Very interesting post, Ben. Most people - even teachers - would swear that the American English 'rider' and 'writer' sound the same, but there is a subtle difference in the diphthong.

And to answer your question: As you'd expect, I have what you would call 'a British accent' and I pronounce these two words very differently. The term is actually meaningless ( Scots and Welsh are also British accents, not to mention Geordie, Scouse and multitude of others) but that's another story. I speak in an RP or Standard Southern British accent, and I do make a clear distinction between /t/ and /d/ between vowels.

That's not the only difference, though. As Phil pointed out, in all accents of native English, the vowel will be slightly shortened in a syllable checked by a phonemically unvoiced consonant. So the diphthong in my /ˈraɪtə/ is shorter than the diphthong in my /ˈraɪdə/.

As for the raising issue, I'm aware that the 'i' sounds in 'rice' and 'rise', for example, may be realised with different allophones by some AmE speakers. When British actors train for roles which require certain Canadian or American accents, this is one of the features they need to acquire.

My mind is blown. I knew about the raising to /ʌʊ̆/ but wasn't aware of the raising to /aɪ̆/. Now I can't stop hearing it in my accent. "Writer" and "rider" sound (like they should be) the same in my head, but they come out differently. I guess I can rest assured that people will know that I'm a writer and not a rider.

Good ear, Ben, "Canadian raising" affects the letter I vowel in the northern USA as you've described. (But usually not the vowel in "out" – that's almost a Canadian shibboleth.) Additionally, in all accents of native English, the vowel will be slightly shortened in a syllable checked by a phonemically unvoiced consonant, even if the consonant is realized as voiced.

You're definitely correct Isaac. I updated the post to sound a little more generalized. Funnily enough, I personally don't use any of your given 'excellents'! I tend to say /ˈɛksəlɪnt/. I also brought it up to my friend from the Southern US and he doesn't say the different either!

Not sure if you meant North Americans, but we Canadians also flap our Ts and Ds where appropriate. I've known about Canadian raising as a concept, but it always felt to me like a really minute difference. At least what I tend to really notice is the vowel length.

I say "rider" with a longer I-sound than "writer", and I can hear the flapped D sound easier. Meanwhile "writer" is shorter, and it almost sounds like the retroflex R dominates the flapped T sound. There's the same shortening of vowel length for "rise" vs "rice" and so on.

I always thought that the supposed American perception of the Canadian pronunciation of "out and about" as "oot and aboot" was a gross exaggeration. Maybe I'm not self-aware enough, but the Americans' way of pronouncing it definitely never sounded extremely different to me, definitely not "owwt and abowwt".