Which gen Miata? IIRC NA had something like 5.5x14" wheels which are tiny. But if we look at bigger production car wheels even modest 8x18" could weigh > 30lbs

Which gen Miata? IIRC NA had something like 5.5x14" wheels which are tiny. But if we look at bigger production car wheels even modest 8x18" could weigh > 30lbs. Second, (unsprung mass/sprung mass) ratio is the thing that counts, not the mass itself. So, while 40 lbs wheel is terrible for the Miata, it might be quite ok for the vehicle twice Miata's weight.