Thread: Manual to power rack question

Tweet

Heidt's sets their Super Ride II suspension (based on MII geometry) to have a minimum of one degree of caster, for use with a manual rack, since it makes the car easier to steer (less self-centering). With a power rack, up to 5 degrees is sometimes used, but only if the suspension permits that much adjustment.

There really is no right or wrong when it come to minor changes to caster. The only way to know if you'd like more caster is to try it. The link below references caster under instruction 7.

http://www.heidts.com/inst/in-027.pdf

What you're really doing by increasing caster is increasing steering trail. Changing the tire diameter also changes the trail, for a given caster angle. The larger the tire, the greater the trail. Smaller than normal front tires need more caster to produce the same trail as larger tires. The subject of steering trail is a big topic for bicycles and motorcycles that use a lot more steering trail than a car. More trail enhances stability (self centering). Over the 25 years that I rode bicycles (an average of 3,000 miles a year), I've spent many hours discussing and analyzing the effect of steering trail.

For a car, the formula for trail would be R (tire radius) x tanC (caster angle). It's more complicated for bicycles and motorcycles.

Try a google search for steering trail.