Prima LPR 450 wheels coming off

[swampydrill]

The steel runners on the top basket run through 4 wheels, 2 each side, problem is they keep coming off for some reason, i have put them on twice but there doesn't seem to be anything that keeps them in place, not sure if i need new ones or not. UPDATE, there is a slight ridge on the insdie of the wheels that locate in a groove, the wheels that are falling off have had this ridge worn down, hence they fall off, having trouble finding spares for them, any ideas??

 

[Leccy758]

Prima are mostly rebadged whirlpool machines

have a look on here it only list the prima 600 but alot of parts are fairly generic.

http://www.espares.co.uk/part/dishw.../714077/494974/dishwasher-lower-basket-w.html