Wheelset development at AC Schnitzer
A few definitions in advance
Wheel/complete wheel = rim incl. tyre
Wheel set = 4 wheels
xi/xd wheel sets = special wheel sets for all-wheel drive vehicles (xDrive)
Mixed-sized tyres = tyres wider on the rear axle than on the front axle
All-round tyres = same tyre size on the front and the rear axle
The wheels have a really important role: they are the postcard-sized connection between the vehicle and the road. They play a key role in the driving and propulsion as well as the deceleration - i.e. braking - of your vehicle. This gives the wheels a key role. Anyone who develops and sells wheels therefore has a great responsibility. We are aware of this responsibility; we have internalized it and implement it with every new development.
AC Schnitzer only uses high-quality brand tyres, which are developed in close cooperation with premium tyre manufacturers. On the one hand, the tyres have to transfer the power of the engine perfectly to the road, on the other hand, properties such as braking behaviour, lateral control, water drainage in rain and the properties in straight running are important decision criteria for or against a tyre.
A wheel set with wide base tyres is always also an investment in increasing driving safety and dynamics. In order to maintain driving comfort when using larger wheel dimensions, we at AC Schnitzer have actively opted against run-flat tyres and for sporty, conventional tyres. Conventional tires build up less rolling resistance and offer noticeably more comfort.
AC Schnitzer specialises in mixed-sized tyres, i.e. wheel sets in which the wheels of the rear axle are wider than those of the front axle. This makes sense in terms of driving dynamics, as it allows strong drive forces to be transmitted while at the same time enabling high steering precision. Although the wider a tyre is, the more power you can put on the road, the rolling resistance caused by the tyre must not become too high. As the rolling resistance increases the wider a tyre is, AC Schnitzer works out the wheel dimensions that are balanced.
AC Schnitzer develops special wheel/tyre combinations for all-wheel drive vehicles and orientates itself on the specifications of the vehicle manufacturer. These AC Schnitzer wheel sets are marked "xi/xd". Only those wheel dimensions are developed and approved for all-wheel drive vehicles that are as gentle on transfer cases as standard wheel sets.
All AC Schnitzer wheel sets are tuned in multi-stage driving tests in traffic and on race tracks. Only after successful test runs the wheels are released for sale. All AC Schnitzer wheel sets are delivered fully assembled and balanced. They are subject to a two-year manufacturer's warranty. The scope of delivery includes mounting materials such as adapters and wheel bolts as well as the homologation certificate (with the exception of marked wheelsets for export).
The wheels not only physically but also optically connect a car to the road. “That‘s why it‘s very important to have the right dimensions between the proportions of the rims to the bodywork,“ explains AC Schnitzer chief designer Michele Viandante. Rims that are too small quickly make a vehicle appear high-legged and unstable. The new Lightweight Forged Rims ”AC3 Evo“ from AC Schnitzer, on the other hand, are truly earthy.
- machined “GESCHMIEDET” logo on the front
- machined original AC Schnitzer logo
- open design in Silver/Anthracite or Anthracite/Silver, giving a clear view to the brakes
- central locking optic in gold or grey
The highlight of the AC Schnitzer rim technology and the exclusive development for the BMW M5 is the latest development stage of the AC3 Lightweight Forged Wheels "Evo" with central locking optic.
Even though the new Lightweight Forged Wheels inch clearly belong to the AC3 design family, their appearance is particularly technical due to the central locking nut and the fact that the wheel bolts are no longer visible. They "disappear" under a special aluminium cover that is screwed together with the additional central lock. In addition to their sporty appearance both together also serve as anti-theft devices, which is why a special key is included in the scope of delivery.
The AC3 Lightweight Forged Rims "Evo" are available in the colour variants BiColor Silver/Anthracite or BiColor Anthracite/Silver. Depending on how extravagant or discreet the customer wishes his wheel set to be, he can choose between grey or gold for the colour of the central locking nut.
The Lightweight Forged Rims have a partly polished and partly painted surface. Regardless of the colour, all AC3 Lightweight Forged Wheels have two noble, milled letterings: "AC Schnitzer" and "GESCHMIEDET" (forged).
The central design element of the AC3 Lightweight Forged Rims "Evo" is not only in a figurative sense the visible central locking nut with aluminium cover. This unit makes a hub cap superfluous for the first time in the "rim history" of AC Schnitzer.
The filigree yet solid spoke matrix with its five triangular struts of the AC3 Lightweight Forged Rims has been further weight-optimised for the new 21-inch version and for the first time also in the visible area of the rims. The side walls of the rim spokes have recesses which minimize the wall thickness of the spokes. However, the "art of omitting" has not only led to a weight reduction in the AC3 Lightweight Forged "Evo" Rims, but also to an even sportier appearance.
