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On-Road Wheel Repairs

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by John "no potato chips, please" Allen
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The art of improvisation...

The usual tools and supplies for wheel repairs would weigh more than the bicycle. Certainly, you can carry a spoke wrench and a few spare spokes as you ride. But, if a wheel gets damaged far from home, you may need to perform a crude repair with improvised tools.

Broken spokes, minor rim bends and even "potato chip" wheels can often be repaired well enough without bike shop tools to get the bicycle rolling again, if your skill level is up to the task. More complicated or deeper bends call for more radical and riskier treatment. Wheel repair is a bicycle mechanic's most demanding task, and there is potential for further damage -- but you have little to lose if your are stuck far from help, or if you would have to replace the rim anyway to repair the damage fully..

Also read Sheldon's article about wheel trueing, along with this one.

Choosing wheels for repairability

A wheel is easiest to repair if it has 32 or more evenly-spaced, conventional steel spokes (more are better) and a shallow-section, lightweight aluminum rim.

Wide, heavy rims and deep-section aerodynamic rims are very stiff. If one is bent or dented, you are less likely to get it back into rideable shape. Avoid wheels which need special replacement spokes and a special spoke wrench. Steel rims crumple: avoid them too. Carbon-fiber rims split and tear, and are unrepairable. The lightest wheels make sense for racers -- but even racers keep a more durable pair of wheels for training.

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On-road wheel repair checklist

Work from top to bottom in this section of the article.

Know your wheels.

Sometimes you know why a wheel was damaged: a pothole, a crash. Sometimes, you don't -- usually there was an invisible problem with spoke tension. An ounce of prevention is worth a pound of cure, as the saying goes. Spin each wheel and check that it is true; also pull pairs of spokes against each other to check whether any are loose. This is a good way to get familiar with any wheel that is new to you, and to forestall problems. It is normal for the spokes on the left side of a dished rear wheel to be looser than the others -- but the spoke tension should be more or less even on each side.

OK, now on to actual wheel repairs.

Don't reach for the spoke wrench first!

If a spoke broke, or if the wheel got bent, the spokes are still in the same adjustment as they were before. Replacing the broken spoke will often bring a wheel back into true. Restoring a bent rim is much easier if you start by leaving the spokes as they are, as a guide.

Broken spoke repair

A spoke may break due to damage (for example if the chain chewed at the spoke); or because the wheel was unevenly tensioned; or because of poor support for the spoke elbow in a thin hub flange. Sometimes spokes break because they are loose and bend back and forth -- the way you break a paperclip, but over a smaller angle, for thousands of turns of the wheel.

You need the replacement spoke, a spoke wrench and tire-changing tools. Long-distance bicycle tourists generally carry spare spokes. Every cyclist, other than racers in competition, should be carrying a pump and tire levers. If the broken spoke is on the right side of the rear wheel, you need either to be carrying special Kevlar spokes, or -- unless the right rear hub flange is accessible from both sides -- a tool to remove your bicycle's cassette lockring or freewheel so you can install an ordinary spoke.

The Stein Mini Cassette Lockring Tool is the portable tool of choice for common Shimano and SRAM cassettes.

Stein Mini Cassette Lockring Tool
Stein Mini Cassette Lockring Tool

Removing a freewheel is more of a problem. You can carry a freewheel remover, but you won't want to carry the large adjustable wrench or bench vise you also need. You'll have to knock on doors till you find someone who will let you use one of these. A portable freewheel remover holder which uses a bicycle's handlebar stem for support was once available; no more.

Don't know whether your bicycle has a cassette or a freewheel? Read this.

You can unscrew the broken spoke from the spoke nipple and re-use the nipple if the threading of the new spoke is the same. Unless the rim has spoke-head recesses, you need to deflate the tire so the spoke nipple doesn't chew through the rim tape and puncture the inner tube as you install the new spoke.

With this rim, spoke nipple heads are not recessed.

Esposed spoke heads

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As the images below show, you can't tell whether the spoke heads are recessed unless you deflate the tire anyway to look inside.

Rim cross-sections
Rim without eyelets Rim with eyelets Rim with recessed spoke holes and no eyelets Rim with recessed spoke holes and eyelets Rim with double eyelets
Rim without eyelets Rim with eyelets Rim with recessed spoke holes and no eyelets Rim with recessed spoke holes and eyelets Rim with double eyelets

Trueing a wheel after replacing a broken spoke is the easiest wheel-trueing job, because you often only have to adjust the one new spoke. Mark the new spoke somehow so you can identify it. Once the spoke is getting tight, continue to tighten it bit by bit, spinning the wheel to check for true. If your skills are limited, the best is the enemy of the good. You may make things worse if you try to correct remaining minor wobbles by adjusting other spokes.

Try to figure out why the spoke broke. Were all the spokes too loose? If you are skillful at wheelbuilding, you may be able to strengthen it by increasing spoke tension. If the wheel is true but spoke tension is uneven, then the spokes were adjusted to pull an untrue rim into line, resulting in an invisible problem. A good repair would then require all the spokes to be loosened, to reveal the natural shape of the rim -- then either straighten it, if possible (see below), or replace the rim, and finally, tension and true the wheel.

Lacking tools and supplies to replace a broken spoke, you can unscrew it from the spoke nipple and remove it if it broke at the hub end; otherwise bend it around others so it can't catch on anything. Then, adjust neighboring spokes to make the wheel rideable. The wheel will still have a wobble, so, loosen a rim brake. Many sidepull brakes have a quick-release adjustment; otherwise adjust cable length. Avoid using a rim brake on a wobbling wheel -- the brake will work unevenly, and a brake shoe could rub on the tire or get caught under the rim.

