The Steering Box and 'Tracking': Setting Up the Ace and Aceca Steering
Owners chasing "tracking", directional wander, the car wanting to steer itself, after a rebuild or a change of tyres often assume the steering box is worn out. More often it is setup. The Ace and Aceca use a cam-and-peg box, and getting the peg adjustment, the toe-in and the caster right matters more than the box's age. Here is how the steering is meant to be set, and where wandering usually comes from.
Confirm against your car
Steering is safety-critical. This is a general guide, not a substitute for the workshop manual or a steering specialist. A correctly set box should feel light with the wheels raised and should self-centre; if the steering behaves oddly, have it checked before driving.
The cam-and-peg box and the peg adjustment
The steering is a cam-and-peg box (a form of worm-and-peg). A key point, easily missed: the cam is machined to give more clearance to the peg in the straight-ahead position, so the peg must not be set too close. Set it too tight and it binds as lock is applied, and you lose the caster self-centring. There should be a little play at the steering-wheel rim.
The cam does not wear the way the peg does, so a common and effective fix is a new peg alone, its clearance adjusted so the wheel self-centres the moment you relax your grip while turning, not so tight that it binds on lock.
Toe-in and caster
The handbook figure for toe-in is 1/16 inch per wheel measured at the rim, about a quarter of a degree each side. Caster should be a few degrees positive; owners quote around three to four degrees. One serious warning: fitting the front uprights on the wrong sides reverses the caster angle and produces alarming directional behaviour, so check the caster reads positive on both sides.
Where wandering really comes from
The Ace is not naturally prone to tramlining, and neither are the tyres usually fitted. When it wanders, suspect setup and wear before the box itself: an over-tight peg (lost self-centring), a stiff or worn steering idler, including wear in its mounting-bolt holes that lets it move, toe-in off the figure, wheel balance, and tyres, since modern radials behave differently from the period ones. Owners with very large mileages report no tracking trouble on a properly set box: one Ace has covered around 450,000 km on its original, unrestored box, and the handbook claims that correctly adjusted the box gives essentially unlimited service.
Specialists
Cam-and-peg boxes of this type are rebuilt by steering specialists such as Marles-Weller. New worms are available through Triumph specialists, but owners report their quality can be variable, so a good rebuild of your original is often the better course.
In short
The Ace and Aceca's cam-and-peg steering box wants the peg set with a little clearance, not tight, so the wheel self-centres and does not bind on lock; toe-in to the handbook's 1/16 inch per wheel; and positive caster both sides. When the car wanders, look to the peg, the idler, toe-in, balance and tyres before condemning the box, which can last enormous mileages when properly set.
Sources. This article draws on the experience of owners in the AC Owners' Club community and the AC handbook's steering figures.
A general guide to setting up the steering, not a substitute for the workshop manual or a steering specialist. Steering is safety-critical, confirm figures against your car and have box overhaul and alignment done properly.
About the author
A lifelong classic-car enthusiast in North Yorkshire, near Thornton-le-Dale, who owns and maintains an AC Aceca, writing the single-model reference he always wished existed. Read the full bio.