Bike furniture: how to classify?  

Its not naif, its too...
Its not naif, its too knowing... more about fun/camp ,not furniture design.Interesting, slightly amusing..lasting,no.

there must
be some 'name' for this kind of 'style'; in the eighties there were a lot of these furniture made of existing parts (i remember a chair that was a supermarket trolley etc) i wouldn't call it "readymade" since the parts were changed. Reminds me of africans who uses rubber car tyres to make sandals out of it. We could say that it is not really beautiful but what the h* are starcks designs always nice? So no-one knowns a name for this style?

In an article in 1968...
Charles Jenkins used the term "Adhocism" It became the title of a book he co-wrote with Nathan Silver in 1973. Although they are both american they were working in England at the time. It's a most remarquable book and I recommend reading it even more than 30 years later.
I do not know if "the case for improvisation" (subtitle of the book)they made applies to these bike-furniture-pieces because they seemed to be too well planned. It is no smart re-cycling in the eco-design sence of the word, at least not in an obvious way as Gerrit points out with one of the many re-uses of tires. (Tires as boat fenders is another one, or the more sophisticated Big Buffer Roll-about...or my favorite: the re-shaping of steel drums into a musical instruments) These pieces of furniture do not seem to have that quality and would probably fail the selection into adhocism...it is just not smart enough and from a conceptual point of view one would have been enough to make the point. the large number of them gives a similar feeling produced by hearing a joke too many times.

Two good reasons
to correct my previous posting. First of all I mis-spelled Charles Jencks name....secondly the book is still available...hence the link
http://www.abebooks.com/servlet/SearchResults?&isbn=0385016174&nsa=1

functional junk
The use of existing (found) objects for other use has been around for a very long time.
Marcel Duchamp introduced the mobile- sculture in 1913 with the "Bicycle Wheel". A bicycle fork and wheel mounted upside down on a stool.
Pablo Picasso's "Bull's Head" (1943?) cosisted of a bicycle saddle and haddlebars...a wonderful confirmation of Duchamps's assertion that for the artist it is only the idea that matters.

I guess we...
all know Marcel Duchamp's "ready mades", the bottle rack, the urenal, and indeed the bikewheel in the stool...but I think that this use of standard components for a purpose they where never designed for is different. In fact the number of variations indicates that this is something else than attracting the attention to an idea. Picasso, nor Duchamp intended any use for the new object, on the contrary. In this case function seems to play an important part.