Usually, once the wheel is at least rideable, you just ride carefully to a bike shop. You probably won't have a bad crash if a rear wheel fails. A front wheel is more of a safety concern. If it collapses or locks, you could land on your head.

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Potato chip wheel, taco wheel

Two places on the rim opposite one another are way over to the right, those in between are way over to the left, and the spokes have lost tension.

Often, surprisingly, a lightweight rim is only flexed, not bent, and the wheel can be sprung back nearly into its original shape.

  1. Do not touch the spoke wrench! The spokes need to stay at their original length.
  2. Remove the wheel from the bicycle. If it has a quick-release assembly, remove that. (Don't lose the two little conical springs). The tire should be on the rim, and inflated.
  3. (You removed the quick release so you wouldn't bend the skewer. Check?) Place the wheel on its side with the end of the axle resting on a firm surface. The sprocket side of a dished rear wheel should face down.

    Stomping a tacoed wheel

  4. Place a foot on one of the high spots of the rim. Hold the rim against the ground with that foot, and place your other foot lightly on the opposite high spot. Shift your weight slowly to the other foot. If you're lucky, the wheel will spring back (nearly) into shape with a "pop".

The wheel will still be somewhat out of true. Skip the next section, unless:

Eyeballing a wheelThe rim is bent to the side at one spot.

This can also happen without the wheel's being tacoed.

Still don't touch the spoke wrench. (It bears repeating.) A side bend can often be undone by an impact opposite the one which caused it. The spokes must be under tension, and the tire must be on the rim and fully inflated.

  1. Identify the location of the bend by spinning the wheel on the bicycle. Or holding the wheel vertically in front of you, spin it and stop it by letting it down with the bend against the ground.
  2. Hold the wheel horizontally in your two hands with the bend facing downward on the far side. Let the far side of the wheel down so you can see that it contacts the ground at about a 35-degree angle. You want the tire, not the rim, to contact the ground.
  3. Raise the far side of the wheel and then slam it down -- like chopping with an axe, at first lightly.
  4. Hold the wheel in front of you again and spin it to see whether the bend is reduced.
  5. Repeat, chopping harder if necessary, until you don't get further improvement.

chopping with a wheel

In his article about wheel trueing, Sheldon suggests bending the rim over your knee. This works with lighter rims, but with a heavier rim, you may not be able to apply enough force unless you use the chopping technique.

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A rim brake grabs each time the wheel comes around.

A stone, curb or other obstacle has flattened the tire against the rim and bent one rim flange, or both, to the outside, making the rim wider at that spot. The slang term for this damage is "blip". Often, the impact also punctures the inner tube with what is called a "snake bite" or "pinch flat". You'll have to fix that, too.

A grabbing front brake is especially hazardous, because of the risk of locking the front wheel.

If the rim is more than flat-spotted -- actually indented, taking on a bit of a heart shape -- see the next section (below) and get the rim pulled out most of the way before attempting to cure blips in the sidewalls.

If the rim is cracked, reach for your cell phone!

Sheldon wrote his article about wheel trueing when steel rims with hollow sidewalls were still common. He warns about pushing a sidewall in too far, and recommends using a hammer to remove blips -- but out on the road, you won't have a hammer. (Maybe a bell, or a song. Apologies to Pete Seeger.) With an aluminum rim, blip removal can be carried out safely with an adjustable wrench. Remove the tire, close the jaws of the adjustable wrench against the rim flange, and lever the rim flange back into position. It is best to place something soft under the jaw whose end is pressing against the rim, to avoid further damage.

removing a rim blip with an adjustable wrench

In the photo, note that the jaw of the wrench which is inside the rim extends all the way to the bottom of the rim, past the bead seat. If it were resting on top of the bead seat, you wouldn't be able to get the other jaw to lie flat against the side of the rim. Some rims do not have a bead seat, and you might place a small Allen wrench under the jaw to space it away from the hooked edge of the rim flange.

A thicker and stiffer cushion such as a chip of wood under the jaw which is outside the rim will spread the force from the wrench farther.

You might check the alignment of the rim flanges by opening the jaws of the adjustable wrench to use as a gauge, spanning the rim flanges. My 6-inch adjustable wrench did not open quite far enough to span this rim, so I used my fingers as a gauge, as in the photo below. Note that I have pressed my thumb and index finger against my middle finger, to help maintain a constant spacing. Only hold the rim lightly. The fingertips are very sensitive, and sliding the hand back and forth along the rim will reveal the high spots.

hand used as guage of rim width

Don't expect perfection, but you can probably at least make the brake work reasonably smoothly.

A rim has a flat spot or is dented inward

Pulling a dent from a rimA pothole, stone or curb has pushed the rim inward. A rim flange, or both rim flanges, may be damaged too -- see the previous section.

Don't touch the spoke wrench yet! A clever on road-repair technique -- I learned it from Sheldon -- is to tie a length of clothesline or a couple of toe straps around a fencepost and the rim so you can lever the wheel up and down. Do this with the inflated tire in place, if possible, to avoid damage at other places on the rim. Once the dent is mostly pulled out, straightening the rim flanges as described in the previous section will also make it easier to remove more of the dent.

Once the rim is pulled out far enough that pulling on it tensions the spokes, then deflate the tire, unless the rim has recessed spoke heads, and use the spoke wrench to loosen the spokes in the immediate area of the dent by a few turns. You need to pull the rim slightly past its final position so it will relax to where you want it. I suggest 6 turns directly over the dent, tapering down for two spokes on either side. Reinflate the tire, give the rim one last tug, then deflate the tire again, retighten the spokes and hope that even spoke tension has been restored.

Still out of true

After you have performed the crude repairs described above, the wheel will almost certainly still be somewhat out of true. Sheldon's article about wheel trueing will take you to the next step, if your skills and the wheel are ready to go there.

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