1958 AC Tire Fitment Guide

1958 AC vehicles use three tire sizes across two models: 550-16 for the AC Ace, plus 185R16 and 670-16 for the AC Saloon. All three sizes mount on 16-inch rims, but they are not interchangeable across the whole 1958 AC range simply because the wheel diameter matches. Rim width guidance also differs by tire size where stated, with 550-16 products shown for 3.25 to 4.00-inch rims, 185R16 radial products shown for 4.50 to 6.50-inch rims depending on brand, and 670-16 products shown for 4.50 to 5.00-inch rims where listed.

That means a buyer should start with the model name first, then the exact size, instead of assuming any 16-inch tire will serve the same role. The Ace is the simpler case because it stays with one bias-ply fitment, while the Saloon requires you to decide whether the car is being kept in a traditional bias-ply specification or fitted with a radial alternative for a different on-road feel.

On a 1958 AC, 550-16 is a numeric bias-ply tire size. The "550" identifies the tire’s nominal section width in the older numeric system, and the "16" identifies the wheel diameter in inches. It is a bias-ply fitment rather than a radial, and in the 1958 AC range it applies to the Ace.

That older numeric format is typical of period tires used on many sports and collector cars of the era. If you are restoring an Ace and want the car to retain its original visual character, 550-16 keeps you in the correct style of sizing language and construction family. When choosing among products in that size, focus on the sidewall look you want and make sure the wheel falls within the listed rim-width range for the specific tire.

On a 1958 AC, 185R16 is a Euro-metric radial size used on the Saloon. The "185" is the section width in millimeters, the "R" designates radial construction, and the "16" is the wheel diameter in inches. When this style of metric size is written without an explicit aspect ratio, it conventionally refers to an 80-series profile.

That makes 185R16 a very different type of fitment from the older numeric bias-ply sizes also seen in the 1958 AC range. A Saloon owner comparing 185R16 with 670-16 is not just comparing two labels that fit a 16-inch wheel; they are comparing radial and bias-ply construction. It is worth checking the exact sidewall marking on the product itself, because tube marking and speed rating are not identical across every 185R16 option.

For a 1958 AC Saloon, the choice between 185R16 and 670-16 is mainly a construction decision. The 185R16 options are radial tires, while the 670-16 options are bias-ply tires, and both fit 16-inch wheels. A radial generally appeals to owners who want a more modern-feeling road manner from a car they plan to use regularly, while a bias-ply usually suits an owner who wants the car to present and behave in a more period-authentic way.

The right answer depends on what you want the Saloon to be. If the car is built around originality, judged presentation, or an era-correct driving experience, 670-16 keeps you in the traditional construction type. If the car is driven more often and originality is less strict, 185R16 is the radial route. Confirm the wheel width and the exact sidewall marking on the product you choose before making the final call.

Sidewall style varies by size on 1958 AC tires. The 550-16 size used on the Ace is offered in both blackwall and wide whitewall form, while the 185R16 radial and 670-16 bias-ply sizes used on the Saloon are offered in blackwall form. That gives the Ace owner more visual choice within the same basic size, while the Saloon choices stay closer to a restrained blackwall look.

For a late-1950s British sports or saloon car, blackwall presentation is usually the safer historical direction unless you are matching a very specific appearance or market-correct restoration theme. Whitewalls can change the character of the car dramatically, especially on a compact sports model like the Ace. If show authenticity matters, compare the sidewall style to period photos and consult an AC marque specialist before settling on a cosmetic treatment.

Several brands cover 1958 AC fitments. In 550-16, the available brands are Excelsior, Avon, BFGoodrich, and Firestone. In 185R16, the brands are Michelin, Avon, and Vredestein. In 670-16, the brands are Firestone and Avon. That gives a broad spread of choices across traditional bias-ply and more modern radial construction, depending on the model and size you need.

Brand choice matters less than making sure the size, construction, and wheel compatibility are right for the car. Still, buyers often narrow the field by the overall character of the tire they want: a heritage-style bias-ply look, a traditional blackwall presentation, or a radial from a brand long associated with European touring and sports-car applications. Once the correct size is settled, compare each brand’s sidewall style, rim-width range, and speed marking where applicable.

