Have you ever encountered an 11 mm bolt/nut?

In all my diy’ering, cars and home projects, I’ve never needed to use my 11 mm socket even one time. (Excepting that it is very close to an sae size, so I use it for sae fasteners sometimes.) 10 mm & 12 mm very commonly used, 11 mm, not.

Do you folks find this same thing, hardly ever come up against an 11 mm fastener? Or are 11 mm fasteners actually a common thing in car repair?

Not common but they exist. The bleed screws on my Mustang’s brakes are 11mm hex. The front undertray is held on with 7mm and 8mm screws. For goodness sake Ford, pick ONE!

The UK and Japanese tend to used even numbered head sizes. The French odd numbered metric head sizes.

The US has a fetish for 10mm, 12mm, 13mm, 15mm and 18mm head sizes. But 19s and 17s are also pretty common.

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Seems I sometimes find something on some bicycles with an 11mm head, or close to it. Maybe a Whitworth near equivalent. Some old Brit bikes used some Whitworth heads on, say, seat binder bolts or stem bolts, IIRC. Maybe Sturmey-Archer 3 speed rear hubs.

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I started using my 11mm very regularly when I lost my 7/16" wrench.



Remember add-on metric sockets? Many omitted 11, 15 and 18 sockets because 7/16, 9/16 and 11/16 were close enough. Not in my experience! Only the 7/16s fit.

Yes, I have used all of my metric wrenches while working on cars, and 10, 11, 12, 13, 14, and 15 mm are all commonly used.

Now that I think about it, I seem to recall using 11mm quite regularly in Ford engine compartments, but I can’t recall for which components. Perhaps someone else here will remember?

I believe the battery cables for GM side terminal batteries use a bolt with an 11mm hex.

In my old 25+ year old Craftsman wrench set that goes from 7mm to 19mm, they left out the 12mm but included the 11mm. It’s a huge problem for working on cars. IT goes 7 8 9 10 11 13 14 15 17 19.

Since you’re missing 2 other common sizes-16 and 18-sounds like it’s time to update your tools.

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Lost my 14mm, 17/32 worked just fine.

All the GM side terminals I’ve encountered were 5/16” and an 8 mm. Would also fit just fine.

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Yes I recall using an 11mm socket quite a bit on the 80-90’s Fords for whatever reason…

I’ll have to remember that, I’ve never used my X/32 tools.

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That’s extremely weird. 12mm is very very common. My Craftsman socket set is about the same age. Mine came with the 12mm. If it didn’t - I’d surely go out and buy one.

Quite a common size on European motorcycles but not so much on Japanese.


Common enough that you should buy 11mm sockets and wrenches

Ford seems to like them, from what I’ve observed

It kind of irks me that you have to complete the set by buying additional loose tools to fill in the gaps. Never know when one of those will come in handy…

I just used my 9mm 1/4" drive deep well as a drift for installing the cup seals in my steering rack. Speaking of which, previously I held the belief that vehicle assembly started with a heater core hanging from a hook and they built the rest of the vehicle around it. That was clearly inaccurate. It’s actually the hydraulic steering lines…

On a related topic, if you buy an American wrench set, they often omit the 11/32". It is commonly used with hex nuts for #8 screws. 9/32 is sometimes omitted as well.

I’ve used 11mm sockets (and 13 and 18) on Piaggio (Vespa) motor scooters quite a bit. What really puzzles me is why metric bolts are sold in the US with SAE dimension heads.