Originally Posted by
fourknees
My existing hitch rack can handle 4 bikes. I am more concerned as you mentioned with 120lbs of bike plus 30 lbs of the hitch still being to much for a class 2. From a pure tongue weight perspective not a big deal, but the set back weight and the air pushing on it while driving is a concern. All the vehicles I've seen with 4 bikes on it are large vehicles such as my dad's full size pick up growing up.
Yes... I'm sure bending moments and the ability of both the hitch and vehicle structure to take these forces are a concern. I would also think that Yakima has engineers that understand this and that the hitch makers have engineers who understand how to calculate forces. I suspect they also test these things. I also think that there is an interface between the Yakima and hitch company engineers (i.e. they exchange information), and between the hitch company and body structure/chassis engineers at the car makers. Are they perfect? No, like in any profession or area of work. Do they mostly get it right?
AFAIK these things aren't unintentionally flying off cars everyday. This is why I point you to their specifications and instructions: they've done the math and sell a 4 bike mount (and they are a large company with,
AFAIK, a decent reputation).
That said, if you contemplate some unusually severe and/or prolonged driving with the 4 bikes, then the Class III might be your thing. One can always find a way to exceed design capacities.