I have a 1 1/4" receiver hitch to carry a bike rack. I recently bought a newer rack that is heavier. Between the hitch, rack, and two bikes, I can feel the weight on the back of the car. That is without having additional people in it. Do they make a heavier duty rear strut? I've searched and only find ones for lowering the car. I'm only looking to stiffen it up a bit, like the coil over shocks on my pickup.