Families of A(1)-contractible affine threefolds

We provide families of affine threefolds which are A(1)-contractible (that is, contractible in the unstable A(1)-homotopy category of Morel-Voevodsky) and pairwise non-isomorphic, thus answering a conjecture of Asok and Doran. As a particular case, we show that the Koras-Russell threefolds of the first kind are A(1)-contractible, extending results of Hoyois, Krishna and Ostvaer.