The 1927 Moon A comes from an era when independent automakers still carved out space with distinctive engineering and upscale ambitions, and tire selection remains a very vehicle-specific part of keeping one on the road today. For a late-1920s car like this, the difference between an antique-style sizing convention and a later numeric bias-ply format matters as much as the tread itself. The 1927 Moon A uses bias-ply fitments in 30X5.25 and 5.25-20, so the first step is confirming which wheel and tire setup the car actually carries. From there, the choice centers on preserving a proper period presentation and matching the tire to the wheel diameter already on the car.
Which Tire Size Is Right for The 1927 Moon A
The 1927 Moon A uses two primary tire sizes, and they do not share the same rim diameter. That makes wheel confirmation the first step before choosing any tire, because 30X5.25 and 5.25-20 represent different fitment paths even though both are bias-ply sizes. Once the wheel setup is confirmed, the real decision is selecting the tire that matches the car's existing configuration and restoration goals.
In the 30X5.25 size, the first number refers to the tire's approximate overall diameter and the second refers to its nominal section width. This is an early antique-style bias-ply format that looks quite different from later numeric sizing and belongs to the prewar character of a car like the 1927 Moon A. Its practical significance is less about modern tire-code interpretation and more about matching the correct wheel diameter and preserving the car's proper visual stance. This size should be evaluated carefully against the actual wheel setup already fitted to the vehicle.
The 5.25-20 size is a vintage numeric bias-ply designation in which 5.25 represents the nominal section width in inches and 20 identifies the rim diameter. On a 1927 Moon A, this format reflects a more familiar early automotive tire code while still retaining the traditional bias-ply construction expected for the period. The main buying decision here is not modernizing the format, but making sure the tire matches the wheel diameter and the car's existing fitment. It is a useful choice for owners aiming to keep the car visually consistent with its late-1920s tire profile.
The covered Moon A sub-model uses the same two bias-ply tire sizes, so fitment is straightforward at the sub-model level but still depends on the wheel setup on the individual car. Checking the exact wheel diameter matters more here than distinguishing between trims.
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1927 Moon A 6 Cyl.
The 1927 Moon A 6 Cyl. uses the same pair of bias-ply fitment paths, 30X5.25 and 5.25-20. Tire selection comes down to confirming which wheel diameter is on the car now and then choosing a period-style tire that matches that established setup.
The tire sizes listed on this page assume factory-standard vehicle configuration. The following modifications may affect tire fitment and are not reflected in this guide:
Suspension changes (lowering, lift kits, spring replacements)
Body alterations (fender modifications, custom bodywork)
If your vehicle has been modified from factory specifications, verify tire clearance before purchase.
Frequently Asked Questions
These 1927 Moon A tire FAQs focus on the two primary bias-ply sizes, the wheel-diameter differences between them, and the practical checks that matter before putting a prewar car back on the road.
Tire Size & Fitment
What tire size fits a 1927 Moon A?
The 1927 Moon A uses two primary bias-ply tire sizes: 30X5.25 and 5.25-20. Both sizes apply to the Moon A 6 Cyl., but they are not interchangeable by name alone because they correspond to different fitment formats and different wheel diameters.
The important next step is checking the actual wheels on the car before choosing a tire. A restored or long-stored Moon A may not still carry its original wheel setup, and early cars are often changed over time. Confirm the rim diameter stamped or measured on the wheel, then match the tire size to that wheel rather than selecting by appearance alone.
What size rim does a 1927 Moon A use?
A 1927 Moon A can use either a 5.0-inch rim with the 30X5.25 size or a 20-inch rim with the 5.25-20 size. That wide difference is why wheel confirmation comes before any tire purchase for this car.
On prewar vehicles, size notation can be confusing because antique tire formats do not read like modern radial sizes. Measure the wheel or verify the marking on the rim itself instead of assuming a tire currently mounted on the car is correct. Once the wheel diameter is confirmed, the proper bias-ply size becomes much easier to narrow down.
What does 30X5.25 mean on a 1927 Moon A?
On a 1927 Moon A, 30X5.25 is an antique diameter-by-section tire size. The 30 refers to the tire's approximate overall diameter, while 5.25 refers to its nominal section width, making it a very different format from later numeric bias-ply sizing.
That matters because a size like 30X5.25 should be matched to the wheel and overall vehicle setup with care, not treated like a modern shorthand tire code. Owners sorting through an older restoration should confirm that the car is actually using the antique-style wheel and tire arrangement before replacing one tire with another in the same broad width range.
Choosing the Right Tire
What should I consider when choosing a 30X5.25 or 5.25-20 tire for a 1927 Moon A?
