RP

aɪə

Lower case a + small upper case i + schwa

Falling, wide, front closing diphthong + /ə/.

In this phonemic combination in which the diphthong /aɪ/ is followed by /ə/, as in e.g. fire, the tongue glides from a position just bebind and above front open, the lips being nuetral, towards a centralized front position just above half close, the lips becoming gradually slightly spread; but before reaching the half close height, the tongue then glides to a central position just below half open, the lips returning to a neutral position at the end of the glide (/aɪə/). The movement of the tongue is therefore extensive. There is a tendency in rapid General and Refined RP to omit the second element /ɪ/, especially when the /ə/ is not felt as a separable morpheme (smoothing) thereby reducing the glide usually to just two elements, the diphthong /aə/, or to one long monophthong /aː/ particularly in Refined RP. Thus, tyre may sound the same as tower.

Spelling
<ire, yre> tired /ˈtaɪəd/, tyre /ˈtaɪə/, lyre /ˈlaɪə/
<ier> flier /ˈflaɪə/, higher /ˈhaɪə/
<ia> via /ˈvaɪə/
Rare cases:
<oir> choir /ˈkwaɪə/
<i> Virus /ˈvaɪərəs/
Examples
shire /ˈʃaɪə/
flier /ˈflaɪə/
wire /ˈwaɪə/
buyer /ˈbaɪə/
iron /ˈaɪən/
liar /ˈlaɪə/
science /ˈsaɪəns/
psychiatrist /saɪˈkaɪətrɪst/
The clients found some iron wire in this tyre.

/ðə ˈklaɪənts ˈfaʊnd səm ˈaɪən ˈwaɪər ɪn ðɪs ˈtaɪə/

In Ireland some buyers hired a car to a liar without finding out if the price was higher or lower.

/ɪn ˈaɪələnd səm ˈbaɪəz ˈhaɪəd ə ˈkɑː tu ə ˈlaɪə wɪðˈaʊt ˈfaɪndɪŋ aʊt ɪf ðə ˈpraɪs wəz ˈhaɪər ɔː ˈlaʊə/

Pronunciation

The tongue moves upwards from above a centralised open front position in the direction of a centralised half-close position and then it moves downwards towards an open variety of /ə/. The lips change from neutral to slightly spread and then back to neutral. The soft palate is raised (unless followed by a nasal).