SELECTING Motorcycle Sprockets
One of the easiest ways to give your bike snappier acceleration and feel just like it has much more power is a simple pulley sprocket change. It’s an easy job to do, however the hard part is figuring out what size sprockets to replace your stock ones 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 is translated into steering wheel speed by the cycle. Changing sprocket sizes, the front or rear, will change this ratio, and for that reason change just how your bike puts capacity to the ground. OEM gear ratios are not always ideal for confirmed bike or riding style, so if you’ve at any time found yourself wishing then you’ve got to acceleration, or found that your motorcycle lugs around at low speeds, you might simply need to alter your current equipment ratio into something that’s more well suited for you.
Example #1: Street
Understanding gearing ratios is the most complex part of choosing a sprocket combo, so we’ll start with a good example to illustrate the idea. My own bike is usually a 2008 R1, and in share form it is geared very “tall” in other words, geared so that it might reach very high speeds, but sensed sluggish on the lower end.) This caused road riding to become a bit of a hassle; I had to really ride the clutch out a good distance to get moving, could really only make use of first and second equipment around village, and the engine felt a little boggy at lower RPM’. What I required was more acceleration to create my street riding more enjoyable, nonetheless it would come at the trouble of some of my top velocity (which I’ not really using on the road anyway.)
So let’s consider the factory set up on my bike, and see why it felt that way. The stock sprockets on my R1 are 17 pearly whites in front, and 45 teeth in the rear. Some simple math gives us the gearing ratio: 45/17=2.647. Now I’ve a baseline to work with. Since I want more acceleration, I’ll want a higher equipment ratio than what I have, but without going too serious 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 trip dirt, and they modify their set-ups based on the track or trails they’re likely to be riding. One of our staff took his motorcycle, a 2008 Kawasaki KX450, on a 280-mile Baja ride. As the KX450 is definitely a huge four-stroke with gobs of torque over the powerband, it currently has a good amount of low-end grunt. But for a long trail drive like Baja where a lot of floor needs to be covered, he wanted a higher top speed to really haul across the desert. His alternative was to swap out the 50-tooth share backside sprocket with a 48-tooth Renthal Sprocket to improve speed and get yourself a lower cruising RPM (or, with regards 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 recommended riding is on short, jumpy racetracks, where optimum drive is needed in a nutshell spurts to distinct jumps and electric power out of corners. To find the increased acceleration he sought he geared up in the trunk, from the stock 49-tooth to a 50-tooth sprocket likewise from Renthal , increasing his final ratio from 3.769 to 3.846 (quite simply about a 2% upsurge in acceleration, just enough to fine tune the way the bike responds to the throttle.)
It’s All About The Ratio!
What’s vital that you remember is usually that it’s all about the gear ratio, and I have to arrive at a ratio that will help me reach my target. There are a variety of techniques to do that. You’ll see a large amount of talk on the internet about heading “-1”, or “-1/+2” and so forth. By using these numbers, riders are usually expressing how many pearly whites they changed from share. On sport bikes, common mods are to proceed -1 in the front, +2 or +3 in backside, or a combo of the two. The issue with that nomenclature is that it only takes on meaning relative to what size the stock sprockets happen to be. At BikeBandit.com, we use specific sprocket sizes to indicate ratios, because all bikes are different.
To revisit my case in point, a simple mod is always to go from a 17-tooth in the front to a 16-tooth. That could change my ratio from 2.647 to 2.813. I did this mod, and I experienced noticeably better acceleration, making my street riding easier, but it does lower my top speed and threw off my speedometer (which may be adjusted; more on that later on.) As you can plainly see on the chart below, there are a large number of possible combinations to reach at the ratio you need, but your options will be tied to what’s likely on your own particular bike.
Variations
For a far more extreme change, I possibly could have attended a 15-tooth front? which would produce my ratio precisely 3.0, but I thought that might be excessive for my taste. There are also some who advise against making big changes in leading, since it spreads the chain drive across less the teeth and around a tighter arc, increasing wear.
But remember, it’s all about the ratio, and we can change the size of the backside sprocket to improve this ratio also. And so if we went down to a 16-tooth in leading, but at the same time went up to 47-tooth in the rear, our new ratio will be 2.938; nearly as extreme. 16 in the front and 46 in back again will be 2.875, a much less radical change, but still a bit more than performing only the 16 in the front.
(Consider this: since the ratio is what determines how your cycle will behave, you could conceivably go down about both sprockets and keep carefully the same ratio, which some riders perform to shave weight and reduce rotating mass when the sprockets and chain spin.)
The important thing to keep in mind when choosing new sprockets is that it’s all about the ratio. Figure out what you have as a baseline, determine what your aim is, and adapt accordingly. It will help to search the web for the activities of various other riders with the same bike, to observe what combos will be the most common. It is also a good idea to make small adjustments at first, and operate with them for some time on your favorite roads to see if you like how your bike behaves with the brand new setup.
FAQ’s
There are a great number of questions we get asked relating to this topic, thus here are some of the very most instructive ones, answered.
When deciding on a sprocket, what does 520, 525, and 530 mean?
Basically, this refers to the thickness of your sprockets and chain (called the “pitch”) 520 may be the thinnest and lightest of the three, 525 is in the middle, and 530 may be the beefiest. A large number of OEM components are 525 or 530, but with the effectiveness of a top quality chain and sprockets, there is generally no danger in switching to the lighter 520 setup. Important note: at all times be sure to install parts of the same pitch; they are not appropriate for each other! The best plan of action is to get a conversion kit so all of your 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 improve sprocket and chain pieces as a established, because they dress in as a set; if you do this, we advise a high-strength aftermarket chain from a top company like EK ,RK >, and DID
However, in many cases, it won’t hurt to change one sprocket (usually the front.) If your chain can be relatively new, you won’t hurt it to change only one sprocket. Considering that a front side sprocket is normally only $20-30, I recommend changing it as an economical way to test a fresh gearing ratio, before you take the plunge and spend the money to improve both sprockets as well as your chain.
How does it affect my velocity and speedometer?
It again depends on your ratio, but both will generally be altered. Since most riders decide on a higher gear ratio than stock, they will encounter a drop in top quickness, and a speedometer readout that says they are going faster than they are. Conversely, dropping the ratio will have the contrary effect. Some riders obtain an add-on module to adjust the speedometer after modifying the drivetrain.
How does it affect my mileage?
Everything being equal, going to a higher gear ratio will drop your MPGs because you will have higher cruising RPMs for a given speed. More than likely, you’ll have so very much fun with your snappy acceleration that you might ride even 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 simpler to change leading or rear sprocket?
It really depends upon your motorcycle, but neither is typically very difficult to change. Changing the chain is the most complicated task involved, so if you’re changing just a sprocket and reusing your chain, you can do whichever is preferred for you.
An important note: going small in the front will loosen the chain, and you’ll need to lengthen your wheelbase to create up for it; going up in the rear will furthermore shorten it. Understand how much room you should change your chain in any event before you elect to accomplish one or the different; and if in question, it’s your very best bet to improve both sprockets and your chain all at one time.
