The other advantage to cartridges is that installing them is easier and quicker. When they do finally wear out, you replace the entire cartridge. But don’t worry — you’ll ride several thousand miles before you need to go shopping for a new bottom-bracket cartridge.
If the bottom bracket is squeaking or if the cranks don’t rotate smoothly by hand with the chain off, it’s time to overhaul. If you hear any squeaking or grinding, if the bottom bracket is slightly loose, or if you feel a vibration when you pull on the cranks, you should also prepare for an overhaul.
Adjustable bottom brackets should be overhauled as part of your annual maintenance. Cartridge bottom brackets are replaced rather than overhauled — and replacement isn’t usually necessary until you’ve ridden a few thousand miles.
Removing and installing a cartridge bottom bracket
To remove a cartridge bottom bracket, follow these steps:
1. Remove the cranks following the procedure described earlier for the type of crankset you have (one-piece, cottered, or cotterless).
2. Attach the appropriate bottom bracket tool to the left side of the bike (as shown in Figure 13-11).
There are many different types of tools designed to fit many specific types of bottom brackets. The different tools usually have a different number of notches or splines, which match the number of notches or splines in the cup that secures the cartridge in place. Check with your local bike shop to determine which tool is appropriate for your bike.
3. Use an adjustable wrench to turn the bottom bracket tool in a counterclockwise direction (as shown in Figure 13-12).
The one common problem in removing cartridges is that the tools slip while under torque, stripping the splines. Because removing the bottom bracket can take a tremendous amount of force, the pressure needs to be applied on the tool in the direction of the bike to avoid stripping the splines or the tool.
Figure 13-11: Attaching a bottom bracket tool.
Figure 13-12: Using the bottom bracket tool.
4. Perform the same procedure on the right side except turn the tool clockwise.
5. When the lock ring is loose, use your hand to unscrew it the rest of the way.
It’s attached to the bottom bracket, which will come out when you’re finished unscrewing it (as shown in Figure 13-13).
To reinstall a cartridge bottom bracket, read the manufacturer’s instructions and follow these steps:
1. Coat the threads of the bottom bracket with grease.
Some bike shops prefer to use an anti-seize agent or plumber’s thread tape, which hardens and expands once it dries, helping to keep the bottom bracket secure and protecting the threads.
2. Examine the cartridge for an R and an L, signifying the right and left side.
3. Insert the L side into the right side through to the left side of the bottom bracket shell of the frame and carefully align the threads of the cartridge with the threads of the frame. Screw in the cartridge in a counterclockwise direction.
Figure 13-13: Removing the cartridge
4. When it becomes more difficult to turn the cartridge, attach the bottom bracket tool.
5. Using an adjustable wrench, fully tighten the cartridge.
Most manufacturers recommend a significant amount of torque for the bottom bracket, which means you need to apply a lot of force to tighten the bottom bracket.
6. Attach the cup to the other side and, using a wrench, tighten it in a clockwise direction.
Removing and installing an adjustable bottom bracket
To remove an adjustable bottom bracket, follow these steps:
1. Remove the cranks following the procedure described earlier for the type of crankset you have (one-piece, cottered, or cotterless).
2. On the left side of the bike, you’ll see a lock ring with grooves cut into it. Unloosen the lock ring in a counterclockwise direction by using a specialized tool called a C-wrench (shown in Figure 13-14) or lock-ring wrench.
If you don’t have a C-wrench, use a chisel or — as a last resort — a flathead screwdriver to tap against the grooves or the lock ring to break it free. Be careful, because this may damage your screwdriver!
Figure 13-14: Using a C-wrench.
3. After removing the lock ring, you’ll see an adjustable cup that holds the bearings. Remove this cap.
Some adjustable cups have pin holes which require a special tool. Figure 13-15 is an example of using a pin spanner to remove the adjustable cup. Unscrew the adjustable cup being careful to catch any loose bearings that may exist. The axle will slide out at this point.
4. On the right side of the bike, remove the fixed cup, which is screwed into the bottom bracket shell of the frame.
You may not be able to remove the fixed cup, so consider taking the bike to your local bike shop where they’ll have a fixed-cup removal tool.
You’ll need a large enough crescent or adjustable wrench to fit around the fixed cup. This time, turn in a clockwise direction. This side may be very tight.
To install an adjustable bottom bracket, follow these steps:
1. Clean all the parts with degreaser.
2. Inspect the ball bearings, cups, and axle.
If they look dull or the bearing surfaces are not smooth, replace them.
Figure 13-15: Using a pin spanner.
3. Fill both cups with a layer of grease.
4. Place the same number of ball bearings in that were originally each cup.
If you aren’t sure of the number, use as many as necessary to fit securely with a small gap to allow each bearing “elbow room.”
5. Use a screwdriver or other tool to push the bearings into the grease.
6. Cover the bearings with another layer of grease.
Figure 13-16 has an example of bearings packed in grease.
Figure 13-16: Repacking the bearings in grease.
7. On the right side, screw on the fixed cup by hand until it tightens. Then very firmly tighten this side with a wrench.
