HOW TO PICK Motorcycle Sprockets
Among the easiest ways to give your bicycle snappier acceleration and feel just like it has far more power is a straightforward pulley sprocket change. It’s a simple job to do, but the hard part is figuring out what size sprockets to replace your stock ones 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 the front and rear sprockets. This ratio determines how engine RPM is normally translated into wheel speed by the bike. Changing sprocket sizes, front side or rear, will change this ratio, and for that reason change the way your bike puts capacity to the ground. OEM gear ratios are not always ideal for a given bike or riding design, so if you’ve ever before found yourself wishing you had better 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 well suited for you.
Example #1: Street
Understanding gearing ratios is the most complex portion of deciding on a sprocket combo, so we’ll start with a good example to illustrate the concept. My own motorcycle is a 2008 R1, and in share form it is geared very “tall” in other words, geared so that it could reach high speeds, but felt sluggish on the low end.) This caused road riding to always be a bit of a hassle; I had to really trip the clutch out an excellent distance to get going, could really only use first and second gear around town, and the engine sensed just a little boggy at lower RPM’. What I required was more acceleration to create my street riding more enjoyable, nonetheless it would arrive at the expense of a few of my top acceleration (which I’ not really using on the road anyway.)
So let’s look at the factory set up on my bicycle, and understand why it felt that way. The stock sprockets on my R1 are 17 tooth in the 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 work with. Since I want even more acceleration, I’ll desire a higher gear ratio than what I’ve, but without going as well severe to where I’ll possess uncontrollable acceleration, or where my RPM’s will always be screaming at highway speeds.
Example #2: Dirt
Several of our team members here trip dirt, and they alter their set-ups based on the track or perhaps trails they’re going to be riding. One of our personnel took his bike, a 2008 Kawasaki KX450, on a 280-mile Baja ride. As the KX450 is usually a large four-stroke with gobs of torque over the powerband, it currently has a lot of low-end grunt. But for a long trail drive like Baja in which a lot of ground has to be covered, he wanted an increased top speed to essentially haul across the desert. His remedy was to swap out the 50-tooth inventory rear sprocket with a 48-tooth Renthal Sprocket to improve speed and get a lower cruising RPM (or, with regards to 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, very different from the big KX450. His preferred riding is on short, jumpy racetracks, where maximum drive is needed in short spurts to apparent jumps and vitality out of corners. To achieve the increased acceleration he sought he ready in the rear, from the stock 49-tooth to a 50-tooth sprocket likewise from Renthal , raising his final ratio from 3.769 to 3.846 (put simply about a 2% increase in acceleration, sufficient to fine tune what sort of 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 have to reach a ratio that can help me reach my goal. There are numerous of techniques to do this. You’ll see a lot of talk on the net about heading “-1”, or “-1/+2” and so forth. By using these numbers, riders are usually expressing how many teeth they changed from share. On sport bikes, prevalent mods are to proceed -1 in the front, +2 or +3 in again, or a blend of the two. The trouble with that nomenclature is normally that it takes merely on meaning relative to what size the inventory sprockets are. At BikeBandit.com, we use actual sprocket sizes to indicate ratios, because all bikes are different.
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 modify my ratio from 2.647 to 2.813. I did this mod, and I possessed noticeably better acceleration, producing my street riding a lot easier, but it performed lower my top quickness and threw off my speedometer (which can be adjusted; more on that after.) As you can see on the chart below, there are a large number of possible combinations to reach 
at the ratio you prefer, but your options will be tied to what’s practical 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 might be excessive for my tastes. There are also some who advise against producing big changes in the front, because it spreads the chain force across less pearly whites and around a tighter arc, increasing wear.
But remember, it’s all about the ratio, and we can change how big is the rear sprocket to alter this ratio also. So if we went down to a 16-tooth in leading, 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 back again will be 2.875, a less radical change, but still a little more than undertaking only the 16 in the front.
(Consider this: because the ratio is what determines how your bike will behave, you could conceivably decrease upon both sprockets and keep the same ratio, which some riders perform to shave pounds and reduce rotating mass seeing that the sprockets and chain spin.)
The important thing to keep in mind when selecting new sprockets is that it’s about the ratio. Find out what you possess as a baseline, determine what your target is, and change accordingly. It can help to search the web for the experience of different riders with the same cycle, to discover what combos are the most common. It is also a good idea to make small adjustments at first, and run with them for some time on your favorite roads to find if you like how your motorcycle behaves with the new setup.
FAQ’s
There are a lot of questions we get asked about this topic, so here are some of the most instructive ones, answered.
When deciding on a sprocket, what will 520, 525, and 530 mean?
Basically, this refers to 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 is the beefiest. Many 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: always be sure to install parts of the same pitch; they aren’t compatible with each other! The best plan of action is to buy a conversion kit hence all your components mate perfectly,
Do I must switch both sprockets simultaneously?
This is a judgment call, and there are differing opinions. Generally, it is advisable to improve sprocket and chain parts as a establish, because they put on as a set; if you do this, we advise a high-durability aftermarket chain from a top brand like EK ,RK >, and DID
However, in many cases, it won’t harm to improve one sprocket (usually the front.) If your chain is usually relatively new, it will not hurt it to improve only one sprocket. Due to the fact a front side sprocket is normally only $20-30, I recommend changing it as an economical way to check a new gearing ratio, before you make the leap and spend the amount of money to improve both sprockets as well as your chain.
How will it affect my velocity and speedometer?
It again depends upon your ratio, but both might generally be altered. Since most riders opt for a higher equipment ratio than stock, they’ll encounter a drop in leading velocity, 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 acquire an add-on module to change the speedometer after modifying the drivetrain.
How does it affect my mileage?
Everything being equal, likely to a higher gear ratio will drop your MPGs because you should have larger cruising RPMs for a given speed. Probably, you’ll have so 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 depends upon your motorcycle, but neither is normally very difficult to change. Changing the chain may be the most complicated task involved, hence if you’re changing simply a sprocket and reusing your chain, you can do whichever is most comfortable for you.
A significant note: going smaller in the front will loosen the chain, and you’ll have to lengthen your wheelbase to create up for it; going up in the rear will likewise shorten it. Understand how much room you have to adjust your chain either way before you elect to do one or the various other; and if in hesitation, it’s your very best bet to improve both sprockets as well as your chain all at once.
