Caster trail

[Arpit]

Hi

Can anbody tell me what exactly is caster trail and what effect does it have on the car?

Thanx

Arpit Gupta
Defianz Racing
Delhi College of Engineering

[Arpit]

Hi

Can anbody tell me what exactly is caster trail and what effect does it have on the car?

Thanx

Arpit Gupta
Defianz Racing
Delhi College of Engineering

[Mark Ortiz]

Caster trail, also called mechanical trail, geometric trail, or simply trail, is the side view horizontal distance from the ground intercept of the steering axis to the contact patch center.

This distance is partly determined by caster angle, which is the side view inclination of the steering axis from vertical. It is also affected by the tire loaded radius and the amount of pin lead or trail at the spindle. It is possible to have trail without caster, or caster without trail, if the steering axis passes in front of or behind the wheel axis.

Trail makes the steering seek an inertial/gravitational center. It makes the car try to run straight on a level surface, or turn downhill on a transverse slope. It increases feedback of lateral force at the front wheels through the steering. This means there is more steering effort in hard cornering, and also more feel of how much grip the front tires have.

When combined with positive caster, increasing the trail also increases "steer drop" - the reduction of ride height with steer. This effect tends to create an anti-centering force, particularly at large steer angles. It is the reason a dragster's front wheels tend to flop over to full lock when the car is at rest.

For a more comprehensive discussion of steering geometry, readers can e-mail me at markortiz@vnet.net and request my August 2002 newsletter, which has an article on the subject. It's free.

[awhittle]

Bottom line If you have about 8 degrees of caster ,top and bottom heim and spindle all in the same plane, and 13" tires you will get about 1 1/2" caster trail. If you move the spindle about 3/4" forward 1/2 of the caster trail will go away and all this will not be a problem.

See http://www.ncs-stl.com/racecar/MVC-011S.JPG

Hope this helps

Andy Whittle