Caster

By Jon R. Belanger

Continuing with our series on chassis set-up, the next step is caster. Caster, according to the VW Manual, is the angle, viewed from the side, between the pivot point of the steering knuckle and the vertical line through the wheel center. For our purposes, caster can be approximated by measuring the angle formed by the relationship of the two tubes making up the axle beam. The VW manual recommends 2 degrees positive caster... this may work well for a street bug but is probably too little for your Vee. Most Vees, vintage and current, run anywhere from 2 1/2 - 5 degrees positive caster. The rule of thumb I use is: too little caster makes the steering light, causes insufficient self return, and creates straight line instability and wander. Too much caster makes the steering heavy and the steering response slow.

To check caster, make sure your car is on a level garage floor with the tires aired properly. Take your camber/caster gauge and lay it against the axle beam tubes... what you're trying to get is a reading of the relationship between the two tubes. On some Vees, especially vintage ones, the beam may be welded to the frame and cannot be changed. In this case you will have to trust the designer did his homework. If you have a TSR or similar Vee, the caster can be adjusted by screwing the axle beam mounts in or out as is necessary... just make sure you keep things even from side to side to prevent it from "crabbing" down the track. Many older Vees are like my Autodynamics, with the beam being fastened to the frame by four "U" bolts. To adjust this type you must shim between the frame and one of the tubes of the beam to get the desired effect.

Keep in mind that what we're measuring hear is axle beam angle, not actually caster... use it as and "easy" and repeatable reference. The numbers indicated will vary slightly from true caster readings, but will allow you to easily compile data to assist in setting up your chassis. Remember, your Vee should be agile and very responsive to drive, but not so much so that it becomes twitchy and hard to keep control of when you approach high speeds!

Like many suspension settings, correct caster can make the difference between a car that is hard to drive and one that is a real pleasure... it's definitely worth the effort.

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