I'm a fitter

Deteriation of the tyre causing it to leak out the sidewalls is a rare occurace mate.

Its a simple bead seal that all, they'll take the tyres off scrub the lip of the rim up with a wire brush and put proper sealer on it , its only a thick glue and works better than anythin with no mess , dont put the slime in it'll make a right mess mate and isnt needed.