Camber , Castor and toe-in

[Noam]

Hi all,
Was wondering if anyone coould shed some more light on these . . .
I know only that negative camber is sometimes used to enhance a car's overall balance - but how??and what are exactly castor and toe-in?
and especially , how does all this pertain to the Ibiza 20vt??
Would a slight negative camber benefit our car's understeer?
Thanks,
Noam.

[edc]

I think Glyn explained the intricacies of this ina an article on the main site.

TBH you're better off buying a book on suspension geometry, cos, not doubting anybody's expertise here, your questions may raise more questions and not give you a definitive answer.

[m0rk]

guide here (http://www.seatcupra.net/reviews.php?descrip=Suspension)

The ibiza should have the -ve camber already mate

Mark

[Noam]

Thanks Mark - a nice and coherent review of the subject :)
When I finally get to sorting out the suspension I'll have a look at the settings and report back.
Thanks you guys.

[josh]

first off , toe in/out is basicly your traking adjustments.

CASTOR, this is when the top of the wheel points out towards the wing.
CAMBER, this is when the top of the wheel points in towards the inner arch.
your car is set to near enough inbetween the two so the tyre surface sits flat on the road.

you can set the camber (negative camber) so the wheel points in under the arch and get more clearance to lower the car and not scrap the arch.

[hopkinsgm]

Originally posted by josh
...CASTOR, this is when the top of the wheel points out towards the wing...
No it's not - castor (or caster, either spelling is correct) is the angle between the vertical and the axis the steering pivots about.

Imagine a line drawn through the pivot points of the steering - the top pivot being the McPhearson strut, the bottom pivot being the ball joint at the end of the wishbone. If you were to extend this line down to the ground, you might assume that this would be where the contact patch of your tyre is. This is seldom the case. The imaginary line usually hits the ground in front of the contact patch of your tyre (positive castor). This helps the steering pull itself central, and makes you car naturally tend to straighten up as you come out of a corner. It also helps keep the car travelling in a straight line at speed.

What you describe as castor is actually POSITIVE CAMBER. It's not too common to (intentionally) set a car up with positive camber these days. Most cars run with up to a couple of degrees NEGATIVE CAMBER for road use, a bit more for track. The benefit of negative camber is that as the car starts to lean as you corner at speed, the contact patch is enlarged as the tyre surface comes into contact with the road surface. The problem with running lots of negative camber is that if you ever drive anywhere in a straight line, you'll wear the inside edges of your tyres out in double quick time.

BTW, if we're talking mk2 or mk3 Ibiza here, there's adjustment of toe and camber at the front and that's about it. Front toe should be fairly neutral, front camber should be about 0.5 deg negative camber. If the front castor is out of spec. (should be about 1.5 deg +/- .5 deg), you probably have a slightly bent wishbone. Note that these angles will all change when the car is being driven, camber changes with suspension travel and roll for example.

There are some excellent books covering suspension set-up in the kind of level that will make your head spin. For a decent overview in enough depth to make sense without making your brain hurt (well, not too much anyway!), I would suggest a quick look at the relevant section of Simon McBeath's book "Competition Car Preparation". There were some excellent features published in Radio Race Car magazine in the late 80's from which my initial interest in the subject of suspension geometry came about - I used to race 1/10th off road buggies in my youth. You'd be surprised how much difference a few choice tweaks can make to the handling of a 1/10th scale off road buggy...

[m0rk]

I agree G, else (if josh could tell us) how can you have castor & positive camber

[hopkinsgm]

Not quite sure what you mean Mark...

[josh]

i don't know what you mean?,mark.