castor angle

[mark.anson]

Ive posted this in Techie talk too but so far no response so hopefully someone in the SS will have the answer.

 

Can anyone tell me what the front suspension castor angle should be on the front upright please, and is there an easy way to set it "as near as" without a proper gauge until I can get the whole thing set up properly.

 

What effect will increasing or decreasing the castor from standard have on the handling. ?

 

 

 

 

[AdamR]

Here's my understanding of it...

 

- More caster gives more self-centering effect, and therefore more weight to the steering.

 

- Caster 'presents' the inside edge of the tyre to the road when cornering, so when turning your front wheels, the camber angle increases. More caster gives more camber increase.

 

- From the above, it may seem that you can gain 'something for nothing' by adding loads of caster (extra camber in the bends where you need it, but 'straight up' tyres under braking for better grip), but then the steering weight increases too much and the feedback decreases. So, wost Westfields have front caster of around 5 degrees.

 

If you have a camber gauge, you can turn your front wheels through an angle of 20 degrees to the left, check the camber, then turn them 20 degrees to the right, and measure the camber again. Multiply the difference in camber by 1.5 and that is a very close approximation. I would say it's more important to have the casters equal to each other than the exact 5 degrees, or the car will 'drive' to one side due to the mismatched self-centering effects.

[Geoff101]

I had a discussion about castor angle when changing the wishbones a while back. There are some suggestions on figures on there:

 

http://forum.wscc.co.uk/forum/index.php/topic/91671-front-upper-wishbone-geometry/