SELECTING Motorcycle Sprockets
One of the easiest methods to give your bike snappier acceleration and feel just like it has a lot more power is a simple sprocket change. It’s a simple job to do, but the hard component is figuring out what size sprockets to replace your stock types with. We explain everything here.
It’s All About The Gearing Ratio
Your gearing ratio is, simply put, the ratio of teeth between the front and rear sprockets. This ratio determines how engine RPM can be translated into wheel speed by the motorcycle. Changing sprocket sizes, front side or rear, changes this ratio, and therefore change the way your bike puts capacity to the bottom. OEM gear ratios aren’t always ideal for a given bike or riding style, so if you’ve ever found yourself wishing you had better acceleration, or found that your motorcycle lugs around at low speeds, you may simply need to alter your current gear ratio into something that’s more suitable for you.
Example #1: Street
Understanding gearing ratios may be the most complex part of deciding on a sprocket combo, so we’ll start with a good example to illustrate the concept. My own bike can be a 2008 R1, and in share form it is geared very “tall” quite simply, geared in such a way that it could reach very high speeds, but experienced sluggish on the lower end.) This caused street riding to always be a bit of a headache; I had to really trip the clutch out an excellent distance to get moving, could really only work with first and second gear around village, and the engine felt a little boggy at lower RPM’. What I needed was more acceleration to make my street riding more enjoyable, but it would come at the trouble of some of my top acceleration (which I’ certainly not using on the road anyway.)
So let’s consider the factory set up on my bicycle, and understand why it sensed that way. The inventory sprockets on my R1 are 17 tooth in the front, and 45 the teeth in the trunk. Some simple math provides us the gearing ratio: 45/17=2.647. Now I’ve a baseline to utilize. Since I want more acceleration, I’ll prefer a higher equipment ratio than what I have, but without going as well severe to where I’ll possess uncontrollable acceleration, or where my RPM’s will be screaming at highway speeds.
Example #2: Dirt
Several of our team members here ride dirt, and they adjust their set-ups based on the track or trails they’re going to be riding. One of our staff took his bicycle, a 2008 Kawasaki KX450, on a 280-mile Baja ride. As the KX450 is definitely a major four-stroke with gobs of torque over the powerband, it currently has lots of low-end grunt. But also for a long trail trip like Baja where a lot of floor should be covered, he wished a higher top speed to really haul over the desert. His option was to swap out the 50-tooth inventory rear sprocket with a 48-tooth Renthal Sprocket to increase speed and get a lower cruising RPM (or, when it comes to gearing ratio, he went from 3.846 down to 3.692.)
Another one of we members rides a 2003 Yamaha YZ125 a light, revvy two-stroke, very different from the big KX450. His favored riding is on short, jumpy racetracks, where optimum drive is needed in a nutshell spurts to clear jumps and electric power out of corners. To achieve the increased acceleration he wanted he geared up in the rear, from the stock 49-tooth to a 50-tooth sprocket also from Renthal , raising his last ratio from 3.769 to 3.846 (in other words about a 2% increase in acceleration, just enough to fine tune the way the bike responds to the throttle.)
It’s ABOUT The Ratio!
What’s important to remember can be that it’s about the gear ratio, and I have to reach a ratio that will assist me reach my aim. There are many of techniques to do that. You’ll see a large amount of talk on the internet about heading “-1”, or “-1/+2” and so on. By using these numbers, riders are typically expressing how many the teeth they changed from inventory. On sport bikes, prevalent mods are to get -1 in front, +2 or +3 in again, or a mixture of both. The trouble with that nomenclature can be that it only takes on meaning in accordance with what size the inventory sprockets happen to be. At BikeBandit.com, we use exact sprocket sizes to point ratios, because all bikes will vary.
To revisit my case in point, a simple mod would be to head out from a 17-tooth in the front to a 16-tooth. That would adjust my ratio from 2.647 to 2.813. I did this mod, and I acquired noticeably better acceleration, making my street riding easier, but it did lower my top acceleration and threw off my speedometer (and this can be adjusted; even more on that later.) As you can plainly see on the chart below, there are a large number of possible combinations to arrive at the ratio you want, but your options will be limited by what’s conceivable on your own particular bike.
