We might think that it is only the engine and the wheels doing all the heavy lifting in the bike, but in reality there are many small things which are doing the major work here to make the bike go the way it does. In all this, there are two concepts one has to remember when it comes to bikes and how the power is transmitted to the wheels. Hence for that there are drives known as the primary drive and secondary/final drive. We are going to check out what they mean and how do they function.But before all that, there is something one has to understand. The rear wheel is where the power goes from the engine, but it does not reach there magically. There is a cog on the front end connected to the engine crankshaft and gearbox to where all the power is transmitted that the engine makes.
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Primary Drive:
When the engine is going at full swing, it burns fuel and produces a lot of power. All this power is transmitted to the crankshaft and this in turn moves on to the gearbox to be twerked and sent to the wheels. This entire process of transmitting power to the gearbox and it when eventually makes it to the front cog of the setup is what is Primary Drive. The power transmission process here is pretty much loss-less (well almost!). The RPM of the engine is calculated right here.
Secondary/Final Drive:
After the primary drive has done its due diligence, it is time to actually get all that power transmitted to the rear wheel to get the bike moving, else it is pretty much useless. This is where the front cog which gets the power from the gearbox comes into play to get connected to the rear wheel to transmit that power. For this purpose the cogs on the front and rear are connected using either a chain drive or a belt drive in some cases. There are even shaft drives, but those are pretty rare to find these days. So the way the front cog and the rear are connected to the wheel is how the power gets transmitted to the rear wheel and makes move which is the secondary or Final Drive.
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Now coming to the difference between the final and primary drive is that, the final drive is what makes the bike move ultimately. The primary drive takes the power from the engine to the gearbox and that is it. Until the time there is no secondary drive, the bike is not going to move at all and hence it is necessary for both the drives to work together and in tandem.But all said and done, one has to understand that the engine modulation that is RPM control, gear shifting and everything else that it takes to control and ride a bike takes care at the primary drive. The Final drive is only to transmit that all power to the rear wheel and that is pretty much it. The amount of maintenance it takes for the primary drive is again more than that of the secondary drive since all it takes is a little chain cleaning and tightening.
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So one has to understand this basic functioning of the bike; not because it is going to make your bike go better or help you ride well. It is only so that you understand to take proper care of your bike accordingly and get it serviced and repaired regularly.
By: Pratik Patole