. As shown in one of those pics above showing the rack and tie rod orientation. Both of those shown would suffer bump steer. So yep I am sure you can change that “c” measurement to what ever you want and lower your car accordingly. But does it change the geometry? Yep. Is it for the better? Nope. I guess like what they say about these cars, and the way they drive, shift, run, or whatever you just have to get use to it.
We are lucky in these cars that where the tie rods pivot and where the A arms pivot are very close in line. So the more parallel you can get them the less bump steer to deal with

the importance to car of c = 108 is that it describes the geometric relationship between the axle the t-bar and and ground, This geometry can exist at any ride height b because it is independent of the absolute t-bar height b It only depends on the distance between the axle and t-bar heights.. It merely defines the relation between axle height and t-bar height This in turn defines the roll steer character of the suspension, when it becomes bigger by whichever method(remember there are 2 ways this can happen) the roll steer gets worse, At best roll steer is mediocre in these cars, see the above roll steer curves, and no it can't be eliminated, You can just move one way or the other along the curves.


No one is saying that 108 is perfect, it is just what the factory engineers recommended. It just places the suspension action in a linear portion of the curve that has the steepest possible slope. i.e a great compromise.

Most lowered car are fine w/o compensation because the curve is so linear and the cars aren't lowered too much. The problems arise at the extremes,

remember there are 2 related issues here
1) available bump travel
2) roll steer

both are changeable, for a better and for worse

lastly no one is telling anyone what to do w/ their cars, All that is described here is the Physics of it the suspension and the consequences of some specific changes.

You do you