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Bike Check Time
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by John "General Practicioner" Allen
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Testing your bicycle

Bicyclists should know how to check their bicycles. Correct adjustment of quick-releases and brakes is especially important for safety. More extensive testing can help you locate and identify mechanical problems.

Quick Safety Check

The ABC Quick Check, which instructor Dan Gutierrez demonstrates in this video, covers most of the basics. (Note: the CyclistView Web site, now is not the same one as when the video was made.

Additional tests

Here are some additional quick tests which are useful if you are checking out a bicycle whose history you don't know, or to see whether it is safe to ride after taking a fall.

Test the wheels

Spin each wheel to see whether it runs true. Look at it from on end to see whether it weaves from side to side. Side-to-side weave can drag the rim against a brake shoe. Look at the rim from the side to see whether it has dents from pothole impacts and the like. These can cause rim brakes to grab.

Grab spokes between your fingers and the base of the thumb to check for looseness. The spokes on the less steep side of a dished wheel (left side of a rear wheel, right side of a front wheel with a disc brake) will be looser, but the tension of all spokes on the same side should be approximately equal.

these problems may require replacing the rim, or only require truing the wheel.

Also examine the tire while a wheel is spinning. It should not have dips or humps. If it does, check for poor seating of the tire, or damage.

Slowly turn the tire and check it for cuts and embedded shards of glass, etc.

Brake lever feel

The brake should start to engage when the lever has moved only slightly. If the brake does not engage until the lever is nearer to the handlebar, you can have what I call a "jiu-jitsu" brake. In an emergency stop, it can fool you into thinking that it will not engage, and then engage unexpectedly and dump you. A brake lever should have a springy feel. If it feels stiff and you can't squeeze it very far, it is probably mismatched to the brake. You should not be able to pull the lever all the way to the handlebar. More detail about this is in our article about cables.

Headset bearing and brake looseness tests

Stand on the left side of the bicycle, to avoid getting chain dirt on your clothing. Hold the bicycle with the front end tilted down so the front fork is vertical. (With a diamond-frame bicycle, you will be resting the top tube on your shoulder, just ahead of the seat tube.) If you wave the front end of the bicycle lightly from side to side, the front wheel should swing freely in the opposite direction. If it hangs up, the headset (steering) bearings are binding.

Then bounce the front wheel lightly off the pavement. The front wheel and fork assembly should vibrate. "brrrrrr". If the headset bearings are loose, it will clunk.

Place your finger over the headset bearing assembly, touching both the part which turns and the part which is attached to the frame. Then hold the front brake lever and rock the bicycle backward and forward. If the headset is loose, you will feel the motion. If the bicycle still clunks back and forth, there is looseness in the brake. Some slight looseness in a rim brake is normal. You can test for looseness in the rear brake the same way.

Dropout alignment tests

Are the dropouts on your bicycle aligned correctly, or are they flexing/bending hub axles? There are a couple of quick ways to check for this.

With the quick release or axle nuts loose, check the gaps between the dropouts and the hub locknuts. Look from above, the front and the rear, with an eye in line with a gap. Are the sides of the gap parallel?

If you bicycle has quick-release wheels, the quick-release lever should engage abruptly, and the force should increase steadily as the lever is pushed home. If a dropout is misaligned, the quick release lever will start to engage earlier, and will tend to spring back.

With a nutted axle, also, engagement of the nut should start abruptly and it should take only a fraction of a turn until the nut is tight.

Shifting

Test shifting with the rear wheel off the ground -- bicycle on a workstand, saddle hanging over a tree branch, a friend hold the rear wheel off the ground.

On a derailer-equipped bicycle, with the chain on the large chainwheel, turn the crank forward and shift up and down to all the rear sprockets. The chain should not bind as it reaches the largest sprocket. If it does, it is too short. Do this test before riding a bicycle where the chain has been replaced, to avoid damage.

Indexing should shift the bicycle reliably onto each sprocket when shifting both up and down. If it doesn't the cable and/or derailer needs adjustment. See our article on derailer adjustment.

