CHOOSING Motorcycle Sprockets
One of the easiest methods to give your bicycle snappier acceleration and feel like it has a lot more power is a straightforward sprocket change. It’s a simple job to do, but the hard component is determining what size sprockets to replace your stock types with. We explain it all here.
It’s ABOUT The Gearing Ratio
Your gearing ratio is, simply put, the ratio of teeth between your front and rear sprockets. This ratio determines how engine RPM is translated into wheel speed by the motorcycle. Changing sprocket sizes, front side or rear, will change this ratio, and therefore change just how your bike puts power 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 you had better acceleration, or discovered that your motorcycle lugs around at low speeds, you might simply need to alter your current gear ratio into something that’s more ideal for you.
Example #1: Street
Understanding gearing ratios may be the most complex portion of deciding on a sprocket combo, so we’ll start with an example to illustrate the idea. My own bike is definitely a 2008 R1, and in inventory form it is geared very “tall” basically, geared in such a way that it might reach high speeds, but experienced sluggish on the low end.) This caused street riding to be a bit of a hassle; I had to essentially ride the clutch out a good distance to get going, could really only employ first and second equipment around area, and the engine sensed a little boggy at lower RPM’. What I needed was more acceleration to create my street riding more enjoyable, but it would arrive at the expense of a few of my top swiftness (which I’ certainly not using on the street anyway.)
So let’s consider the factory setup on my bike, and understand why it felt that way. The stock sprockets on my R1 are 17 the teeth in front, and 45 the teeth in the rear. Some simple math provides us the gearing ratio: 45/17=2.647. Now I’ve a baseline to work with. Since I want even more acceleration, I’ll wish a higher equipment ratio than what I’ve, but without going too serious to where I’ll have uncontrollable acceleration, or where my RPM’s will always be screaming at highway speeds.
Example #2: Dirt
Several of we members here ride dirt, and they alter their set-ups predicated on the track or trails they’re likely to be riding. One of our personnel took his bicycle, a 2008 Kawasaki KX450, on a 280-mile Baja ride. Because the KX450 is a huge four-stroke with gobs of torque across the powerband, it already has lots of low-end grunt. But for a long trail drive like Baja in which a lot of surface should be covered, he sought a higher top speed to essentially haul over the desert. His answer 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, when it comes to gearing ratio, he gone from 3.846 down to 3.692.)
Another one of we members rides a 2003 Yamaha YZ125 a light, revvy two-stroke, completely different from the big KX450. His preferred riding is on brief, jumpy racetracks, where optimum drive is needed in short spurts to apparent jumps and vitality out of corners. To get the increased acceleration he wanted he ready in the trunk, from the stock 49-tooth to a 50-tooth sprocket likewise from Renthal , increasing his last ratio from 3.769 to 3.846 (in other words about a 2% increase in acceleration, sufficient to fine tune the way the bike responds to the throttle.)
It’s ABOUT The Ratio!
What’s important to remember is certainly that it’s all about the apparatus ratio, and I must reach a ratio that will help me reach my target. There are a variety of techniques to do this. You’ll see a lot of talk on the web about going “-1”, or “-1/+2” etc. By using these figures, riders are typically expressing how many teeth they changed from share. On sport bikes, prevalent mods are to head out -1 in front, +2 or +3 in again, or a combo of the two. The issue with that nomenclature can be that it only takes on meaning relative to what size the inventory sprockets happen to be. At BikeBandit.com, we use actual sprocket sizes to indicate ratios, because all bikes will vary.
To revisit my case in point, a simple mod would be to proceed from a 17-tooth in leading to a 16-tooth. That could change my ratio from 2.647 to 2.813. I did so this mod, and I possessed noticeably better acceleration, producing my street riding a lot easier, but it does lower my top rate and threw off my speedometer (which is often adjusted; more on that soon after.) As you can see on the chart below, there are a large number of possible combinations to arrive at the ratio you desire, but your options will be limited by what’s conceivable on your own particular bike.
For a more extreme change, I could have attended a 15-tooth front? which would make my ratio specifically 3.0, but I thought that would be excessive for my tastes. There are also some who advise against making big changes in the front, since it spreads the chain induce across less teeth and around a tighter arc, increasing wear.
But remember, it’s all about the ratio, and we are able to change the size of the back sprocket to improve this ratio also. And so if we transpired to a 16-tooth in the front, but simultaneously went up to 47-tooth in the trunk, our new ratio will be 2.938; not quite as extreme. 16 in the front and 46 in again will be 2.875, a much less radical change, but still a bit more than undertaking only the 16 in the front.
(Consider this: since the ratio is what determines how your bicycle will behave, you could conceivably go down upon both sprockets and keep the same ratio, which some riders do to shave fat and reduce rotating mass as the sprockets and chain spin.)
The important thing to bear in mind when selecting new sprockets is that it’s about the ratio. Figure out what you have as a baseline, determine what your goal is, and modify accordingly. It will help to find the web for the encounters of other riders with the same cycle, to discover what combos are the most common. It is also smart to make small adjustments at first, and operate with them for a while on your selected roads to discover if you want how your bike behaves with the new setup.
There are a great number of questions we get asked about this topic, so here are a few of the very most instructive ones, answered.
When choosing a sprocket, what will 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 happen to be 525 or 530, but with the effectiveness of a top quality chain and sprockets, there is usually no danger in switching to the lighter 520 setup. Important note: always be sure you install pieces of the same pitch; they aren’t compatible with each other! The best course 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 really is advisable to change sprocket and chain elements as a collection, because they have on as a set; if you do this, we suggest a high-strength aftermarket chain from a top manufacturer like EK ,RK >, and DID
However, in many cases, it won’t hurt to improve one sprocket (usually leading.) If your chain can be relatively new, it will not hurt it to improve only one sprocket. Considering that a front sprocket is normally only $20-30, I recommend changing it as an inexpensive way to check a new gearing ratio, before you make the leap and spend the amount of money to improve both sprockets and your chain.
How does it affect my rate and speedometer?
It again depends on your ratio, but both definitely will generally be altered. Since most riders decide on a higher gear ratio than stock, they’ll experience a drop in best quickness, and a speedometer readout that says they are going faster than they will be. Conversely, dropping the ratio could have the contrary effect. Some riders invest in an add-on module to adjust the speedometer after modifying the drivetrain.
How does it affect my mileage?
All things being equal, likely to an increased gear ratio will drop your MPGs because you will have larger cruising RPMs for confirmed speed. More than likely, you’ll have so very much fun with your snappy acceleration that you may ride more aggressively, and further decrease mileage. But hey, it’s a bike. Have fun with it and become glad you’re not driving a car.
Is it easier to change the front or rear sprocket?
It really depends on your cycle, but neither is normally very difficult to improve. Changing the chain may be the most complicated process involved, thus if you’re changing just a sprocket and reusing your chain, that can be done whichever is most comfortable for you.
A significant note: going more compact in the front will loosen the chain, and you’ll need to lengthen your wheelbase to create up for it; increasing in the rear will also shorten it. Know how much room you have to adapt your chain in any event before you elect to do one or the different; and if in hesitation, it’s your best bet to change both sprockets as well as your chain all at one time.
CHOOSING Motorcycle Sprockets