1968 Amphicar Tire Fitment Guide

The 1968 Amphicar uses two tire sizes: 640-13 and 650-13. Both are bias-ply tires for 13-inch rims, and both apply to the Amphicar model. The 640-13 fits a 4.00 to 4.50 inch rim width range, while the 650-13 fits a 4.50 to 5.00 inch rim width range, so the wheel itself helps determine which size belongs on your car.

That means a 1968 Amphicar owner should start by measuring or confirming the wheel width before focusing on sidewall appearance or brand. If your car already has one of these sizes mounted and the wheel width matches the tire's intended range, that is usually the most practical starting point for a correct replacement.

On a 1968 Amphicar, 640-13 is a traditional numeric bias-ply size. The 640 designation refers to the tire's nominal section width in the older bias-ply sizing system, and the 13 identifies the rim diameter in inches. In current Amphicar applications, this size appears as a 13-inch bias-ply fitment with a recommended rim width range of 4.00 to 4.50 inches.

For an owner, the important takeaway is that 640-13 is the narrower of the two Amphicar sizes. It is a sensible choice when the car has the narrower wheel and when you want a period-style bias-ply look without stepping up to the wider 650-13 fitment.

The 1968 Amphicar range centers on a single Amphicar model, but that model is associated with two sizes rather than one. Both 640-13 and 650-13 are used on 13-inch rims, yet they are not interchangeable without considering wheel width because each size has its own recommended rim-width range.

In practical terms, a 1968 Amphicar owner cannot assume that any 13-inch bias-ply tire will do. The right approach is to confirm the size already fitted, compare it to the actual wheel width, and then choose the matching size before narrowing the choice by brand or whitewall style.

Both sizes are authentic-looking bias-ply choices for a 1968 Amphicar, so the decision comes down primarily to wheel width and the stance you want to preserve. The 640-13 is intended for 4.00 to 4.50 inch rims, while the 650-13 is intended for 4.50 to 5.00 inch rims. The 650-13 also carries a higher load figure at the same 32 psi rating and offers more sidewall-style variety.

If your Amphicar has narrower wheels, the 640-13 is the more appropriate path. If the car has the wider 13-inch wheel and you want more flexibility in whitewall appearance, the 650-13 opens up more choices. Matching the tire to the wheel should come first, and visual preference should come second.

The 1968 Amphicar has whitewall options in both available sizes, but the selection differs by size. The 640-13 is offered as a wide whitewall, while the 650-13 is available in both wide whitewall and narrow whitewall versions. All of these choices remain bias-ply, so the visual difference is in sidewall treatment rather than a change in tire construction.

That gives Amphicar owners room to tailor the car's appearance without moving away from an era-appropriate tire type. A wide whitewall generally leans more toward a period show-car look, while a narrow whitewall can give the car a slightly cleaner and subtler presentation. Owners restoring to a particular event standard should compare their choice with period photos and marque advice.

Three brands cover 1968 Amphicar tire sizes: BFGoodrich, Coker Classic, and US Royal. BFGoodrich appears in 640-13, while Coker Classic and US Royal both offer 650-13. All of those offerings are bias-ply tires on 13-inch rims, with the 650-13 size carrying both narrow and wide whitewall options depending on the product selected.

Brand choice on a 1968 Amphicar often comes down to which size you need first, then which sidewall look best matches the car's restoration style. Once the correct size is established, the remaining decision is usually about sidewall appearance and brand preference rather than changing the car's basic fitment direction.

The two tire sizes used on the 1968 Amphicar do not share the same recommended rim width range. The 640-13 is intended for 4.00 to 4.50 inch rims, and the 650-13 is intended for 4.50 to 5.00 inch rims. Both fit 13-inch diameter wheels, but the width requirement is what separates them during setup.

That makes wheel measurement one of the most important checks before ordering replacement tires for a 1968 Amphicar. If the wheel falls right at 4.50 inches, either size may be compatible in diameter, but the final choice should still reflect the fitment already established on the car and the look you want to maintain.

Original-style 1968 Amphicar wheels can often accept either 640-13 or 650-13 because both sizes mount on 13-inch rims. The key difference is wheel width, since 640-13 suits 4.00 to 4.50 inch rims and 650-13 suits 4.50 to 5.00 inch rims. A shared rim diameter does not automatically mean every original wheel is equally correct for both sizes.

Owners should confirm the actual wheel width on the car before assuming a simple swap from one size to the other. That matters on an Amphicar because a tire that is correct in diameter but mismatched in width can alter fit, appearance, and how naturally the tire sits on the wheel.

A 1968 Amphicar should be stored away from direct sunlight, electric motors, generators, welders, and other ozone-producing equipment that can age rubber prematurely. Keep the car on a clean, dry surface, maintain proper inflation, and move it periodically so the same section of each bias-ply tire is not supporting the load for months at a time. Bias-ply tires are more prone to flat-spotting during long static storage than radials.

