Alfa Romeo Alfetta GTV Gruppo 4 Turbodelta
Magnesium wheels in such extreme dimensions take us back to the golden era of rally racing in the late 1970s, when the Autodelta racing division (under the leadership of Carlo Chiti) was building brutal race cars based on the Alfa Romeo Alfetta GT / GTV for Group 4 (Gruppo 4). The combination of 10J at the front and 11J at the rear represents the absolute pinnacle of engineering at the time for tarmac rallies (such as Rallye Sanremo or Tour de Corse) and circuits. The supplier was none other than the best of the best—Campagnolo. These wheels carried the full designation 10J x 15" (front) and 11J x 15" (rear). At that time, a 15-inch diameter was ideal because the Italian tire manufacturer Pirelli had developed revolutionary low-profile radial slicks, the Pirelli P7 Corsa, specifically for these widths (the front was fitted with 250/40 x 15 tires, while the rear took a massive 295/35 x 15 size).
Autodelta experimented with various setups for the Group 4 versions, and Campagnolo cast both monoblocks (one-piece wheels) and extremely rare multi-piece variants for them (where a Campagnolo magnesium center face was bolted to duralumin barrels and lips). One-piece wheels were preferred for rally events due to their maximum rigidity during jumps and impacts on gravel, whereas multi-piece split wheels were used to fine-tune the car's track width on tarmac.
The wheels were cast from a special magnesium-aluminum alloy, at the time often referred to as Elektron. The wheels were manufactured using a specific sand-casting method. The result was an extreme reduction in weight—they weighed roughly 35–40% less than equivalent aluminum wheels of that era. This allowed racing teams to drastically reduce unsprung mass and wheel inertia, which was crucial for the quick handling responses of a chassis utilizing a transaxle layout.
These wide racing Campagnolos featured a very deep, concave shape (known as a "deep dish" design). Consequently, the engineers at Autodelta massively widened the fenders (using riveted fiberglass fender flares) and deployed a wider track with wider wheels on the rear axle (11J) to give the car brutal mechanical grip when exiting corners. This was particularly important for the GTV Turbodelta versions (pushing around 300 horsepower), where the turbocharger sent an enormous amount of torque to the rear axle.
The colored stripes on the wheels (red and yellow) are not random decorations, but authentic period markings from the pit lanes of yesteryear. In 1970s and 1980s motorsport, these stripes carried very specific technical and logistical meanings. During a Group 4 rally, Pirelli P7 Corsa tires had to be changed in a flash, and mechanics in the service zone didn't have time to visually gauge the wheel width. Thus, the yellow and red stripes served as visual navigation for the crew (red = 11J rear, yellow = 10J front).
Magnesium is extremely light, which is worth its weight in gold in motorsport. However, it suffers from two major flaws—it is brittle and highly flammable. Furthermore, it insidiously degrades from the inside out. A wheel can look flawless from the outside, but its internal structure might be corroded to dust (magnesium oxide forms a white powder hidden beneath the paint). Additionally, magnesium is highly intolerant to moisture. Original, period-correct 15" Campagnolo magnesium wheels in 10J and 11J dimensions from the Autodelta workshops are practically impossible to find today. If any do surface, they are usually no longer usable for spirited driving or racing due to magnesium degradation (material aging and microcracks). In one of the photographs, you can see a comparison with a 6Jx15 BWA rim. :-)
Photo: Filip Hron 2026