The /ɪə/ diphthong is spelled <eer> or <ear>. The /ʊə/ diphthong is spelled <ure>, <our> or <oor>.
This is a contrast between two diphthongs with widely different starting positions and a difference of lip rounding. It is not a problem for learners.
The density figure is 2.56%. The set makes 15 semantic contrasts giving a loading of 55%.
ameer amour ameers amours beer boor beers boors bier boor biers boors dear dour dearly dourly deer dour geared gourd leer lure leered lured leering luring leers lures mere moor meres moors peer poor pier poor shear sure sheer sure sheerer surer sheerest surest spear spoor spears spoors tear tour tears tours year you're
John Higgins, Shaftesbury, December 2009