Strange buzzing noise on ride. Oh, it’s a saggy trunk bag on top of a Nitto Campee rack. No top plate to rack. Bottom of trunk sagged down to touch rear tire. Thought: Use a bit of paracord to make an X across the open area to act as a bit of a support. Ideas solicited

Polycarbonate cut to shape of rack. Drill three holes along the border of each side, two in front, two in back. Use zip ties to attach.

If the trunk is always on the bike, you can put that piece of polycarbonate in the bottom of the trunk, rathe than on the rack.

picture?

Saggy baggy

Open squares

My cheap go to on other bikes.

I like the Nitto but it's not a good match for this bag. Putting a polycarbonate top plate or liner to the bag may solve the issue. The idea with paracord is to just weave a tight X pattern across the squares as a support.

Even simpler is fiberglass strapping tape. No stretch to it, & tensile strength about 100# - doubled if you fold it around & stick it to itself. One piece above the tire would meet your need; could make a cargo net out of it if you like.

The simplest thing to do is to just span the rack opening with a velcro strap, before you put the bag down on the rack:

On my Ostrich bag and Inujirushi bag, I put a snug cardboard box inside to stiffen them up:

^ this works very well. The bags stay nice and square. If your bag is squarish , this is the best solution. I have a cardboard inside my Carradice Barley bag as well, but due to the more rounded shape, it's not easy to make it a good snug fit, and I am not able to really get rid of the sagging issues on that bag.

As an alternative to paracord, small bungee cord or ribbons cut from inner tubes - multiple narrow elastic cords/strips under tension would have no tendency to sag. Or just cut a rectangle of sheet aluminium and curve the edges down to locate over that part of the rack.

All good solutions. Thanks all!

corroplast signs and zip ties are everywhere

I took a wine box, knocked the end panel out. Radius the end to match the rack. Lots of polyurethane spray, then zip ties. A little thicker than needed but is should work for now and adds that extra panache needed to ride in style!

That is a very stylish solution.