How to make a bicycle briefcase

This was a weekend project from many years ago — an old, beat-up briefcase that used to belong to my dad converted to mount on my bicycle's rack like a typical pannier. I decided it was time to take a few photos and do a better job of documenting the process.

From the side it looks like an unassuming briefcase:

Flip it around though and you'll see what makes it a little different:

For good measure, here's a view from the top, as you'd see it while walking with it to and from your bicycle I imagine:

Inside it's an ordinary looking briefcase circa the late 70s or early 80s I think. Behind the leather document holders you can see the nuts holding in the bolts and washers peeking out, just a little bit:

It mounts  on the back pretty much exactly like an ordinary bicycle pannier. The bungee-cord in the middle with the hook catches a loop lower down on the rack so there's enough tension to keep the hooks pulling-down tightly along the edge of the rack:

Here is another view from the back with a better angle on the hooks. The bungee has actually loosened up enough now that it's pretty comfortable to get on and off, but initially it was extremely tight and difficult to attach. The rubber coating on the right hook got scraped off during one of those attempts:

I'll have to go out and take better photos when it stops snowing, but here's a shot from the side. My heel just barely clears the bottom-left corner of the briefcase when I'm pedaling — anything larger and I'd clip it on every rotation. It might've made more sense to not center the hooks and bungees in retrospect:

That's it!

If you want to make your own all you'll need is:

• A briefcase, obviously. You can find some interesting vintage briefcases on Etsy or Ebay sometimes, but the prices jump around. This briefcase on Amazon is only about $25 and would work well. The aluminum briefcase is also $25 and would be even better, though drilling the holes  might be a little trickier.
• A bungee with a hook. It doesn't have to something specifically designed as pannier part — it's just a piece of bungee with a hook  in the middle after all — but this replacement part from Axiom is already assembled and less than $5.
• Two hooks to attach to the back and mount on the rack. Another obvious component but one that was surprisingly tricky to track-down. I imagine you could peruse a local hardware store and find something easy to adapt for this purpose, but these pannier hooks by Jandd are what I went with and they fit perfectly. Axiom also offers a replacement hardware hook kit that comes with some additional mounting pieces.
• A little drilling, screwing, eyeballing and patience.  You'll need to drill holes to mount the hooks and you'll also need to create something that the bungee can be anchored to at each end. From the photo above you can see I used two tiny strips of leather.

Ta-da! Now when I pull up on my bicycle for meetings with clients in my suit I have luggage to match.

If you've made your own bicycle briefcase I'd love to see it — please send me pictures!