Hubs

The hub is the middle part of the wheel, to which the inside ends of the spokes attach. Consists of an axle which attaches to the fork ends; a shell, to which the spokes attach, and bearings to connect the axle to the shell, permitting the shell to revolve around the axle. In the case of a rear hub, the shell would also have a provision for attaching the rear sprockets.

There are two general types of hubs:

1. Adjustable cup-and-cone: has loose ball bearings that can be adjusted for bearing play
2. Cartridge: the bearings, races, and cones are all assembled as a complete cartridge unit.

The freewheel is the mechanism that makes coasting possible. A ratchet mechanism allows the rear sprockets to drive the wheel forward but also allows the wheel to turn forward independently even when the sprockets are not turning. Freewheels are commonly sold with the sprockets attached, so this term is frequently used as a synonym for a cluster. A standard freewheel attaches to a hub by screwing on external threads that are part of the hub. The action of pedaling tightens the freewheel down to the threads, so no tools are required for installation. Removing a freewheel requires a special tool known as a "freewheel puller/extractor".
The freewheel puller/extractor is a splined unit that may be mounted on a vise or turned with a wrench. The splines engage matching splines in the interior (non-rotating) part of the freewheel body. Different brands of freewheels have used different spline patterns, but there is a recent tendency to standard on the Shimano pattern.The freehub is the Shimano trademark for a rear hub in which the freewheel mechanism is built into the hub itself, rather than being part of the sprocket cluster.

A cluster is a group of rear sprockets on a multi-speed bicycle. If the bicycle uses a thread-on freewheel, the term "cluster" would include the entire assembly including the freewheel mechanism. In the case of a cassette hub, the "cluster" would only consist of the sprockets and the spaces that separate them.

A cassette is a cluster of sprockets and spacers designed for use on a freehub. Some of the sprockets and spacers may be semi-permanently attached on one another by bolts or rivets.

What is the main difference between freewheels and cassette freehubs?

Traditional rear hubs come with a standardized set of threads to which a standard freewheel/sprocket cluster can be screwed onto. This allowed any brand of freewheel to be mounted on any brand of hub. If you wore out your sprockets, or wanted different gear ratios, you could unscrew the cluster and install a new one. Almost all bikes through the late '80s used this system.

Over the last few years, the Shimano freehub has largely replaced the conventional threaded rear hub. These hubs work better but you can no longer interchange hubs.

Why do you need to overhaul your hubs?

To maintain performance levels. Once dirt enters the bearing system, it acts like sand paper grinding down all the moving parts.

Tools to overhaul an adjustable hub:

1. Rags
2. Grease
3. 17mm open end wrench
4. 13mm cone wrench for the front hub
5. 15mm cone wrench for the rear hub

How to disassemble and service an adjustable FRONT hub

1. Remove the quick release skewer
2. Place the wheel on its side and slide a cone wrench onto the cone flats and then loosen the locknut with the 17mm open end wrench by turning it counter-clockwise against the cone wrench
3. Completely unthread and remove the cone, locknut and any washers
4. Put your hand over the end of the hub from which you removed the nuts and spacers (to catch bearings) and flip the wheel over. Have a rag underneath to catch stray bearings.
5. Slide the axle out fro the right side of the hub. Unless your axle is bent and needs replacing, leave the cone and locknut in place. If you do need to replace it, measure the amount of axle sticking out beyond the locknut.
6. With a screwdriver, gently pop off the seals that are pressed into either end of the hub shell. Be careful not to deform them; leave them on if you can't pop them out without damage.
   
7. Clean off all of the old grease off of the axle and cones and remove all of the bearings from both sides, making sure to count how many you take out.
8. Clean the insides of the hubs thoroughly and carefully inspect both the cones and the inner bearing races. Use a ballpoint pen to trace the bearing path. Roughness and wear twill be felt as the small ball of the pen passes over pits. If there is any damage such as pitting then the cone and/or hub should be replaced.
9. If you don't replace the ball bearings, make sure to clean them thoroughly by rubbing all of them between two rags. A lack of sheen on either balls or cones indicates wear and is cause for replacement.

