On or around Wed, 11 Jan 2006 10:03:00 +0200, Bob <firstname.lastname@example.org>
enlightened us thusly:
>> The heavy duty springs have raised the vehicle, causing reduced caster
>> on the front axle. This is what is causing your steering problems - fit
>> some caster-corrected radius arms and the problem will disappear.
>Can you explain what caster does?
>And where does one get caster corrected radius arms? In South Africa
caster (or castor) is what makes the steering self-straighten. Effectively,
the front wheels operate like a supermarket trolley wheel, in other words,
once moving forwards, they tend to run straight. in reverse, the opposite
applies, which is why if you reverse very fast it can be more difficult to
keep it straight.
If you raise the front end, you alter the angle of the swivel bearings,
since the axle/swivel is held on the radius arm - the change in angle can be
calculated by measuring the effective length of the radius arm (to the
middle of the axle) and applying trigonometry to that and the amount of lift
you have achieved. If you lowered the radius arm attachment at the rear of
the front arms by the same as the lift, you'd get the same caster angle as
you had before.
There are 2 fixes: different radius arms, which have the mountings for the
axle bushes at a different angle, so the axle is returned to its intended
orientation, or different swivel housings, in which the swivel bearing
positions are altered to get the angle correct. In either case, you need to
know how much lift to get the correct one for the job.
Austin Shackles. www.ddol-las.net
my opinions are just that
"Nessun maggior dolore che ricordarsi del tempo felice nella miseria"
- Dante Alighieri (1265 - 1321) from Divina Commedia 'Inferno'