Forward facing steering arms

[Colin Reed]

THE Ackerman  Angle is a line drawn between the centreline of the Diff and the centreline of the Kingpin ,
and the steering arm tie rod connection is on that line ether front or rear of the kingpin.

Colin
NZ

[Scarlet O'Hara]

Hi, I think the actual requirement is that the pivot on the track rod / steering arm should lie on a line drawn from the kinkpin to the middle of the back axle. Tha's why the pin on the standard steering arms are within the wheel rim. If you fit the arm at the front and want to keep the ackerman steering geometry you need to fit a longer trackrod which will then foul the wheel rim.

If the track rod is fitted at the front but made too short the steering will still work but one tyre needs to scrub across the surface when lock is applied as the two wheels are basically pointing in different directions. Does it make any difference - possibly not if you're regularly doing four wheel drifts and the tyres are scrubbing along the tarmac anyway but I'd say it's technically wrong.

[Alan]

At all but very slow speeds, a car doesn’t change direction by rolling along the arcs described by the front wheels. For the car to change direction there needs to be an external force applied (see Newtons Laws of Motion). When the wheels are turned the tyres scrub across the ground in the direction of travel- it’s the reaction to this that supplies the force to change the cars direction. The greater the angle or speed the greater the force. If you don’t believe this, try changing direction on a sheet of ice. That’s why when you are going quickly you don’t need as much steering angle. It’s also why Ackerman isn’t as important as you might think, except to stop you ripping tyres to bits while parking.

[Bob Culver]

To be pedantic the line is actually thru the point on road about which wheel turns; not always directly below kp. I am not sure about the meeting at diff gudeline but as explained the outer wheel does more work so the rim is more turned than the contact patch, esp with crossplies. So wheels are arranged to stay more parallel than Ackerman ie the outer wheel turned more then theoretical.

[Colin Reed]

HI All ,
As Alan, has explained from experience, makes little difference at speed,
What does happen if you just reverse steering arms is when you put the car on angle plates the outer wheel scribes a tighter radius than the inner wheel which is the complete reverse of standard
This can cause problems on positive wheel set ups mainly on relatively  slow  tight corners                                                                                                                                                                                                                           Colin                                                                                                                       
NZ