Keith Bontrager introduced himself over the PA at the 24/12 as ‘bon-tray-ger’ (with a hard g) so whatever the euro pronounciation I suppose we should go with his version if we are talking about bike things with his name on them.
As a half frenchie I can advise that the name Commencal has a soft c in the middle, and the ‘en’ bit is that French vowel sound half way between ‘on’ and ‘an’. You say ‘on’ with your voice but open your mouth wide. (try it out loud!)
But where do you stop? Michelin has its own very recognised pronounciation in English and you’d sound well wierd going into your lbs or garage and asking for the French (ie real) way of saying it. (meesh-lang in my accent!)