8. On the left side of the bike, insert the longer end of the axle into the bottom bracket shell and into the fixed cup.
9. Screw on the adjustable cup until tight. Try rotating the axle. If it’s tight, slightly loosen the cup.
10. Place the lock ring on the bottom bracket and tighten, checking to ensure that the axle rotates smoothly and not too tightly.
It may take a few tries to get an adjustment that is not too tight and not too loose.
Shopping for a new crankset and bottom bracket
If you have an older bike and you’d like to upgrade the crankset and bottom bracket, there are a few things to think about:
Buy a cartridge bottom bracket. This is the most popular style of bottom bracket on the market and shouldn’t be a problem unless your bike requires a special bottom bracket. When the cartridge bottom bracket is in place, you’ll be able to relax knowing that most likely you won’t have to touch it for a number of years.
If you’re moving from a cottered crankset to a cotterless one, you’ll to need replace both the cranks and the bottom bracket. You can’t mix a cottered crank with a cotterless bottom bracket.
Make sure that the axle style and the threads match. There are different types of bottom bracket threading. The threads need to match your frame and the axle style needs to match the crankset.
Consult with your local bike shop to confirm which bottom brackets will fit the threads on your bike.
Make sure you have the right size bottom bracket. There are many different widths for bottom brackets. You need to know the width of the bottom bracket shell on the frame and the overall length needed for the specific crankset you’re using. Sometimes mountain bikes have wider bottom brackets than road bikes. In addition, cranks with three chainrings need wider bottom brackets than two-chainring cranks.
Again, talk with the folks at your local bike shop to make sure you’re getting the right size for your bike.
Pay attention to crank-arm length. Crank arms change the circumfe
rence in which the pedals rotate, so with larger crank arms you’ll be pedaling in a wider circumference and getting more leverage as you pedal. Having longer cranks and more power is beneficial if you’re doing a lot of climbing. The downside of a larger crank is that, because of the wider circumference, it takes more effort to spin quickly — so if speed is a consideration, a smaller crank may be in order.
The most common crank-arm lengths are 172.5mm or 175mm. If you’re a short person, you’ll want to try using a shorter crank. At the same time, if you’re tall, a longer crank will work with your leg muscles better. A few manufacturers sell cranks of 185mm or more. The best advice is to work with your local bike store to find the crank the best suits you.
With longer crank arms, it’s important to make sure the bottom bracket has enough clearance or else the crank arms could hit the ground when you’ re cornering or climbing over logs.
Chapter 14
Dropping It into Gear: The Shifting System
In This Chapter
Understanding how derailleurs work
Removing, installing, and adjusting the rear and front derailleurs
Changing derailleur cables
Removing and installing the shifters
This chapter covers inspection, removal, installation, and adjustment of the shifting system, including the cable system, shifters, and derailleurs. Whew!
Demystifying Derailleurs
Derailleurs are the mechanisms for “de-railing” or moving the chain from cog to cog and chainring to chain ring, allowing you to shift and change gears when you ride. The derailleurs don’t so much move the chain as they guide it from one side to the other, which is only possible if you’re pedaling forward and the chain is moving.
Both the front and rear derailleurs work through the use of an internal spring, which pulls the derailleur toward the bike or pushes the derailleur away from the bike, while the cable attached to the bike’s shifter opposes the force of the spring. When the shifter pulls the cable, the cable overcomes the spring and moves the chain toward or away from the bike. When the shifter releases the cable, the derailleur moves back to its normal position.
The fact that springs and cables are pushing and pulling on the derailleurs would be a problem if there were nothing stopping the derailleurs from moving the chain too far in one direction or the other. Fortunately, derailleurs are designed with a pair of stop-limit screws, which limit the movement of the derailleurs in both directions. These screws are usually marked with an H and an L, for high and low. The high-limit screw controls the distance that the derailleur can move away from the bike (toward the higher gears), and the low-limit screw controls the distance the derailleur can move toward the bike (toward the lower gears).
Limit screws physically limit movement as they’re screwed deeper into the derailleur. Turning the screws clockwise drives them in deeper and restricts the range of movement; turning the screws counterclockwise loosens them and increases the range of movement. If you were to tighten both limit screws to their maximum depth, you would limit the derailleur to a single position. This is good to know if you break a derailleur or chain and need to set the bike up for just one gear to get home.
Both derailleurs have difficult jobs when it comes to keeping up with the demands of a biker who is shifting to higher and lower gears. Moving the chain toward the frame puts the bike in a lower gear, whereas moving the chain away from the bike puts the bike in a higher gear. Just as with a car, lower gears are useful when you’re going slow (for example, climbing a steep hill), whereas higher gears serve you on the descent, when you’re riding at a faster speed.
The front derailleur has the unenviable task of moving the chain sideways as it’s under force. This part of the chain transmits power to the rear wheel, which is why when you’re applying a lot of power and moving slowly (such as climbing a hill) it’s hard for the front derailleur to shift.
