front or rear steer?

[falcon65]

which is better, I have heard rear steer is better for tunning ackerman angle. This doesnt make sense.

Is there a performance advantage either way. Strictly from a steering geometry perspective.

i would think weight distribution of a rear steer would be better. Also for us ford guys the rear steer is easier to package.

[Rhino]

Rear steer is easier for tuning ackerman due to the fact that it's typically done via a steering box. The center link is much easier to modify than a rack.

In theory, with no deflection, there should be zero differences between front and rear steer. In a real world scenario you do have deflection. A rear steer setup typically adds over-steer under deflection, a front steer setup typically causes under-steer while deflecting. This is why it's generally considered to be superior.

[Norm Peterson]

With rear steer, Ackermann correction has the steering arms angling inward as you go from the knuckle to the tierod end. Front steer requires that the steering arms angle outward, and this will reduce the maximum amount of backspacing that you can run on the wheels unless you also run wheels big enough to fit the steering arm and the TR end inside the barrel of the wheel. Given that wheel sizes for the cars of interest here were OE at 15" or smaller, that didn't happen as OE, so the amount of Ackermann correction may be limited.

Running "drop spindles" can make it harder to play around with Ackermann.


Norm

[falcon65]

thanks for the insight.

I was think and a front steer would have teh outside tierod in tension under cornering and the rear steer would be under compression.

From a stress point of view the tie rod with max load under tension, not compression, could be made lighter. since you dont need to worry about buckling.

But i like the idea about deflection and oversteer vs understeer.

i will have to give that some thought and determine how much deflection and angle change in steering would be seen.

[Rhino]

I was doing some related searches on the board and ran across this thread. It does a great job of explaining the handling characteristics of a rear steer setup.
http://www.pro-touring.com/forum/showthread.php?t=4400

[falcon65]

thats a good read.

i think i will go rear steer with stiffer tierods. i will be using heims on both ends. with a left/right hand threaded tube.