Dave - the "moulding dents" as you call them are caused by a problem in the construction process with control of the "splice" width at the point at which components are joined. If the overlap of the component being spliced is too large it can cause a visible hollow and bulge. The area immediately behind a heavy splice stretches, spreading the gap between radial cords in the body ply of the tyre or reducing the gauge in the sidewall at that point. In extreme cases this can cause a serious weakness in the integrity of the tyre. All manufacturers should control the amount of undulation variation to prescribed limits laid down by O/E customers with a slightly looser limit for replacement tyres. Tyres exceeding these latter limits should be scrapped. Ruud's tyre photo illustrates a serious level of undulation and it would be wise to replace that tyre immediately.
Don.
