Bike Repair & Maintenance For Dummies®
Page 12
4. Remove the locknut, washers, and cone from the axle, keeping them in order as you remove them.
5. Hold a towel or cup under the hub as you pull out the axle, because some bearings may fall out.
Figure 7-6 illustrates the removal of an axle.
Leave the cone, washers, and locknut in place on the other side of the axle. This will make reassembly easier.
6. Using a screwdriver, remove the bearings from both sides of the hub (see Figure 7-7).
A magnetic screwdriver makes bearing retrieval easier, although a screwdriver tipped with grease will work. Another trick is to push them down through the center of the hub and out the other side.
Figure 7-5: Undoing the locknut.
Figure 7-6: Removing the axle.
Figure 7-7: Removing the bearings.
Count the bearings in the hub. Some hubs are designed for ten bearings in the front and nine in the back. Because you’ll probably want to replace the bearings with new ones (they’re cheap), you’ll want to know how many to purchase (and how many to use for reassembly).
7. After the bearings are removed, wipe the inside of the hub shell with a cloth and then use a degreaser to clean the cups.
Examine the cups for wear. If they have dents in the surface, you may need to replace the entire hub.
8. Clean the axle, nuts, and cones by removing dirt and grime from the threads.
Examine them for signs of wear and tear. If you roll the axle across a flat surface and it wobbles, it may be bent and need replacing.
9. Wipe down the dust seals with a cloth.
If they’re especially dirty, you can pop them off using a screwdriver for leverage.
10. After cleaning all parts, allow them to dry thoroughly before reassembly.
Reassembling the hubs
When you’re all done overhauling the hubs, it’s time to reassemble them. To reassemble the hubs, follow these steps:
1. If you removed the dust seals, press them back into place.
2. Apply a fresh layer of grease to each of the cups (as shown in Figure 7-8).
The general rule is to use enough grease so that a bearing will be covered halfway when placed in the cup.
3. Using tweezers or pliers, place half the bearings in one cup, spreading them out evenly across the cup (as shown in Figure 7-9).
The bearings should be held in place temporarily by the grease. Make sure there is at least a 1mm gap between all the bearings placed in the cup. If the bearings are too tight, remove one, so that each bearing has a few microns of elbow room.
4. Grease the axle and slide it halfway into the hub to hold the bearings in place while you fill the other cone with bearings.
Make sure that no bearings fall out during this procedure.
Figure 7-8: Filling cups with new grease.
Figure 7-9: Inserting the bearings.
5. While you’re holding the axle with one hand, place the other half of the bearings into the other cup.
After you’ve finished with all the bearings, slide the axle the rest of the way through.
6. Thread the cone onto the axle until it begins to press against the bearings in a secure fashion.
Twist the axle to ensure that the bearings are snug and in place.
7. Slide the washers and any spacers on in the axle in the correct order.
8. Thread the locknut onto the axle by hand (as shown in Figure 7-10) and, after it tightens, use a wrench to tighten it further while holding the cone in place with a cone wrench.
You don’t want to tighten the cone, because it could press forcefully against the bearings and damage them.
When tightening the locknut, leave a slight amount of play in the axle so that it can accept the additional force from the tightening of the quick-release lever.
9. Adjust the tightness of the hubs by following the procedure in the next section.
Figure 7-11 shows an example of tightening the cones in the hub.
Figure 7-10: Attaching the locknut.
Figure 7-11: Tightening the cones.
Adjusting a hub
The cones on a hub cannot be too loose or too tight — they need to be just right. What does that mean exactly? The tightness should be such that there is little to no play in the hub, but the axle rotates freely. If you have trouble finding the right point between too loose and too tight, err on the side of being slightly loose.
To adjust the tightness of a hub, you need a wrench for the axle locknuts and a cone wrench to fit the cone. To tighten the hub, hold the cone in place with the cone wrench and tighten the locknut with your other wrench. Only the locknut should move; if the cone is moving, it could press against the bearings and damage them. To loosen the hub, loosen the locknut.
If only a small adjustment is needed in the hub, you can adjust the locknut and cone on just one side of the bike.
Whenever you adjust the hubs of a wheel that uses quick releases, leave the cones just a little loose. Tightening the quick release will apply extra pressure to the bearings and take that little wiggle out when clamped in the frame. Be sure to check the adjustment once the wheel is clamped into the bike.
I Spoke Too Soon: Working on the Spokes
Wheels are an amazing feat of engineering — a handful of thin spokes woven together to provide enough structural integrity to support the weight of a rider going across various types of surfaces. To accomplish this feat, the spokes must be laced to the wheel in just the right pattern and tensioned evenly across the wheel. This aspect makes working on spokes a slightly complicated affair for a beginner. But with some practice, you can master some basic techniques — and that’s what this section is about.
Replacing a spoke
Replacing a spoke is manageable and a good place to get started. If you do end up needing to replace a broken spoke, take it with you to your bike store so that you can replace it with another spoke of the same size and width.
