See if you can find some taller skinny tires to put under it to kill some of the gear.
Also make sure that you do not have any of the brakes dragging, this could also kill milage.
No brakes dragging, I had everything except the carrier fixed a few months ago because a cylinder went bad. Would've done it myself so I could learn to do it, but it was -5* and I have no garage lol
My fender well is pretty full now. There is only an inch between my tire and fender well on the back
