1978 BMW 733i Tires

The 1978 BMW 733i uses two primary radial tire sizes: 205/70R14 and 220/55R390. The 205/70R14 size fits cars equipped with conventional 14-inch wheels, while 220/55R390 fits cars using the Michelin TRX millimetric wheel system. Both sizes are associated with the 733i Base, so the actual wheel setup on the car determines which tire belongs on it.

The practical difference is that these are not two interchangeable tires on the same wheel. A 14-inch tire belongs on a 14-inch rim, while a 390mm tire belongs on a 390mm rim. Before choosing a replacement, check the wheel markings, measure the rim correctly, and confirm whether the car still has its original wheel type or has been converted at some point in its life.

A 1978 BMW 733i may use either a 14-inch rim with 205/70R14 tires or a 390mm millimetric rim with 220/55R390 tires. The conventional fitment uses inch-based wheels, while the TRX fitment uses a dedicated millimetric wheel and tire combination. That distinction matters because the tire and wheel must match exactly.

Rim size should be verified on the actual wheel rather than assumed from the model alone. Many collector cars have seen wheel changes over the years, and the BMW 733i is no exception. Confirming the wheel diameter and the wheel system first prevents ordering the right tire size in the wrong measuring standard, which is the most common fitment mistake on cars that may retain TRX wheels.

220/55R390 is a metric radial size used with the Michelin TRX system. The 220 refers to nominal section width in millimeters, 55 is the aspect ratio, and 390 is the rim diameter in millimeters rather than inches. On a 1978 BMW 733i, that size points to a specialized wheel-and-tire arrangement different from the more familiar 205/70R14 setup.

The key takeaway is that a 390mm tire does not mount on a 14-inch wheel, even though the dimensions may seem close to a modern buyer. Owners evaluating an older 733i should inspect the wheel carefully, confirm the millimetric designation, and avoid mixing inch-based and TRX components. Once the wheel system is verified, replacement selection becomes much more straightforward.

Start with the wheel system on the car, because that determines whether the 1978 BMW 733i needs 205/70R14 or 220/55R390. After size is confirmed, compare tire construction, rim-width compatibility, sidewall style, tire series, and any load information shown for the available products. The 205/70R14 fitment offers the broadest variety, while 220/55R390 stays within the specialized TRX format.

Appearance and intended use usually drive the final decision. A blackwall Michelin XWX or TRX-B keeps a more European touring presentation, while narrow whitewall, redline, dual-redline, or raised white letter options create a different period-style look. It also helps to think about how the car will be used, whether for preservation, weekend driving, or a more personalized presentation on conventional 14-inch wheels.

Sidewall choices for the 1978 BMW 733i include blackwall, narrow whitewall, redline, dual-redline, and raised white letter styling, depending on the tire size selected. Most of that variety appears in 205/70R14, while the 220/55R390 Michelin TRX-B is offered as a blackwall. Those options give the car a noticeably different visual character even when overall fitment remains within the correct size.

Choosing a sidewall style is largely an appearance decision once size and wheel type are settled. A blackwall often suits a restrained European sedan look, while whitewall or stripe treatments can shift the car toward a more restoration-oriented or personalized presentation. Owners trying to match an earlier look should compare old photos, wheel style, and the car’s overall finish before settling on a sidewall treatment.

Tires for the 1978 BMW 733i are available from Maxxis, BFGoodrich, and Michelin. In 205/70R14, the choices include Maxxis, BFGoodrich, and Michelin across several tire series, while the 220/55R390 fitment is represented by Michelin through the TRX-B line. That makes the brand mix broader on conventional 14-inch wheels than on the specialized millimetric setup.

Brand choice should be considered alongside size, wheel system, sidewall style, and series rather than as a stand-alone decision. Some buyers are looking for a particular visual theme, such as redlines or raised white letters, while others want to preserve the BMW’s late-1970s European flavor with a blackwall Michelin presentation. Once the wheel type is confirmed, comparing the available brand and series combinations becomes much more meaningful.

A period-style 1978 BMW 733i tire choice starts with the wheels currently on the car. Cars retaining the millimetric TRX setup naturally point toward the 220/55R390 Michelin TRX-B, while cars on conventional 14-inch wheels use 205/70R14 and can be matched with several radial series that still suit a late-1970s executive sedan. Both paths can support a restoration-oriented presentation when the wheel system is correct.

The decision then becomes one of visual tone rather than simple fitment. A blackwall generally preserves a restrained European look, while whitewall, redline, dual-redline, or raised white letter styling creates a different period flavor. Owners pursuing exact originality should compare the car against marque references, historical photos, or other authoritative records, especially if the wheels may have been changed sometime after the car was new.

Tire construction is straightforward on the 1978 BMW 733i because both primary fitments are radial. Even so, construction and tire series still influence appearance through sidewall profile, lettering, and overall presentation. A Michelin TRX-B blackwall gives the car a distinctly late-1970s European look, while a conventional 205/70R14 radial opens the door to several visual treatments that can change the car’s character noticeably.

For a restoration-minded owner, the more important appearance choice is often wheel system plus sidewall style rather than radial versus bias-ply. Conventional 14-inch wheels allow more flexibility, including narrow whitewall, redline, dual-redline, and raised white letter options. Cars preserved with TRX wheels usually call for a narrower visual path, so checking the existing wheels and the restoration goal together helps keep the finished result coherent.

Yes, modifications can affect tire fitment on a 1978 BMW 733i even when the tire size itself is correct. Aftermarket wheels, wheel-width changes, suspension alterations, and ride-height changes can all influence clearance and tire selection. That matters especially on this car because one fitment uses conventional 14-inch wheels and the other uses a 390mm TRX system, so the wheel setup needs to be clearly understood first.

A modified car should be checked for steering clearance, fender clearance, and wheel compatibility before new tires are installed. Even on an unmodified car, decades of ownership can bring wheel swaps that change what belongs on it today. Looking at the wheel markings, confirming actual rim dimensions, and inspecting the suspension condition helps avoid choosing a tire that matches the catalog size but not the car’s current configuration.

Before driving a 1978 BMW 733i on new tires, inspect wheel condition, correct mounting size, inflation pressure, valve stems, and overall tire seating on the rim. It also makes sense to check for obvious suspension or steering wear, because a fresh set of tires can reveal problems that older tires may have masked. On this model, confirming the correct wheel system is part of that inspection.

A short road test should be paired with another visual check afterward. Look for uneven contact, rubbing, unexpected air loss, or any sign that the tire is too close to suspension or body components. On a collector sedan that may sit for long periods, it is also wise to inspect the spare, verify lug torque, and make sure the tires are set up for the way the car will actually be driven.

Tires on a collector 1978 BMW 733i should be maintained with regular pressure checks, periodic visual inspections, and attention to age-related condition rather than tread depth alone. Radial tires that spend long stretches parked can develop cracking, flat spotting, or slow air loss even if the car is driven only occasionally. Clean, dry storage away from prolonged sunlight and ozone sources also helps preserve the tire’s condition.

Routine maintenance should include checking sidewalls for cracks or bulges, confirming the tires still match the car’s wheel system, and watching for uneven wear that could point to alignment or suspension issues. Cars stored for extended periods benefit from being moved occasionally or supported in a way that reduces long-term stress on one contact patch. Any collector BMW returning to regular road use deserves a careful inspection before longer drives.