Sprockets are a set of teeth attached to the rear wheel of a bicycle. Each ring is considered a gear. The chain (which connects to the pedals) turns the sprockets to propel the bike. Over time, gear teeth start to wear out, weakening the chain and causing you to push yourself too hard. At worst, this can make the chain slippery, preventing you from pedaling at all until you fix the problem.
Part 1 of 2: Disassemble the Old Sprockets
Step 1. Remove the wheel from the bike
To easily perform this procedure you must unfasten the spit or the axle nuts, unfasten the quick release of the brake and remove the wheel. Once you're done, you should put the bike aside.
The chain is likely wrapped around the sprockets. If you have trouble removing it, shift the front gear into the smallest ring. You want to find the point where the chain is threaded through two small wheels on the derailleur (a derailleur that sits on the rear wheel) and press it down to loosen it
Step 2. Examine the sprockets for wear and damage and determine if they need to be replaced
Also, this is a good time for you to examine the axle bearings for proper lubrication. If the shaft moves, the bearing cones need to be adjusted. You may need to replace these items. If you wish, you can go to a bike shop so that the staff can perform all these procedures for you. Signs that your bike needs new sprockets include the following:
- The chain comes loose or slips while you drive.
The bicycle has problems with the gears (Note:
You should verify that the derailleurs are properly adjusted before changing the sprockets.)
- You notice visibly worn teeth (dots are lower and rounder on some gears than others).
- You detect cracked, broken or warped gears.
Step 3. Remove the spit
Place the wheel on a flat surface that gives you easy access to the sprockets and remove the spit (the long bar that runs through the center of the wheel). Often times, the spit and coupling bolt can be easily threaded onto the other end by hand.
Step 4. Place the locking tool in the center of the sprockets
You should replace the spit using a puller (a large hex bolt attached to a small bar) that has a grooved ring on one end that locks inside the sprockets. This will be the pressure point for unscrewing the pinions.
Some older pullers do not have a bar but are intended to replace the bolts on the bike spit and are then used as usual. You just have to unscrew the ends and place the extractor on the old skewer
Step 5. Wrap the chain hose clockwise around the largest sprocket
This element keeps the pinions turning while you unscrew it. It is simply a long handle with one foot (30 cm) of bike chain on the end, which allows the sprockets to stay in place. You want to wrap as much chain as possible to the right on one of the larger gears.
- Then you need to turn to the left to loosen the bolt. This is the opposite pressure that maintains the stability of all the elements.
- Alternatively, you can use a piece of chain instead of the hose.
Step 6. Place a large adjustable wrench over the puller holding the chain hose in place
It may be easier to do this with the help of another person. You must tighten the wrench around the extractor to make it tighten tightly.
Make sure the tool is firmly wedged between the sprockets. This way, you will easily recognize it by the 12 tooth lock nut on the sprockets
Step 7. Hold the chain hose in place and turn the wrench counterclockwise to release the puller
This nut has a regular thread that you must turn counterclockwise. You may need to exert a little force and make a loud squeak as you remove it (due to the locking teeth). This procedure requires a considerable amount of force (especially if you've never done it before), but you should avoid breaking any part of the bike.
- This entire procedure is necessary to disassemble the puller (the usually silver-plated small piece that keeps the sprockets from moving).
- You should put the extractor in a nearby place to prevent it from getting lost.
Step 8. Slide the sprockets after removing the puller
These items are usually accompanied by a few spacers and a large set of riveted gear teeth. You must keep all the elements in the same order in which you are disassembling it to guide you when placing the new sprockets. Also, there may be a plastic chain guard between the sprockets and the spokes of the wheel that you can keep or dispose of.
- Some teeth can slide on their own and others can dig in.
- You may need to use a thin object to slightly pry some gears.
Step 9. Clean the bike hub with an old rag and a little light cleaning fluid
When you clean your bike, you hardly ever get to this area, so take the time to get all the dirt out. You can use an old cloth and a little rubbing alcohol or a mild dishwasher (or all-purpose cleaner) and a little hot water.
Part 2 of 2: Replacing the sprockets
Step 1. Replace the sprockets with the same gear ratio
Count the number of teeth on the smallest gear, then the largest gear. You must put these numbers together to get the relationship. For example, an 11-32 should be replaced by another 11-32. You can find the tooth counts stamped on the sprockets. You might also find the part number or name helpful. Also, you can take the sprockets to a bike shop to get a nearly identical set.
Step 2. Replace the sprockets with a different ratio
Most sprockets can be interchanged between brands. For example, Shimano gear teeth can be mixed with others of the same brand. You can even use older ones if you make some adjustments to them. To get gear teeth, you must purchase them separately or as a complete unit. The sprockets can be disassembled by removing the bolts that hold them together. The bolts serve no other purpose than to facilitate assembly. Then you just have to join the sprockets with the gear ratios you want. Some gear tooth counts are less common than others. You should take this detail into account when shopping, since you could end up with identical sprockets to the ones you already have.
Note that if you change gear ratios, you may need a longer or shorter chain to match the new size teeth
Step 3. Slide the sprockets onto the hub in the order you purchased them
Fit the new sprockets the same way you removed the old ones. You should note that there is a set of smaller teeth on the hub that the sprockets slide on. One of them is bigger or smaller than the others. One of the openings on the sprockets is the same size, which tells you how to align the new sprockets with the hub. You should immediately slide the extractor to prevent all the elements from moving.
- You will likely have to add one gear at a time. If they are separated, you should find some spacers (a small plastic ring) between them when you buy the sprockets. These must go in order.
Step 4. Tighten the sprocket lock nut
You should use the chain hose as described above, but turn it to the right this time. Then use the wrench to gently tighten the bolt. You should never tighten it too much, as the thread is very small and does not support too much force. The sprockets are equipped with locking teeth to prevent them from coming off, producing a distinctive squeak or hum as you remove them for replacement.
- Tighten the bolt by hand as much as you can. Then use the wrench to tighten it just a little bit more so it won't move.
- The gears must all move together. There should be no play or wobble in any of the gear teeth.
Step 5. Refit the spit and put the wheel back on the bike
Once the sprockets are installed, you must install the wheel and chain. Once this procedure is finished, the bike is ready for you to ride again.
You should always place the chain close to the gear the bike is in so it doesn't squeak violently when you start pedaling. If you are confused, you should change an entire side of gears and place the chain on the two rings farthest from that side
Step 6. Replace the chain each time you replace the sprockets
As the chain wears out, this places more and more stress on the rear sprockets. In fact, proper chain replacement (every six months or so if you ride your bike regularly) is the best thing you can do to avoid replacing your sprockets too often. If you are installing new sprockets (even if they are identical to the old ones), you should also replace the chain for the best results.
- It is likely that it will be cheaper for you to buy the tools over the Internet than in a store, since you do not need to pay the prices of the intermediaries.
- This is a simple activity, as it does not require specialized knowledge. Also, it does not involve the use of spring loaded parts or small ball bearings.