Start with the correct primary size for the wheel already on the car, since 30X5.25 and 5.25-20 are both valid Moon A fitments but use different size conventions and different rim diameters. Both are bias-ply choices suited to the vehicle's period character.
After size confirmation, focus on how the car will be used and presented. A restoration-minded owner may prioritize a traditional profile and period-style appearance, while a touring owner may be more focused on consistent condition across a full set. It also helps to inspect all wheels for matching dimensions so a mixed setup does not create confusion during replacement.
How do I choose between the available 1927 Moon A tire sizes?
Choosing between the two Moon A tire sizes is really a matter of identifying the wheel diameter and tire system already on the car. The 30X5.25 size belongs to an antique diameter-based format, while 5.25-20 uses a vintage numeric bias-ply format tied to a 20-inch rim.
That means the right choice usually comes from the car's existing wheel configuration rather than personal preference alone. On an older restoration, one axle or spare may not match the others, so it is worth checking every wheel before ordering a full set. Consistency across the vehicle is especially important on cars from this era.
What rim-fitment details matter when choosing tires for a 1927 Moon A?
The key rim-fitment detail on a 1927 Moon A is diameter, because the two valid tire sizes use very different wheels. A 30X5.25 tire corresponds to a 5.0-inch rim, while a 5.25-20 tire corresponds to a 20-inch rim.
Beyond diameter, condition matters just as much on a vehicle of this age. Check for damage, corrosion, distortion, and any signs that wheels have been changed during earlier restoration work. A tire that matches the size marking still needs a sound wheel under it, especially on a collector car that may have spent long periods in storage or limited road use.
Restoration & Appearance
Which tire should I choose for a period-style 1927 Moon A?
For a period-style 1927 Moon A, the best starting point is the bias-ply size that matches the wheel setup already on the car: either 30X5.25 or 5.25-20. Both sizes suit the vehicle's late-1920s character far better than trying to force a modern sizing logic onto a prewar fitment.
Appearance and authenticity on a restoration often depend on preserving the right proportions as much as the right tread style. Owners pursuing a highly accurate restoration should also compare the car against marque references, period photos, or other vehicle-specific historical sources. That extra step helps confirm the setup before replacing a full set of older tires.
Does correct tire fitment matter for a 1927 Moon A restoration?
Correct tire fitment matters a great deal on a 1927 Moon A restoration because the tire contributes heavily to the car's stance, wheel appearance, and overall period presentation. Using the wrong format or wheel diameter can make a carefully restored prewar car look visibly out of place.
Fitment also affects practical use, especially on an older chassis where wheel and tire dimensions influence clearance and drivability. A restoration should not rely on whatever tires happen to be mounted when the car is acquired. Verifying the correct size family first helps keep both the visual result and the mechanical setup aligned with the car's intended character.
Fitment, Maintenance & Road Use
Can modifications affect tire fitment on a 1927 Moon A?
Yes, modifications can affect tire fitment on a 1927 Moon A, especially because this car already has two valid bias-ply size paths with very different wheel diameters. Wheel swaps, brake changes, suspension work, or earlier restoration alterations can all change what size should be mounted.
A prewar car should be checked as it exists today rather than assumed to match a historical baseline. Look at all four wheels and the spare, confirm the rim diameter, and inspect for clearance around fenders, steering components, and suspension parts. Even a correct vintage tire size still needs to suit the actual configuration currently on the vehicle.
What should I inspect before driving a 1927 Moon A on new tires?
Before driving a 1927 Moon A on new tires, inspect the wheels for structural condition, make sure all tires match the intended size and mounting direction, and verify that inflation is set appropriately for the tire being used. It is also wise to check valve hardware, wheel fasteners, and basic brake function.
Collector cars often spend long periods parked, so the rest of the chassis deserves attention too. Look over steering play, suspension wear, and any signs of rubbing once the car is back on the ground. A short, careful test drive can reveal vibration, pull, or clearance problems before the car is taken on a longer outing.
How should tires on a collector 1927 Moon A be maintained?
Tires on a collector 1927 Moon A should be maintained with regular pressure checks, routine visual inspection, and careful storage habits. Even when tread looks good, an infrequently driven prewar car can develop age-related issues such as sidewall cracking, flat spotting, or slow air loss.
Good maintenance also means keeping the car away from prolonged sunlight, excess heat, moisture, and ozone sources when stored. Periodic movement helps reduce set-in flat spots, and every drive should begin with a quick walkaround for cuts, bulges, or unusual wear. On a vehicle of this age, condition matters just as much as nominal tire size.