For seasonal or long-term storage, many collectors either roll the car occasionally or support it in a way that reduces sustained load on the tires. Because an Amphicar may spend long periods as a hobby vehicle, smart storage habits do more for tire life than low annual mileage alone.

Tire life on a 1968 Amphicar should be judged more by age and condition than by mileage. Collector-car tires are commonly evaluated closely once they reach about five to seven years of age, and replacement becomes a serious consideration as they approach ten years, even if tread wear appears minimal. The DOT date code on the tire helps establish the true age of the casing.

That rule matters especially on a lightly used Amphicar, where the car may see infrequent road miles but long periods of sitting. A tire can look acceptable at first glance and still be aging out internally, so date code, sidewall condition, and pressure retention should all be part of the replacement decision.

Tires on a 1968 Amphicar should be inspected before every drive and again before any longer outing. Look for sidewall cracking, cuts, bulges, uneven wear, embedded debris, and pressure loss, and do not forget to inspect the spare if the car carries one. On a collector vehicle, visual inspection is one of the simplest and most useful habits you can build.

A quick check before each outing is especially worthwhile on an Amphicar because hobby cars often sit for stretches and then return to service without much warning. Catching a problem in the garage is far better than discovering it during a club event, parade route, or longer drive away from home.

A 1968 Amphicar would have been fitted in bias-ply form during its period, and the two Amphicar sizes associated with the model today are 640-13 and 650-13. Both are 13-inch bias-ply fitments, which aligns with what buyers expect from a specialty vehicle of the late 1960s. Original-market details can still vary by country, production period, and surviving wheel setup.

For a restoration, the safest path is to begin with the wheel width on your own car and then choose the corresponding 640-13 or 650-13 bias-ply size. If you are preparing for marque judging or a highly exact restoration, period photos and Amphicar club resources are the right next step for confirming the most authentic presentation.

Correct tire fitment absolutely matters when showing a 1968 Amphicar, especially because the car is unusual enough that judges and knowledgeable enthusiasts tend to notice visual details. Size, construction type, and sidewall appearance all influence whether the car looks right for its era. On an Amphicar, moving away from a proper 13-inch bias-ply look can change the character of the car surprisingly quickly.

That does not mean every event judges to the same standard, but originality-minded venues will typically care about more than simple tire diameter. Choosing between 640-13 and 650-13 should follow the wheel on the car, and the whitewall width should suit the look you are trying to recreate. Event-specific standards are best confirmed through Amphicar and marque contacts.

On the 1968 Amphicar, the visual difference between wide whitewall and narrow whitewall tires is straightforward: the white band occupies more sidewall area on the wide version and a more restrained portion on the narrow version. The 640-13 is offered as a wide whitewall, while the 650-13 offers both wide and narrow whitewall choices. All remain bias-ply 13-inch tires, so the main difference is appearance rather than construction.

That makes sidewall width a styling decision once the correct size has been established. Wide whitewalls tend to emphasize the period character of a specialty 1960s vehicle, while narrow whitewalls can look slightly more understated. Owners pursuing a specific restoration theme should compare the tire's visual profile against period Amphicar photographs before settling on one look.

1968 Amphicar tires can be suitable for normal road use when they are the correct size, properly inflated, in good condition, and mounted on the right wheel width. The current Amphicar tire choices here are bias-ply rather than radial, so their road feel will be more period-correct in character, with the steering and tracking traits owners expect from vintage construction. Safe highway use depends at least as much on the condition of the vehicle's suspension, steering, and brakes as on the tire itself.

For an Amphicar, that means treating the tire as one part of the larger roadworthiness picture. Before regular highway use, confirm age, condition, pressure, and wheel match, then evaluate the rest of the car to the same standard. A well-sorted vintage vehicle on fresh tires is very different from one that has simply had new rubber installed.

The available 1968 Amphicar tire sizes carry load ratings at 32 psi, with 640-13 rated at 1,045 pounds at 32 psi and 650-13 rated at 1,150 pounds at 32 psi. Those figures describe the tire's rated load condition, not necessarily the exact running pressure your Amphicar should use in service. Factory inflation recommendations belong to the vehicle, while tire rating figures belong to the tire.

The best practice is to compare your owner's manual or factory literature with the tire manufacturer's guidance for the specific reproduction tire you choose. Do not assume that a pressure tied to one size or one tire's rated load should automatically be transferred to the other size just because both fit 13-inch wheels.

Before taking a 1968 Amphicar on a longer drive, inspect each tire for cracking, cuts, bulges, punctures, irregular wear, and proper inflation. Make sure the spare is usable, and check that the valve stems are in sound condition. On a collector vehicle of this age, a tire inspection should sit alongside checks of fluid levels, steering response, brakes, lights, and any age-sensitive rubber components elsewhere on the car.

That broader inspection matters because an Amphicar is not just an old car; it is a specialty collector vehicle with unique ownership expectations. Confirming the tires are healthy and correctly matched to the wheels helps prevent avoidable roadside trouble and gives you a much better baseline before heading farther from home.