1940 De Soto Tire Fitment Guide

1940 De Soto vehicles in the 6 Deluxe & Custom line use two listed tire sizes: 600-16 and 650-16. Both are bias-ply sizes and both mount on 16-inch rims. The 600-16 products shown use rim widths in the 4.00 to 4.50 inch range, while 650-16 products use rim widths in the 4.50 to 5.00 inch range.

That means a 1940 De Soto owner should verify more than just the year and make before choosing a tire. Start by checking the actual wheel width on the car, then compare it to the size you intend to run. Because both sizes appear within the same model line, the wheel itself is often the deciding factor, along with whether you want the slightly narrower or wider prewar look.

On a 1940 De Soto, 600-16 is a numeric bias-ply tire size. The first number is the nominal section width designation used in period sizing, and the 16 identifies the wheel diameter in inches. It is not a modern metric size, so it should be read as a traditional prewar American tire code rather than compared directly to a P-metric radial size.

That older sizing format matters when you are restoring or maintaining a 1940 De Soto because the visual profile, sidewall height, and overall period character are tied to the original bias-ply convention. If your car is set up for 600-16, look for products built specifically in that format instead of trying to translate it loosely into a modern radial equivalent without first confirming wheel and clearance requirements.

On a 1940 De Soto, 650-16 is another numeric bias-ply size, using the same period code structure as 600-16. The 650 identifies the nominal width class, and the 16 identifies the rim diameter in inches. Within the listed offerings, this size is paired with 16-inch wheels and rim widths from 4.50 to 5.00 inches.

For a buyer, the important point is that 650-16 is not just a cosmetic variant of 600-16. It calls for a different wheel-width range, so the correct match depends on the wheel fitted to the car. If your 1940 De Soto has original-style wheels and you are unsure which width they are, measuring the wheel before selecting a tire is the safest way to avoid choosing the wrong size.

A 1940 De Soto can use either 600-16 or 650-16 within the listed 6 Deluxe & Custom line, but the right choice depends on wheel width and the configuration of the individual car. Both are bias-ply tires on 16-inch rims, so this is not a bias-versus-radial decision. The practical difference is that 600-16 fits the narrower listed rim-width range, while 650-16 fits the wider listed range.

If your goal is an accurate restoration, match the size to the wheel and the way the car was originally equipped. If your goal is to preserve the car’s intended prewar appearance, staying within one of these two correct numeric bias-ply sizes keeps the visual character in period. Measuring the wheel before deciding between 600-16 and 650-16 is more useful here than comparing brand names alone.

1940 De Soto tires are available in both blackwall and wide whitewall styles. In 650-16, blackwall and wide whitewall options appear from several brands, including BFGoodrich, Coker Classic, Firestone, and Garfield. In 600-16, both blackwall and wide whitewall choices are also available, with brands including BFGoodrich, Coker Classic, Avon, and Firestone.

That gives a restorer some room to match the character of the car. Blackwalls usually suit a more restrained, utilitarian prewar presentation, while wide whitewalls better fit the dressed-up look many buyers associate with upper-trim American cars of the era. For a judged restoration, sidewall style can matter almost as much as size and construction, so it is worth comparing the look you want before settling on a tire.

Several brands offer tires for 1940 De Soto vehicles. The 650-16 size includes BFGoodrich, Coker Classic, Firestone, and Garfield, while the 600-16 size includes BFGoodrich, Coker Classic, Avon, and Firestone. All of the listed options are bias-ply products, which suits the period character of a prewar De Soto.

Brand choice on a 1940 De Soto often comes down to details such as sidewall style, the visual identity you want on the car, and whether the exact size you need is offered by the brand you prefer. A buyer comparing brands should first narrow the search to the correct size, then decide whether a blackwall or wide whitewall better matches the car’s restoration style and intended presentation.

Rim width requirements differ between the two listed 1940 De Soto tire sizes. The 600-16 size is paired with 4.00 to 4.50 inch rims, while the 650-16 size is paired with 4.50 to 5.00 inch rims. Both sizes use a 16-inch rim diameter, but they do not share the same wheel-width range.

That overlap at 4.50 inches is useful, but it should not be treated as permission to assume every 16-inch De Soto wheel can use either size. Measure the wheel and confirm the intended size before mounting tires. On a prewar car, getting the rim width right helps preserve proper bead seating, intended proportions, and the overall look of the car on its wheels.

Original-style 1940 De Soto wheels can potentially work with both listed tire sizes because both 600-16 and 650-16 use a 16-inch rim diameter. The catch is wheel width. The 600-16 size is associated with 4.00 to 4.50 inch rims, while 650-16 is associated with 4.50 to 5.00 inch rims.

A 4.50-inch wheel sits at the overlap between the two ranges, but a narrower or wider wheel pushes the decision toward one size or the other. That is why wheel diameter alone is not enough when preparing a 1940 De Soto for new tires. Before fitting either size, confirm the wheel width on the car so the tire matches the wheel rather than relying on appearance or assumption.

A 1940 De Soto should be stored away from direct sunlight, damp concrete, electric motors, welders, battery chargers, and other ozone-producing equipment that can accelerate rubber aging. Keep the tires properly inflated during storage, and if the car will sit for long periods, move it periodically or support it to reduce long-term flat spotting. Bias-ply tires are especially prone to developing temporary flat spots when they remain in one position for extended periods.

