How To Choose Motorcycle Sprockets
One of the easiest methods 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, but the hard portion 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 wheel speed by the cycle. Changing sprocket sizes, the front or rear, will change this ratio, and therefore change the way your bike puts capacity to the ground. OEM gear ratios aren’t always ideal for confirmed bike or riding design, so if you’ve ever found yourself wishing you had better acceleration, or discovered that your motorcycle lugs around at low speeds, you might 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 start with an example to illustrate the idea. My own bike is a 2008 R1, and in stock form it is geared very “tall” in other words, geared so that it could reach high speeds, but experienced sluggish on the lower end.) This caused pulley street riding to become a bit of a hassle; I had to really trip the clutch out an excellent distance to get moving, could really only make use of first and second equipment around village, and the engine experienced just 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 some of my top velocity (which I’ not using on the street anyway.)
So let’s look at the factory setup on my motorcycle, and see why it sensed that way. The inventory sprockets on my R1 are 17 the teeth in the front, and 45 tooth in the rear. Some simple math offers us the gearing ratio: 45/17=2.647. Now I’ve a baseline to utilize. Since I want more acceleration, I’ll prefer a higher equipment ratio than what I’ve, but without going as well serious to where I’ll possess uncontrollable acceleration, or where my RPM’s will be screaming at highway speeds.
Example #2: Dirt
Several of we members here trip dirt, and they alter their set-ups based on the track or trails they’re likely to be riding. One of our staff took his bike, 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 lots of low-end grunt. But for a long trail drive like Baja where a lot of surface has to be covered, he wished a higher top speed to essentially haul over the desert. His remedy was to swap out the 50-tooth share rear end sprocket with a 48-tooth Renthal Sprocket to improve speed and get yourself a lower cruising RPM (or, with regards 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, completely different from the big KX450. His favored riding is on short, jumpy racetracks, where maximum drive is needed in short spurts to obvious jumps and ability out of corners. To find the increased acceleration he needed he geared up in the trunk, from the stock 49-tooth to a 50-tooth sprocket likewise from Renthal , increasing his last 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 that it’s all about the gear ratio, and I have to arrive at a ratio that can help me reach my goal. There are numerous of techniques to do this. You’ll see a lot of talk online about heading “-1”, or “-1/+2” etc. By using these statistics, riders are usually expressing how many pearly whites they changed from share. On sport bikes, common mods are to get -1 in front, +2 or +3 in again, or a mixture of both. The difficulty with that nomenclature is certainly that it takes merely on meaning relative to what size the share sprockets are. At BikeBandit.com, we use actual sprocket sizes to point ratios, because all bikes will vary.
To revisit my example, a simple mod is always to head out from a 17-tooth in leading to a 16-tooth. That would transform my ratio from 2.647 to 2.813. I did so this mod, and I got noticeably better acceleration, making my street riding easier, but it do lower my top velocity and threw off my speedometer (and this can be adjusted; more on that in the future.) As you can plainly see on the chart below, there are always a multitude of possible combinations to reach at the ratio you really want, but your alternatives will be limited by what’s practical on your particular bike.
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 might be excessive for my flavour. There are also some who advise against making big changes in the front, since it spreads the chain power across less 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 back sprocket to improve this ratio also. Therefore if we transpired to a 16-tooth in the front, but simultaneously went up to a 47-tooth in the rear, our new ratio will be 2.938; nearly as extreme. 16 in the front and 46 in again will be 2.875, a a lesser amount of radical change, but still a little more than doing only the 16 in the front.
(Consider this: since the ratio is what determines how your cycle will behave, you could conceivably decrease upon both sprockets and keep carefully the same ratio, which some riders carry out to shave excess weight and reduce rotating mass when the sprockets and chain spin.)
The important thing to keep in mind when selecting new sprockets is that it’s all about the ratio. Find out what you have as a baseline, know what your aim is, and adjust accordingly. It will help to find the web for the encounters of other riders with the same cycle, to check out what combos are the most common. Additionally it is a good idea to make small changes at first, and operate with them for a while on your preferred roads to see if you like how your bicycle behaves with the new setup.
There are a great number of questions we get asked relating to this topic, therefore here are a few of the most instructive ones, answered.
When deciding on a sprocket, what 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 is the beefiest. Many OEM components happen to be 525 or 530, but with the effectiveness of a top quality chain and sprockets, there is usually no danger in switching to the lighter 520 setup. Important note: always make sure you install components of the same pitch; they are not appropriate for each other! The best course of action is to get a conversion kit so all 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 components as a collection, because they have on as a set; if 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 harm to change one sprocket (usually the front.) If your chain is normally relatively new, you won’t hurt it to change only one sprocket. Due to the fact a the front sprocket is typically only $20-30, I would 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 and your chain.
How will it affect my rate and speedometer?
It again is determined by your ratio, but both can generally end up being altered. Since many riders decide on a higher equipment ratio than stock, they will experience a drop in leading swiftness, and a speedometer readout that says they go faster than they will be. Conversely, dropping the ratio could have the contrary 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, going to an increased gear ratio will drop your MPGs because you should have larger cruising RPMs for a given speed. More than likely, you’ll have so very much fun with your snappy acceleration that you might 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 simpler to change the front or rear sprocket?
It really depends upon your motorcycle, but neither is typically very difficult to improve. Changing the chain may be the most complicated activity involved, thus if you’re changing simply a sprocket and reusing your chain, that you can do whichever is most comfortable for you.
A significant note: going scaled-down in the front will loosen the chain, and you’ll need to lengthen your wheelbase to make up for it; going up in the trunk will moreover shorten it. Know how much room you must adjust your chain either way before you elect to do one or the additional; and if in hesitation, it’s your very best bet to change both sprockets and your chain all at one time.
How To Choose Motorcycle Sprockets