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Motorcycle manufactures make bike for a middle ground. Some of rider’s ride spirited, some sedate, some look for fuel economy. Not to forget the umpteen regulations and emission norms which the manufactures need to adhere too. Considering all the factors manufactures ride to reach a middle ground n performance. Something that they feel will appeal to most of customer base or target audience.
I have always said this, Motorcycles are a personal choice. This middle ground that manufactures try to achieve may not match my style of riding. Hence the need for making personal. This is first part of our new series “Throttle Up – Basics to making your machine more fun”.
Part 1 – It’s all in the Gearing.
Part 1 of this article we will be looking at the Gearing Ratios of the bike and what we can we achieve by altering it and the basic mods we can do. Before we speak about the mods. Let’s try to understand what Gearing Ratio is and how it affects the ride ability.
“One of the easiest way to make your bike accelerate faster and adding more power at lesser rpms is by doing a sprocket change.”
Gearing Ratio:
Gearing ratio is simply determines how the engine rpm of your bike is translated to actual wheel spin speed. As explained above the middle ground achieved by manufactures may not always suit your style of riding. So, if you are a person who feel that you need more acceleration or feel that your bike lugs around in low rpms you should be looking at a sprocket change.
Before we do any mods to the gearing ratio we will need to understand the OEM gearing ratio. The basic formula for that if given below. For the sake of reference, I will be using my current ride Royal Enfield Interceptor 650 as an example.
Rear Sprocket Teeth / Front Sprocket Teeth = Gear Ratio
38 / 15 = 2.533 (Interceptor 650 OEM Gearing Ratio)
This 2.533 is something we will need to remember. This will serve as the critical reference point for all the mods that we will discussion after this.
“I want Torque”
Many a times you would have heard people on YouTube or Biking magazines mention that a particular bike is geared tall. What they actually mean that the bike has been made with the idea of going to faster speeds and will have very little power in lower rpms. Predominantly most of the sport bikes are geared this way, this means you need to rev the engine harder to extract power. Such bikes are abysmal to ride in Low speeds at lower rpm. For eg, every day riding in the city.
To tackle this scenario and increase the acceleration of the bike in slow speeds you will need to increase your gearing ratio. Albeit, there will be a slight loss to your top end acceleration. In our case with the OEM gear Ratio of 2.533 I will need to change my ration to value that is greater than 2.533.
This logic equally applied to MX and ADV bikes where people want more torque in the lower rev bands to tackle such tricky conditions and obstacles when riding off-road.
“Give me BHP”
Deviating from the above case let’s say that are not looking for more bottom end grunt and looking for our right acceleration. Let’s assumes your aim is to make your bike go faster. If faster is all you need you will need to look at reducing your gearing ratio that the stock ratio. In our case your final gearing ratio is should be lesser than 2.533
Always remember for a Higher Top Speed your Ratio should be lesser than Stock. For more acceleration, you need to go to a Higher ratio that than stock.
1 Down = 3 Up.
As you are already aware motorcycle has two sprockets. You can achieve a change to your gearing by altering either the front or rear. In Extreme cases, both of them. Before we see the advantages of changing a front or a rear. We will need understand this (+1) Front = (-3) Rear or (-1) Front = (+3) Rear. Let me explain the same below the formulae we used above.
38 / 15 = 2.533 (Interceptor 650 OEM Gearing Ratio)
38 / 14 = 2.71 (1 Tooth reduced in Front, Stock is 15)
41 / 15 = 2.73 (Adding 3 Tooth to the Rear sprocket)
Now if you see the above formulae you can see that to achieve the desired Gearing ratio of approx. 2.7. I can either reduce one Tooth on the Front or add 3 in the Rear.
Remember its always wise to do small modification first. Ride the bike for some time and make more changes if needed.
“The Dilemma of Front or Rear”
As we have explained above you can achieve a change in gearing ratio by modifying either the Front or the Rear Sprocket. Once you have decided on the ratio you want to achieve the next task will be deciding which sprocket to change. Frankly this will depend on what factor like the bike you ride. What aftermarket items are readily available in the locality you are placed in. I have put some of the key factors for you to consider when doing this.
- Rear Sprockets are costlier than Front sprockets.
- Rear Sprockets are easier to find and much safer.
- If your bikes rpm sensor is connected to the drive shaft. Then changing the front sprocket will give incorrect reading.
- Reducing the front sprocket means you chain has lesser area to rotate. Which translates to more wear and tear for the chain.
“What have I done for my bike”
The picture you see in the start of this article is 40T Rear sprocket (2 more than stock) made by Way2Speed Performance who make quality aftermarket part for bikes and cars. This Rear sprocket is currently being used by people in our riding group “Club ROFL”. I personally felt that I need more low end acceleration and have planned to go for a 14T front sprocket (Higher gear ratio than adding 2 Teeth the rear). I will be getting that fitted once the lockdown restrictions are removed.
Hope this article has provided some insight to you guys and will help you in making a decision when you looking at making performance mods for your own bike. This is Part 1 for the new series “Throttle Up – Basics to making your machine more fun”. Stay tuned for more articles in this series.
“Some Factors to consider”
- Going for a higher gearing ratio means you will have a drop-in mileage. Mostly because you will have higher cruising RPM for the given speed. Even more likely is that the you will ride the bike harder due its peppy acceleration.
- There will be variance to your speedo reading.
- Aluminum sprocket are light and cheap and tend to wear off quickly. Steel ones are heavier and last longer.
If you are doing any radical change to you change. There is change your chain length will become short. So keep that in mind
