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CHOOSING Motorcycle Sprockets
Among the easiest ways to give your motorcycle snappier acceleration and feel just like it has a lot more power is a straightforward sprocket change. It’s an easy job to do, but the hard part is figuring out what size sprockets to replace your stock types with. We explain it all 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 definitely translated into steering wheel speed by the bike. Changing sprocket sizes, entrance or rear, changes this ratio, and therefore change the way your bike puts power to the bottom. OEM gear ratios aren’t always ideal for confirmed bike or pulley riding design, so if you’ve at any time found yourself wishing then you’ve got to acceleration, or found that your cycle lugs around at low speeds, you may simply need to alter your current gear ratio into something that’s more suited to you.
Example #1: Street
Understanding gearing ratios may be the most complex portion of choosing a sprocket combo, so we’ll start with an example to illustrate the concept. My own bike is certainly a 2008 R1, and in inventory form it is geared very “high” basically, geared in such a way that it could reach high speeds, but sensed sluggish on the low end.) This caused street riding to always be a bit of a hassle; I had to really drive the clutch out a good distance to get going, could really only employ first and second equipment around town, and the engine experienced just a little boggy at lower RPM’. What I necessary was more acceleration to make my street riding more enjoyable, but it would arrive at the expense of some of my top speed (which I’ not really using on the road anyway.)
So let’s consider the factory setup on my bike, and see why it sensed that way. The inventory sprockets on my R1 are 17 tooth in front, and 45 pearly whites 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 want a higher gear ratio than what I have, but without going too serious to where I’ll possess uncontrollable acceleration, or where my RPM’s will always be screaming at highway speeds.
Example #2: Dirt
Several of we members here drive dirt, and they adjust their set-ups based on the track or trails they’re going to be riding. One of our personnel took his motorcycle, a 2008 Kawasaki KX450, on a 280-mile Baja ride. As the KX450 is definitely a big four-stroke with gobs of torque across the powerband, it currently has a good amount of low-end grunt. But for a long trail trip like Baja where a lot of surface needs to be covered, he required an increased top speed to really haul across the desert. His option was to swap out the 50-tooth stock backside sprocket with a 48-tooth Renthal Sprocket to increase speed and get yourself a lower cruising RPM (or, when it comes to gearing ratio, he proceeded to go from 3.846 right 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 favored riding is on short, jumpy racetracks, where optimum drive is needed in short spurts to very clear jumps and electricity out of corners. To find the increased acceleration he required he geared up in the rear, 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 what sort of bike responds to the throttle.)
It’s All About The Ratio!
What’s important to remember is certainly that it’s about the apparatus ratio, and I have to arrive at a ratio that will help me reach my goal. There are a variety of techniques to do this. You’ll see a lot of talk on the net about going “-1”, or “-1/+2” and so on. By using these numbers, riders are typically expressing how many teeth they changed from stock. On sport bikes, prevalent mods are to go -1 in the front, +2 or +3 in backside, or a mixture of the two. The issue with that nomenclature is usually that it only takes on meaning relative to what size the share sprockets are. At BikeBandit.com, we use precise sprocket sizes to indicate ratios, because all bikes are different.
To revisit my case in point, a simple mod is always to choose from a 17-tooth in the front to a 16-tooth. That could alter my ratio from 2.647 to 2.813. I did so this mod, and I experienced noticeably better acceleration, producing my street riding a lot easier, but it do lower my top speed and threw off my speedometer (which is often adjusted; more on that soon after.) As you can plainly see on the chart below, there are always a large number of possible combinations to reach at the ratio you prefer, but your options will be limited by what’s conceivable on your own particular bike.
Variations
For a far more extreme change, I could have gone to a 15-tooth front? which would produce my ratio accurately 3.0, but I thought that might be excessive for my tastes. There are also some who advise against making big changes in leading, since it spreads the chain power across less the 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 rear sprocket to alter this ratio also. Hence if we went down to a 16-tooth in the front, but concurrently went up to a 47-tooth in the trunk, our new ratio would be 2.938; nearly as extreme. 16 in front and 46 in back will be 2.875, a significantly less radical change, but still a bit more than carrying out only the 16 in front.
(Consider this: as the ratio is what determines how your motorcycle will behave, you could conceivably decrease about both sprockets and keep the same ratio, which some riders do to shave pounds and reduce rotating mass as the sprockets and chain spin.)
The important thing to keep in mind when choosing new sprockets is that it’s all about the ratio. Find out what you have as a baseline, determine what your target is, and modify accordingly. It can help to search the net for the activities of other riders with the same cycle, to see what combos are the most common. It is also a good idea to make small adjustments at first, and work with them for a while on your favorite roads to observe if you like how your bicycle behaves with the brand new setup.
FAQ’s
There are a lot of questions we get asked concerning this topic, hence here are a few 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 centre, and 530 may be 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 generally no danger in switching to the lighter 520 setup. Important note: constantly ensure you install pieces of the same pitch; they aren’t appropriate for each other! The best course of action is to buy a conversion kit so your entire components mate perfectly,
Do I must switch both sprockets at the same time?
That is a judgment call, and there are differing opinions. Generally, it really is advisable to change sprocket and chain components as a collection, because they dress in as a set; if you do this, we suggest a high-durability aftermarket chain from a top brand like EK ,RK >, and DID
However, oftentimes, 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. Due to the fact a entrance sprocket is typically only $20-30, I recommend changing it as an inexpensive way to check a new gearing ratio, before you take the plunge and spend the money to change both sprockets as well as your chain.
How does it affect my rate and speedometer?
It again depends on your ratio, but both will certainly generally always be altered. Since many riders opt for a higher gear ratio than stock, they’ll experience a drop in best acceleration, and a speedometer readout that says they are going faster than they happen to be. Conversely, dropping the ratio will have the opposite effect. Some riders purchase an add-on module to adjust the speedometer after modifying the drivetrain.
How does it affect my mileage?
Everything being equal, likely to an increased gear ratio will drop your MPGs because you should have bigger cruising RPMs for a given speed. More than likely, you’ll have so much fun with your snappy acceleration that you may ride even more aggressively, and further reduce mileage. But hey, it’s a bike. Have fun with it and be glad you’re not driving a car.
Is it simpler to change leading or rear sprocket?
It really depends on your bicycle, but neither is typically very difficult to improve. Changing the chain is the most complicated activity involved, consequently if you’re changing only a sprocket and reusing your chain, that you can do whichever is preferred for you.
An important note: going more compact in front will loosen the chain, and you’ll need to lengthen your wheelbase to create up for it; going up in the trunk will likewise shorten it. Know how much room you must adjust your chain in any event before you elect to do one or the additional; and if in uncertainty, it’s your best bet to improve both sprockets and your chain all at once.