How To Choose Motorcycle Sprockets
Among the easiest ways to give your bike snappier acceleration and feel like it has a lot more power is a straightforward sprocket change. It’s a fairly easy job to do, however the hard portion is figuring out what size sprockets to replace your stock types with. We explain everything 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 normally translated into steering wheel speed by the bike. Changing sprocket sizes, the 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 a given bike or riding design, so if you’ve at any time found yourself wishing you had better acceleration, or found that your motorcycle lugs around at low speeds, you may should just alter your current equipment ratio into something that’s more suitable for you.
Example #1: Street
Understanding gearing ratios is the most complex component of choosing a sprocket combo, so we’ll start with a good example to illustrate the concept. My own motorcycle is usually a 2008 R1, and in inventory form it is geared very “high” in other words, geared so that it could reach very high speeds, but felt sluggish on the lower end.) This caused street riding to end up being a bit of a headache; I had to really ride the clutch out a good distance to get moving, could really only apply first and second equipment around city, and the engine experienced a little boggy at lower RPM’. What I needed was more acceleration to create my road riding more enjoyable, nonetheless it would come at the expense of some of my top quickness (which I’ not using on the road anyway.)
So let’s consider the factory set up on my bicycle, and understand why it sensed that way. The stock sprockets on my R1 are 17 teeth in front, and 45 pearly whites in the rear. Some simple math offers us the gearing ratio: 45/17=2.647. Now I’ve a baseline to work with. Since I want more acceleration, I’ll prefer a higher gear ratio than what I have, but without going also intense to where I’ll have uncontrollable acceleration, or where my RPM’s will be screaming at highway speeds.
Example #2: Dirt
Several of our team members here drive dirt, and they switch their set-ups based on the track or perhaps trails they’re likely to be riding. One of our personnel took his bicycle, a 2008 Kawasaki KX450, on a 280-mile Baja ride. As the KX450 is a large four-stroke with gobs of torque across the powerband, it already has a good amount of low-end grunt. But for a long trail ride like Baja in which a lot of floor has to be covered, he required an increased top speed to essentially haul across 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 a lower cruising RPM (or, in conditions of 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 recommended riding is on short, jumpy racetracks, where optimum drive is needed in short spurts to very clear jumps and electric power out of corners. To obtain the increased acceleration he needed 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 (basically about a 2% increase 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 about the apparatus ratio, and I have to arrive at a ratio that will assist me reach my objective. There are a variety of methods to do that. You’ll see a lot of talk on the internet about going “-1”, or “-1/+2” etc. By using these numbers, riders are usually expressing how many teeth they changed from share. On sport bikes, common mods are to move -1 in front, +2 or +3 in back, 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 inventory sprockets will be. At BikeBandit.com, we use actual sprocket sizes to point ratios, because all bikes will vary.
To revisit my example, a simple mod would be to move from a 17-tooth in leading to a 16-tooth. That could change 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 performed lower my top swiftness and threw off my speedometer (which may be adjusted; more on that soon after.) As you can see on the chart below, there are always a large number of possible combinations to reach at the ratio you really want, but your choices will be limited by what’s likely on your particular bike.
Variations
For a more extreme change, I could have attended a 15-tooth front? which would produce my ratio specifically 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 power across less pearly whites and around a tighter arc, increasing wear.
But remember, it’s about the ratio, and we are able to change how big is the rear sprocket to alter this ratio also. Consequently if we went down to a 16-tooth in the front, but at the same time went up to a 47-tooth in the rear, our new ratio will be 2.938; not quite as extreme. 16 in the front and 46 in again would be 2.875, a a smaller amount radical change, but still 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 on both sprockets and keep the same ratio, which some riders carry out to shave weight and reduce rotating mass while 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 possess as a baseline, know what your goal is, and adjust accordingly. It can help to search the web for the encounters of other riders with the same motorcycle, to check out what combos will be the most common. Additionally it is a good idea to make small adjustments at first, and work with them for some time on your preferred roads to find if you want how your motorcycle behaves with the brand new setup.
FAQ’s
There are a lot of questions we get asked relating to this topic, therefore here are some of the most instructive ones, answered.
When choosing a sprocket, what truly does 520, 525, and 530 mean?
Basically, this identifies the thickness of your sprockets and chain (called the “pitch”) 520 is 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 effectiveness of a high quality chain and sprockets, there is normally no danger in switching to the lighter 520 setup. Important note: often make sure you install components of the same pitch; they are not appropriate for each other! The best plan of action is to buy a conversion kit consequently all of your 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 is advisable to improve sprocket and chain parts as a set, because they put on as a set; in the event that you do this, we recommend a high-power aftermarket chain from a high brand like EK ,RK >, and DID
However, in many cases, it won’t hurt to change one sprocket (usually leading.) If your chain is certainly relatively new, it will not hurt it to change only one sprocket. Considering that a front sprocket is normally only $20-30, I would recommend changing it as an economical way to test a new gearing ratio, before you take the plunge and spend the amount of money to change both sprockets as well as your chain.
How does it affect my speed and speedometer?
It again depends upon your ratio, but both might generally always be altered. Since most riders opt for a higher gear ratio than stock, they’ll encounter a drop in leading acceleration, and a speedometer readout that says they are going faster than they are. Conversely, dropping the ratio could have the opposite pulley 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 should have bigger cruising RPMs for a given speed. Probably, you’ll have so very much fun with your snappy acceleration that you may ride more aggressively, and further lower mileage. But hey, it’s a bike. Have fun with it and be glad you’re not driving a car.
Is it easier to change leading or rear sprocket?
It really depends upon your bike, but neither is normally very difficult to change. Changing the chain may be the most complicated activity involved, and so if you’re changing simply a sprocket and reusing your chain, you can do whichever is most comfortable for you.
A significant note: going small in the front will loosen the chain, and you’ll have to lengthen your wheelbase to create up for it; going up in the trunk will similarly shorten it. Know how much room you should adjust your chain in any event before you elect to do one or the additional; and if in question, it’s your best bet to change both sprockets and your chain all at one time.
