1966 AC Grayhound Tires

A 1966 AC Grayhound uses two primary tire sizes: 640-15 and 670-15. Both are vintage numeric bias-ply sizes built for 15-inch rims, so the Grayhound stays within one traditional construction type even though there are two size paths to consider.

The practical question is which setup is actually on the car now. Since the Grayhound Base is associated with both sizes, it helps to confirm the wheel and tire combination already fitted before ordering replacements. That is especially important on a collector car that may have changed wheels, tires, or suspension over time.

The 1966 AC Grayhound uses 15-inch rims with its primary tire fitments. Both 640-15 and 670-15 are built around a 15-inch rim diameter, so rim diameter stays consistent even though the car can use more than one tire size.

Rim diameter is only part of the fitment picture. Before choosing a tire, it is smart to verify the actual wheel width on the car as well, because different products within these sizes call for different rim-width ranges. That check becomes even more important if the Grayhound has replacement wheels or a radial-equivalent conversion under consideration.

The 1966 AC Grayhound is associated with both 640-15 and 670-15, which means there is more than one primary fitment within the covered model range. Both sizes are bias-ply and both use 15-inch rims, but they represent different nominal widths within the same vintage sizing system.

That makes wheel and vehicle inspection more important than assuming one size belongs on every car. A Grayhound that has kept one setup for decades may differ from another that has seen wheel changes during restoration or road use. Confirming the current wheel width and existing tire size helps narrow the correct choice before comparing brands or sidewall styles.

On the 1966 AC Grayhound, 640-15 is a primary bias-ply tire size. It uses the older numeric sizing format rather than a modern radial format, which makes it a traditional fitment choice for buyers who want the car to retain its vintage tire construction and visual character.

Radial alternatives do exist for this size, but they should be treated as equivalent options rather than automatic substitutions. Keeping a 640-15 bias-ply tire preserves the original-style construction approach, while changing to a radial calls for attention to wheel width, tire dimensions, and clearance. That choice often comes down to how the car is used and how closely the owner wants to maintain a period-style presentation.

Radial equivalents for 670-15 include 195R15 as an 80-series metric radial, P205/75R15 as a 75-series P-metric radial, P215/70R15 as a 70-series P-metric radial, and 670R15 as a bias-look radial. Those options give the 1966 AC Grayhound owner several modern-format comparisons for the larger primary tire size.

Each equivalent uses the same 15-inch rim diameter, but they are not all the same type of radial. The metric and P-metric choices differ in sizing convention and profile family, while the 670R15 bias-look radial is aimed at a more traditional visual impression. Checking wheel width, actual tire dimensions, and body or steering clearance is the right next step before making the switch.

A radial conversion on a 1966 AC Grayhound starts with matching the original tire size to the correct radial-equivalent family, then confirming the wheel setup. The car's primary fitments are 640-15 and 670-15 bias-ply sizes, with radial equivalents available in metric, P-metric, and in one case a bias-look radial format.

Wheel width is an important checkpoint, especially because the recommended equivalent rim-width ranges are 5-6 inches for 640-15 and 5-7 inches for 670-15. It is also wise to compare clearance at the fenders and steering components, inspect suspension condition, and verify that the car has not been altered with different wheels or ride height changes before settling on a radial alternative.

Choosing a 640-15 tire for a 1966 AC Grayhound starts with staying in the correct primary size and deciding what kind of presentation suits the car. In this size, available choices include blackwall, narrow whitewall, and wide whitewall designs from brands such as BFGoodrich, Firestone, Avon, and Excelsior.

Once the appearance is narrowed down, compare the tire series and wheel-width compatibility of the specific products you are considering. Some 640-15 options call for slightly different rim widths, and the sidewall treatment changes the character of the car visually. That makes this less about finding any 640-15 tire and more about selecting the one that matches the Grayhound's wheel setup and restoration direction.

