SELECTING Motorcycle Sprockets
One of the easiest ways to give your motorcycle snappier acceleration and feel just like it has far more power is a straightforward pulley sprocket change. It’s a fairly easy job to do, but the hard portion is determining what size sprockets to displace your stock ones 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 usually translated into wheel speed by the bicycle. Changing sprocket sizes, entrance or rear, will change this ratio, and therefore change the way your bike puts power to the bottom. OEM gear ratios aren’t always ideal for a given bike or riding style, so if you’ve at any time 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 suitable for you.
Example #1: Street
Understanding gearing ratios is the most complex part of choosing a sprocket combo, so we’ll focus on a good example to illustrate the idea. My own motorcycle is certainly a 2008 R1, and in stock form it is geared very “tall” in other words, geared so that it might reach high speeds, but experienced sluggish on the lower end.) This caused street riding to become a bit of a hassle; I had to really trip the clutch out a good distance to get going, could really only make use of first and second equipment around community, and the engine felt a little boggy at lower RPM’. What I necessary was more acceleration to make my road riding more enjoyable, but it would arrive at the expense of a few of my top speed (which I’ not using on the street anyway.)
So let’s look at the factory set up on my cycle, and see why it experienced that way. The share sprockets on my R1 are 17 the teeth in the front, and 45 teeth in the rear. Some simple math provides us the gearing ratio: 45/17=2.647. Now I’ve a baseline to utilize. Since I want more acceleration, I’ll want a higher equipment ratio than what I’ve, but without going too 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 we members here trip dirt, and they modify their set-ups based on the track or trails they’re going to be riding. One of our staff took his bicycle, a 2008 Kawasaki KX450, on a 280-mile Baja ride. As the KX450 is a big four-stroke with gobs of torque across the powerband, it already has lots of low-end grunt. But for a long trail trip like Baja where a lot of surface has to be covered, he needed a higher 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 increase speed and get a lower cruising RPM (or, when it comes to gearing ratio, he went from 3.846 right down to 3.692.)
Another one of we members rides a 2003 Yamaha YZ125 a light, revvy two-stroke, very different from the big KX450. His desired riding is on brief, jumpy racetracks, where optimum drive is needed in a nutshell spurts to obvious jumps and electricity out of corners. To obtain the increased acceleration he desired he geared up in the trunk, from the stock 49-tooth to a 50-tooth sprocket likewise from Renthal , raising his last ratio from 3.769 to 3.846 (basically about a 2% upsurge in acceleration, sufficient to fine tune the way the bike responds to the throttle.)
It’s All About The Ratio!
What’s important to remember is certainly that it’s about the gear ratio, and I have to arrive at a ratio that can help me reach my target. There are numerous of techniques to do this. You’ll see a lot of talk on the web about heading “-1”, or “-1/+2” and so forth. By using these numbers, riders are usually expressing 
how many the teeth they changed from share. On sport bikes, common mods are to move -1 in the front, +2 or +3 in again, or a combination of the two. The trouble with that nomenclature can be that it only takes on meaning in accordance with what size the share sprockets are. At BikeBandit.com, we use actual sprocket sizes to point ratios, because all bikes are different.
To revisit my case in point, a simple mod is always to move from a 17-tooth in leading to a 16-tooth. That could transform my ratio from 2.647 to 2.813. I did so this mod, and I experienced noticeably better acceleration, making my street riding easier, but it did lower my top velocity and threw off my speedometer (that 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 wish, but your choices will be tied to what’s conceivable on your particular bike.
Variations
For a far more extreme change, I could have gone to a 15-tooth front? which would make my ratio precisely 3.0, but I thought that would be excessive for my tastes. There are also some who advise against making big changes in the front, since it spreads the chain push across less pearly whites 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 back sprocket to alter this ratio also. So if we transpired to a 16-tooth in leading, but at the same time went up to 47-tooth in the trunk, our new ratio will be 2.938; nearly as extreme. 16 in the front and 46 in back again will be 2.875, a fewer radical change, but nonetheless a bit more than undertaking only the 16 in the front.
(Consider this: because the ratio is what determines how your cycle will behave, you could conceivably go down on both sprockets and keep carefully the same ratio, which some riders carry out to shave weight and reduce rotating mass seeing that the sprockets and chain spin.)
The important thing to bear in mind when selecting new sprockets is that it’s all about the ratio. Find out what you possess as a baseline, know what your objective is, and adapt accordingly. It will help to search the net for the activities of different riders with the same cycle, to look at what combos are the most common. Additionally it is smart to make small improvements at first, and run with them for a while on your chosen roads to check out if you like how your bicycle behaves with the new setup.
FAQ’s
There are a lot of questions we get asked relating to this topic, so here are a few 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 middle, 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 usually no danger in switching to the lighter 520 setup. Important note: usually make sure you install components of the same pitch; they are not appropriate for each other! The very best plan of action is to get a conversion kit consequently your components mate perfectly,
Do I have to switch both sprockets at the same time?
This is a judgment call, and there are differing opinions. Generally, it is advisable to improve sprocket and chain pieces as a placed, because they use as a set; in the event that you do this, we recommend a high-power aftermarket chain from a top brand like EK ,RK >, and DID
However, in many cases, it won’t hurt to improve one sprocket (usually the front.) If your chain is certainly relatively new, you won’t hurt it to change only one sprocket. Considering that a entrance sprocket is typically only $20-30, I would recommend changing it as an inexpensive way to check a new gearing ratio, before you make the leap and spend the money to change both sprockets and your chain.
How will it affect my speed and speedometer?
It again will depend on your ratio, but both will certainly generally become altered. Since the majority of riders decide on a higher equipment ratio than stock, they will encounter a drop in best acceleration, and a speedometer readout that says they go faster than they are. Conversely, dropping the ratio will have the contrary effect. Some riders order an add-on module to change the speedometer after modifying the drivetrain.
How will it affect my mileage?
Everything being equal, likely to an increased gear ratio will drop your MPGs because you will have higher cruising RPMs for a given speed. More than likely, you’ll have so much fun with your snappy acceleration that you might ride 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 easier to change the front or rear sprocket?
It really depends on your cycle, but neither is typically very difficult to improve. Changing the chain may be the most complicated job involved, so if you’re changing just a sprocket and reusing your chain, that you can do whichever is most comfortable for you.
An important note: going small in front will loosen the chain, and you’ll have to lengthen your wheelbase to make up for it; going up in the trunk will furthermore shorten it. Understand how much room you must alter your chain in any event before you elect to accomplish one or the additional; and if in uncertainty, it’s your best bet to change both sprockets and your chain all at one time.
