Quenya Phonetics P22: long vowels shortened before consonant clusters
Q. long vowels shortened before consonant clusters; [V̄CC|V̄tj|V̄kw] > [V̆CC|V̄tj|V̄kw]
In Eldarin languages in general, where a long vowel appears before a consonant cluster, that long vowel was shortened. This was true in Primitive Elvish, but also applied to long vowels that came into contact with clusters after Quenya-only sound changes like the Quenya syncope. For example: