I have seen percentages quoted for the amount of antidive or squat in a suspension. Please could someone explain how a percentage can be calculated from a given suspension geometry. I suppose this will be a diagram type explanation or possibly one of you knows of a book that explans this properly. My copy of Staniforths books are very light on this issue, no mention of percentages at all.
no idea
i understood to get anti dive the geometry of the suspension when extended back intersects the cog of the car if that is the case you either have 100%
as it intersects or none as it doesn't.
As I understand it to get 100% anti-dive/squat you'd need to angle the chassis pickups but quite a fair amount - in the models I have the front
would need to be about 15deg. This would cause fairly severe camber/castor changes which negate the advantages of anti-dive.
So people reduce the angle, e.g. if you needed 20degrees to get true anti-dive, and you actually used 5 degree inclination, you'd have 25%
anti-dive.
On a lotus 7 type chassis, which has low centre of gravity and low roll centres you don't really need full anti-dive. My chassis has 1.5 degrees
inclination on the lower pickups and 1.25 on the upper, which gives about 10% anti-dive - same on rear for anti-squat.
Just pulled out my copy of Tune to Win by Carroll Smith for a refresher...
In 100% anti-either, lines drawn through the suspension pickup points will intersect at a line drawn from the tire contact point through the CoG.
For a lesser percentage, say 10%, a line drawn from the contact patch to where the lines through the pickups intersect will itself intersect a
vertical line from the CoG to the ground, at 10% of the height of the CoG from the ground. (Wish I had a picture)
Too much "anti" can cause the suspension to bind and not handle bumps well. Smith says that no anti-dive is needed in light cars such as F1
and sports racing cars, and that anti-squat is OK in a high power-to-weight situation, with about 20% being the maximum practical amount.
Superformance apparently has both anti-dive and anti-squat, but not much from the pictures
I've seen.
I like the idea of a little "anti" at both ends as I plan to use fairly soft springs, with a small anti-roll bar at the front. I will be
pretty conservative in this, because the CoG location will be just a guess.
quote:
Originally posted by pbura
... For a lesser percentage, say 10%, a line drawn from the contact patch to where the lines through the pickups intersect will itself intersect a vertical line from the CoG to the ground, at 10% of the height of the CoG from the ground. (Wish I had a picture)
...
I tried to estimate the height of my projected CofG a while back to determine what my brake bias should be, I got 16" off the deck in a BECn This
is not far from the height of the top wishbones.
I'm not bothering with anti-dive/squat, reckon there won't be much & what there is gives useful "driver feedback"!
Cheers
Bob