Received Pronunciation has centering diphthongs. They are found in words with post-vocalic r. The centering diphthongs of Received Pronunciation consist of a high lax vowel and schwa.
Examples of words in Received Pronunciation that have centering diphthongs include beer, cure, here, tour and you're. The result is that words such as be and beer sound quite different.
The word bee has a high front unrounded tense vowel. However, in beer there is a diphthong. The first component of the diphthong is a high front unrounded lax vowel and the second is a schwa
In rhotic accents of English, centering diphthongs do not occur. However, in Received Pronunciation, they do. They consist of a high vowel followed by a schwa. The lax high vowel is either front unrounded or back rounded.
