-ial stress-imposing BrE AmE i‿əl —This suffix sometimes causes a change in the stressed vowel: ˌ mana ˈ gerial -ˈdʒɪər i‿əl AmE \ -ˈdʒɪr-
-IAL
Meaning of -IAL in English
Longman Pronunciation English Dictionary. Английский словарь произношений Longman. 2012