S.4(1) of the MOT Inspection Manual for Class 3-7 vehicles states:
"This inspection applies to tyres fitted to road wheels only. The vehicle presenter should be informed when it is noticed that there is a defective tyre on the spare wheel".
S.4(2) goes on to state:
"This inspection applies to the road wheels fitted to the vehicle at the time of inspection only. The vehicle presenter should be informed if a defect is noticed on the spare wheel".
Note that both quotes make specific reference to the fact that the MOT test only inspects the road wheels, not the spare wheel(s). Furthermore, no reference is made to the spare wheel or its condition in the "reasons for rejection" section of either
S.4(1) or
S.4(2).
Section 4 of the Class 3-7 MOT Inspection Manual:
http://www.motinfo.gov.uk/htdocs/m4s04000001.htm