Title. Looking at hitch mounted bike racks, specifically two types: racks that have a vertical bar and the bike hangs down by the frame, and racks with a horizontal platform that the wheels sit in. Think things like Thule.
I see heavy ebikes being held by heavy duty racks, or multiple MTBs on one. How is it that they are stable? I would think that – especially the hanging ones – they would act like a giant breaker bar against the hitch opening. I know that they are designed not to really wobble right and left, but how does that little 1.25 or 2” square slot stop 3-4 feet of steel bar with 30-100lbs of weight on the end from breaking loose?
Definitely not asking because I’d like a hitch rack for my bike and have trust issues. Lol. I can’t fathom how these work, and why they don’t need to be secured from the top at least.
In: Engineering
[read this.](https://rockymounts.com/blog/the-ugly-truth-and-confusion-about-class-i-hitch-bike-racks-and-the-125-size/)
It pretty much answers all of your questions. They do act like a huge breaker bar and can and do tear right the fuck off if not installed on the proper hitch type.
The hitch is attached to the frame, so the lever effect is not just acting on the small part of the hitch you can see but the whole weight of the vehicle. The part experiencing the highest forces are probably the angle of the bike rack itself. But a 1″ square steel tube is really strong. Many vehicle frames themselves are not that much larger.
That said, hitches do have a vertical weight rating, usually around 500lbs or so.
They can cause issues on smaller cars. You want a class lll hitch or better. Put one on a 1.25 hitch on a sedan and you’ll have a bad time. Hitches are designed with a tongue weight. You are right that the leverage arm magnifies the weight of the bikes. But the big issue is hitting bumps or rollers on the road. That creates a huge moment that will bend many hitches.
I regularly haul my 250# dirt bike AND 2 mountain bikes on mine. When built right, they are fine.
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