Le Baron wrote:It only 'disappears' as a final consonant if compared to the very pronounced 'r' elsewhere in other language, but it's really there. Otherwise 'bar' would be 'ba'!
R after A is actually a good case for observing the disappearance of post-vocalic R. In many other combinations 'vowel' + R it turns into schwa /ə/ (so 'near' is pronounced /nɪə/), which makes it distinct from the R-less words, but for some combinations of 'vowel' + R it turns into a 'long vowel', creating homophonous pairs with some R-less words (that have the corresponding long vowel). It works for words with /ɔ/ + R and, /ɑ/ + R, (so when words are pronounced in isolation /ɔ/ + R turns into /ɔː/ and /ɑ/ + R into /ɑː/). Some examples are: 'saw' - 'sore' (both sound like /sɔː/ in non-rhotic varieties of British English) for /ɔ/, and 'spar' - 'spa' (/spɑː/) for /ɑ/.