Usually à 10mm allen key.
*hollow laugh*
…UPDATE…
So, after trying all my allen keys, it turned out to be a 12mm. Which I had to order in as it’s against the law to stock allen keys bigger than 10mm in major UK city’s it would appear…
Big ass allen-key arrives: nothing happening… try whacking it with lump hammer, scaff pole as leverage… nothing. Take it to LBS who put it in a vice… nothing. So, whole wheel in the bin. New wheel/hub bought.
Put it all back together yesterday. Lovely weather today so looking forward to a good ride out. Get it about ten yards down the road and CLANK. The problem is still there.
So now I’m looking at chain/chainrings/BB as possible culprits. Could anything here cause these symptoms? Borked BB? Worn chainring teeth? Stretched chain?
Here’s a photo of my middle chainring. The teeth look pretty worn to me? Opinions?