Make sure the derailleur is shifted to the smallest cog or the position farthest to the outside.
2. Wind the other part of the chain through the front derailleur and around the largest chainring.
Make sure the front derailleur is shifted to the smallest chainring or the farthest gear away from the bike.
3. Using a little bit of force, bring both ends of the chain together (as shown in Figure 10-12).
This will pull the pulleys of the rear derailleur forward.
4. Shorten the chain by hand, one link at a time, until you get the correct length.
You know you’re at the right length when there’s approximately 1/2 inch to 1 inch of space between the top pulley and the chain.
5. On the end of the chain with extra links, pinch the link with your thumb and forefinger where you need to cut the chain.
This will help you remember where to break it.
Figure 10-12: Measuring the chain
Reassembling your chain
After you’ve repaired and measured your chain, it’s time to reattach it to your bike. If you have an SRAM PowerLink-type chain, here’s how:
1. After having measured the chain (see the preceding section), remove any extra links using the chain tool.
2. Grab both connecting pieces that make up the master link.
3. Making sure to use inner links only, connect one piece from the inside of the chain and another piece from the outside of the chain.
4. Press the pins on both pieces through the rollers in the links, and snap the master link together (as shown in Figure 10-13).
5. Pull the chain to lock the pieces in place.
6. Visually examine the master link to make sure it’s securely in place.
If you have a Shimano- or Campagnolo-type chain or a chain with reusable rivets, follow these steps:
1. After having measured the chain (see the preceding section), remove any extra links using the chain tool.
2. Making sure to use inner links only, connect one piece from the inside of the chain and another piece from the outside of the chain.
Figure 10-13: Connecting an SRAM PowerLink-type chain.
3. Where the two ends of the chain come together, insert the replacement pin into the links just far enough to hold the chain together while you place it into the chain tool (as shown in Figure 10-14).
Figure 10-14: Inserting the pin.
If you have a chain with a reusable rivet, the rivet will already be in place.
The pin has a tapered head that looks like a rocket ship. Make sure you insert the pin with the tapered head first. The head of the pin is designed to guide the pin into the chain and not to hold the chain together.
4. Rotate the handle of the chain tool to press the rivet into the chain.
Be careful not to push the rivet too far into the chain. You want to push the tapered head of the rivet all the way through and out the other side to have the non-tapered head protruding only as far as the neighboring rivets protrude.
5. Using pliers, snap the tapered head off the pin (as shown in Figure 10-15).
If you have a chain that uses reusable rivets, here’s how to reinstall it:
1. Grab both connecting pieces where the chain was broken.
2. Join the links together and place into the chain tool.
3. Turn the handle of the chain tool until the rivet is pressed into the chain.
An equal amount of rivet should be showing on each side of the chain
4. Remove the chain tool from the chain.
Figure 10-15: Snapping off the replacement pin’s head.
Chapter 11
Gearing Up: Freewheels and Cassettes
In This Chapter
Getting clear on cassettes and freewheels
Inspecting, cleaning, and lubricating cassettes and freewheels
Removing and installing cassettes and freewheels
One of the most enjoyable experiences when riding is the exhilaration that comes after having reached the top of a tall peak, when the downhill begins almost immediately and you’re rewarded with a long descent. The satisfaction of having conquered the ascent, the relief of being able to rest your legs for a moment, and the rush of coasting at high speed with the wind in your face are what keeps people coming back for the climb.
What makes the coasting part possible is the topic of this chapter. Freewheels and cassettes are like the clutch on your car — disengage it and the car is rolls free in neutral. In a bike’s case, stopping pedaling does the trick. In this chapter, we fill you in on some of the basics of how the freewheel and cassette work and how coasting is possible, as well as everything you need to know about their maintenance, including inspecting, removing, and reinstalling them.
The Dirt on Freewheels and Cassettes
Think about a kid’s fixed-gear bike: Every time the rear wheel spins, the pedals and cranks rotate with it or the front wheel. For young children, this isn’t a big deal — they usually don’t ride very fast, and they have more energy than they know what to do with. However, if your bike worked the same way and you were riding down a hill at a high rate of speed, your legs would have to keep up with the pedals and cranks, which would be spinning at a furious rate. Talk about dangerous.
Fortunately, modern bikes have a clutch system that allows you to coast when you stop pedaling, and move forward again by pedaling when you slow down. This system is made up of either a freewheel or a cassette, the subject of this section.
To determine whether you have a freewheel or cassette, examine the smallest cog. If there is a screw-on lock ring with the word lock on it, which rotates with the cogs when you spin the freewheel, you probably have a cassette. If in doubt, take your bike to your local bike shop and ask the people there.
What’s so free about a freewheel?
The freewheel (shown in Figure 11-1) is a part of a clutch-like system that was a significant advance in the design of bicycles. Older bikes are designed with freewheels that consist of individual cogs (toothed disks surrounding the hub on your rear wheel that combine to form the freewheel of your bike), bearings, pawls, pawl springs, and gears that are screwed directly on to the hub.
