You may find an explanation in this interesting thread https://forums.dovetailgames.com/threads/the-class-710-from-a-real-710-driver.79882/
Whoa !! I think Bombardier placed an Easter egg. Jokes apart but how does a multi million dollar machine has a crucial part that no one knows about !! Don't they detail stuff like this in their maintenance manuals & such ?! I remember that episode of 'Seconds from Disaster' where an ICE1 derailed due to a non-standard wheel design under it's restaurant car. How can they put an odd looking wheel and 'no one knows about it'. Somebody would've done testing, some documentation etc. Assuming that it's not some sort of conspiracy, it's hard to believe that the train came out of production & not a single person who noticed something that obvious, raised the question !
They run out of standard wheels in factory so this new lad found some old ones in a shed and put them on, thought nobody would notice. That is untill Shackamaxon above blew the whistle lol, they fired the poor lad, he meant well. Col.
On the aventra those are non powered bogies, so its a normal trailer axle. The 345 has even both sides without brake calipers on the front axle. My guess the answer is rather unspectacular, as they made the brake specifications / calculations, bombardier probably just wanted to lower maintenance costs by not assembling unnecessary brake calipers.
