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Dymag Carbon Auto Wheels Manufacturing

Comparison of Lightweight vs OEM WheelsVideo of BX-F carbon rim manufacturing process.

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Dymag Carbon Auto Wheel Manufacturing

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Find out why our wheels make such an impact on performance and handling.

Read our Technical Guide – The Performance Benefits of Lightweight Motorcycle Wheels

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Why is lightweight better?

Comparison of Lightweight vs OEM Wheels

Dymag’s lightweight motorcycle wheels can improve the handling, performance and fuel economy of your bike. This is because you need more energy to move heavy objects, than to move light objects over the same distance.

We can measure these physical benefits scientifically, but as riders, we also feel the subjective improvement in ride quality and “flickability” of lighter bikes.

For example, look at the impact on the BMW S1000RR fitted with a set of “Dymags” compared to the OEM supplied wheels. There is a significant improvement when switching to forged aluminium wheels and even greater benefits when trading up to the ultimate – our carbon fibre CA5s:

Unsprung mass

A bike’s suspension supports most of its components, including the chassis, the engine and the rider – these components are known as “sprung” weight. However, some bike components are not supported by the suspension and are therefore “unsprung”; they include the lower part of the forks, the whole swingarm, brakes, tyres and the wheels.

Fig 2. Sprung vs Unsprung Weight
Fig 3. Two Wheels of Different Weights and Forces

When a bike passes over a bump in the road, the rider will feel the unsprung weight being forced upwards. At high speeds this causes unpleasant vibrations – the greater the bike’s unsprung weight, the stronger these vibrations become.

High unsprung weight can also lead to “bouncing” and “hopping”, where the tyres temporarily lose contact with an uneven road, causing the bike to buck around – which is potentially dangerous.

You can significantly improve on this problem by installing Dymag’s lightweight wheels – just look at how much weight you could save!

Moment of inertia

Moment of Inertia (MOI) is a measure of how easily an object spins or stops spinning – a high MOI means that an object is difficult to spin. Spinning objects are unusual: the energy you need to start or stop spinning an object (accelerating or braking) increases as the square of the object’s radius (distance from centre to the edge). In figure 3 there are two wheels of equal weight but different sizes. The equation for the MOI is I=mr² where the MOI (I) is equal to the weight (m) times the radius(r) squared.

The important point of this equation is that the radius influences the MOI significantly more than the weight – if you divide the radius by two, you will divide the MOI by four. This effect is extreme for larger changes: if you divided the radius by ten, you would divide the MOI by one hundred!

Fig 4. Moment of Inertia
Fig 5. Moment of Inertia - Two Objects Accelerating

A motorcycle wheel is the same: if you reduce the weight of the wheel at the radius (the rim), you reduce the MOI of the wheel more than if you had removed the same amount of weight at the hub. Dymag’s wheel replaces a typical heavy metal rim with a lightweight carbon fibre, magnesium or aluminium rim, so it therefore has a lower MOI than conventional OEM wheels.

Wheels with low MOI will will accelerate or brake more quickly. If you roll two cylinders of equal weight and diameter down a slope then the one with a lower MOI will reach the bottom first. You can see this in figure 4; the hollow cylinder has a higher MOI than the solid cylinder, because most of its weight is concentrated at the rim. Dymag’s carbon fibre wheel will greatly improve your bike’s acceleration and braking performance because of its lightweight rim.

Gyroscopic torque or "flickability"

Spinning objects are unusual in another way too. If they are constrained and you tilt them, they will react with a rotational force against their constraints.

You can (carefully) try this yourself with a bike wheel. If you hold the wheel on its axle while it is spinning and you try to tilt the wheel, you will feel that it pushes back and pivots into a different direction.

The equation for this rotational force is is T=Iw^ where the rotational force (T) equals the wheel’s MOI (I) times the wheel’s spinning speed (w) times the speed with which you are trying to tilt the wheel (^). Importantly, the rotational force with which the wheel resists your tilting depends on the MOI. A wheel with a low MOI will therefore exert a lowerrotational force as you try to tilt it.

On a bike the rider is constantly trying to tilt the spinning front wheels through the bike’s steering mechanism. The rotational force which these wheels exert on the rider drops significantly if the bike’s wheels have a low MOI. Dymag’s lightweight motorcycle wheels will reduce the forces that are constantly going into your bike’s steering mechanism – the result is that your bike handles more responsively and precisely.

Fig 6. Gyroscopic effect - Wheel
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