Originally Posted by NowhereFast
There's a reason big rigs have air brakes!
the BIGGEST reason is because of the coupling to the trailer...
if all of the brakes were hydraulic it wouldve been a lot harder to couple and uncouple a trailer if all on one system.. imagine having to bleed hydraulics every time you hitched up
one couldve used electrically actuated hydraulic brakes... however brake controller technology didnt exist when big rigs were conceived and air brakes designed...