Whether lightweight cast, forged, polished, milled, with cross, double or Y-spokes: BMW M rims never fail to make an impression. An essential part of the design of M cars since the beginning, these lightweight aluminium wheels contain more knowledge than a first glance into the wheel arch might suggest. Beyond their aesthetic appeal, rims are not only responsible for transferring power to the road but can also have a positive influence on the overall dynamics of the vehicle.
It goes without saying that BMW M GmbH is particularly committed to developing model-specific and extremely high-performance wheels. This is also emphasised by Kristian Groth and Andreas Krause, exterior detail designers in the wheels division at BMW. They are well aware of the extensive list of requirements for M rims and provide an insight into the enormous depth of detail involved in developing new designs.
The development costs for M specific wheels are significantly higher overall than for non-performance-oriented variants.
Exterior Detail Designer
The specifications for all M rims state: low weight, maximum dynamics, iconic design and the ability to accommodate the powerful M braking system.
Exterior Detail Designer
M WHEELS: FORM FOLLOWS FUNCTION.
M WHEELS: FORM FOLLOWS FUNCTION.
“BMW M wheels always add an exterior highlight,” says Krause. The design rounds off the progressive design of the M models and really makes the vehicles shine. But regardless of whether they feature classic spokes or a modern aero design, performance is always the top priority at M GmbH. This means that wheels from and for M models must meet a range of requirements that go beyond the characteristics of ‘standard’ rims.
Specifically, this means that an M wheel must be particularly rigid in order to offer maximum precision even under high dynamic forces – such as those that arise on the racetrack in conjunction with high-grip track tyres. At the same time, it must be very light in order to keep the rotating mass low. This is important for dynamic handling and good acceleration. The rim dish, i.e. the distance from the centre of the wheel to the outermost part of the wheel, the rim flange, is also deeper on M wheels. The resulting more extreme spoke pattern shifts the tyre further outwards.
In addition, the design of the wheels must be suitable for the extremely powerful braking systems from BMW M: it must leave space for the large brake discs and multi-piston calipers of the M Sport and M ceramic brakes. These components must also be adequately ventilated.
We continuously challenge ourselves and always strive for technological leadership. With unique designs, state-of-the-art manufacturing processes and outstanding product performance.
Exterior Detail Designer
HIGH TECH IN THE WHEEL HOUSING.
HIGH TECH IN THE WHEEL HOUSING.
How can these multiple objectives be achieved and combined in a single aluminium component? “M wheels are generally manufactured using a forging process or lightweight casting process,” says Groth. This allows for narrower spokes, less material overall and, ultimately, lower weight. As a general rule, a forged wheel can absorb higher forces than a cast wheel due to the specific properties of the material.
Another measure is the different wheel sizes on the front and rear axles, which is standard on M high-performance vehicles such as the BMW M2, M3 and M4. The rim on the front axle of these models is one inch smaller, which serves two purposes: lower weight and more grip when cornering thanks to the higher tyre sidewall, which creates a larger wheel contact patch under load.
“Some of our designs from the accessories range, which feature perforations in the spokes to remove every last unnecessary gram from the wheels, show how the issue of weight can be taken to the extreme,” says Krause about the particularly striking 1063 M rims. BMW M Performance Parts wheels are always designed as technology carriers: state-of-the-art manufacturing processes such as 5-axis milling allow such openings to be created for maximum performance.
Y-spokes and cross-spokes are practically part of the DNA of BMW M. Like M GmbH itself, these designs originated in motorsport and will continue to live on in new interpretations in future M vehicles.
Exterior Detail Designer
AERODYNAMICS FOR BMW M WHEELS.
One topic that is often associated with fully electric vehicles is the aerodynamic effect of the rims. Ultimately, a wheel that causes as little air resistance and turbulence as possible while driving benefits every performance-oriented model, regardless of its drive system. Kristian Groth says, “Aerodynamics will continue to be an important factor in wheel design in the future.” After all, M GmbH has a tradition of wanting to create an iconic rim that is optimally suited to the requirements of each model, rather than a standard design. “Whether fully electric, hybridised or with a classic combustion engine – the overall performance of the vehicle is our top priority.”
BMW M WHEEL EXPERTISE.
Facts about alloy wheels.
Forged wheels are characterised by their high material density and low weight. Compared to conventional cast rims, forged rims are often up to 40 percent lighter. This results in better braking and driving characteristics. Forged wheels are formed from a single aluminium blank using a complex, multi-stage pressing process under high pressure. This process compacts the material, resulting in the advantages mentioned above.
