Optimum amount of camber

[Bildon]

Found this nice technical synopsis of camber issues relating to lateral grip.

The optimum amount of camber for a tire depends on the construction of the tire. Generally speaking, cross-ply likes small negative camber, radial likes more.

Camber thrust.
If N is the normal force on the tire, C the camber angle, then camber thrust, T = N.tan© in the direction of the camber angle.

Aside from the effects of camber on temperature gradients, there is a major effect on the peak tire force. Lateral force is generated by slip angle, where slip angle is the angle between the direction the tire is heading and the direction it's actually pointing (see attatchment).
If you induce a negative camber angle, the curve shifts up the graph (increased y intercept) resulting in an increased lateral force (F=KA+T). However, camber also causes the non-linearities to occur at smaller slip angles reducing the peak lateral force (i.e. K becomes non-linear at smaller slip angles), camber roll off. Too much camber and the roll off is so severe that you can have lower peak lateral force than with no camber at all (law of diminishing returns).

Increasing the caster angle will increase the negative camber gains of the outside wheel (positive camber gain for the inside) when steering. Basically, you can run with low static camber on the straights, but increase the negative camber during cornering (where you need it) by just steering.

Hope that made sense.

[MIKEGTR]

By increasing the caster angle do you mean moving the tire toward the front of the car or towards the center?

Mike

[Spinnetti]

Originally posted by Bildon@Oct 9 2005, 07:58 PM
Found this nice technical synopsis of camber issues relating to lateral grip.

The optimum amount of camber for a tire depends on the construction of the tire. Generally speaking, cross-ply likes small negative camber, radial likes more.

Camber thrust.
If N is the normal force on the tire, C the camber angle, then camber thrust, T = N.tan© in the direction of the camber angle.

Aside from the effects of camber on temperature gradients, there is a major effect on the peak tire force. Lateral force is generated by slip angle, where slip angle is the angle between the direction the tire is heading and the direction it's actually pointing (see attatchment).
If you induce a negative camber angle, the curve shifts up the graph (increased y intercept) resulting in an increased lateral force (F=KA+T). However, camber also causes the non-linearities to occur at smaller slip angles reducing the peak lateral force (i.e. K becomes non-linear at smaller slip angles), camber roll off. Too much camber and the roll off is so severe that you can have lower peak lateral force than with no camber at all (law of diminishing returns).

Increasing the caster angle will increase the negative camber gains of the outside wheel (positive camber gain for the inside) when steering. Basically, you can run with low static camber on the straights, but increase the negative camber during cornering (where you need it) by just steering.

Hope that made sense.

62157


Good stuff...

Many cars (like mine) have adjustable caster, but most today have little to none. In my case, there is just no room to get more postive caster due to tire contact with the wheel house. (to see a really good example of caster effect, look at any older Mercedes with the wheel cranked - they have a TON)

Simple rule of thumb is you want as much negative camber as it takes to overcome the roll of the car in the most important corner of the particular track. One way to determine this is a picture from track side, or via instrumentation.

I typically run asymetric camber too.. more on the left and the right since there are more right turns at the tracks I run.

Finally, the more neg. camber you have, the worse the car is under braking - both in stopping distance and lockup/squirlyness.

[Z3_GoCar]

Originally posted by MIKEGTR@Oct 9 2005, 03:45 PM
By increasing the caster angle do you mean moving the tire toward the front of the car or towards the center?

Mike

62161


I do believe that caster is defined as the angle between the contact patch and the steering piviot. To increase it you'd want to angle your struts toward the rear more. On racing Karts you can really see the caster effect, especially if it's empty. The outer tire will rotate up but also into the turn, so caster affects camber, cross weighing, and self centering of the steering wheel. The camber change effect is what is measured on the Longacre type gauges.

James

[Bildon]

>>> you want as much negative camber as it takes to overcome the roll of the car in the most important corner of the particular track.

But you need a bit more than that due to camber thrust that my post above illustrates.

A modern tire actually gains grip by the deformation. You'll get better grip with the tires being slightly deformed due to the camber.