Good storage habits protect both appearance and ride quality on a prewar car. Wide whitewalls also benefit from a clean, dry environment that helps prevent staining and discoloration. If your 1940 De Soto is a seasonal driver, a little attention during off-season storage can preserve the tire’s shape and keep the car more pleasant to drive when it goes back on the road.

Tires on a 1940 De Soto should be judged more by age and condition than by miles traveled. On collector vehicles, many owners begin evaluating tires closely once they reach the five- to seven-year range and give serious replacement consideration by around ten years, even if the tread still looks usable. The DOT date code on the tire is the starting point for knowing its age.

That approach is especially important on a low-use prewar car, where long periods of sitting can age the rubber faster than mileage would suggest. A 1940 De Soto that only sees occasional drives may still need replacement tires long before the tread appears worn out. Regular age checks help prevent the common mistake of trusting old-looking rubber simply because it has not covered many miles.

Tires on a 1940 De Soto should be inspected before every drive, and they deserve an extra close look before tours, shows, or longer road trips. Check for sidewall cracking, weathering, cuts, bulges, uneven tread wear, and pressure loss. On an older collector car, it is also wise to inspect valve stems and the spare at the same time.

Frequent inspection matters because a lightly used car can hide tire aging that does not show up in normal wear patterns. A quick pre-drive walkaround can catch small issues before they become trip-ending problems. For a 1940 De Soto, tire condition should be treated as part of the broader routine of checking fluids, brakes, and other age-sensitive components before the car heads onto modern roads.

A 1940 De Soto 6 Deluxe & Custom would have been fitted in period with bias-ply tires rather than modern radials. The listed sizes for the model line are 600-16 and 650-16, both traditional numeric bias-ply sizes on 16-inch rims. That matches what buyers expect from an American prewar passenger car of this era.

For an accurate restoration, matching the correct size, construction type, and sidewall appearance matters more than chasing a modern substitute. Whitewall width and overall presentation can vary depending on how the car is being restored, so event-specific or trim-specific authenticity questions are best checked against factory literature or a De Soto marque specialist. Staying with the correct bias-ply format preserves the car’s proper period character.

Correct tire fitment matters on a 1940 De Soto because judges and knowledgeable enthusiasts often notice tire size, construction, and sidewall style immediately. A prewar De Soto shown for authenticity is generally expected to wear period-appropriate numeric bias-ply tires rather than a visibly modern replacement. Sidewall treatment also affects how accurate the finished car looks.

That does not mean every event uses the same standard, but the closer the tire is to the proper size and era-correct appearance, the fewer questions it tends to raise. A wide whitewall can be appropriate on a more formal presentation, while a blackwall can better suit a plainer look. Before entering a judged event, compare your tire choice to the standards used by that club or organization.

For a 1940 De Soto, the basic fitment difference between blackwall and wide whitewall tires is visual rather than structural when comparing products within the same size. Both 600-16 and 650-16 are available in blackwall and wide whitewall versions from multiple brands. The underlying construction remains bias-ply in the listed offerings.

That makes sidewall style an authenticity and presentation decision. Wide whitewalls give a 1940 De Soto a more upscale prewar appearance and are often chosen for cars restored to a formal showroom look. Blackwalls feel more restrained and can better suit a driver-focused or less ornate presentation. When originality matters, choose the sidewall style that best aligns with the way your specific car would have been equipped and presented.

1940 De Soto tires can be suitable for highway use when they are the correct size, in sound condition, properly inflated, and used within their design limits. The listed offerings are bias-ply tires, and at least one 600-16 product carries an H speed rating, which corresponds to a 130 mph ceiling. Even so, the driving character of a prewar De Soto is shaped as much by its suspension, steering, and brakes as by the tire itself.

On a car of this age, safe highway driving depends on the entire vehicle being prepared for the trip, not just the tread depth on the tires. Bias-ply tires will also feel different from modern radials in tracking and road response, which is normal for the construction. A well-sorted 1940 De Soto should be driven with respect for its age, setup, and intended road manners.

Inflation pressure on a 1940 De Soto should be matched to the specific tire size and the manufacturer’s guidance for that tire. Among the listed products, 600-16 examples show load figures such as 1400 pounds at 32 psi, while 650-16 examples show 1580 pounds at 32 psi. Those numbers are part of the tire’s rated capacity information and should not be transferred casually from one size to the other.

The best practice is to consult the vehicle’s original literature for baseline factory pressure recommendations, then compare that with the reproduction tire maker’s guidance for the exact tire you are using. A prewar De Soto can feel markedly different with only modest pressure changes, so avoid guessing. Correct pressure affects ride quality, steering feel, tread wear, and the way the car sits on its bias-ply tires.

Before taking a 1940 De Soto on a longer drive, inspect every tire for sidewall cracking, cuts, bulges, irregular wear, and proper inflation, and do not forget the spare. Look closely at the valve stems and confirm the tires are seated properly on the wheels. A quick road-use check should also include the rest of the car’s age-sensitive systems, especially brakes, steering, cooling, and fluids.

That broader approach matters because a 1940 De Soto is a prewar automobile, and trip reliability depends on the full condition of the car rather than any single component. Tires are one of the easiest places to begin because visible deterioration often appears there first. If the car has been sitting, give it a short local test drive before committing to a longer run so any vibration, flat spotting, or pressure issue shows up early.