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I figure that "tacoing" is a typo but I can't work out what it should be.

What is a taco, or tacoing a wheel?

Originally from this question

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Criggie
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To taco a wheel means you've bent it so badly its a write-off and cannot be salvaged through truing.

This is significantly worse than going out of true, because the rim will be creased or torn, spoke holes will be pulled through on the outside of the taco curve. A damaged rim alone is not a taco, there has to be a folded wheel to earn the title.

Examples: from http://blog.bikeridr.com/wp-content/uploads/2011/07/WheelTaco.jpg

Cause

Tacoing normally happens on the front wheel, and the usual cause is side-loads caused by having the wheel not facing the direction of your travel. That is, an aggressive turn, or a poorly landed jump can all push the rim over, exceeding the wheel's lateral strength maximum limits.

A Taco in progress: from http://i.imgur.com/qR5RnYt.jpg Thankfully this chap already has his full-face helmet on; going to need it in about 1/20 of a second. Video http://www.pinkbike.com/video/91552 More info https://i.stack.imgur.com/PDa6f.jpg .

Name

Why is it called a Taco? because the wheel looks vaguely like the Mexican/American taco

enter image description here

Other Names

  • Potato Chip - tend to be less damaging than a taco, and can be stomped back to shape.

  • Buckled / Buckling - this may or may not be damaged beyond recovery. I've heard it used for both tacoed wheels and also wheels that are slightly out of true.

  • others? Feel free to edit them in here.

Recovery

The rider is pretty likely to have suffered physical injury too - Collarbones are are particularly vulnerable because the rider has gone Over The Bars (OTB) as the bike stops.

The wheel is very probably scrap. The best fix is to replace the whole wheel (rim/spokes/hub/QR/axle/rotor)

You should be able to salvage the tyre/tube, but examine closely the bead near the fold. Stretching may stop it from seating safely on the new rim.

Also check the forks closely. Look for damage to the legs, and misalignment. If you have problems getting the wheel out/in because the dropouts are too close OR too far apart then the fork needs servicing, or full replacement.

Headsets can suffer as well due to the leverage applied, putting steering bearings under additional load. Any doubts and you should disassemble the headset, and examine the steerer for bending, bearings for damage, and cups for dents.

Frames - a classic pattern of damage on older steel bikes was a ring of rust around the top tube and the down tube, approximately 50mm/2 inches aft of the headset weld or 25mm/1 inch after the end of a lug. However modern alloy bikes tend to be much better at resisting damage here. Do inspect for cracks, and include a periodic crack check in your usual maintenance procedure.

At best, you will be able to reuse the hub and rotor, and relate them onto a replacement rim and spokes. Examine them very closely for damage before reuse. Reusing spokes/nipples is a bad idea because the ones on the outside of the taco have been stressed and could be elongated. So the minimum damage is a new rim and spokes.

Criggie
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    Taco'd wheels in a lot of cases do not need to be written off. In a decent number of cases (esp. on road riding), the rim is not actually bent permanently, but flexed out. With a bit of elbow grease and work, you can have a perfectly ridable wheel again (even as an on-road repair). – Batman Jan 24 '17 at 20:20
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    I've also heard this referred to as a potato chip – Paul Jan 24 '17 at 20:29
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    @Batman then its a difference of degree thing - if it can be unbent then its not tacoed, just a bent or badly out of true wheel. The examples above will have suffered tearing of the rim's metal. – Criggie Jan 24 '17 at 20:32
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    Also, steel rims are much more elastic and can come back from much more damage, whereas alloy rims can exceed their elastic limit and be damaged permanently, even with less overall bending. – Criggie Jan 24 '17 at 20:33
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    Yeah, but the usual usage of Taco'd doesn't preclude wheels which can be recovered (and in many cases, are wheels that can be recovered). – Batman Jan 24 '17 at 21:56
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    @batman Then its not a taco. Perhaps the defining difference is whether there was a crunch (like biting into a crispy taco) vs it is bent, like a potato chip. This may be a regional distinction, but tacoed is another way of saying the wheel is dead. If its not dead, its not a taco. – Criggie Jan 24 '17 at 22:07
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    I've only ever heard Taco'd in the USA as a reference to the food and to indicate the rim is in that shape, but it's not a requirement that the wheel be completely destroyed (though it usually is). – whatsisname Jan 25 '17 at 03:14
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    If the rim is taco-shaped it underwent defformation that high it must have ben made of Ni-Ti superelastic alloy to have a chance to be reused. If the rim is potato chip-shaped there is still high chance it underwent plastic deformation and thus it's very bad idea to reuse it. – Crowley Jan 25 '17 at 15:20
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    The word is also used in whitewater rafting. When a raft is folded by the force of water (pitching out the passengers) it is said to have tacoed. (I couldn't find a good image). – Jeremy Miles Jan 25 '17 at 17:10
  • @Crowley yes - the elastic limit by Hooke's Law, is the point where it will unbend vs where it becomes permanently elongated. More often used with respect to springs, but still applicable here. – Criggie Jan 26 '17 at 00:22
  • As far as I know the correct engineering term for this failur mode is buckling. "In science, buckling is a mathematical instability that leads to a failure mode." from WP. It would be good if this expression were to show up in the answer, preferably the header since (a) it may make it more findable and (b) somene used to the expression does not need read on. – gschenk Jan 26 '17 at 19:56
  • @gschenk done - good point. – Criggie Jan 26 '17 at 22:27
  • @paul same for your comment. – Criggie Jan 26 '17 at 22:27