The /aʊ/ diphthong is spelled <ow> or <ou>. The /ɪə/ diphthong is spelled <ear>, <eer> or <ier>, and <eir> in weir.
This is a contrast between two diphthongs with different starting positions, direction of movement and lip-rounding. It is not a problem for any learner.
Interesting pairs include:
The density figure is 1.92%. The set makes 29 semantic contrasts giving a loading of 70.7%.
arouse arrears bough beer boughs beers bough bier boughs biers bow beer bows beers bow bier bows biers bowed beard carouse careers chow cheer chows cheers cloud cleared dhow dear dhows dears dhow deer endow endear endowed endeared endows endears endowment endearment endowments endearments how hear how here house hears loud leered mow mere mows meres rehouse rehears rouse rears row rhea rows rheas row rear rowed reared rows rears spouse spears vow veer vowed veered vows veers wow weir wows weirs
John Higgins, Shaftesbury, December 2009