Figure 11-1: A freewheel
One disadvantage to freewheels is that the force from pedaling can tighten them, making removal difficult. Another problem with freewheels is that, because of the spacing requirements, the bearings on each side of the hub are located closer together toward the center of the hub, while the axle is extended outward from the bearings to support the freewheel. As a result, the axle receives less support and can break or bend under the right amount of force.
If you have a traditional freewheel, when your cogs wear out you may want to think about converting to a cassette system (see the following section). If you do opt for a cassette system, your best bet is to replace the hub with a free hub. The alternative is to buy a freewheel hub and rebuild your wheel.
The best things come in packages: The cassette
Cassette systems (see Figure 11-2), which are found on most modern bikes, improved many of the deficiencies with freewheels (see the preceding section). One of the biggest changes with cassettes is that the ratcheting system is built into the hub itself. Cassettes use a free hub, which looks like a traditional hub but with a thick extension on one side with grooves or splines built into it. This design allows the bearings to be spaced farther apart, providing greater support for the axle.
Figure 11-2: Cassettes improved upon freewheels.
Another advantage of the cassette system is removal: Cassettes have cogs that are normally held together as a unit and that slide on and off the hub. After the lock ring (which holds the cogs in place) is removed, the cogs slide off together as one. Freewheels, on the other hand, are a group of cogs held together as a unit but must be threaded onto the hub.
Cassettes come with a variety of different gearing options. The gears are defined by the number of teeth on each cog and, depending on your biking needs, you
may need a specific range of gears. For example, if you’re planning on touring, you’ll want high enough gears to help you ascend inclines while your bike is weighed down with packed pannier bags.
Some cogs are manufactured with the number of teeth marked on the side. These markings will save you from having to count the teeth in order to determine the gear.
If you’re shopping for a cassette, be sure you buy one that’s compatible with your hub. Manufacturers like Shimano and Campagnolo have designed cassettes that work only with their hubs. If you aren’t sure about which cassette will work with your hub, check with the folks at your local bike shop.
Inspecting Your Freewheel or Cassette
Just like other parts of a bike, a freewheel or cassette will eventually wear out and have to be replaced. You can identify a worn freewheel the same way you identify a worn chainring (see Chapter 10) — by the teeth. Here are some clues for identifying worn teeth on a freewheel or cassette:
They no longer have sharp edges.
They look like they’ve been filed down.
They lack symmetry.
They have the shape of an ocean wave.
If your chain is skipping when you apply force when pedaling, it may be due to worn teeth on either the freewheel or cassette cogs or the chainring. Examine both and replace them as needed.
Sometimes only one cog will wear out — if this happens, it’s usually the cog that corresponds with the gear you use most when riding. (For many bikers, this’ll be cogs with 15 to 18 teeth.) If you have just one cog that needs to be replaced, you may be able to buy just that one cog — although often buying the entire cassette or a freewheel is cheaper.
Cleaning the Freewheel or Cassette
Caring for a freewheel or cassette is pretty straightforward. Unlike other components of the bike, where you’re concerned about the internal parts, with freewheels your goal is to keep the outside of the cogs clean. Dirt and grime quickly work their way onto the surface of the cogs and in between them. This buildup can muck up the chain, spread dirt around your bike, and cause premature wear for all the parts.
You don’t have to remove the freewheel or cassette to clean it.
To clean the freewheel or cassette , follow these steps:
1. Remove the rear wheel from the bike by following the directions in Chapter 7.
Removing the rear wheel gives you better access to the cogs.
2. If the freewheel or cassette is very dirty, wash it with soap and water.
Avoid spraying water directly. Use a brush on the freewheel as you wash the wheel.
3. If the freewheel or cassette is not overly dirty, clean it with a rag.
Drop an edge of the rag between each freewheel cog and, while holding each corner of the rag with your hands, clean between the cogs in a back-and-forth motion.
Dip the cloth or brush in degreaser before using it. But try to keep the degreaser from getting on the tire.
4. To remove dirt that’s trapped between the cogs, use a narrow brush or a screwdriver to scrape it out.
Some manufacturers make a tool with a brush specially designed for this purpose.
If the freewheel or cassette is really dirty, try removing and soaking it in a degreaser.
Lubricating the Freewheel or Cassette
Although you won’t be overhauling a freewheel or cassette the way you would with a bottom bracket or headset, you can do some simple lubrication of the bearings using a lightweight oil.
Follow these steps to lubricate the freewheel or cassette while it’s on the wheel:
1. After you’ve cleaned the freewheel or cassette (see the preceding section), wipe off any excess degreaser and let it dry.
2. Lay down the wheel with the freewheel on its side, with the freewheel facing up.
3. Using a light to medium oil, drip or spray the oil into the gap between the freewheel and the center, fixed part of the hub axle, while you’re spinning the free hub in a counterclockwise direction.
