1968 Amphicar Amphicar Tires

The 1968 Amphicar Amphicar uses two primary tire sizes: 640-13 and 650-13. Both are bias-ply sizes intended for 13-inch rims, and the Base sub-model is associated with both sizes rather than a single exclusive fitment.

That means the first step is checking the tires and wheels actually on the vehicle now. Since both sizes are valid for this model, the practical choice depends on confirming the mounted wheel width, keeping the tire size consistent across the vehicle, and deciding whether the goal is a period-style bias-ply presentation or a radial-equivalent alternative.

The 1968 Amphicar Amphicar uses a 13-inch rim diameter with both primary tire sizes, 640-13 and 650-13. Even though the tire sizes differ slightly, they share the same rim diameter, so the key distinction is not wheel diameter but the specific tire size and wheel width combination.

That shared 13-inch diameter simplifies selection, but it does not make every tire automatically interchangeable. Wheel width still matters, especially because the available products for 640-13 and 650-13 carry different rim-width ranges, so checking the wheel before selecting a replacement helps avoid mismatched fitment or an unintended change in appearance.

Both 640-13 and 650-13 are vintage numeric bias-ply tire sizes. In that format, the first number represents the nominal section width with the decimal omitted, so 640 is roughly 6.40 inches wide and 650 is roughly 6.50 inches wide, while 13 refers to the rim diameter in inches.

For an Amphicar owner, that old sizing system matters because it points to a traditional bias-ply fitment rather than a modern metric radial size. Understanding the code makes it easier to compare available whitewall options, choose the correct rim-width range, and evaluate radial equivalents without confusing an alternative size with the original primary fitment.

On the 1968 Amphicar Amphicar, both 640-13 and 650-13 are primary bias-ply tire sizes. Those are the original fitment formats represented in the available vehicle-size options, and the product choices in those primary sizes are traditional bias-ply tires rather than modern radials.

That distinction is important because a radial equivalent is an alternative format, not the same thing as the primary fitment itself. Anyone considering a change in construction should compare wheel width, tire dimensions, and clearance carefully, especially on a specialty collector vehicle where appearance, steering feel, and suspension condition can all influence the result.

Radial equivalents for both 640-13 and 650-13 include 175R13, P175/75R13, P185/70R13, and 650R13. That gives the 1968 Amphicar Amphicar an 80-series metric radial option, a 75-series P-metric radial, a 70-series P-metric radial, and a bias-look radial alternative.

Each of those sizes follows a different sizing convention, so the decision is not only radial versus bias-ply. The recommended rim-width range for the equivalents is 4-6 inches, and the smartest next step is comparing the vehicle’s actual wheel width and available clearance before treating any equivalent as a usable alternative.

A bias-look radial equivalent is available for the 1968 Amphicar Amphicar in size 650R13. That option gives owners a radial-format tire that is meant to retain a more traditional visual presentation than a modern-looking metric radial, while still being separate from the primary 640-13 and 650-13 bias-ply fitments.

This can be appealing when the goal is to preserve a vintage appearance without staying with a pure bias-ply construction. The wheel still needs to fall within the recommended 4-6 inch rim-width range, and overall tire dimensions and body clearance should be checked before making the switch on a low-production specialty vehicle.

Start by confirming whether the vehicle currently uses 640-13 or 650-13, because both are valid primary sizes for the 1968 Amphicar Amphicar. From there, the key considerations are maintaining bias-ply construction, matching the tire to the wheel’s width, and deciding how much importance to place on whitewall style and period-style presentation.

The available products also differ by tire series, brand, load figure, and rim-width specification, so selection should go beyond size alone. A collector-focused owner may lean toward visual authenticity, while another may be comparing the broader choice in 650-13 against the simpler BFGoodrich option in 640-13.

The available sidewall styles for the 1968 Amphicar Amphicar are wide whitewall and narrow whitewall. The 640-13 offering is a wide whitewall, while 650-13 gives a broader mix with both wide whitewall and narrow whitewall options across Coker Classic and US Royal tire lines.

That makes sidewall style one of the biggest appearance decisions on this vehicle. A wider whitewall creates a more formal, traditional presentation, while a narrower whitewall gives a slightly more restrained look, so the choice should reflect the way the Amphicar is being restored, displayed, or driven rather than being treated as a one-style-only fitment.

Tires for the 1968 Amphicar Amphicar are available from BFGoodrich, Coker Classic, and US Royal. BFGoodrich appears in 640-13, while Coker Classic and US Royal offer multiple 650-13 choices in different whitewall treatments and classic bias-ply series.

Brand choice should be considered alongside the actual size being used on the vehicle, since the strongest variety appears in 650-13 rather than across both sizes equally. It also helps to compare the tire series and sidewall style with the wheel width on the car, because those factors shape the final fit and appearance more than the brand name alone.

A period-style 1968 Amphicar Amphicar usually starts with one of its primary bias-ply sizes, 640-13 or 650-13, rather than jumping immediately to a modern radial format. The right choice depends on which size is on the vehicle now, along with whether a wide whitewall or narrow whitewall better matches the look being pursued.

Because this is a collector vehicle with a very distinctive visual identity, tire appearance has an outsized effect on the finished presentation. Owners seeking exact originality should compare their selection against marque-specific historical references, while others may simply choose the bias-ply size and sidewall treatment that best preserve a convincing vintage profile.

Tire construction changes the visual character of a restored 1968 Amphicar Amphicar more than many owners expect. A primary bias-ply tire keeps the vintage sizing style and traditional look associated with the vehicle’s era, while a radial equivalent can shift the presentation even when the rim diameter remains the same.

That does not make one construction universally right or wrong, but it does make the decision important for restoration planning. Owners focused on a road-ready vintage appearance may compare a bias-look radial with the original-style bias-ply sizes, while appearance-first restorations often begin by preserving the original construction type and sidewall style.

Yes, modifications can affect tire fitment on a 1968 Amphicar Amphicar even when the tire size itself appears correct. Changes such as aftermarket wheels, altered wheel width, suspension work, ride-height changes, or body repairs can influence how a 640-13, 650-13, or radial-equivalent tire sits within the vehicle.

That is why a modified vehicle should be measured rather than assumed to match stock wheel and clearance conditions. Checking wheel width, steering clearance, and fender space before mounting replacement tires is especially worthwhile on an uncommon collector vehicle where small setup differences can matter more than the size code alone suggests.

Before driving a 1968 Amphicar Amphicar on new tires, inspect the wheels for correct diameter and width, verify that all tires are the intended size, and make sure there is adequate clearance at the fenders and steering components. It also helps to confirm inflation pressure, valve condition, and general suspension soundness.

On a collector vehicle, the pre-drive check should continue after installation with a careful look for rubbing, uneven stance, or air loss once the tires have been run. A short initial drive followed by another visual inspection can reveal issues early, which is especially useful when changing size within the original fitment range or moving to a radial equivalent.

Collector-car tires such as 640-13 and 650-13 on a 1968 Amphicar Amphicar should be maintained with regular pressure checks, routine visual inspection, and careful storage practices. Sidewall cracking, bulges, cuts, tread condition, and unexplained air loss deserve attention even if the vehicle is driven only occasionally.

Low-use vehicles often age their tires before they wear them out, so maintenance is as much about condition as mileage. Keeping the Amphicar away from prolonged sunlight, excess heat, moisture, and ozone sources helps preserve the tires, and a periodic inspection of the wheels and suspension supports safer road use when the car does go back into service.