Rim width depends on the specific tire size used on the 1958 AC. For 550-16, listed products show a 3.25 to 4.00-inch rim-width range. For 185R16, listed products show 4.50 to 6.00 inches on one option and 5.0 to 6.5 inches on another. For 670-16, listed products show 4.50 to 5.00 inches where rim width is stated. All of the sizes mount on 16-inch rims, but width guidance is not the same across them.

That is why wheel diameter alone is not enough when choosing a tire for a 1958 AC. A Saloon owner considering a switch between 670-16 and 185R16 especially should verify the actual wheel width on the car before deciding. If your wheel falls near the narrow or wide edge of a listed range, it is wise to confirm the exact product’s fitment characteristics instead of treating all tires in the same nominal size as identical.

Tube status varies by size and by product on 1958 AC tires. The Michelin 185R16 is marked TT, meaning tube type, while the other 185R16 products shown are not marked the same way. The 550-16 and 670-16 products are bias-ply offerings and should be checked by their specific sidewall marking and wheel type rather than assumed one way or the other from size alone.

That makes wheel construction and exact tire selection important before final assembly. If your 1958 AC still runs original-style wheels, it is worth confirming whether the chosen tire is intended for tube-type service and whether the wheel condition supports that setup. Tube, flap, and valve-stem choices should be treated as part of the complete installation plan, not as an afterthought once the tires have already been selected.

All of the listed 1958 AC tire sizes use a 16-inch rim diameter, so wheel diameter compatibility is consistent across the Ace and Saloon range. That said, the widths associated with those tires are not identical. The Ace’s 550-16 products suit narrower rims than the Saloon’s 185R16 radial products, and the 670-16 Saloon bias-ply sits in its own range as well.

In practice, an original 16-inch wheel may still be unsuitable for another 16-inch tire if the width is wrong for that product. The safest approach is to verify the actual width of the wheel on the car and compare it to the tire you intend to use, especially if a Saloon is being moved from one construction type to another. Original wheels should also be inspected for trueness, corrosion, and bead-seat condition before refitting.

A stored 1958 AC should be kept in a cool, dry, dark space away from direct sunlight, electric motors, welders, battery chargers, and other ozone-producing equipment. Clean concrete is fine, but standing moisture and wide temperature swings are not. If the car will sit for extended periods, maintaining proper inflation and moving it occasionally helps reduce flat-spotting. Bias-ply tires tend to show temporary flat spots more readily after storage than radials, so the Ace and a bias-ply Saloon may need a little more attention than a radial-equipped Saloon.

Long-term storage is about preserving the whole tire, not just the tread. Sidewalls age from light, ozone, and inactivity, and collector cars often spend more time parked than driven. If the storage period will be lengthy, some owners use stands to reduce sustained loading, but they should still avoid leaving the suspension in an unnatural state for years. A quick inspection before returning the car to use is always worthwhile.

On a 1958 AC, tire life should be judged more by age and condition than by mileage. Collector cars often accumulate very few miles, yet the rubber still hardens and the sidewalls still age. A good rule is to begin paying closer attention once tires are around five to seven years old and to treat roughly ten years as a point where replacement deserves serious consideration, even if tread remains. The date code on the tire is the starting point for that age check.

That matters because a low-mileage Ace or Saloon can appear fine at a glance while still riding on old tires. Visual checks alone are not enough if the tire has spent years supporting a parked car or sitting in a warm garage. If you have just acquired a 1958 AC and the age of the tires is uncertain, confirming the date code early is one of the simplest and most important safety steps you can take.

Tires on a 1958 AC should be inspected before every drive and more thoroughly before any longer outing. Look for sidewall cracking, cuts, bulges, uneven wear, and signs that the tire is losing pressure between uses. On a collector car, long periods of inactivity can mask a problem until the next drive, so regular checks matter even when mileage is low.

Inspection should include more than the four tires touching the ground. Check the spare, and if your setup uses tubes or tube-type service, pay attention to valve stems and any slow-leak behavior. A 1958 AC that is headed out for a tour or event also deserves a pressure check when cold, since proper inflation and early detection of deterioration can prevent a minor issue from becoming a roadside problem.

A 1958 AC Ace would have been a bias-ply car when new, and the listed fitment for the Ace is 550-16. That aligns with the period, when bias-ply construction was still standard on many British sports cars. Original-equipment branding could vary by market and supply, so the main restoration takeaway is the size and construction type rather than assuming one universal brand for every car.

