AC Ace Tire Pressures

• Typical tire pressures for the AC Ace range generally fall between 22-33 PSI, depending on model, year, purpose and tire type.
• To find the ideal tire pressures to match your car's year, model, and chosen tires follow the link to our AC Ace Tire Pressure Guide.

• Longstone's recommended (1953−1961) AC Ace and AC Ace Bristol tire is the 5.50 R 16 Michelin X.
• The best (1961−1963) AC Ace and AC Ace Bristol tire is the 185 VR 15 PIRELLI CINTURATO CA67.
• For more information follow the link to our AC Ace Tires Section.

From the launch in 1953 until 1961 the AC Ace fitted 550 - 16 crossply tires. In this size the best AC Ace crossply tire is the 5.50-16 PIRELLI STELLA BIANCA. The PIRELLI STELLA BIANCA is Pirelli’s high-performance crossply road tire, originally developed for some of the world’s greatest classic sports and racing cars and offering period-correct handling with a high speed rating.

For the best handling, we suggest switching to radial tires. Radial tires offer better grip, improved directional stability, and more predictable handling compared with crossply tires, they also help old cars drive in a straight line on high-speed modern roads, where crossply tires tend to wander.

Longstone's recommended early AC Ace tire is the 5.50 R 16 Michelin X. This tire is a radial tire from Michelin (hence 5.50 R 16 Michelin X), but it is built with crossply dimensions and a crossply size description. This tire is perfectly sized and perfectly suited to the 1953-1961 AC Ace, and was factory fitted to some later models.

The AC Ace Bristol arrived in 1956, sporting a much faster engine than the antiqued AC unit that was fitted during the first 3 years of production. These models fitted the same 550 - 16 tires as the early models, so we recommend the 5.50 R 16 Michelin X.

Our 1963 Tire fitment guide from Dunlop (see below) states that in 1961 new AC Ace and AC Ace Bristol models began transitioning from 550 - 16 tires to 640 - 15 tires, and by 1962 640 - 15 is the only standard size listed for the Ace. The only crossply tire we have in this size is the 640 H 15 Avon Super Safety which is a good quality crossply, but we instead suggest switching to radial tires.

The best radial equivalent sizes are 180 R15 and 185 R15, in the 180 R15 size we can recommend Michelin's 180 HR 15 Michelin XAS. A friend of Longstone has an Ace with the 180 HR 15 XAS fitted and loves the light handling it affords. The best 185 R15 AC Ace tire is the 185 VR 15 PIRELLI CINTURATO CA67.

The PIRELLI CINTURATO CA67 was the world’s first true sports-car radial tire, developed in 1952 and adopted as standard fitment by the leading performance cars of the 1950s and 1960s. It is a particularly good match for the AC Ace because it is a proper period sports radial, offering the steering precision and directional stability that suit a light, responsive 1950s–1960s sports car like the Ace.

If you're stuck between the XAS and CA67 then select the 180 HR 15 Michelin XAS if you favour light handling, or the 185 VR 15 PIRELLI CINTURATO CA67 if you favour better grip.

There can also be a case for the 185 VR 15 Michelin XVS as an alternative, but it does not have the same sporting pedigree as the PIRELLI CINTURATO CA67, so the CA67 and XAS are better matches for the AC Ace’s character in most cases.

Some AC Ace models are used for racing. The ideal track tire is the 5.50 × 16 Dunlop R5 Racing, which has the added advantage of being road-legal, allowing the car to be driven to and from the circuit. However, for regular road use the Michelin X and PIRELLI CA67 are far better suited.

Classic racing tires have special innertubes optimised for track use. The ideal tube for 550 - 16 racing tires is the Race Inner Tube (Metal Valve Stem) 550-650X16.

The AC Ace was fitted with tube-type wire wheels throughout production, often using original Borrani wire wheels (see below). With wire wheels inner tubes are required at all times, even when fitting radial tires that can be run tubeless.

Although tires such as the PIRELLI CINTURATO CA67 and Michelin X are themselves capable of being run tubeless, the wheels fitted to the AC Ace were never designed to seal air without an inner tube. Running wire wheels tubeless is unsafe and should be avoided.

Michelin inner tubes are consistently the most reliable option for classic cars, with excellent material quality, accurate sizing, and a very low failure rate in long-term use. For 550 - 16 and 550 R16 tires, including both crossply and radial fitments, we recommend the Michelin 16E Offset Valve Inner Tube. For 640 - 15 crossply tires and 185 R15 radial tires, the correct choice is the Michelin 15F Offset Valve Inner Tube, offering the correct sizing and valve position for wire wheels.

The AC Ace was fitted with wire wheels throughout production, the best wire wheels were supplied by Ruote Borrani Milano. These lightweight wire wheels are a fundamental part of the Ace’s character and contribute directly to its light, responsive steering and ride quality.

Borrani wire wheels use aluminium rims with steel spokes and steel wheel centres, giving an excellent balance of strength, durability, and low unsprung weight. All original AC Ace wire wheels are tube-type, so inner tubes must always be used, even when fitting period-correct radial tires such as the PIRELLI CINTURATO CA67 or Michelin X.

Having the correct tire pressure provides the best balance of ride comfort, stability, steering precision, and safety for classic and vintage cars on modern roads. These recommendations are based on guidance from the original car manufacturers and period tire makers, who best understood the chassis, weight distribution, and tire construction.

Crossply tires on the AC Ace were originally run at relatively low pressures, an older source from AC suggests 22 psi front and rear however, improvements in tire construction, road surfaces, and traffic conditions mean that modern recommended pressures are often higher than those quoted in some older period documentation. A slightly newer period Michelin guide offers 22 psi front and 27 psi rear, which is a good pressure for AC Ace crossply tires.

Radial tires require higher pressures due to their different construction and load-carrying characteristics, we suggest 28 psi front and 33 psi rear as a good starting point.

To the discerning driver tire pressures should be regarded as a guideline rather than an absolute. It is good practice to set the recommended pressures, drive the car, assess how it responds, and then make small adjustments to suit the individual car, tires fitted, driving style, load, and road conditions. Some drivers may prefer slightly higher or lower pressures to achieve the balance that feels best for their particular AC Ace.