B. A Well-Maintained Bike is a Safe Bike
Motor vehicles must pass State-enforced inspections before being permitted on the open road. There are no such rules for bicycles. Nevertheless, maintenance issues have a significant impact on bike safety. For example, a sudden, unexpected mechanical failure, such as a brake cable snapping during a panic stop, can be deadly. In order to protect yourself and others, consider performing routine preventive-maintenance rituals and safety inspections, before each ride (or whenever you notice something unusual). Use the following checklist as a basic guide:
Something that I have found to be particularly dangerous is if the pedal "gives way" -- the cranking action "slips" -- under heavy pressure (such as when you are going uphill and must stand on the pedal in order to crank). This may be due to the following:
Condition of the chain: it should be clean, well-lubricated, rust-free, and not stretched or otherwise worn. Chains can break, especially when they are subject to high pedal force. This situation arises especially for a commuting/camping bike (think payload: camping gear, groceries, books) because a rider must apply more pedal force in order to propel the bicycle. This scenario is different than that in a standard mountain or road bike -- unless the rider is particularly heavy. A stretched chain can also cause an unexpected shift (caused by the chain jumping from one cog or chainring to another). Again this is potentially dangerous if one is "stand-pedaling", as may be necessary on up-grades. Replace the chain if worn or stretched. The chain may also be too long (i.e. too much slack). In this case, remove links accordingly. top of page
Above: A simple, no-tools-required
chain-stretch test: Shift gears so that bike is in 3rd gear on the front
derailleur (largest chainring) and on the lowest gear on the rear derailleur
(largest cog on the cassette or freewheel). Grab the chain by a link on
the chainring, as shown above, and try to pull it away from the teeth.
Ideally, it should only pull out a few millimeters.
If you can pull it so far that an entire tooth is exposed, the chain is
worn. This is also a good test to perform after installing a new
chain: if the chain is too tight, add a link; if it's too loose, remove
link(s).
Condition of the teeth on cogs and chainrings also affect drivetrain smoothness. Examine the teeth on all cassette cogs and chainrings carefully. Make sure none are broken or bent. Bent teeth may be straightened with a pair of pliers or an adjustable wrench. Teeth may also be worn. If teeth are broken or show excessive wear, replace the chainring(s) or cog(s). top of page
Above: Broken tooth on outer
chainring. This is often a result of the tooth actually hitting something
with ample force. This particular tooth was broken when I was carrying
the bike up a flight of steps: the chainring hit a concrete step, chipping
this tooth.
Tightness of cassette or freewheel is important: a loose cassette or freewheel can cause the chain to jump a cog. This is the same type of hazardous condition as in the case of the worn chain or worn/broken teeth noted above. top of page
Above: check the tightness of the cassette or freewheel by grasping the the largest cog and then attempting to wiggle it back and forth (perpendicular to the chain). If it's loose, it will need to be tightened. If it can't be corrected by tightening, the cassette body or the hub (and/or its bearings) will have to be adjusted or replaced.
Tightness of the Crankset is important and may also cause (or contribute to) hazardous chain jumping. Have an assistant hold the bike. Grab both crankarms firmly and attempt to wiggle the crankset back and forth (perpendicular to the chain). There should be no play. If there is play, determine if any hardware (bolts) is loose. If nothing is loose, the crankset may need an overhaul.
In addition to some of the conditions noted above, Adjustment and Precision of Shifting (as well as the chain staying on the desired cog or chainring) may be affected by these factors:
- Condition and/or fine-tuning of handlebar shifters
- Condition of shifting cables
- Condition and/or fine tuning of front and rear derailleurs
Drivetrain fine-tuning is an art and science in and of itself. Please check the References and Resources section for books and links that can help you develop skills to successfully address these issues.
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Guide to Bicycle Safety: [Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6 | Part 7]