HOW TO PICK Motorcycle Sprockets
Among the easiest ways to give your motorcycle snappier acceleration and feel like it has far more power is a simple sprocket change. It’s a fairly easy job to do, but the hard portion is figuring out what size sprockets to replace your stock ones with. We explain it all here.
It’s All About The Gearing Ratio
Your gearing ratio is, to put it simply, the ratio of teeth between your front and rear sprockets. This ratio determines how engine RPM is translated into wheel speed by the bicycle. Changing sprocket sizes, front side or rear, changes this ratio, and for that reason change the way your bike puts power to the ground. OEM gear ratios are not always ideal for confirmed bike or riding design, so if you’ve ever before found yourself wishing you had better acceleration, or found that your bike lugs around at low speeds, you may 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 component of choosing a sprocket combo, so we’ll focus on an example to illustrate the concept. My own bike is normally a 2008 R1, and in share form it really is geared very “high” put simply, geared in such a way that it might reach very high speeds, but felt sluggish on the low end.) This caused street riding to become a bit of a hassle; I had to really drive the clutch out an excellent distance to get moving, could really only employ first and second equipment around city, and the engine sensed a little boggy at lower RPM’. What I necessary was more acceleration to make my street riding more enjoyable, but it would come at the trouble of some of my top velocity (which I’ certainly not using on the street anyway.)
So let’s consider the factory create on my cycle, and understand why it felt that way. The stock sprockets on my R1 are 17 the teeth in the front, and 45 pearly whites in the rear. Some simple math offers us the gearing ratio: 45/17=2.647. Now I have a baseline to utilize. Since I want more acceleration, I’ll wish a higher equipment ratio than what I have, but without going also severe to where I’ll have uncontrollable acceleration, or where my RPM’s will become screaming at highway speeds.
Example #2: Dirt
Several of our team members here trip dirt, and they change their set-ups based 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 definitely a big four-stroke with gobs of torque over the powerband, it already has a good amount of low-end grunt. But also for a long trail trip like Baja where a lot of floor must be covered, he desired an increased top speed to essentially haul across the desert. His remedy was to swap out the 50-tooth stock rear end sprocket with a 48-tooth Renthal Sprocket to increase speed and get yourself a lower cruising RPM (or, in terms of gearing ratio, he proceeded to go from 3.846 down to 3.692.)
Another one of our team 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 maximum drive is needed in short spurts to obvious jumps and electricity out of corners. To find the increased acceleration he wanted he geared up in the trunk, from the stock 49-tooth to a 50-tooth sprocket also from Renthal , raising his final ratio from 3.769 to 3.846 (in other words about a 2% upsurge in acceleration, sufficient to fine tune what sort of bike responds to the throttle.)
It’s All About The Ratio!
What’s important to remember is usually that it’s about the gear ratio, and I have to reach a ratio that will help me reach my goal. There are many of methods to do that. You’ll see a large amount of talk on the net about heading “-1”, or “-1/+2” and so forth. By using these figures, riders are typically expressing how many teeth they changed from stock. On sport bikes, common mods are to get -1 in the front, +2 or +3 in rear, or a blend of 
the two. The issue with that nomenclature is usually that it takes merely on meaning in accordance with what size the share sprockets happen to be. At BikeBandit.com, we use specific sprocket sizes to point ratios, because all bikes will vary.
To revisit my example, 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 had noticeably better acceleration, producing my street riding a lot easier, but it have lower my top rate and threw off my speedometer (which is often adjusted; even more on that afterwards.) As you can plainly see on the chart below, there are always a large number of possible combinations to reach at the ratio you need, but your alternatives will be limited by what’s possible on your own particular bike.
Variations
For a more extreme change, I possibly could have attended a 15-tooth front? which would make my ratio accurately 3.0, but I thought that would be excessive for my style. Additionally, there are some who advise against making big changes in the front, since it spreads the chain force across less tooth and around a tighter arc, increasing wear.
But remember, it’s all about the ratio, and we can change how big is the backside sprocket to improve this ratio also. Hence if we went down to a 16-tooth in leading, but concurrently 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 returning would be 2.875, a a smaller amount radical change, but still a bit more than performing only the 16 in front.
(Consider this: for the reason that ratio is what determines how your motorcycle will behave, you could conceivably go down in both sprockets and keep carefully the same ratio, which some riders do to shave weight and reduce rotating mass seeing that the sprockets and chain spin.)
The important thing to keep in mind when choosing new sprockets is that it’s about the ratio. Figure out what you have as a baseline, determine what your goal is, and change accordingly. It can help to search the net for the encounters of different riders with the same bike, to check out what combos are the most common. Additionally it is a good idea to make small changes at first, and operate with them for a while on your preferred roads to find if you want how your bike behaves with the new setup.
FAQ’s
There are a lot of questions we get asked concerning this topic, hence here are some of the most instructive ones, answered.
When choosing 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 centre, and 530 may be the beefiest. Many OEM components are 525 or 530, but with the strength of a high quality chain and sprockets, there is usually no danger in switching to the lighter 520 setup. Important note: generally be sure to install components of the same pitch; they are not appropriate for each other! The very best course of action is to buy a conversion kit so your components mate perfectly,
Do I have to switch both sprockets as well?
That is a judgment call, and there are differing opinions. Generally, it really is advisable to change sprocket and chain pieces as a established, because they wear as a set; if you do this, we recommend a high-power aftermarket chain from a top brand like EK ,RK >, and DID
However, oftentimes, it won’t harm to change one sprocket (usually leading.) If your chain is certainly relatively new, it will not hurt it to improve only one sprocket. Considering that a the 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 money to improve both sprockets and your chain.
How does it affect my swiftness and speedometer?
It again will depend on your ratio, but both might generally be altered. Since most riders decide on a higher equipment ratio than stock, they’ll experience a drop in leading rate, and a speedometer readout that says they go faster than they will be. Conversely, dropping the ratio could have the contrary effect. Some riders purchase an add-on module to adapt the speedometer after modifying the drivetrain.
How will it affect my mileage?
All things 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 may ride more aggressively, and further reduce mileage. But hey, it’s a bike. Have fun with it and be glad you’re not worries.
Is it simpler to change leading or rear sprocket?
It really will depend on your bicycle, but neither is typically very difficult to improve. Changing the chain is the most complicated job involved, and so if you’re changing simply a sprocket and reusing your chain, that you can do whichever is most comfortable for you.
An important note: going scaled-down in front will loosen the chain, and you’ll need to lengthen your wheelbase to make up for it; going up in the rear will similarly shorten it. Know how much room you have to adapt your chain either way before you elect to do one or the additional; and if in uncertainty, it’s your very best bet to change both sprockets and your chain all at one time.