The ol' car failed its MOT last week - and one of the things was a bulge on a tyre side wall. Which they'd chalked. Just as well, because I'd not have found it otherwise. What are the actual regs? If there is a bulge, I'd say it's no more than a 1/16th of an inch proud. Almost just tolerance in the rubber.
"a lump, bulge or tear caused by separation or partial failure of its structure is a fail. care should be taken to distinguish between normal undulations in the carcass, resulting from manufacturing, and lumps or bulges caused by structural deterioration "
If you are unhappy with the failure then ask for a form VT17.
If you think the tyre is actually OK then why not make it the spare?
No damage visible.
I'd not want an unsafe spare either.
Take it off teh rim and have a look inside. Ofc that may leave you none the wiser really.
Would anything necessarily show inside? If a 'cord' or whatever had broken?
Probably not :)
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