Shift the front derailer to each chainwheel with the chain on the largest rear sprocket. Again, there should be no binding. Now repeat this with the chain on the smallest rear sprocket. The chain may hang loose or rub on the side of a larger chainwheel when on a smaller one. That can be normal with a multi-range system. You shouldn't be using the criss-cross combination anyway. See our article on gear theory for details. It should be possible to shift the front derailer so the chain does not rub.

A bicycle with an internal-gear hub should shift smoothly to every combination. Start in the lowest gear and shift up while turning the crank. With each shift, you will have to accelerate the rear wheel. Apply the rear brake lightly after each downshift, so you can tell that the hub is engaged.

Excess drag tests

The front wheel bearing is easy to test -- see Sheldon's article about bearing cone adjustment. It is common for quick-release wheels to be adjusted too tight, because the quick release mechanism compresses the axle.

Because the rear wheel is connected to the drivetrain, you need to do more complicated testing to identify the source of excess drag.

On a bicycle with a non-derailer drivetrain (fixed gear, singlespeed or internal-gear hub), try pressing down on the top run of the chain with a wrench handle as you turn the cranks. If the chain straightens out completely at any time in spite of the downward force from the wrench, it is too tight. Readjust it as described in Sheldon's article about fixed-gear bicycles. Then test again.

If the bicycle has a fixed gear, first test the entire drivetrain at once. Holding a pedal, spin the cranks forward with the rear wheel off the ground. Then let go of the pedal. The drivetrain should take 30 seconds or more to coast to a stop. If it only takes a short time, the bicycle could have a tight wheel bearing, tight bottom bracket bearing, or binding chain. You might also have a brake shoe rubbing, but you would probably hear that.

On any bicycle which does not have a fixed gear, hold a pedal and, spin the cranks forward with the rear wheel off the ground,.so the rear wheel also turns. Stop turning the crank. There should be only a very light forward push. With an internal-gear hub, you might try this in the different gears to see whether there's a problem in some gears.

With the rear wheel off the ground, hold a pedal and give the crank a spin backwards. Unless the bicycle has a fixed gear, the crank should turn easily and the rear wheel should follow only sluggishly. If the chain turns the rear wheel backward strongly, the freewheel or internal-gear hub has friction -- usually, a tight bearing. If you feel drag but the rear wheel does not turn backward, the drag is in the bottom bracket bearing or in the chain. You can isolate which by removing the chain from the chainwheel so the cranks turn freely. Give them a spin. They should take a long time to coast to a stop.

Spin each pedal. It should turn smoothly without binding.

Test Ride

If a bicycle is new to you, has just had work one on it, or has been crashed but still looks OK, take a short test ride to check the steering, brakes and shifting.

Brake test

You need to learn a feel for the brakes, so check while applying them lightly while riding slowly. You could go over the handlebars if the front brake is more sensitive than you expect. Or braking may be weak, in which case the brake needs to be adjusted or replaced.

Drivetrain testing

The drivetrain may test OK with the bicycle on a workstand, yet the pedals may jump forward when under a pedaling load. This may be due to worn sprockets, chain or freewheeling mechanism. While applying power, test every combination except the ones where you found that the chain drags on a larger chainwheel or hangs loose.

Does the bicycle track straight?

During your test ride, lift one hand off the handlebar, keeping the other hand close to the handlebar. If the bicycle tends to weave from side to side, get both hands back on the handlebars and disable that bicycle so it can't be ridden! It has negative trail and will immediately dump the rider if ridden no-hands. If the bicycle is stable with one hand on, then carefully try to ride no-hands. If the bicycle steers to one side, something is out of line. Usually it is the front fork, but it may also be the frame, or a misaligned wheel.

A properly assembled bicycle is quiet. A rattle as you ride is a warning that something may be about to fall off. Lift each end of bicycle about 4 inches and drop it to locate a rattle.

Noises

Sheldon's article on creaks, clicks and clunks describes other noises your bicycle could make as you ride, and how to identify the causes.

 

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