Keep in mind that the spokes on your wheels are probably of different sizes. In many cases, front-wheel spokes are not the same length as rear-wheel spokes. The same is likely true for spokes on the right side of the wheel hub versus the left side.
Here’s how to replace a spoke:
1. Insert the new spoke into the spoke hole from the broken spoke you removed from the hub.
You may need to remove the wheel from the bike to perform this procedure (see “Taking off a wheel,” earlier in this chapter).
2. Weave the spoke through the other spokes, following the same pattern, crossing and interweaving the same number of spokes as the others.
3. If the old nipple (the nut part that the spoke threads into) is undamaged and still in place, thread the end of the new spoke into it.
If the nipple is damaged, you’ll need to remove the tire, tube, and rim tape to replace the damaged nipple with a new one.
4. So that you don’t lose track of the spoke, mark it with a piece of tape or string.
5. Using a spoke wrench, tighten the spoke to the same tension as the other spokes.
6. To finish the procedure, true the rest of the wheel (see the following section).
Truing a wheel
Although wheel truing is an activity that takes time and practice to master, some basic wheel truing is possible for the casual biker. If you have a wheel that’s so out of true that it needs to be rebuilt, you probably should leave the job to your local bike shop. But if the wheel just has a slight wobble and needs a little tweaking, you may want to consider doing it yourself.
If the rim is bent, simple truing won’t suffice — the rim will have to be repaired.
Here are the steps for truing a wheel when there are only minor imperfections
in the wheel:
1. Remove the tire, tube, and rim strip from the rim.
For some truing stands, you can leave the tire, tube, and rim strip on the rim, although we find that we get the best results when working only with the rim.
2. Secure the wheel in a truing stand (as shown in Figure 7-12) if you have one; otherwise, you can keep the wheel on the bike.
If you have to true the wheel while it’s attached to the bike, use a bike stand to support the bike. Other options are to hang the bike from the ceiling or to turn the bike upside down on its handlebars.
Figure 7-12: Using a truing stand
3. Before you begin spinning the wheel, check it for loose or damaged spokes (as shown in Figure 7-13).
4. Make sure the wheel rim is 1/4 inch away from the calipers in the truing stand or the brakes on the bike.
5. Give the wheel a gentle spin and keep your eye on the calipers (or brakes).
You’ll be able to identify wobbles in the rim by where the wheel comes close to or comes in contact with the brakes.
Figure 7-13: Feeling for loose areas.
6. If the rim comes in contact on one side, use a spoke wrench to tighten the nipples of the spokes that come from the opposite hub and loosen those that come from the hub on the same side.
Loosen and tighten in small increments, around a quarter of a turn each time. Start in the middle of each wobble and work your way outwards from the center. Decrease the amount for each turn the farther away you move from the center. (Figure 7-14 demonstrates using a spoke wrench.)
Spoke nipples come in various sizes. Be sure to check the size of your spokes before you buy a spoke wrench.
Figure 7-14: Using a spoke wrench.
To tighten a spoke at the bottom of the wheel, turn the nipple in a counterclockwise direction. When the spoke is at the top of the wheel, the change of position makes it appear as if it’s in a clockwise direction.
7. After the wobble has been reduced, you can tighten the calipers to find any smaller wobbles.
As the wobbles become smaller, reduce the amount by which you turn the spoke wrench.
Don’t worry about eliminating all the wobble of a rim. It’s more important to have evenly tensioned spokes than to have a rim without a wobble.
If you can’ t get the rim perfectly straight, loosen and adjust your brakes to make them farther away from the rim so they don’t rub. If these brakes are no longer satisfactorily strong, however, you may need to replace the rim/wheel.
Chapter 8
Stopping Short: The Brakes
In This Chapter
Identifying the different types of brakes
Removing and installing brakes and brake pads
Adjusting your brakes
Addressing brake issues
When Dennis was a kid, one of his bikes had a braking system that required him to use his foot to stop the pedals and cranks from rotating forward in order to come to a halt. The advantage of this design was that he could look cool by skidding out when he needed to stop the bike.
Somewhere between then and now, skidding out has lost its appeal, and odds are, you’re less concerned with impressing your friends than you are with stopping safely. Fortunately, today’s bikes have braking systems that can consistently stop the momentum of the bike and the rider’s weight with little more than a firm squeeze of the brake levers.
Although brakes designs have evolved to be highly reliable when it comes to stopping a bike, this doesn’t mean that you should take them for granted. Proper maintenance and inspection of your brakes will increase the chances that, if you round that next turn too fast or if someone backs his car out in front of you without looking, you won’t have to make one giant skid mark.
We start this chapter with a quick overview of the different types of brakes on the market today. Then we narrow our discussion, focusing on the most popular type of brakes — rim brakes — and the various styles of rim brakes. We tell you how to remove and install brakes and brake pads, make adjustments to your brakes, and address common braking issues.
