Side wall damage is only an issue if steel belt is damaged if not then you are throwing money away, The strength is in the steel belt not the rubber

If tyres have bulge then get it changed ASAP and don't even use it as a spare tyre

jimbob79: I'm finding it hard just to find any official guide lines on the safety of the tyres.

Here you go.
https://vehicleinspection.nzta.govt.nz/virms/in-service-wof-and-cof/general/tyres,-wheels-and-hubs/tyres-and-wheels

 

Tyres (excluding spare tyres)

 

12. A tyre shows damage that is likely to compromise its ability to operate in a safe manner or lead to premature tyre failure, such as:

 

a) a lump or bulge that is likely to be caused by separation or partial failure of the tyre structure, or

 

b) a cut or crack in a sidewall or tread more than 25mm long that reaches the cords, or

 

c) exposed or cut cords, or

 

d) the tread of a retreaded tyre shows signs of separation, or

 

e) nails or other sharp objects embedded in the tyre, or

 

f) significant perishing, eg due to age, moisture or exposure.