Cobra Linear Inner Tube – From BMX to Velomobile?

photo of cobra Inner-tube

A rather ingenious product that came to my attention while reading up on the ELF velomobile was the Cobra Linear Inner-tube by flybikes.

Rather than having a full anulus as in a normal inner-tube the Cobra is a stright length of tubing sealed at both ends with a small loop allowing the both ends to be joined into a circle at the valve point.  I was not aware of the product before, but in hind sight it is really obvious and goes to show how one’s thinking can easily be limited by just doing things the way they have always been done.

This has several advantages.  Besides the claimed improvement in the speed of changing a flat tyre, flats can also be easily changed without the need to remove the wheel.  This obviously is of very significant use to most velomobiles.  While velomobile wheels are often cantilever mounted allowing access for a traditional inner-tube there is usually at least one wheel which is more difficult to access.  For example the the rear wheel in a tadpole based velomobile is usually mounted in a fork with the added complexity of a rear drive train and often partially or completely hidden within the body.  In such a case the Cobra would be a life saver.

The following video on Vimeo demonstrates the tube changing process.

While designed for BMX, Flybikes supply many BMX components, it is not clear in what sizes the tube is available besides the 20″ 406 standard BMX wheel size however, since many velomobiles use this size, it should be possible to fit the tube to several models.  It is interesting that Organic Transit explicitly recommend the use of a “Cobra or similar” tube for the ELF rear wheels which appear to be 26″.Photo showing cobra Inner-tube join

Some questions remain as to how the tube performs both in the short and long term but assuming you can source a tube in your wheel size it would still be a good idea to keep one and a pair of scissors in your velomobile emergency kit.

If any readers have any experience with this or similar inner-tubes please let us know via the comments below.

 

2 thoughts on “Cobra Linear Inner Tube – From BMX to Velomobile?

  1. I have a tadpole trike and am keen to buy a few 26 inch tyres for my rear wheel and I’d happily buy a few 20 inch ones for my front wheels, but the rear wheel linear tube would be an absolute life – saver. I would regard it as the most important ( to me ) cycling advance ( after modern hub generators and LED lights) in the past forty years.
    I you can provide me with details ( Cobra don’t seem to be interested ) of where I can buy 26 inch linear tyres I shall be eternally grateful.

    Regards,

    David Rand.

    • David,

      Your query has prompted me to do some more digging which has resulted in some small success.

      The last time I looked into this I was only able to find the 20″ tube for sale, for example at Evans in the UK, and I had come to the conclusion that there were no other sizes available. Some more persistent digging this time has turned up more prospects.

      Via some cycle forums, e.g. the CTC forum and here, an alternative tube (with a similar reptile name) the Sidewinder, can be obtained in 24″ and 26″ sizes from St. John Street Cycles for less than £1 a piece! There is also reference to similar (maybe the same) tubes, formerly sold by Halfords, but there is some negative feedback about these, that they tend to fail prematurely at the tube ends. Based on the SJS Cycles photo and the price it would seem these are a cheaper design with likely cheaper performance.

      Returning to the Flybikes, Terracycle in the US have a page for a 26″ Cobra, however it is currently out of stock. Further search via the Flybike site and another forum confirm that 24″ and 26″ versions were produced when the Cobra originally launched in 2009. A B2B distributor site also confirms the existence of the larger sizes but they don’t deal with the general public. I’ll continue to chase this and if I can source a supplier I will post the link here.

      As a final thought Schwalbe have released a specialist tyre for trikes. Perhaps they will get round to making a similar split inner-tube to serve the same market.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>