Rear derailleurs have the job of swinging their arm or cage back and forth under the freewheel, guiding the chain from one cog to the next. The rear derailleur cage has the familiar S shape, with two jockey wheels. The top jockey wheel guides the chain onto the cog and the bottom jockey wheel is designed to keep tension on the chain and take up slack.
The rear derailleur
Rear derailleurs (shown in Figure 14-1) have been known to give even experienced bike mechanics headaches at times. They do double-duty: keeping the chain under tension and guiding it back and forth between the cogs as the rider shifts. Slight changes in tension of the cable to which the derailleur is attached can cause shifting to become out of whack. Just as with the front derailleur, you can improve its functioning and longevity if you keep it clean, lubricated, and adjusted as needed.
The following sections describe how to remove and reinstall the derailleur.
Figure 14-1: A rear derailleur.
Removing the rear derailleur
To remove your rear derailleur, follow these instructions:
1. Shift the rear derailleur to the smallest cog.
2. Using an Allen wrench or box wrench, loosen the bolt that’s holding the cable in place.
Note that if you don’t shift the rear derailleur to the smallest cog, it could spring back at you because it’s under tension from the cable.
3. Use an Allen wrench or box wrench (as shown in Figure 14-2) to remove the bolt that is holding bottom jockey wheel in place.
Spray some lubricant on the jockey wheel if the bolt will not budge.
4. After the bolt is removed, lift out the jockey wheel.
5. Use an Allen wrench or box wrench (as shown in Figure 14-3) and reach around the derailleur to loosen the bolt that holds the top jockey wheel in place.
Figure 14-2: Loosening the bottom jockey wheel.
Figure 14-3: Loosening the top jockey wheel.
6. After the bolt is loose, you should be able to separate the cage (as shown in Figure 14-4).
7. With the cage separated, lift the chain off the top jockey wheel and away from the derailleur.
Rest the chain on one of the cogs, letting the slack hang down.
8. Use an Allen wrench to remove the pivot bolt (see Figure 14-5), which will allow you to remove the derailleur.
Figure 14-4: Separating the cage.
Figure 14-5: Undoing the pivot bolt.
Installing the rear derailleur
To install the rear derailleur, follow the steps in this section.
1. Position the derailleur so that the chain wraps around the right half of the top jockey wheel (as you’re facing the right side of the bike).
2. Align the mounting bolt with the gear hanger on the frame.
3. Insert the mounting bolt and tighten with an Allen wrench.
4. Pull the chain through the cage and, while holding the cage and chain with one hand, insert the bottom jockey wheel so that the chain wraps around the left side of the wheel.
5. Close the cage so that the holes align with the hole in the bottom jockey.
6. Insert the bolt and tighten both jockey wheel mounting bolts securely.
7. Adjust the H limit screw (see Figure 14-6) and the L limit screw (see Figure 14-7) so that they limit the derailleur from throwing the chain off the bike or, even worse, into your spokes.
Tighten both screws in a clockwise direction two turns. This will restrict the movement further than it was before.
Figure 14-6: Adjusting the H screw.
Figure 14-7: Adjusting the L screw.
8. To stimulate shifting with the cable, practice turning the pedals with your right hand while pushing inward and upward on the derailleur with your left thumb. Wrap your index finger around the cage and push on the cage with your thumb.
Note: These steps are for the most common type of rear derailleur. If you have a rapid-rise rear derailleur, the spring is opposite and pulls the derailleur toward the low gear. Therefore, you’ll need to reverse the process when moving the derailleur with your hand.
9. Using the method in
Step 8, try to shift the chain to the largest cog. (It won’t succeed on the first attempt because you tightened the L limit screw as a safety precaution.) Loosen the L limit screw by a slight amount, about one-quarter to one-half a revolution, and then begin turning the pedals again.
Do this in incremental steps until you’re able to shift the chain onto the largest cog. The chain should spin smoothly on the largest cog and not make any grinding sounds.
10. Perform Step 9 in the opposite direction making incremental adjustments to the H limit screw until the chain arrives on the smallest cog.
You won’t need to move the derailleur with your hand because the spring in the derailleur will pull it down and outward. Now you’re ready to attach the cable and make finer adjustments to the shifting.
11. Run the cable through the cable-adjusting barrel hole and through the cable anchor bolt clamp.
There should be a notch in the cable anchor bolt clamp where the cable is designed to sit when the clamp is tightened.
12. Tighten the clamp with an Allen wrench or box wrench (as shown in Figure 14-8).
13. To make the cable taut, use a pair of pliers or a fourth-hand tool, and pull the cable as you tighten the cable clamp bolt.
14. Test the shifting of the derailleur down onto the highest gear.
Sometimes when you’re tightening the cable, you can pull the derailleur over just a little and then it’ll not drop down onto the highest gear.
15. Attach a cable cap (see Figure 14-9) to the end of the cable and use a pair of pliers to crimp it into place.
This will prevent the cable from fraying.
Always leave about 2 inches of cable on the outside or past the cable anchor bolt. This will make future adjustment to the cable and/or derailleur much easier.
Bike Repair & Maintenance For Dummies® Page 20