Variations
For a more extreme change, I could have gone to a 15-tooth front? which would produce my ratio specifically 3.0, but I thought that would be excessive for my flavor. Additionally, there are some who advise against making big changes in the front, because it spreads the chain pressure across less pearly whites and around a tighter arc, increasing wear.
But remember, it’s all about the ratio, and we can change the size of the rear sprocket to improve this ratio also. Consequently if we transpired to a 16-tooth in the front, but at the same time went up to 47-tooth in the trunk, our new ratio would be 2.938; not quite as extreme. 16 in the front and 46 in again will be 2.875, a significantly less radical change, but still a bit more than undertaking only the 16 in front.
(Consider this: for the reason that ratio is what determines how your bike will behave, you could conceivably go down on both sprockets and keep carefully the same ratio, which some riders do to shave pounds and reduce rotating mass while the sprockets and chain spin.)
The important thing to keep in mind when selecting new sprockets is that it’s about the ratio. Figure out what you have as a baseline, determine what your aim is, and adapt accordingly. It will help to find the web for the experience of additional riders with the same bike, to discover what combos are the most common. It is also a good idea to make small adjustments at first, and work with them for some time on your favorite roads to discover if you like how your cycle behaves with the new setup.
FAQ’s
There are a great number of questions we get asked concerning this topic, and so here are a few of the most instructive ones, answered.
When deciding on a sprocket, what truly does 520, 525, and 530 mean?
Basically, this identifies the thickness of your sprockets and chain (called the “pitch”) 520 is the thinnest and lightest of the three, 525 is in the middle, and 530 is the beefiest. Many OEM components are 525 or 530, but with the effectiveness of a high quality chain and sprockets, there is usually no danger in switching to the lighter 520 setup. Important note: constantly make sure you install pieces of the same pitch; they are not compatible with each other! The best plan of action is to buy a conversion kit so your entire components mate perfectly,
Do I must switch both sprockets at the same time?
This is a judgment call, and there are differing opinions. Generally, it is advisable to change sprocket and chain components as a arranged, because they have on as a set; in the event that you do this, we recommend a high-durability aftermarket chain from a high company like EK ,RK >, and DID
However, oftentimes, it won’t harm to change one sprocket (usually leading.) If your chain is definitely relatively new, you won’t hurt it to change only one sprocket. Considering that a front sprocket is typically only $20-30, I recommend changing it as an inexpensive way to test a fresh gearing ratio, before you take the plunge and spend the amount of money to improve both sprockets as well as your chain.
How does it affect my velocity and speedometer?
It again depends upon your ratio, but both definitely will generally end up being altered. Since many riders opt for a higher equipment ratio than stock, they’ll knowledge a drop in best acceleration, and a speedometer readout that says they go faster than they are. Conversely, dropping the ratio could have the contrary effect. Some riders obtain an add-on module to change the speedometer after modifying the drivetrain.
How will it affect my mileage?
Everything being equal, going to a higher gear ratio will drop your MPGs because you will have bigger cruising RPMs for a given speed. More than likely, you’ll have so much fun with your snappy acceleration that you might ride more aggressively, and further lower mileage. But hey, it’s a bike. Have fun with it and become glad you’re not worries.
Is it much easier to change the front or rear sprocket?
It really will depend on your cycle, but neither is typically very difficult to improve. Changing the chain may be the most complicated activity involved, thus if you’re changing only a sprocket and reusing your chain, that can be done whichever is preferred for you.
A significant note: going smaller in front will loosen the chain, and you’ll have to lengthen your wheelbase to make up for it; going up in the rear will furthermore shorten it. Understand how much room you must change your chain in any event before you elect to accomplish one or the other; and if in question, it’s your very best bet to change both sprockets and your chain all at once.