- high quality lightweight forged wheels save approx. 25-35% weight, compared with conventional cast wheels
- perceptible reduction in unsprung mass and gyroscopic forces on the car, therefore
- significantly improved driving dynamics
- significantly improved acceleration and deceleration due to lower masses
- improved cornering handling
- high quality clear lacquer protects the wheel against corrosion, therefore
- long life
About 97 percent of the melt consists of aluminium, but the remaining three percent of the wrought alloy also helps to influence the desired properties of the material for the ideal wheel. In addition to the main component aluminium, the alloy also contains one percent magnesium and one percent titanium each (which ensures finer grain size). The precise composition of the material alloy has a decisive influence on the subsequent properties of the wheel.
Approximately 97 percent of the alloy consists of pure aluminium. The remaining three percent of the wrought alloy is important for the properties of the material.
The AlCr20 master alloy with the hard metal chromium improves recrystallisation resistance. Master alloy means a mixture of aluminium with other materials, in this case it is a maximum of 0.25% by weight of chromium, i.e. a very small amount.
Together with pure silicium, magnesium leads to a higher strength of the total alloy. The maximum proportion of these materials is 1.2 and 1.3 percent by weight, respectively.
These glossy ingots are the master alloy AlTi5B1, which serves a finer grain structure of the total alloy. The proportion of the expensive raw material titanium is only 0.1 percent by weight.
These irregularly shaped lumps are only added to the alloy together with magnesium. This increases the strength. The silicium content is between 0.7 and 1.3 percent by weight.
The addition of 0.4 to 1.0 % manganese makes the alloy tougher. Manganese has a positive effect on recrystallisation behaviour.
Forging - an elaborate process that must offer maximum safety. In many steps the wheel is prepared for its important task for a long car life. The process control guarantees excellent material properties, which are the reason for the low weight of our forged wheels. Even in critical driving situations, forged wheels offer the occupants optimum safety.
Step 1: The nozzle
A cast block more than 6 m long manufactured by OTTO FUCHS is the starting material from which a socket, which is precisely matched to the later wheel, is sawn off.
Step 2: Pre-forging
In the first forging stage, the nozzle is pre-forged into a rotationally symmetrical blank with a force of 4,000 tons.
Step 3: Design forging
In the second forming stage, the styling is pressed into the pre-forged blank under a 7,000 ton press, which gives the wheel its later appearance to a large extent.
Step 4: Punching
In the last forging stage with 800 tons of pressing force, the later ventilation hole windows and the hub bore are punched out and the burr of excess material sheared off at the outer circumference.
Step 5: Flow pressing
The outer edge of the blank is heated. The entire rim area, from outer to inner horn, is rolled out.
Step 6: Finishing
The final step is finishing: turning, drilling and deburring. Painting rounds off the complex process.
Source: Material and Production: Otto Fuchs KG
In this process, the wheel is first primed and then completely painted. Now the surfaces, which are later to shine metallically bright, are turned off and then polished to a high gloss. Finally, a two-layer clear coat is applied, consisting of a polyester primer and the acrylic clear coat.
Test Procedures / Safety
After their design, the first sample rims are manufactured under real production conditions. These must undergo a multitude of tests. Among other things, the strength is tested. The "rim life" is simulated in the bending circumferential test. Every AC Schnitzer rim must withstand this intact in order to be allowed to be produced and sold at all.
This is followed by vehicle-specific tests, including test installations with check of unobstructed movement and driving tests on public roads and on race tracks. Only after these procedures our rims receive their homologation, i.e. the approval to be used in road traffic.
Wheels are safety-relevant components. Therefore, they are checked and tested with the greatest care. This starts with the first chemical material tests and ends with hard testing machine endurance runs:
- § 30 StVZO wheel guideline
- ECE R124
- Bending-rotation tests
- 90° impact test
- unwinding tests
Scope of delivery
- 4 complete wheels:
AC Schnitzer AC3 “Evo” Lightweight Forged Alloy Wheels with premium tyres - mounted and balanced
- 4 central locking nuts either in gold or grey
- special tool for central locking nuts
- vehicle and rim-specific mounting and fastening material
- quality tag
- certificate of authenticity
- care instructions
- homologation certificate
Uniqueness of the wheel set with AC3 “Evo”Lightweight Forged Wheels
- Weight-optimized rims through forging technology paired with premium tires
- Vehicle-specific tuning through multi-stage driving tests on road and race track
- rim with integrated lettering: "AC Schnitzer" and "GESCHMIEDET"
- open design in Silver/Anthracite or Anthracite/Silver, giving a clear view of the brakes
- Compatible with standard RDC system
- Rim also available separately
- 2 years warranty
- Developed exclusively for BMW vehicles
- Production monitored according to ISO standard
- KDS mount for wheel alignment according to BMW specification is available