07.2018 - The differential lock - briefly explained.


The C30 already had a Torsen differential from HEICO SPORTIV installed on delivery. It is a differential from the Quaife brand with a distribution effect of 25%. Why it is not written here of locking effect, is explained further below in the text.

What are the advantages of a differential lock?
The differential gear is simply expressed between the two wheels. In the case of the C30 it sits at the front axle, because it is a front-wheel drive. The differential gear ensures that both wheels can rotate at different speeds. Especially in bends, this is very helpful in normal road traffic, as the wheel inside the bend rotates slower than the wheel outside the bend. If both wheels would turn same speed, they would cover the same distance in the curve - this results in a "spinning" of the outer and thus faster wheel. This effect may be desirable for drifting, but it would be rather disadvantageous in road traffic.

A differential lock therefore has the opposite effect, which varies greatly depending on the locking effect. The lock ensures that the faster rotating wheel is braked in favour of the slowly rotating wheel, i.e. that the torque is diverted.

There are different areas of application for a differential lock and therefore also different variants:

  • Lamellar locks, torque sensing - have been preferably used in motor sports since the 1950s.
  • Torsendifferential, torque-sensing - Slides the drive torque back and forth between the wheels, but, unlike the multi-disc lock, cannot lock.
  •  Viscous locks, speed-dependent - Locking above a certain continuous speed difference. This type of lock is used in some BMW models, among others.
  • Electronically controlled lamellar locks - The locking effect is generated by an electronically controlled pressure plate.
  • Rigid drive-through, 100 % locking effect - Used, for example, in pure drift vehicles.


What does the blocking effect / distribution effect mean, stated in %?
Our Ring-C30 has a Torsen differential with a distribution effect of 25 %.
In this case, 25% means that four fifths and 80% of the drive torque go to the spinning wheel and one fifth and 20% respectively to the wheel with grip, which "grips". For comparison: Without the differential lock, 100% of the drive torque would go to the spinning wheel. With a locking effect of 100 %, 50 % would go to each wheel.

 

How does the Torsen differential work?
As already mentioned above, the Torsen differential distributes the drive torque back and forth between the wheels, but does not lock. If the C30 would be a pure tracktool, a lamellar differential, as offered by Drexler, for example, would make more sense due to its locking capability. However, since the C30 is still in everyday use, I would like to briefly point out the advantages of a Torsen differential.

On the one hand, the vehicle has no inclination to understeer up to the apex of a bend, as the differential opens completely as soon as you step off the accelerator. This goes hand in hand with a more agile tail. In addition, the effect of the Torque Differential is easier to control from the driver's point of view, as the distribution of the torque appears "more harmonious" and is not completely blocked. Since the C30 is front-wheel driven, the Torsen differential has no noticeable negative influence on the steering compared to the lamellar differential due to the lack of locking effect. Last but not least, the Torsen differential has no noticeable effect on wear, e.g. of the tyres on the drive axle, unlike the multi-disk lock.

In summary, the effect of the Torsen differential is easier to handle and brings with it at most little additional wear. These arguments make the Torsen differential a suitable alternative to the multi-disk lock for everyday use, which is why it is used in sporty vehicles, high-performance road vehicles and for very high-performance vehicles used in endurance races.

There is no question that a lamellar differential is technically superior to the Torsen differential and can be adapted much more flexibly to the application. Nevertheless, you have to consider the intended use and make compromises if the vehicle is still being driven in normal road traffic.

More information about the differential lock can be found at http://www.limitedslip.de
Here, the different variants with their advantages and disadvantages, the purpose of use, the lamellar lock in detail and the basic function of a differential lock are explained in a comprehensible manner.