Robot’s Useless Reviews – The 7mm Hex

Howard Carter, the archaeologist who excavated the Tomb of Tutankhamun, and many of his crew endured a series of unfortunate events afterwards, including the death just six weeks later of Lord Carnarvon, the sponsor of the whole tomb raiding project. Some claimed a curse, as they will. We humans, we love a curse. You might call it a trope in fact, the removal of something essential, followed by the wrath of some unseen force. Woe betide the person who dares take my sandwich from the work fridge!

Did you ever wonder why, 9 times out of 9, you drop a wrench while working on your bike? Clang, bang, clang. Goddamnit!

Some mechanics believe that’s not a case of butter fingers or poor manual dexterity. That’s the 7mm hex. The origin of this hex is hard to pin down. Some say there was a meeting of bicycle product managers way back in the day, in which there was some basic agreement about what bolts could be used on bikes. They all agreed the 5mm was best, but some argued for the 4 and the 6. The pedal guy begged for 8. No one stood up for 7, and so somewhere in the ether, wherever it is that hardened steel gets ready to be drop-forged, the 7mm cast this spell on the bike mechanics of the world.

“What could possibly go wrong,” he said.

I bet you thought that ‘hex’ was short for hexagonal. That, I’m afraid, is only an amusing coincidence.

Can you imagine the scene when the hex wrenches pick teams for kickball, and the 5mm — always the stupid 5mm, right? — says, “I’ll take the 2.5mm.” And the 7mm is like, “What?!?! You’re picking a non-whole number instead of me?!?! What lunatic even specs a 2.5mm bolt on a bike part?!?!”

And the 5mm, so smug, says, “No one picks you 7. No one picks you.”

“No one picks me? No one picks me? Everyone picks me! I’m THE lucky number for chrissakes! I’m prime! I’m the mostly likely outcome from a rolling of two dice! I’m the number of continents and seas! I’m the days of the week! ” howls the forsaken number, and thereupon curses the others to a lifetime of jarring impacts with floors of every type, but most often concrete.

So clang, bang, clang! That’s the wrench — probably the 5 — slipping out of your hand, clipping the handlebar and the frame on its way to that hard, hard floor. In many shops I’ve visited there is a 10 push up penalty for dropping a tool, the mechanics all curiously firm of pec and nervous of disposition. They all know they’re going to drop tools. A person who never drops a coffee cup, will daily drop a hex wrench.

Make that make sense.

As this is a review, I will just say that I have nothing negative to say about the 7mm hex. 7 is a fine number. I think it’s better than 8, which is a lucky number in China. I think 7 should have gotten pedal spindles. I think my friends (I know no one) at Park Tool should put the 7 into their P-Handle Hex Wrench Set, of which I am a big fan. I’d suggest, rather in the mode of Field of Dreams, if you make the tool, someone will write the spec. Think of all the time we’d save not bending over to pick up the stupid 5.

This post and so many others is brought to you by TCI subscribers and by Shimano North America.

Join the conversation
  1. papogi says

    I had to chuckle just a little at this one because I still ride a vintage bike with C-Record cranks with built in extractors, and they take a 7mm hex. I’m with you though. Other than on that old relic, my 7mm hex wrench gets absolutely no use.

    1. Emlyn Lewis says

      Leave it to Campy to find a use for the 7mm.

    2. eborling says

      I had a double chuckle on this. As I was reading, I was thinking about my Campy Chorus cranks and the 7 mm hex and how I was going to leave a comment to that effect. The second chuckle came when I saw your comment was exactly what I was going to say.

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