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This photograph was circulating on social media on 20th November 2021

Image of parrot next to bicycle wheel that has been chewed.
(Click image to enlarge)

It was widely described as a carbon wheel that had been destroyed by a parrot. e.g.

  • Cycling Tips (Archived link, since the article has now been updated)

    There’s a full spectrum of ways for bike parts to be destroyed – crashing, driving into a garage, simple neglect. But it’s safe to say we’ve never heard of a parrot writing off a carbon wheel with its beak.

  • Bike Snob NYC

    They say carbon can fail catastrophically, but it can also fail hilariously.

However, some people expressed doubts:

  • BangAverageCat3:

    It's funny - but that's 100% not real. The chunks are foam rubber. I know this because my cat chews my foam roller and the debris looks exactly like that - and carbon doesn't look remotely like that when delammed

Has a parrot really destroyed a carbon fibre rim?

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  • 1
    I have added a link claiming it is carbon. There is another one here: facebook.com/groups/AndaBertanyaSainsMenjawab/posts/… but I don't propose to add it , as it is in Indonesian, so a bit confusing. Suffice to say people with even vague knowledge of bicycles are likely to believe this is carbon, and some have said so.
    – thelawnet
    Nov 22 at 11:27
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    Pedantry mode: (1) Are we distinguishing between "carbon" and "carbon fiber" here? Because foam is primarily made of carbon as it is a plastic derivative. (2) Destroying a carbon fibre wheel does not inherently mean destroying the carbon fibre component of the wheel. I could cut the metal spokes and destroy the wheel without ever touching its carbon fiber rim. In that sense, even if the bird is chewing foam, as long as it causes the wheel to be written off; the statement appears to be correct.
    – Flater
    Nov 23 at 11:32
  • We aren't distinguishing anything in the question, because the quote is from the world of cycling where 'carbon' refers exclusively to CFRP and only CFRP (and not, say, GFRP, and certainly not to a foam polymer).
    – thelawnet
    Nov 23 at 17:24
  • 1
    The Cycling Tips article has been updated to "But it’s safe to say we’ve never heard of a parrot writing off a high-end wheel with its beak." Nov 23 at 19:48
  • 1
    One thing to note is that this is an unusual construction. I know quite a bit about bikes and have changed tyres on aero wheels, but I've never handled a wheel with a foam fairing like this. People concluding that a high end aero rim with clearly non-metal parts means a carbon rim aren't being stupid by not expecting this
    – Chris H
    Nov 24 at 10:15
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Although there is no proof beyond the photo, it seems reasonable that the parrot did cause the damage. However, the rim, no longer in production, does not contain any carbon fibre - instead, it is structurally aluminium, with damage only to the aerodynamic foam.

The original source of this image is by Vanessa Wallace, the owner of the bicycle, a BMC TM01, from Winfield, Queensland, Australia, who was interviewed in the CyclingTips article, and who originally posted the picture on the Facebook group Brisbane Bike Market on 20 November 2021, along with a second photograph.

enter image description here

The bird is a 10-year-old female Eclectus parrot called Gypsy.

Meanwhile the wheel contains no carbon fibre at all.

The source of confusion about this image might be that some people are only aware of bicycle rims being made from carbon-fibre reinforced polymer (CFRP), a plastic often referred to simply as 'carbon fibre', from aluminium (or rarely magnesium) alloy, or from steel.

This rim is a Mavic CXR Elite Exalith. The word 'CXR' is clearly visible on it, and it is fitted to a BMC Timemachine triathlon bicycle.

A page selling the (now discontinued) wheel:

Blackcell™ flange is as light as carbon, easy to maintain and weatherproof

Blackcell is a marketing term meaning foam.

The technical specification says:

▪Material : Maxtal alloy with Blackcell flange

'Maxtal' is another marketing term meaning 'lightweight aluminium alloy'.

There is more information here on 'Blackcell':

Bikeboard Austria says that these wheels were fitted to OEM bikes from Canyon, Cervelo, BMC (the bike in the photo), and Rose, and offer a cost saving over carbon fibre, while improved aerodynamics compared to the wheel without the foam fairing (the depth of which is likely to be around 15mm).

There are three models listed, CXR Elite, CXR Elite Disc, and CXR Elite Exalith, with a depth of 60mm, and weighing 1.9kg-2kg.

Therefore:

  • the structural integrity of the aluminium underneath does not appear to have been damaged.
  • it would be possible to remove the rest of the damaged foam, with loss of the aerodynamic properties afforded by the deep rim.
  • however it is not clear if the underlying aluminium rim has a brake track, and whether or not the stripped down wheel could be safely stopped using the bicycle's brakes after the foam is fully removed.
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    Great answer, just a quibble over the last line: things don't have to be easily damaged for parrots to be able to break them. Although that particular species prefers softer fruits, their beaks can easily crush nuts and seeds. They might not be able to crush metal, but most hard plastics are no problems. Nov 22 at 11:27
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    Re the last point: you wouldn't be able to brake on foam, and putting a brake track on top of (even rigid) foam would add a major new failure mode (especially as brake tracks get rather hot); the braking surface also needs to be stiffly coupled to the spokes. The brake track is right next to the tyre bead, and you can see a material contrast & a join to the foam (clearer in 2nd pic @CyclingTips). That all implies the brake track is as on a normal aluminium rim, with the foam moulded to the inner face (that's manufacturable too). The brake track does look rather dull though, a bit odd
    – Chris H
    Nov 22 at 13:52
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    I think that this answer burys the lede which is that the bird did not destroy a carbon fiber rim; the bird did destroy a (non-structural) foam component of a wheel.
    – Dave
    Nov 22 at 15:36
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    I had to read halfway through this post to figure out the answer is "not exactly, but ...". Having that at the top would be helpful.
    – BurnsBA
    Nov 22 at 16:32
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    @NeilMeyer welcome to Bicycles Stack Exchange
    – Chris H
    Nov 23 at 14:42

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