The Spoke Curriculum - Session 2
Tire & Tube Service
Description
Demo of changing a flat
Details
Explanation of tire, tube, rim (i.e. wheel anatomy), proper pressure & the fact that tubes aren't air-tight. Have sample tubes so people can practice hands-on.
Content
| Primary Content | Instructor Notes |
|---|---|
| The wheel of a bike consists of the hub, the spokes, the rim, the tube, and the tire. The spokes hold the rim to the hub, and keep it straight through tension. The tire mounts on the rim, and the inner tube goes inside the tire. The tire is held in place through air pressure in the tube. The recommended pressure of the tube is usually written on the side of the tire: you should generally inflate a tire to the maximum recommended pressure. Once you have a tire inflated, squeeze it so you get a feel for what proper pressure should be. It should be quite firm. Keeping the proper pressure helps to avoid flats (if your pressure is too low, you can get "pinch flats", from the tube being pinched against the rim when you hit a curb or bump), and makes the ride much faster and easier.
Tubes are made of a rubber that isn't air-tight. So tires lose air pressure over time, even if they don't have any holes. This is normal, and means that you should check and re-inflate your tires every few weeks. If you do get a flat, it's usually due to a hole in the tube (not the tire: often, there's no damage at all to the tire). You can usually patch the puncture with a patch, which costs 25 cents. Patching a tube is a permanent fix: it's as good as new if done correctly. Some times the valve itself fails, or starts to break away from the tube. In this case, a patch won't work, and the tube should just be replaced. To fix a flat, put your bike in a bike stand. If you don't have a bike stand, lie the bike on its left side (non-drive side). Never lie the bike on its rear derailleur, nor sit the bike upright on its rear derailleur, as this can very easily damage it. Please refer to http://www.parktool.com/blog/repair-help/tire-and-tube-removal-and-installaton for full instructions on removing wheels, tires and tubes, checking for damage, and replacing tubes, tires, and wheels. Quick-release skewers must be fully-closed. Tighten the adjusting nut of the skewer so that when you close the lever, it meets resistance halfway through the swing. It should take a fair amount of force to fully close the lever (not superhuman strength, though). If the lever isn't closed all the way, it can open up from vibrations while riding, and the wheel could fall out. When the lever is fully closed, it will tend to stay closed from vibrations. |
Specific Skills
| Skill | Content | Reference |
|---|---|---|
| Tire and Tube Removal and Installation | http://www.parktool.com/blog/repair-help/tire-and-tube-removal-and-installaton | |
| Inner Tube Repair | http://www.parktool.com/blog/repair-help/inner-tube-repair |
Bolts
Description
Torque, lube
Details
Very quick demo of how to make sure bolts don't seize. Righty-tighty, but mention that there are two parts on the bike that are "reverse threaded", and describe cross-threading.
Content
| Primary Content | Instructor Notes |
|---|---|
|
In general, if a bike component has threads (for screwing things on or off, such as bolts), then the threads should be greased so that parts won't seize together. Grease is thick, as opposed to oil, which is runny. Most parts of the bike have a regular, "right-hand" thread. Turn clockwise to tighten, and counter-clockwise to loosen (remember: "righty-tighty, lefty-loosey"). Two parts normally don't, though. These have a left-hand thread and are "reverse threaded". The driveside (right) bottom bracket cup, and the non-driveside (left) pedal have reverse threads so that they don't unthread themselves from riding. These must be turned clockwise to remove them, and counter-clockwise to screw them in. If you're working on the pedals or the bottom bracket, always double-check that which way you need to turn the wrench! Always thread parts in mostly by hand, and only use a tool once it starts to become snug. This prevents cross-threading (threading in a part at an angle, which cuts new threads through the old threads), since you can't apply enough force by hand to damage the threads. If a part is cross-threaded, special tools called taps are required to fix it, if it's fixable at all. A rule of thumb for tightening parts is that you can turn them until they're snug, and then another 1/4 or 1/2 turn. Loose parts can fall out or cause damage from wiggling, while over-tightening parts can strip threads. Wrenches are generally sized to give an appropriate amount of leverage for the size of bolt: small bolts need less torque than big ones! |
Free Repair
Description
Work through chart.
Details
Try to do it in a similar order to diagnosis; dependent on student interests and skills, but the order has some reason.