How to reassemble an adjustable hub

1. Press the dust covers in both ends of the hub shell
2. Grease heavily inside the hub shell cup. Sheldon Brown says it's impossible to use too much.
3. Carefully insert all of the new bearings by pushing them down into the grease. When all of the bearings are installed, there should be at least half a bearing space left. Cover all bearings with a layer of grease.
4. Lightly grease the axle threads and the cone that is still attached to the axle and then slide the axle into the hub shell. Lift the wheel up a bit (30 degree angle) so that you can push the axle in until the cone slides into position and keeps all the bearings in place.
5. Holding the axle pushed inward with one hand to secure the bearings, turn the wheel over.
6. Smear grease into the bearing race that is now facing up. Lift the wheel and allow the axle to slide down just enough so that it is not sticking up past the bearing race. Make sure no bearings fall out of the bottom.
   
7. While the top end of the axle is still below the bearing race, place the remaining bearings uniformly around the grease.
8. Slide the axle hub back into place by setting the wheel down on the table, so that the cone is seated up into the bearings.
   
9. With your fingers, screw the top cone into place, seating it snugly onto the bearings. Covering the top cone with a film of grease is also a good idea.
   
10. In the correct order, slide on the washer and any spacers. Watch for those washers with a little tooth or "key" that fits the lengthwise groove in the axle.
    
11. Use your fingers to screw on the lock nut. Note that the two sides of the locknut are not the same.
    

Adjusting the bearings determines how far apart the cones are from one another on the axle. If they're too close together they will pinch and bind against the balls and the axle will be difficult to turn. This means that the bearings would have too much friction and the parts will wear out prematurely. If the cones are too far apart, everything may roll freely enough, but there will be looseness or play in the bearings and your wheel will wobble side to side like a loose tooth. The ideal is to find the point where the cones are loose enough that the axle turns as freely as it does when the cones are too loose, but with as little play as possible.

You

Clincher Tires

Bike Tire Sizes

• Diameter (the A part of A x B)
  
  • The size of a tire can be found on the sidewall. This measurement is written as two numbers, separated by an X. For ex: 700 x 23 or 26 x 2.10. The first number is the diameter of the bead of the tire, in mm or in. Most adult bikes come in either the 700mm size or the 26in size. You'll find 700 tires on road bikes and 26 tires on mountain bikes.
    
• Width (the B part of A x B)
  
  • The second number on the tire's sidewall. On a 700 x 23 tire, the width of the tire is 23mm. As the width increases, the tire will have more surface contact with the ground. More surface contact gives you a more stable and comfortable ride. Less, however, means less friction and a faster ride.
• Width Fractions and Decimals
  
  • If you ride a bike with a 26in tire, the tire width will be denoted with either a decimal or a fraction--for ex: 26 x 1/75 or 26 x 1 3/4. Take note that even though the two tires appear to have the same width, if one is marked with a decimal and the other a fraction, they are actually two different sizes. If you're looking for an exact size match, make sure you don't choose one fraction tire and one decimal tire.
    
• Measurement Discrepancies and the ISO
  
  • If you measure the diameter and width of your tire, you'll find that they don't exactly match what's written on the tire. The numerous sizing systems -- and companies that try to cheat on their sizes -- make it hard to know what the numbers on a tire really mean. Fortunately, the International Organization for Standardization, or ISO, has created a system for tire sizing to regulate tire measurement and take the guesswork out of choosing the proper tire. Most new tires and rims will show the ISO measurement. The measurement marks width first, followed by diameter. If you want an exact match when you replace an old tire, match the ISO number.
• Compatibility
  
  • When it's time to buy new tires, always get tires with the same diameter as your old ones but you can choose a different width. Your bike's rims will hold a range of tire widths, although not all widths are recommended for every tire. See a tire width chart that shows proper compatibility.

Four most common tire sizes (for adult bikes):

Each group is roughly defined by the diameter of the tire with varying widths available within the same diameter.

1. 700C: the most common tire size. Found on most road and hybrid bikes. Widths range from 20-23mm for fast road bikes and from 38-42mm for hybrids/touring bikes. It has an inner diameter measure (a.k.a. "bead seat diameter" [BSD]) of 622mm. A tire labeled 25-622mm == 700 x 25. There is, however, a huge variation of the "true" outer diameter among 700C tires. For ex: a 700 x 20 road bike tire may be as small as about 660mm in diameter. There is no foolproof way to know if it'll fit your wheel other than trial and error.
2. 27 inch: 2nd most common tire size. Very popular on 10-speeds common from the '60s to '80s, but not many (or none) bikes are being made today based on this tire size. However, replacement 27-inch wheels are still available for these bikes, and the tires will probably continue to be produced for years to come. Though 27-inch and 700C tires use the same inner tubes, the tires themselves are not the same and should not be used interchangeably.
3. 26 inch: prevalent on mountain and comfort bikes. Became the de facto standard of the mountain bike since the '70s. Commonly available in widths from 1.25 inches up to 2.5 inches. Standard BSD is 559mm. As with 700C tires, the true outer diameter of the 26 inch will vary from one brand and model of tires to the next.
4. 650C: used on some triathlon/time trial bikes and smaller-framed women-specific bikes. Typically 1 inch in width. Not the same as 26-inch tires. 650C uses a BSD of 571mm. Similar to 700C and 27-inch, however, 650C and 26-inch inner tubes are interchangeable, given a close enough width.

Types of Bicycle Tires

1. Road
   
   • smooth and narrow; no tread
   • typical size: 700 x 23c
   • heavier riders can ride up to 25-28mm widths
   • racers will use a narrower (18-20mm) width
2. Hybrid
   
   • similar to road tires, but usually wider
   • typically at least 28mm and wider
   • may have tread pattern, but more for wet-weather street riding than for off-road
3. Mountain
   
   • comes in a variety of width and tread patterns
   • width and tread are best determined by terrain
   • be sure to check rim width and frame and brake clearance when buying new MTB tires

29 (MTB) = 28 (Vintage) = 700C (modern designation) = 622 ISO. And 27 is bigger than them all at 630.

How to pick the right replacement tube

1. Identify the valve type (Presta vs. Schraeder)
2. Find the tire size written on the tire sidewall and find the closest tube match
3. Diameter: It is always best to buy a tube that matches your tire in diameter. A 24" tube for a 24" tire, but close metric equivalent will also do the job as long as it's not too big of a difference
4. Width: It's not as important to purchase the exact width of tire as the typical tube has a fair amount of elasticity to conform to your existing bicycle tire. However, it is the best approach to get in the habit of purchasing tubes that closely match your tire size. If you buy a slightly wider tube, say 1/2" more, it will not cause any harm or remain under-inflated, however it will be much heavier with the extra rubber. If you h
   

Wheels

A bicycle wheel consists of a hub, rim and spokes.

The hub is the middle part of the wheel, to which the inside ends of the spokes attach. It consists of an axle which attaches to the fork ends; a shell, to which the spokes attach; and bearings to connect the axle to the shell, permitting the shell to revolve around the axle. In the case of the rear hub, the shell would also have a provision for attaching the rear sprockets.


The clincher tire is used on 99% of all bikes and consists of an outer tire with a U-shaped cross section and a separate inner tube (basically a doughnut shaped rubber balloon) with air pressure keeping everything in place. The outer tire is made up of 3 parts:

1. The beads: two hoops of strong wire that make up the edge of the tire and holds the tire to the rim
2. The fabric cords forming the body of the tire, woven between the two beads.
   
3. The rubber that covers all the other parts is mainly there to protect the fabric and has no structural importance. The thicker rubber that contacts the road is called the tread.

Wheel truing is the process to make a wheel spin straight and round by evening out the tension in the spokes. The typical bike wheel is composed of a rim suspended with tensioned spokes around a center hub. Each spoke pulls on a section of rim. Spokes coming from the right side hub flange pulls the rim to the right and vice versa. Spoke attached at the rim are then offset in a left-right-left-right pattern to counter the pull of the other side.

How is spoke tension adjusted?

By tightening or loosening a threaded nut, called the nipple, at the end of the spoke. Spoke nipples come in different sizes so the correct wrench must be used. The correct wrench is the smallest size that can be used. Make sure that the wrench is fully engaged before turning.

Are you tightening the spoke or the nipple?

You are ALWAYS rotating the nipple. Therefore, when you true a wheel and you view the wrench and nipple upside down, you will tighten by turning the wrench left. Just imagine a screwdriver at the nipple end and turn clockwise/counter-clockwise as needed.

Steps for Lateral Truing

1. Carefully inspect the wheel for broken/bent spokes
2. Grab the rim and flex it side to side to check for play in the hub bearings. If the bearings are loose, the wheel will clunk side to side. The hub will need to be tightened before you true the wheel, or else the wheel will behave erratically
3. Mount the wheel in the truing stand, with the right side of the wheel on the right side of the stand
4. Where the rim scrapes, loosen the spoke(s) closest to it and tighten the spoke(s) on the opposing end. This approach will pull the rim away from the caliper. When correcting a wheel that is laterally out of true, always adjust spokes in pairs: one spoke coming from one side of the wheel, the other from the opposite side.
   
5. Check the wobble first on one side of the wheel and then the other, adjusting spokes accordingly, so that you don't end up pulling the wheel off-center by chasing wobbles only on one side. As the wheel gets closer to true, you will need to decrease the amount you turn the spokes to avoid overcorrecting.

How to stress-relieve spokes

• You should always pre-stress the spokes and re-adjust before riding. Failure to do so can cause broken spokes later. There are two ways to do this:
  
  1. Squeeze together parallel spokes on both sides of the rim OR
     
  2. Rest the wheel sideways on the floor and gently push down on both sides of the rim, all the way around the wheel in 1/8 increments
• After pre-stressing the spokes you will have to re-check and make some minor adjustments. If the rim looks severely warped afterwards, it means your spoke tension was too high. Loosen all spokes 1/2 turn and re-true the wheel.

Front Derailleur

The front derailleur consists of a cage that can move back and forth and from side to side. As it does so, it moves the chain between chainrings. It is attached to the frame, usually by a clamp surrounding the seat tube. There are different types of front derailleurs, the most notable differences include the type of mount and the direction that the cable pulls.

**Note: When using the barrel adjuster to change cable tension: counter-clockwise = increases the wire tension = towards bigger sprockets; clockwise = decreases wire tension = smaller sprockets.

The four front derailleur adjustments:

1. Height
   
   • Height is the principle factor in how well it will shift. Best performance results from the very lowest position that still barely keeps the cage from hitting the chainring teeth. A 2mm clearance between the bottom of the outer cage plate and the teeth of the large chainring is often recommended.
     
   1. Shift to the outermost chainring and rear sprocket
      
   2. Common front derailleurs need a 5mm allen key or 8mm box wrench to loosen the band-clamp bolt
   3. The outer cage plate must be positioned over the largest chainring when viewing height
   4. Tighten the clamp so that it is secure, but loose enough to move around with your hand
   5. Position the bottom of the derailleur cage as close to the largest sprocket teeth as possible so that it still clears. Move on to setting the angle.
      
2. Angle
   
   • This is set by looking down at the cage from above. This can be tricky and require some patience, as the shape of the derailleur cage is often not straight. You must position the outer plate of the derailleur cage parallel to the chainring so that the chainring sits equidistant and parallel to the cage plates.
   1. After following the above instructions for height, sight the chain from directly above to see if the outer cage plate and chainwheel are parallel.
      
   2. Rotate as needed and secure the bolt when you're done
3. Limit Stops
   
   • The L-screw controls inward-most travel and the H-screw controls outward-most travel; just like the rear derailleur. On older derailleurs, the low-gear limit screw is closest to the frame, but some newer models have reversed the screw's positioning.
4. Indexing Adjustments
   
   • Not all front derailleurs have an index setting. If the front shift lever is friction, there is no index setting.
   1. Shift to middle chainring and innermost rear sprocket
   2. View gap between inner cage plate and chain. Gap should be as small as possible without rubbing the chain.
      
   3. To reduce gap, increase wire tension by turning barrel adjuster counter-clockwise.
   4. If the chain is rubbing the cage, increase gap by lessening wire tension by turning barrel adjuster clockwise.
   5. If the adjuster is all the way in or out and no adjustment is possible, reset inner wire tension. Shift to innermost chainring and loosen inner wire pinch bolt. Turn in the barrel adjuster almost all the way clockwise. Pull wire gently with third-hand tool and tighten pinch bolt. Repeat steps 1 - 4.
   6. Test shift to all 3 chainrings.
      

Cables and Housing

Cables are used to control the gear shifting and brakes. They transmit force by a combination of tension on the inner cable and compression to the housing. Housing is the outer sleeve through which a brake or gear cable is pulled. The housing transmits an equal push to counter the pull on the inner cable.

BRAKE CABLESBrake cables should be tight enough so that the lever cannot be pulled all the way to the grip, yet loose enough that the brakes are not dragging on the rims.

To increase cable tension (so the levers don't hit the grip) you must turn counter-clockwise. If you need to tighten the cable more than you can by simply fiddling with the barrel adjuster, first screw the barrel adjuster in clockwise most of the way to leave some adjustment in the system. Loosen the bolt clamping the cable at the brake and check the cable for wear. If you don't need to replace it, pull the cable tight and retighten the clamping bolt. Tension the cable as needed with the barrel adjuster.

To reduce cable tension (so the levers aren't so stiff/brakes don't drag) you must turn clockwise. Make sure that the cable is tight enough so that the lever cannot be squeezed all the way to the grip.

How to lubricate brake cables

1. Release the brake cable
2. Compress the lever, pull on the housing and slide it through the barrel adjuster until the inner wire is exposed
3. Carefully squeeze a few drops of oil into the inner cable just above where it runs down into the housing
4. Slide the cable housing back into the barrel adjuster and re-connect the brake

Cable Installation

1. Remove the old cable, making sure not to lose any parts of the cable clamps or straddle-cable holders
2. Cut the housing sections long enough to reach the brakes and route them so they do not make any sharp bends. If you are replacing existing housing, look at where they bend before removing them. If the bends are smooth and do not bind when the wheel is turned or the suspension moves, cut the new housings to the same lengths
3. After cutting, make sure that the ends are clean. If not, shear off extra bits or file it down until it's a flat circle.
4. If the housing liner is mashed shut after cutting, open it up with a sharp object.
5. Slip a ferrule over each housing end for support
6. Tighten the adjusting barrel with one turn of being screwed all of the way in. Rotate the barrel adjuster and locknut so that their slots line up with those on the lever and lever body
7. Insert the round head of the cable into the lever's cable hook
8. Pull the cable down into the lined-up slots on the barrel and nut. Once the cable is in place, turn the barrel so that the slots are offset to prevent the cable from slipping back out
9. REAR: Slide the rear-wheel brake cable through the housing sections and then route the cable and housing from the brake lever to the brake, snapping the housing and cable into the slot in each stop
10. FRONT: With a V-brake, terminate the housing in the top of the "noodle" guide tube. On a cable-actuated disc brake, the housing usually terminates at a stop on the brake caliper. With a cantilever brake and a suspension fork, terminate the front-brake housing at the stop on the fork brace. For cantilevers without suspension, you may have a cable stop that is integral to the stem or one attached to the headset.
11. Attach the cable to the brake. Pull the cable taut and tighten the cable-clamping bolt. Pull the lever as hard as you can and squeeze it repeatedly for about a minute to stretch the new cable.
    
12. Adjust cable tension with the lever barrel adjuster
13. Cut off cable ends about 2.5" past the cable anchor bolts. Crimp end caps on all exposed cable ends to prevent fraying and bend the extra to the side.

How long should housing be?

The less drag on the cables, the better the shifting/braking. If housing is too short, it'll kink and bind, creating even more friction.

SHIFT CABLES

Increasing cable tension by turning the barrel adjuster counterclockwise (towards the spokes) will move the derailleur towards the lower gears/bigger sprockets. Decreasing cable tension by turning the barrel adjuster clockwise will move the derailleur towards the high gears/smaller sprockets.

How to lubricate the front shift cable

1. Shift the front derailleur to the largest sprocket and then stop the freewheel
2. Move the shift lever all the way to the opposite direction.
3. Disconnect and lube the upper housing of the front shift cable the same way as the rear
4. Reconnect the cable and once again make sure to shift the lever back where it was before rotating the crank.

How to lubricate the rear shift cable

1. Shift the gears until the chain is on the largest sprocket and stop the freewheel
2. Shift your shifter all the way into the opposite direction
3. Pull the cable and housing up and out of the first cable stop
4. Pull the upper section of the housing down leaving a section of cable exposed
5. Lube the cable the same way as a brake cable and reconnect the housing to the cable stop
6. Pull the lower section of housing free from the frame (out of the cable stop) and slide it away from the derailleur
7. Repeat the lubrication process and reconnect the housing
8. Move your rear shifter back to the largest sprocket before rotating the rear wheel

How to install new shift cables
(Carefully observe how the cable is routed before removing anything)

1. Removing the cable: Relieve the cable tension by shifting your derailleur so the chain is on the smallest sprocket on either your front or rear derailleur.
2. Disconnect the cable at the pinch bolt and cut the cable just before the flattened part where it was pinched.
   
3. Slide the cable out.
   
4. Turn the shifter barrel adjuster all the way clockwise and then back it off one full turn.
5. Turn the derailleur barrel adjuster all the way clockwise and then back it off one full turn.
   
6. Drop some light oil into the housings and make sure the housing's ferrules are firmly in place.
7. Route your cable the same way it was before and thread it under the derailleur's pinch bolt washer. Tighten it.
8. Adjust the derailleur as needed. Cut the wire and crimp it.
   

Chainrings

A chainring is a front sprocket, specifically of the type that would attach to the crank by being bolted on to a spider.

When should you check your chainring for wear? What should I check for?Check for wear whenever you replace your chain. There are three things to check for:

1. Checking wear on chainring teeth:
   
   • Wipe the chainring down and inspect each tooth. The teeth should be straight and uniform in shape and size. If the teeth are hook-shaped, the chainring needs to be replaced. The chain should be replaced as well because a worn chainring accelerates wear on a chain and because a worn chain causes hook-shaped teeth in the first place.
2. Checking wear on chainring bolts:
   
   • Check that the bolts are tight by turning them clockwise (usually with a 5 mm allen wrench). If the nut one the backside turns, hold it with a two-pronged chainring nut tool or do it carefully with a screwdriver.
     [Remember, chainring bolts can be different in that some will take a star-shaped TORX T30 tool instead of a 5mm hex key and others take a 6mm hex key for the nut on the backside]
3. Checking for trueness on chainrings
   
   • Look down from above and turn the crank slowly to see if the chainrings wobble. If they do wobble, make sure there's no play in the bottom bracket. It is possible to fix small, localized bends with an adjustable wrench but if it's really bent, replace it.
     [Note: It is normal to have a small amount of chainring wobble and flex when you pedal hard, but excessive wobbling will compromise shifting
     If you've installed a new chainring and still see serious back-and-forth wobble, chances are good that the spider arms on the crank are bent]

How to replace chainrings

1. Remove the right crank
2. Before moving your largest two chainrings you'll usually need to remove the smallest one as well, which is often threaded directly into your crank. Use the allen key to loosen all the bolts that hold the chainring in place.
3. Note the position of the chainring in relation to the crank before removing it completely. Sometimes chainrings have a bump sticking out that should be lined up with your crank.
   
4. The largest two rings are usually held together with a nut and bolt. First note their positions relative to the crank and after removal, remember the order and number of washers in between them.

Chainring Installation

1. Apply a thin layer of grease to the threads to keep out moisture
2. Reassemble your chainrings the same way they came apart with just your hands
3. Thread on all bolts finger-tight and then use your allen key to tighten them all in a star pattern, repeating this pattern until all bolts are tight (but don't overtighten)
   

Brakes

There are two basic types of brakes: Caliper and Cantilever

Caliper brakes are self-contained mechanisms that attach to the bicycle's frame via a single bolt. The brake arms reach downward from above the tire and need to be long enough to get around the tire.

Cantilever brakes attach to the sides of the bicycle's frame/fork, separately on each side. They can only be used on bikes that are designed to use them because they require special brazed-on fittings on the frame, commonly called "studs" or "bosses". The brake for each wheel consists of two separate arms, each of which is individually attached to the frame or fork.

Cantilever brakes divide into four sub-groups:

1. Direct Pull "V-brakes": used on most bikes since the mid-1990s
   Frame Pivot Studs: Below the rim
   Levers: Long pull; low tension
   Cable Routing: Cable comes in from the side; lower housing stop is part of the cantilever
2. Center-Pull (traditional) cantilevers: used on almost all MTBs before the 1990s and are still popular on touring and cyclocross bicycles
   Frame Pivot Studs: Below the rim
   Levers: Short pull; high tension
   Cable Routing: Cable runs down the bicycle's center tire; lower rear housing stop on frame, either special braze-on or mounted on the seatpost bolt; front housing stop on headset, fork or handlebar stem
3. U-brakes: were fashionable for MTBs around 1987, typically mounted beneath the chain stays
   Frame Pivot Studs: Above the rim
   Levers: Standard; short pull; high tension
   Cable Routing: same as center-pull
4. Roller Cam brakes: predecessor of the U-brake and had a brief vogue in the mid-'80sLever Compatibility
   
   Direct-pull "V" brake cantilevers require special brake levers. V brake levers pull the cable twice as far and half as hard. It is generally not safe to mix & match levers/cables between direct pull and other types for this reason.

V-brakes

The V-brake is a simpler design than the traditional cantilever brake. The V-brake only uses a single cable. The cable housing connects to one arm, the inner cable runs across the top of the tire to the opposite arm. When the brake is applied, the housing pushes on one cantilever while the inner cable pulls the other.

Since the cable runs straight across the top of the tire, V-brakes need longer arms to get the cable high enough to clear the tire. This increases the mechanical advantage of the system, requiring the use of special matching brake levers.