We’ve decided for this week to cover a topic we come across quite regularly from our users.
Caster is the angle of the king pin in relation to the center line of the tire.
We recommend 0 to +3 degrees castor at ride height on the axle suspension any caster reading that comes in at more than -2 degrees is an issue for steer axle stability known as castering or shopping cart effect. Although caster is set at the factory there are situations that can change your factory caster setting.
Fifth wheel coupler height of your tractor must match the trailer specification for example a flat deck that has a 49’’ coupler height and a tractor tats set up for 47’’ can reduce your caster reading by 2 degrees.
Another situation that can change factory caster settings is ride heights of the primary suspension as well as the steer axle suspension ride height.
Example: if your suspension has a 19’’ ride height and you’re only getting 17’’, your caster again is reduced by 2 degrees.
The last thing that can change caster is tire diameters on both the primary and steer axle.
Example: if you go to a larger tire on the steer axle the ride height will change and so will the caster.
Beware of these changes from the original factory settings as it will all relate to tire wear issues as well as steer axle stability.
Rudy & Phil