Earlgray09

My 56 plate blobeye wagon (gx) is lowered on prokit springs, think about 25/30mm and I'm running 8x18 et43 225/40/18s. If I go over say a speed bump or a particularly crappy bit of road in an 'eager' fashion, occasionally I hear a weird sort of banging ish noise from the rear end, usually one side or the other. It's more pronounced with more weight in the back and usually on the side with the weight ie rear passenger on left bangs near side rear. My first thought was that it's the wide tyres/rims smacking the arch lip? Is this more likely than it bottoming out the shockers? I am planning to get the arches rolled after Christmas