Bearing unit for a bottom bracket bearing of a bicycle or the like

A bottom bracket bearing unit receivable in a pedal-crank axle housing of a bicycle or the like, said bottom bracket bearing unit comprising:

• a long sleeve composed of a synthetic resin and formed with a flange at one end;
• a short sleeve composed of a synthetic resin, interfitting with an opposite end of said long sleeve and formed with a flange, said long sleeve being formed internally with a plurality of axially spaced inwardly open grooves defining respective outer bearing races, said grooves being provided in two pairs of closely spaced grooves respectively located proximal to each of said ends of said long sleeve and having a spacing between said pairs which is greater than a spacing of the grooves of each pair from one another;
• a crank axle received in said sleeves and having opposite axial ends projecting outwardly from said sleeves, said crank axle being composed of metal and having a respective outwardly open groove extending circumferentially around the crank axle and opening toward and registering with a respective one of said grooves of said sleeves to form another inner bearing race therewith;
• and
• bearing balls received in the registering bearing races of said sleeve and said crank axle and rolling in direct contact with the synthetic resin of said long sleeve, the bearing balls of each of said pairs together with the respective races forming a respective double ball bearing journalling said crank axle in said sleeves.