1966 AC Grayhound tires are available with blackwall, narrow whitewall, and wide whitewall sidewall styles. Those choices appear across both primary sizes, although the larger 670-15 size offers the broadest spread of whitewall treatments and product variety.

Sidewall style has a strong effect on how the car sits visually even when the tire size stays the same. A blackwall usually gives a more understated look, while narrow and wide whitewalls create progressively stronger period-style emphasis. Once the correct size is confirmed, the sidewall decision becomes one of the most noticeable ways to tailor the Grayhound's finished appearance.

Tires for the 1966 AC Grayhound are available from BFGoodrich, Firestone, Avon, Excelsior, US Royal, Universal Vintage Tire, Coker Classic, Goodyear, and STA. Brand availability varies by size, with 670-15 carrying the broader assortment and 640-15 focusing on a smaller but still useful mix of classic offerings.

The brand name is only one part of the decision. It helps to compare each brand's available tire series, sidewall treatments, and wheel-width specifications within the size you need. On a car like the Grayhound, that approach usually leads to a better match than choosing by brand alone, especially when the intended result may be touring use, a traditional blackwall look, or a more formal whitewall presentation.

For a period-style 1966 AC Grayhound, the starting point is one of the two primary bias-ply sizes: 640-15 or 670-15. Staying with the original-style numeric bias-ply format keeps the car aligned with the tire construction and visual language of its era, while still leaving room to choose among several classic series and sidewall presentations.

The final choice depends on the setup already on the car and the look you want the finished Grayhound to carry. A blackwall gives a restrained presentation, while narrow or wide whitewalls add more visual emphasis. When exact originality matters, it is wise to compare your car against period photos, marque-club guidance, or restoration records before selecting a specific sidewall treatment.

Tire construction affects a restored 1966 AC Grayhound both visually and contextually. A bias-ply tire in 640-15 or 670-15 keeps the car in a traditional vintage format, which tends to suit the look of a mid-1960s British grand touring car more naturally than a modern radial sidewall profile.

That does not mean a radial equivalent cannot be used, only that the appearance changes along with the construction. A standard metric or P-metric radial usually reads more modern, while the 670R15 bias-look radial offers a way to stay closer to a classic presentation. The right answer depends on whether the restoration priority leans more toward period-style appearance or modernized road use.

Yes, modifications can affect tire fitment on a 1966 AC Grayhound even when the car uses one of its primary sizes. Changes such as aftermarket wheels, altered wheel width, suspension revisions, ride-height changes, or bodywork adjustments can all influence whether a given 640-15, 670-15, or radial-equivalent setup clears properly.

That matters because the Grayhound already has two primary tire sizes within the same 15-inch rim family. Any modified car should be checked for actual wheel dimensions, steering clearance, and fender space rather than assuming a stock-style tire choice will behave the same way. Collector cars often accumulate changes over time, so a quick physical verification is worthwhile before replacement.

Before driving a 1966 AC Grayhound on new tires, inspect the wheels, valve stems, and overall mounting setup, then make sure the tires are inflated appropriately for the application. It also helps to confirm that the chosen size matches the car's actual wheel arrangement and that no rubbing appears at full steering lock or under normal suspension movement.

A broader road-use check is just as important on a collector-era car. Look over suspension and steering components, recheck lug hardware after installation, and watch for any unusual vibration or air loss during the first miles. Even a correctly sized tire deserves a cautious first outing when the car may have spent long periods stored or only lightly driven.

Collector-car tires on a 1966 AC Grayhound should be inspected regularly for air loss, sidewall cracking, cuts, bulges, uneven wear, and signs of age even if the tread still looks good. That advice applies to both 640-15 and 670-15 because low annual mileage often hides condition issues that matter more than tread depth on an older specialty car.

Storage conditions also play a big role in tire life. Keeping the Grayhound away from prolonged sunlight, heat, moisture, and ozone sources helps protect the rubber during periods of inactivity. A car that sits for long stretches benefits from more frequent visual checks and pressure checks, especially before any longer drive where sustained speed and heat can expose neglected tire problems.