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January 7, 2020

How To Choose Motorcycle Sprockets
Among the easiest ways to give your bicycle snappier acceleration and feel just like it has far more power is a straightforward sprocket change. It’s a fairly easy 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, to put it simply, the ratio of teeth between the front and rear sprockets. This ratio determines how engine RPM is translated into steering wheel speed by the motorcycle. Changing sprocket sizes, front or rear, will change this ratio, and for that reason change the way your bike puts power to the bottom. OEM gear ratios aren’t always ideal for confirmed bike or riding style, so if you’ve ever found yourself wishing you had better acceleration, or discovered that your cycle lugs around at low speeds, you may should just alter your current gear ratio into something that’s more suited to you.
Example #1: Street
Understanding gearing ratios is the most complex component of choosing a sprocket combo, so we’ll focus on a good example to illustrate the concept. My own bike is usually a 2008 R1, and in stock form it is geared very “tall” basically, geared in such a way that it might reach very high speeds, but sensed sluggish on the lower end.) This caused street riding to become a bit of a hassle; I had to essentially ride the clutch out an excellent distance to get moving, could really only make use of first and second gear around area, and the engine experienced a little boggy at lower RPM’. What I required was more acceleration to create my street riding more enjoyable, but it would come at the trouble of some of my top swiftness (which I’ certainly not using on the street anyway.)
So let’s consider the factory set up on my motorcycle, and see why it experienced that way. The stock sprockets on my R1 are 17 tooth in front, and 45 the teeth 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 even more acceleration, I’ll really want a higher gear ratio than what I have, but without going as well excessive 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 transform their set-ups predicated on the track or trails they’re likely to be riding. One of our personnel took his motorcycle, a 2008 Kawasaki KX450, on a 280-mile Baja ride. Because the KX450 can be a huge four-stroke with gobs of torque over the powerband, it currently has lots of low-end grunt. But for a long trail trip like Baja in which a lot of ground needs to be covered, he needed an increased top speed to essentially haul across the desert. His choice was to swap out the 50-tooth stock rear sprocket with a 48-tooth Renthal Sprocket to improve speed and get a lower cruising RPM (or, with regards to gearing ratio, he gone from 3.846 down to 3.692.)
Another one of our team 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 short spurts to clear jumps and electricity out of corners. To get the increased acceleration he wanted he ready in the rear, from the stock 49-tooth to a 50-tooth sprocket likewise from Renthal , increasing his final ratio from 3.769 to 3.846 (basically 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 vital that you remember is usually that it’s about the gear ratio, and I must reach a ratio that will help me reach my objective. There are numerous of ways to do that. You’ll see a lot of talk on the net about going “-1”, or “-1/+2” etc. By using these figures, riders are usually expressing how many teeth they changed from stock. On sport bikes, common mods are to go -1 in the front, +2 or +3 in returning, or a combo of both. The difficulty with that nomenclature is definitely that it takes merely on meaning in accordance with what size the stock sprockets will be. At BikeBandit.com, we use precise sprocket sizes to point ratios, because all bikes will vary.
To revisit my case in point, a simple mod is always to proceed from a 17-tooth in leading to a 16-tooth. That would change my ratio from 2.647 to 2.813. I did so this mod, and I acquired noticeably better acceleration, making my street riding easier, but it have lower my top speed and threw off my speedometer (which can be adjusted; even 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 alternatives will be limited by what’s practical on your particular bike.
Variations
For a far more extreme change, I could have attended a 15-tooth front? which would generate my ratio accurately 3.0, but I thought that would be excessive for my tastes. There are also some who advise against producing big changes in the front, because it spreads the chain pressure across less tooth and around a tighter arc, increasing wear.
But remember, it’s about the ratio, and we can change the size of the rear sprocket to alter this ratio also. Consequently if we transpired to a 16-tooth in the front, but concurrently went up to 47-tooth in the rear, our new ratio would be 2.938; nearly as extreme. 16 in front and 46 in back will be 2.875, a a smaller amount radical change, but nonetheless a bit more than carrying out only the 16 in the front.
(Consider this: for the reason that ratio is what determines how your bicycle will behave, you could conceivably decrease in both sprockets and keep the same ratio, which some riders carry out to shave fat 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 all about the ratio. Figure out what you have as a baseline, know what your goal is, and adjust accordingly. It can help to search the web for the experience of different riders with the same cycle, to look at what combos are the most common. It is also smart to make small changes at first, and work with them for a while on your chosen roads to check out if you like how your bike behaves with the brand new setup.
FAQ’s
There are a great number of questions we get asked about this topic, so here are some of the most instructive ones, answered.
When choosing a sprocket, what really does 520, 525, and 530 mean?
Basically, this identifies 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 is the beefiest. A large number of OEM components will be 525 or 530, but with the effectiveness of a high quality chain and sprockets, there is often no danger in switching to the lighter 520 setup. Important note: constantly ensure you install parts of the same pitch; they are not appropriate for each other! The very best plan of action is to buy a conversion kit therefore all your components mate perfectly,
Do I have to switch both sprockets simultaneously?
This is a judgment call, and there are differing opinions. Generally, it really is advisable to change sprocket and chain elements as a set, because they dress in as a set; if you do this, we recommend a high-strength aftermarket chain from a top company like EK ,RK >, and DID
However, in many cases, it won’t harm to change one sprocket (usually the front.) If your chain is 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 inexpensive way to test a fresh gearing ratio, before you take the plunge and spend the amount of money to improve both sprockets and your chain.
How does it affect my velocity and speedometer?
It again is determined by your ratio, but both will generally end up being altered. Since most riders opt for a higher gear ratio than stock, they’ll encounter a drop in leading velocity, and a speedometer readout that says they go faster than they happen to be. Conversely, dropping the ratio could have the opposite effect. Some riders purchase an add-on module to change 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 larger cruising RPMs for confirmed speed. More than likely, you’ll have so very much fun with your snappy acceleration that you may ride even more aggressively, and further reduce mileage. But hey, it’s a bike. Enjoy it and become glad you’re not worries.
Is it much easier to change the front or rear sprocket?
It really depends on your bicycle, but neither is normally very difficult to change. Changing the chain is the most complicated job involved, and so if you’re changing just a sprocket and reusing your chain, that you can do whichever is preferred for you.
An important note: going smaller in the front will loosen the chain, and you’ll have to lengthen your wheelbase to make up for it; increasing in the rear will also shorten it. Understand how much room you should change your chain in any event before you elect to do one or the other; and if in uncertainty, it’s your best bet to change both sprockets as well as your chain all at once.