Wheels & Tyres
The AC Aceca left Thames Ditton on 16-inch wheels — wire or disc — shod with 5.50 or 5.75 × 16 crossplies at cold pressures around 22 psi front and 24 psi rear. Modern radials in an equivalent size are widely fitted. Whatever the choice, the single most important safety check on a classic-car tyre is its age.
Present these figures as a guide only. Verify against your car's handbook and the tyre maker's data.
Original sizes and wheels
Standard fitment was a 16-inch wheel, offered as painted pressed-steel discs or as knock-on wire wheels — the latter a popular period option that suits the car's coachbuilt character and is now almost universal on surviving cars.
Original tyres were crossply construction in 5.50 × 16 or 5.75 × 16 depending on build date and specification. Whitewall or plain black sidewalls were both period-correct.
Recommended cold pressures
Original recommended pressures were in the order of 22 psi front and 24 psi rear for normal road use, cold, with modest increases for sustained high-speed running. These are period guide figures. Confirm the correct pressures against your car's handbook and the tyre maker's fitment guidance — especially if you have moved to modern radials in an equivalent size.
| Use | Front (cold) | Rear (cold) |
|---|---|---|
| Normal road | ~22 psi | ~24 psi |
| Sustained high speed / touring | +2–4 psi | +2–4 psi |
Modern tyre options
Two respectable routes exist for a road-driven Aceca. The period-correct route runs crossplies in the original size from makers such as Blockley, Michelin or Vredestein — preserving original handling character and appearance. The modern route runs a radial in an equivalent original size, typically for better grip, longer life and more predictable wet-road behaviour. Both are defensible.
Two rules apply to either choice. Never mix crossply and radial construction on the same axle. And whichever construction is fitted must be matched by pressures the tyre maker specifies — modern radials may prefer slightly different figures from the period recommendation above.
The classic-tyre age rule
Old tyres are dangerous regardless of tread depth. Rubber perishes with age and UV exposure — it goes hard, cracks and loses grip long before its tread wears out. A ten-year-old tyre with good tread can fail catastrophically at speed. This is not a theoretical risk; classic-car tyre failures kill people every year.
Every tyre carries a four-digit DOT date code on the sidewall (week / year of manufacture). Read it, write it down, and replace any tyre approaching or over ten years old — irrespective of how much tread is left, how little the car is used, and how good the tyre looks.
Routine checks
Check pressures cold, fortnightly and before any long journey. Inspect sidewalls for cracks, bulges, cuts and dry-rot crazing; any sidewall damage means replace, not repair. Read tread wear for its story: centre wear indicates over-inflation, shoulder wear indicates under-inflation, one-shoulder wear indicates tracking, and feathering across the tread indicates a toe-setting problem.
Balancing and tracking
Balancing and tracking are not one-off jobs. Kerb strikes, replaced steering components and tyre changes all disturb geometry. On knock-on wire wheels, retighten the spinners after the first few miles following any wheel change, and check regularly for loose spokes.
Flat-spot prevention in storage
A car left standing for months on tyres of any age develops flat spots that never fully recover. Where possible, raise the car onto axle stands with the tyres just clear of the ground, or move it a full wheel-turn every few weeks. Over-inflating by 4–6 psi during winter storage also helps.
When to consult a specialist
Fitting new tyres to knock-on wire wheels, straightening a buckled rim, rebuilding a wire wheel or diagnosing a persistent wheel-wobble or tracking fault are jobs for a wire-wheel or classic-alignment specialist. Do not persevere with a steering-wheel shimmy at speed — get it diagnosed.
Frequently asked questions
What tyre size did the AC Aceca come with from the factory?
Original Acecas were fitted with 5.50 × 16 or 5.75 × 16 crossply tyres on 16-inch wire wheels or, on later cars, pressed-steel disc wheels. Exact fitment varied with build date and specification — verify against your car's build sheet and the workshop manual.
What are the correct tyre pressures?
Original recommended cold pressures were in the region of 22 psi front and 24 psi rear for normal road use, with modest increases for high-speed running. Confirm against the handbook for your specific car and always follow the tyre maker's guidance when running modern radials in an original size.
How old is too old for a classic-car tyre?
Tyres over ten years old are widely considered unsafe for road use, however good the tread looks. Rubber perishes with age and UV exposure, losing grip and gaining a tendency to fail without warning. Read the DOT date code on the sidewall and replace anything older than ten years.
Should I fit modern radials or period-correct crossplies?
Both are defensible. Period crossplies preserve original character and handling and suit concours use. Modern radials in an equivalent original size give better grip, longer life and are widely regarded as safer for touring. Never mix crossply and radial construction on the same axle.
About the author
An independent classic-car enthusiast in North Yorkshire with decades of hands-on experience on British classics — including the AC Aceca — writing the single-model reference he always wished existed. Read the full bio.