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Inspecting your bike

To keep your bicycle safe and running well, periodically check for potential mechanical trouble. You or your favorite bicycle mechanic should deal with any of the following issues:

Does either tire look cracked, frayed, worn, or somehow uneven? If so, consider replacing one or both tires.

Lift each wheel slightly with one hand and spin it with your other hand. Does the wheel stop prematurely, wobble, or rub against anything?

Stand in front of the bike, facing it. Hold the front tire between your legs. Try to turn the handlebar while preventing the tire from turning. If you succeed, then the stem needs to be tightened.

While riding, squeeze each brake lever as far as it will go. The brakes need work if:

Does any cable not pull easily? Do any cables look slack, frayed, rusty, or otherwise damaged?

Is the drive chain rusty?

Does the bike seem to try to shift gears without you touching the shift levers?

Does any part look or feel looser than it should be?

Do you hear any rattles or other abnormal noises?

Do you see cracks, dents, unexpected bending, or other damage on any part of the bike?

Once your bike gets thousands of miles/kilometers of riding, the chain may need replacement. As chains experience wear-and-tear, they lengthen slightly; this causes them to mesh incorrectly with the cogs and chain rings. That creates inappropriate wear on their teeth that eventually could ruin those parts.

At least in the USA, it seems that all bike chains have a length of ½ inch (1.27 cm) from pin to pin when they are new. Place the zero mark of your ruler at the edge of a pin, and skip 24 pins to the right. With a good chain, you'll measure a distance of 12 inches (30.48 cm).

Based on that fact, I suggest the following method to check for chain stretch.

Put the zero mark of a ruler at either the left or right edge of a pin. Hold the ruler steadily in that position.

Ruler's zero at the left edge of a bicycle chain pin

Look 12 inches (30.48 cm) to the right. You should see a pin near to that point. You can assume that this is the 24th pin to the right of your zero mark. If it's located right at that 12 inch point then the chain is good.

Ruler inch mark is also at the left edge of a bicycle chain pin

If the measurement exceeds that by perhaps 116 inch (1.6 mm) or a little less, then have your bike shop replace that chain with a new one. Pictured here is an actual measurement for one of my bikes; it looks like my chain is a little more than 116 inch too long.

Bad chain: ruler's inch mark is not at the left edge of a bicycle chain pin

If the measurement is more than 12116 inch (and especially if 1218 inch or more), you may have enough wear on your cogs and chain rings that you will have to replace them also. Ask your local bike shop to look at your bike.

You can buy chain wear gauges that will easily tell you whether a chain is still good or not. For the chain I just showed in the last picture, I tried a gauge (not the one I just linked to). It claimed that more than just my chain would need replacement!