Hi - came up with a good idea for stashing a spare key. I hid the key deep in the bike in a place that requires a wrench to disassemble. I then used two of those rubber-coated metal ties, like an 8 gauge wire twist tie, to fix a wrench wrapped in rubber to the underside of the rear subframe, out of view.

Sounds good, but where is the "deep in the bike in a place that requires a wrench to disassemble"?

I always do this, but hiding the wrench is redundant. If someone can find the wrench, they can find the key.

Do you not ride with a toolkit? That's unimaginable to me.

There are a number of places you could choose.

Tool kit is locked. I don't like to share my tools with thieves. Key to the tool kit is also hidden in the same place.

If they are motivated to disassemble half the bike using an open ended wrench to find a key (if they put two and two together that the wrench is there to allow access to a hidden key) then they would probably just hotwire the damn thing which is easier, or more likely move on to steal another bike.

Or just pick the whole bike up and toss it in a van/truck so they can take their time with it somewhere else.

Yup. Pick up and drive off is a much more likely scenario than 1) Think there might be a wrench hidden under the fender 2) Figure out why the wrench is there 3) Decide to look around for things the wrench could open and 4) Be successful and find the key and then 5) Put the bike back together so it is rideable.

Yup. Pick up and drive off is a much more likely scenario than 1) Think there might be a wrench hidden under the fender 2) Figure out why the wrench is there 3) Decide to look around for things the wrench could open and 4) Be successful and find the key and then 5) Put the bike back together so it is rideable.