When you see oil coming through the other side, there is sufficient oil to lube the pawls and bearings. (In general, the higher the quality of the freewheel, the tighter the tolerances and the longer this takes.)
4. Use a rag to wipe off any excess lubrication between the cogs.
Removing a Freewheel or Cassette
You’ll have to remove a freewheel or cassette in the following situations:
If you’re replacing the freewheel or cassette
If you’re replacing a spoke and need to insert it into the flange (the part that flares out at the ends of the hubs)
If you’re overhauling the hubs
If you’re replacing the hubs
In the following sections, we walk you through removing a freewheel and removing a cassette, as well as removing individual cogs and removing the free hub.
Removing a freewheel
If your bike has a freewheel, follow these steps to remove it. (If you’re not sure whether your bike has a freewheel or cassette, turn to “The Dirt on Freewheels and Cassettes,” earlier in this chapter.)
1. Remove the rear wheel from the bike (see Chapter 7).
2. Remove the quick-release skewer or axle nut.
3. Stand the wheel up on the floor.
4. Attach the freewheel remover tool to the center of the freewheel.
Be sure to use the correct type of freewheel remover tool. Check with your local bike shop or read your bike owner’s manual to find out which model is appropriate for your freewheel.
To hold the freewheel removal tool in place, use the axle nut or insert the quick-release skewer through the center of the tool and tighten the nut to hold it in place.
5. Using an adjustable wrench, turn the freewheel remover in a counterclockwise direction.
6. When the freewheel remover loosens, remove the quick-release skewer or axle nut.
7. Continue to unscrew the freewheel remover either by hand or with the wrench, until the freewheel is unthreaded from the hub.
Removing a freewheel, which tightens at every pedal stroke, can often be extremely difficult. If you can’t remove it with a full-size crescent wrench, more leverage is needed. You may be able to use an extension pipe or, more effectively, a heavy-duty vice (maybe borrowed from your local bike shop). Being unable to remove a freewheel is a very common frustration of home mechanics.
Removing a cassette
Most modern cassettes are designed to slide onto the free-hub body with splines and then be held in place by a cassette lockring. On some older cassettes, the cassette is secured to the hub by the first cog.
To determine which type of cassette you have, look at the first cog. If it has grooves or splines cut into the center of it, you have the lockring style. If not, you have the older cassette style. (When in doubt, check with the people at your local bike shop.)
On many lockrings, you can sometimes find the word lock with an arrow pointing in the direction for locking.
In order to remove a splined cassette, you need a freewheel removal tool, a chain whip, and an adjustable crescent wrench. If you have a traditional cassette, you’ll need two chain whips.
Different types of cassettes require freewheel removers that are specially designed to work with the number of splines in the hub. Make sure you purchase one that’s compatible with your cassette.
Splined cassettes
To remove a modern-style, splined cassette, follow these steps:
1. Remove the rear wheel from the bike (see Chapter 7).
2. Remove the quick-release skewer or axle nut.
3. Stand the wheel up on the floor.
4. Insert the freewheel remover to the center of the cassette (as shown in Figure 11-3).
To hold the lockring in place, insert the quick-release skewer through the center of the tool and lightly tighten the nut to hold it in place. You can do the same thing with the axle nut if you have axle nuts instead of a quick release.
5. Wrap the chain of the chain-whip tool around one of the larger
cogs.
6. Secure an adjustable wrench to the flat edges of the freewheel tool.
Figure 11-3: Inserting the freewheel remover tool into the center of the cassette.
7. Holding the chain-whip tool in one hand and the adjustable wrench in the other (as shown in Figure 11-4), push down on the adjustable wrench.
You’ll hear a clicking sound as the lockring loosens.
You may be able to get greater leverage by standing behind the wheel and leaning over the top as you push down on the wrench.
8. After the lockring loosens, remove the nut or quick-release skewer.
9. Unscrew the lockring by hand until you can remove it.
10. Slide the cassette off the freehub.
Some of the first few cogs may not be attached to the cassette body (as shown in Figure 11-5). Keep track of any spacers that exist in between the cogs — these should be returned to their proper position when you reinstall the cassette.
Figure 11-6 shows the free hub after the cassette is removed. Notice the splines cut into the extended part of the hub.
Figure 11-4: Using a chain whip to loosen the lockring.
Figure 11-5: Removing the cogs on a cassette
Figure 11-6: Free-hub splines.
Traditional cassettes
To remove a traditional cassette, follow these steps:
1. Remove the rear wheel from the bike (see Chapter 7).
2. Remove the quick-release skewer or axle nut.
3. Stand the wheel up on the floor.
4. Facing the cassette, attach the chain of one chain whip to the largest cog and hold the handle of the chain whip with your right hand at the two or three o’clock position.
5. Attach the chain of the other chain whip to the smallest cog and support the tool with your left hand in the nine or ten o’clock position.
6. Push down on the chain attached to the smallest cog while holding the other chain whip in place.
Bike Repair & Maintenance For Dummies® Page 16
