Many moons ago i had an MG Metro turbo (the ones with the 6r4 shell ) i used to drive it really hard, one day i was scraping the door handles off the car (just an expression, the door handles don't actually get scraped) on a roundabout (it handled like a go-kart) when a big truck cut me up/ changed lanes and blocked me off - i had no where to go exept to batter into the kerb (at high speed) there was no suspension damage, the tyre stayed up but there was 2 (inside and outside) big bulges in the tyre, and 2 small dents in the rim, when i went to replace the tyre i discovered that the MG Metro turbo has special tyres made for it by one manufacturer - hard to get/ must pay full price etc

So i kept running it like that for a year or so, / or untill the tyre wore out, continuing to drive very hard with no problems (untill i blow the engine up)

Im older and wiser now, and i would remember which corner i put the tyre back on so that i would be ready when the car spins off backwards, (on the rear) or understeers straight on (on the front) if (when) the tyre explodes (just kidding - tyres are an important safety issue)

Unscrupulous dealers would turn the tyres round till the bulje was on the inside, Its an MOT failure and dangerous, i don't even think you could (or could not advise you to) use it as an emergency "get you home" spare untill you replaced it next payday etc or to fill up the space in the spare wheel well, if you sold the car with it as a spare you should inform the buyer it has bulges or needs to be replaced.

The 4 litte contact patches of rubber are often underestimated by many drivers (pressure/ condition etc) but its all there is between you and the road