Types of Brakes
There are three major categories of braking systems on modern bikes:
Rim brakes: When you squeeze the brake levers of rim brakes, the brake cables pull on one or both brake arms, which causes the rubber brake pads to come in contact with the wheel rims and slow the bike down. The benefits of rim brakes are that they’re cheap and relatively easy to maintain, and they have a lot of stopping force. The drawback is that they don’t work well in wet or muddy conditions and they can wear out quickly.
The three popular models of rim brakes are:
• Cantilever brakes: Cantilever brakes (see Figure 8-1) have short, L-shaped brake arms that bolt to the frame and are connected by a straddle cable, which looks like an upside-down Y. They’re mounted on two pivots, one on each side of the wheel. The pivots (bosses) are set close to the wheel, which increases their mechanical advantage. Cantilever brakes have very good braking power. They’re commonly found on road bikes, mountain bikes, and touring bikes.
• V-brakes: V-brakes (see Figure 8-2) are sometimes referred to as linear-pull or direct-pull brakes. The brake arms are at nearly a 90-degree angle to the brake pads. V-brakes are mounted on two pivots on the frame, one on each side of the wheel. The longer arms give V-brakes improved leverage and greater stopping power. They’re commonly found on mountain bikes and hybrid bikes.
• Center-mount brakes: With center-mount brakes (see Figure 8-3), the brake cable attaches to one of the brake arms. The brake arms are together as one unit and mounted to a single pivot, which sits above the wheel. (In the double-pivot variety, there are two pivots — one on each side of the wheel — but still only one center mounting bolt.) The brake pads are at the bottom of the arms. Center-mount brakes don’t provide as much power as V-brakes or cantilevers. They’re commonly found on road bikes and lower-price bikes.
Disk brakes: Squeezing the brake levers on disc brakes (see Figure 8-4) causes the brake pads to squeeze against a metal disc that surrounds the hub. There are two main types of disc brakes — mechanical and hydraulic. Mechanical disc brakes utilize a cable to actuate the brake pads, whereas hydraulic brakes use a brake fluid pushed down by a piston through a brake line to generate braking power. Both types work well in both dry and wet conditions, and they’re quite responsive, requiring less effort from the hand when breaking. The advantage of disk brakes is they don’t heat up the rim on long descents, causing the tire pressure to increase and possibly blow out. Also, they don’t wear out the sidewall of a thin and lightweight alloy rim. The disadvantage of disk brakes is that they’re usually heavier, cost more, and require a hub that can accept a disk. Disk brakes are commonly found on mountain bikes.
Hub brakes: Sometimes called drum brakes, hub brakes are similar to disk brakes except the brake pads are pushed outward against the inside of a cylindrical drum inside the hub. The fact that they’re on the inside of the hub means they aren’t affected by wet, muddy, or dusty conditions. However, they are the heaviest of all the brakes. They’re found on some tandem bikes.
Figure 8-1: Cantilever brakes.
Figure 8-2: V-brakes.
Figure 8-3: Center-mount brakes.
Figure 8-4: Disk brakes.
Inspecting the Brakes
To ensure that your brakes are in good working order before you set off on your next ride, follow these steps to inspect them:
1. Examine the brake pads for excessive wear.
If they’re worn down such that the grooves in the pads are not visible, they should be replaced.
You may notice uneven wearing of the brake pads, which is usually caused by improperly fitted brake pads that aren’t parallel and contact the rim unevenly. Wh
en this happens, a curved ridge forms in the brake pad, which sometimes can cause the brake to grab the rim and get stuck.
The solution for uneven wear on brake pads is to use a utility knife to cut off the ridge and flatten the pad (see Figure 8-5). Another option is to use sandpaper or a file to smooth it out. This is also a good time to adjust the brakes so that they don’t continue to wear unevenly (see “Adjusting Brakes,” later in this chapter).
Figure 8-5: Resurfacing brake pads.
2. While you’re examining the brake pads, make sure they’re about 1mm to 2mm from the rim.
They might rub the rim if they’re too close or not give you enough braking power if they’re too far away.
3. Squeeze the brake lever and confirm that the brakes grab the rim firmly and parallel to the rim.
4. Examine the cable to make sure it’s firmly attached to the brakes and is not kinked, frayed, or worn in any spot.
5. Check the rims to make sure they aren’t dirty.
If they are dirty, use a rag and a solvent like rubbing alcohol to clean them.
6. If you just finished working on the brakes, give them a test drive while biking at a slow speed.
Removing and Installing Brakes and Brake Pads
If you ride your bike regularly, you’ll eventually have to change your brake pads. In this section, we tell you how to change brake pads and how to remove and install brakes (in case you need to overhaul or completely replace them).
Removing brakes and brake pads
The procedures for removing V-brakes and cantilever brakes are the same. Here are the steps to follow: