Bikes are cool. Today I learned about a crank attachment system that uses tapered square plugs on the axle and then socket bolts to hold them on. Neither side is righty-loosy, but since the pedals don't push on the bolts to do the turning, they don't unwind. To get them off, you thread in an adapter where the bolt goes, and then use a second inner threaded bit to screw in and that pushes on the square bit and pops the crank arm off. Non-self-extracting 3-piece crankset.

Also worked on a fixie where the chain tension was controlled by moving the mounting point of the rear axle within slots in the frame.

Cranksets

1, 2, or 3 pieces. Pedals, crank arms, spindle, front sprocket(s). Spindle goes in the bottom bracket (bearings), which goes in the bottom bracket shell (part of the frame). Can be self extracting, that dust cap may be part of the self extraction mechanism and not a dust cap.

Bottom bracket

The bottom bracket is the set of bearings the spindle turns in. Bottom brackets may be press fit, thread together, or thread into the shell; can't tell without removing the crank arms. One piece crankets have bearings that slide over the arms and a retaining nut.

Cassette vs Freewheel (rear gearset)

In the cassette system, the one-way ratcheting mechanism that allows for coasting is built into the free hub. The rear sprockets slide onto splines in the freehub and are secured with a retaining nut. Sprockets may be separate pieces. This is newer.

Free wheel has the one-way ratcheting mechanism attached to the sprockets as a single piece, which gets threaded onto the non-free hub. Usually sprockets are part of the single piece. This is older.

If you spin the sprockets backwards while the wheel is stationary, and the retention tool mount spins with the wheel, it's cassette (tool mount attached to ratchet). If the retention tool mount does not spin, it's attached to a non-free hub and is thus a freewheel.

Headsets, handlebars, and forks

Disc brakes

Rim brake calipers

Grease on pivot bearing surfaces, threadlocker on pivot retaining hardware usually. Pads should aim for top or bottom of rim surface depending on if the pads swing down or up to contact the rim (relative pad/pivot positioning). Pads can be threaded or non-threaded and have various types of adjustments. Sometimes toe is achieved by bending the caliper arms.

Install calipers
Adjust pads in the calipers
Attach cable
Set clearance
Centre

Single pivot side pull (above rim)

Side pull. Centre by rotating the caliper axle. Pads won't contact the rim at the same time, that's okay.

Symmetric and asymmetric dual pivot side pull (above rim)

Side pull. Centre using spring tension.

Symmetric dual pivot center pull (above rim)

Center pull with saddle wire carrier.

Symmetric dual pivot linear pull (below rim)

"V-brake." This is what I have on my current bike. Centre using spring tension adjustment screws.

Symmetric dual pivot (below rim, suspension)

Cantilevered outward with a saddle wire carrier. Centre using spring tension and maybe relative length of the saddle arms?

Symmetric dual pivot (above rim, linear pull)

U-brake. The arms cross inwards and pull across, instead of being cantilevered outward and pulling up. Centring springs are built into the pivot nuts.

Front derailleur

Loosen the cable barrel adjuster and L limit screw until you can push the derailleur off the smallest gear. Dial the L screw tighter until the chain starts to rub on the second smallest gear, then loosen just barely until the sound goes away. Pushing the shifter down should not move the derailleur.
Adjust the barrel adjuster until shifting between all gears is sound-free and smooth.
On the second-largest gear, tighten the H screw until shifting to the largest gear doesn't work. Then loosen the H screw until shifting is smooth and sound-free.
Double check that every thing works.

Adjust the derailleur cage height/spacing from the chain so that it doesn't rub but isn't so far away the chain can slip out. Make the cage parallel to the sprockets. Not all cages allow adjustment, may need to bend things with pliers.

Rear derailleur, hanger

Some bikes have hangers built into the frame, some (mostly fixies?) have them inside of the rear dropout slot. Most are bolted onto the frame. There are way too many different hanger styles and they can be hard to find, so consider having an extra on hand. Use a tap or thread replacement spring if the threads for the hanger get screwed up. Hanger needs to be parallel to the sprockets for rear derailleur to work.

Loosen the cable barrel adjuster and H limit screw until you can push the derailleur off the smallest gear. Dial the H screw tighter until the chain starts to rub on the second smallest gear, then loosen just barely until the sound goes away. Pushing the shifter up should not move the derailleur.
Adjust the barrel adjuster until shifting between all gears is sound-free and smooth.
On the second-smallest gear, tighten the L screw until shifting to the smallest gear doesn't work. Then loosen the L screw until shifting is smooth and sound-free.
Double check that every thing works.

Rear derailleurs also have a B-screw used to adjust the spacing between the derailleur sprocket and the cassette/freewheel sprocket. 3-6mm is probably good.

Chains

If you're cleaning or swapping your chain, it's a good time to clean your sprockets, including the ones inside the rear derailleur.

Clean the chain with degreaser and then soapy water. Give it a good scrub. Put a dab of chain oil on each pin, trying to get it down where the surfaces bear rather than dousing the whole thing. Wipe off excess on the outside with a clean rag; oil on the outside doesn't lubricate the links, but does attract dirt.

Fixies have wide chains. Bikes with 2-8 rear sprockets use an 8-speed chain. Higher gears use gear-count-specific chains.

Measure chain wear using a chain wear tool. Fixies get replaced at 1%, 10 rear sprockets or less at 0.75%, and 11+ rear sprockets at 0.5%. If the tool fits into the chain, that's an indication that the indicated wear % has reached or exceeded that threshold. Start at 0.5% and work up until you find a setting that won't fit.

Take pictures of how the chain is routed through the front and rear derailleurs, for later reference.

When breaking a chain, use a quick link if the chain has one. Otherwise, push the rivet out until it's only being held by the outer plate. That way in an emergency you can push the rivet back in. Quick links don't have that problem, but can be tricky to deal with unless you have the right pliers.

If you have a chain that gives proper tension, you can use it to measure out the length of the new chain. Lay them out side by side and make sure you're measuring outside-to-outside or inside-to-inside plates. Since the worn chain has stretched, make sure to line them up rivet for rivet to get the measurement right. For riveted closure, measure inside on one end to outside on the other. For quick link, measure inside to inside one link shorter to account for the quick link length.

If you don't have a good chain to measure from, or you're changing sprockets or derailleurs, it's best to measure a new chain from scratch. Shift the front derailleur to the largest sprocket and the rear derailleur to the smallest (so the rear is out of the way). Start by draping the chain over the largest rear sprocket and pulling it forward to the largest front sprocket, around to the 5 o'clock position and hold it. Pull the other end of the chain the rest of the way around the rear largest sprocket and bring it up to meet the the first end. If you are using a quick link, remember to include that in your measurement. Find where an inner and outer meet (or inner inner, for quick links). If they don't line up the way they need to, loosen the chain by one link so they do. Then add two links to your measurement (one of them being the quick link, if appropriate) to get your chain size. The two largest sprockets are the furthest the chain would ever need to stretch, and the two extra links account for the rear derailleur.

If your largest rear sprocket has more than 36 teeth, get help.

To install, first shift the front derailleur to the smallest sprocket. Route the chain through the rear derailleur, using your photos for reference. Over the smallest rear sprocket, then over the smallest front sprocket. Sanity check the length of the chain by bringing the ends together and make sure the chain is not too loose. Then either quick link or rivet to finish the installation.

Hubs

Hubs are the center component of wheels. They have attachment points for spokes. They may have attachment for disc brake rotors. The rear hub mounts either the freewheel or cassette. The number of holes total on the hub (count both sides) should equal the number of holes in your wheel rim.

Hubs attach to the frame either by having the axle slot into dropouts, or by having the axle go through closed holes in the frame. They can be secured to the frame with nuts or skewers with quick releases. Adjust the inner nuts on the axle to center the rim in the frame. Some wheels are asymmetric to account for sprockets and brakes etc (this is called dishing).

The hub also contains the bearings that allow the hub housing to rotate around the axle. Note that when adjusting the bearings to remove play, if you're using skewers with quick release, the tightening of the quick release applies additional pressure to the system. Set bearing adjustment/tightness based on the installed wheel's behaviour with the quick release secured.

A freehub (for cassettes) includes the ratcheting mechanism that allows for coasting without pedalling.

If you have to disassemble a hub, take measurements and photographs of where all the components are arranged.

A rear hub with integrated brake, backpedal braking, includes brake shoes that get squeezed against the left cone of the hub shell. The left side has an extra arm that secures to the frame to help handle the torque generated by braking. The clutch when driven forward engages the sprocket, when at rest allows for coasting, and when pedaled backwards applies pressure to the brake shoes. Consider using a higher temperature lubricant for the parts inside these hubs since they encounter so much friction.

If your hub has internal gearing, seek assistance.

Wheels

Hub, rim, spokes, tubes, tires. The valve hole in the rim makes a useful reference point.

Truing

Get the rim to be a perfect circle when viewed axially and planar when viewed edge-on. Accomplish this by adjusting the tension in the spokes by turning the nipples. Consider removing the tire so the rim is easier to visualize.

If the wheel has been bent or damaged or cracked, truing is unlikely to correct problems. After truing the wheel, ride the bike to de-stress the wheel. A bit of popping and pinging is normal as they settle into their new positions.

Lateral

Using a truing stand or some zip ties on the bike frame, find the point of most lateral deviation. Get specific with it, down to a single spoke if you can. Tighten the spokes on the side of the wheel opposite the direction of deviation; if you're rubbing on the left indicator, tighten the right side spokes. 0.5mm deviation is acceptable.

Radial

This is the same process as lateral truing, but adjusting both sides together to try to eliminate deviations in the radius of the wheel. Try to balance the tightening efforts so that you don't pull the rim out of radial true. Some radial deviation is likely to be introduced even if you're careful, so every few radial adjustments, go back and verify the lateral truing before continuing. The rim will have an imperfect flexible tire on it, so don't get too caught up on perfect radial truing. 1mm is acceptable.

Dishing

Dishing refers to the symmetry or asymmetry created by the spokes that is used to center the rim relative to the frame. On a front wheel with rim brakes, the wheel is generally symmetric. Rear wheels with sprockets, or wheels with disc rotors, may use dishing to shift the rim to one side, allowing the additional components more room.

Dishing is measured by comparing the surface of the rim plane with the surface of the axle's inner bearing surface on the frame. A dishing tool can be used to measure this accurately. The hub body will not be centered between the forks for asymmetric wheels. If you don't have a dishing tool, observe the position of the rim relative to the frame when it's installed.

To adjust dishing, tighten the spokes on the side you want the rim to move toward. It is typical to have higher tension on the drive side of wheels that have brake rotors or sprockets.

Overall tension

While it's generally better to increase tension than decrease it, there are limits. Rim manufacturer will have a specification for overall wheel tension. You can use a tension gauge (with appropriate conversion table) to check the tension of every spoke in the wheel, identifying outliers and calculating the overall tension. If it's too low, the wheel will have more flex, and the rim will fall out of true and experience wear faster. If it's too tight, you may cause damage to the spokes, hub, nipples, or rim.

If there is a specific spoke that is too high or too low, adjust it towards the average for its side of the wheel. The spokes on either side of the same side of the wheel can be adjusted the opposite direction to maintain dishing and overall tension.

To increase or decrease overall tension, adjust every spoke on the wheel either tighter or looser 1/8 of a turn. Then remeasure to check your progress. After adjusting overall tension, you may need to redo the lateral and radial truing and the dishing procedures.

Lacing

Spokes can be connected to hub and rim in a variety of patterns. Radial uses shortest spokes and is nice for weight but not very durable. 1-cross, 2-cross, and 3-cross use progressively longer spokes, and their patterns and angles result in better resistance to torquing forces, lateral and radial deviation, and wear (but are slightly heavier). 3-cross is typical, especially for back wheels where drive torque is applied. Hard pushing, hard braking, and rough terrain all benefit from higher cross patterns. 3 should be the default unless you have specific performance needs and are willing to trade durability to get there.

Tubes and tires

15mm wrench, tire levers, spare tube and/or patch kit, pump, hex wrench for fixing the brakes afterwards.

Remove the tube and inspect for damage. If you can't find any, inflate it to twice its normal diameter and check again, or put it underwater. Also examine the rim and the tire for possible penetrations or other problems. "Snake bites" can indicate you're riding with too low pressure, causing the rim to impact a hard obstacle with the tube caught in between.

The tube needs to be properly supported by the rim (no holes, no pokey spoke ends) and by the tire (no holes, no thorns or other pokey bits). No gaps between tire and rim where the tube could squeeze out. Wherever it isn't constrained, the tube will bubble out until it pops.

When reinstalling, put a little bit of air in the tube to make it hold its shape, making it easier to position it inside the tire.

When installing the tire, position it so that the tire pressure values are in line with the valve stem, making them easy to find. Check to ensure the tube is not between the tire and the edge of the rim. Make sure the bead along the rim is not too high and not too low. Inflating can put pressure to pop a low one a little higher. Soapy water can make the tire slide into the right spot on the rim more easily.

Pump it up a little, check and adjust, pump it up a little more, repeating until the wheel is back at the desired ride pressure. Too high may exceed the ratings of the rim, rim tape, or tire, plus less cushioning for the bumps in the road. Too low may lead to rim damage and flats, plus increased rolling resistance.

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