What my car should look like when finished - Stoneleigh 2015

Monday, 21 March 2016

Front Suspension Geometry

With the rear geometry finished, I started to the front.

I opted for the adjustable front wishbones which are connected to the chassis with front and rear rod ends.

I used a length of wood (planed straight) and two plumb bobs to project some lines down to the floor.  I drew a parallel line to the centre line so that I could ensure that the hubs were pointing directly ahead.  I then drew on two lines 20 degrees from the centre point to setup the caster.

I straightened the hubs and then measured the camber.  I made sure both rod ends were screwed out the same distance before starting.  I then screwed them in / out to suit.  I found out the following:

1 turn of the rod end alters the camber by 0.3 degrees.

I then used the following method to measure the caster using my digital camber gauge.

On the left hand side:

Rotate the hub to the left by 20 degrees using marks on the floor and the plumb bob.  Rotate the digital gauge to vertical.  The camber angle measurement is then noted (eg. +1.1)

Rotate the hub to the right by 20 degrees using marks on the floor.  Rotate the digital gauge to vertical and take the camber reading (eg. -1.86)

Since one of the readings is negative camber, and the other is positive then these numbers should be added together (ignoring the + & - signs - eg. 2.96

Since I used 20 degrees as the angle of rotation, this number needs to be multiplied by 1.5 to give the caster angle. (eg. 4.44)

Repeat the above for the right hand side.

I did have an instruction manual describing this in detail - I will attach it when I can find it again!

To adjust the caster, depending on which way it had to go, each rod end has to be screwed opposite to one another to maintain the camber angle.

This was a little more trial and error and I didn't seem to have an exact figure for 1 turn of movement.  Although roughly it seemed to be 1/2 turn on the rod end altered the caster by 0.3 degrees.

Once I connect up the steering arms then I can set the front toe.

The settings I aimed for at the front are:

Front toe: 5min toe in to 5 toe out to suit conditions and driving style.
Front camber: 0.75 to 1.5deg to suit track – check for even tyre temp.
Front caster: 4 to 4.5 deg neg to suit driver.

I need to think about how to set the bump steer.......

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