HHR Performance » Dymag Performance Wheels

You’re a tech savvy rider who wants to get the best riding experience out of your high
performance bike. The buzz in the automobile and motorcycle industry is all about
decreasing weight whilst still stepping ahead in performance, safety and sophistication.
Simply put, there is no other modification that gives such an instant boost in motorcycle handling and
performance as lightweight wheels.
Dymag, the British company that pioneered carbon fibre motorcycle wheels, leads the market with a
comprehensive range of carbon, magnesium and aluminium wheels that are some of the lightest and
strongest on the market. All tested and certified for road use.
Designed with the benefit of 30 years of lightweight wheel technology, our stylish, ultra-light - and ultra
strong Dymag motorcycle wheels will transform your bike’s handling and performance.
Motorcycle racers understand that the primary technical attributes of a Dymag lightweight racing wheel are
the dramatic reductions in unsprung mass, moment of inertia and gyroscopic torque, as well as stiffness.

WHY IS LIGHTWEIGHT BETTER?
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:

WHAT DOES THIS ALL MEAN?
Unsprung Weight
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 swingarm, fork lowers, brakes, tyres and wheels.
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

A 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 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!
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
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.