For an owner restoring an Ace with authenticity in mind, staying with a 550-16 bias-ply tire keeps the fitment in the right historical lane. Sidewall appearance then becomes the next decision, since blackwall and wide whitewall versions exist in the current offerings. If the car is being judged at a high level, confirm market-specific expectations with AC owners’ clubs or event-specific rules before finalizing the sidewall treatment.

Correct tire fitment absolutely matters when a 1958 AC is judged for authenticity. Size, construction type, and sidewall style all affect how correct the car looks and how closely it matches period expectations. A radial on a car judged to factory-era standards may be viewed differently from a proper bias-ply, and a sidewall treatment that looks out of place for the model or market can also draw attention.

That does not mean every shown 1958 AC must wear the same tire, but it does mean the choice should be intentional. The Ace and Saloon have different fitment paths, and the Saloon’s radial-versus-bias decision can influence how original the car presents. Before a concours event, compare your selection to period photography and consult the relevant judging standard or marque club so your tire choice supports the rest of the restoration.

For the 1958 AC Saloon, Firestone and Avon appear in different ways depending on size. In 670-16 bias-ply, Firestone lists a blackwall tire with a stated load of 1,130 lbs at 30 psi and a listed rim-width range of 4.50 to 5.00 inches, while Avon offers the 670H16 89H blackwall bias-ply with a stated load of 1,279 lbs. In the radial 185R16 size, Avon appears with a 185VR16 93V blackwall option rather than the Firestone name.

That means the comparison is really two-fold: within the bias-ply Saloon size, and across the Saloon’s two construction paths. A buyer choosing between the Firestone and Avon 670-series offerings should compare wheel width and the exact sidewall marking. A buyer deciding between Avon’s 670H16 and Avon’s 185VR16 is comparing a bias-ply versus radial approach, not just two variants of the same basic tire.

1958 AC tires can be suitable for highway use when the correct size, construction, condition, and speed rating are matched to the car and its intended driving. The 185R16 radial options include S and V speed ratings, which correspond to 112 mph and 149 mph ceilings respectively. The 670H16 Avon bias-ply carries an H rating, which corresponds to 130 mph. Other bias-ply options shown in 550-16 and 670-16 are not uniformly presented with speed letters, so the exact sidewall marking matters.

Real-world safety in a 1958 AC depends on more than the tire alone. Brakes, steering, suspension condition, alignment, and the car’s age all matter, especially on a handmade British collector car with very different manners from a modern vehicle. For normal highway use, a sound tire in the correct size is only one part of the equation, so it is smart to treat the whole car as the system that needs to be road-ready.

Inflation pressure for a 1958 AC should be guided first by the vehicle’s factory recommendations and then checked against the tire manufacturer’s own limits for the exact product. Some of the listed tires include load-and-pressure figures: one 550-16 Firestone is shown at 840 lbs at 32 psi, the 670-16 Firestone is shown at 1,130 lbs at 30 psi, and one 185R16 Vredestein is shown at 1,433 lbs at 51 psi. Those figures are rated maximum references for those products, not a universal pressure setting for every 1958 AC tire.

The practical takeaway is not to transfer a pressure number from one size to another or from one tire brand to another just because the wheel diameter matches. A Saloon on 185R16 radial tires should not be inflated by using a bias-ply 670-16 reference, and the Ace’s 550-16 should be treated as its own case. Start with the car’s period guidance, then confirm that your chosen tire’s sidewall and manufacturer information support that use.

Before a longer drive in a 1958 AC, inspect each tire for cracking, cuts, bulges, irregular wear, and signs of age-related hardening. Check cold inflation pressure, verify that the spare is usable, and look closely at valve stems and any tube-type components if your tire setup requires them. A car that has been sitting should also be watched for temporary flat-spotting or a tire that has slowly lost air in storage.

Tires are only one part of the pre-drive routine, but they are among the easiest things to inspect and one of the most important for confidence on the road. Because a 1958 AC is a collector-era machine, a longer outing should also include a broader look at brakes, steering play, suspension, and fluid condition. If the tires pass inspection but the car itself feels unsettled at speed, stop and sort out the mechanical issue rather than trying to drive through it.