Crack in aluminium rim? I recently discovered this horizontal line on my double walled aluminium rim (Triban road bike), pics attached, and was wondering if this was a crack or just a manufacturing artifact. Could anyone confirm if they've seen something like this? To me this looks too perfect a straight line to be a crack. Any ideas/opinions would be appreciated.
Many thanks
JJ
left side - 
right side -
That is the seam where the two edges of the rim were jointed.  Cracks, as you have noted, do not form in such a perfectly uniform way.
As long as the edges remain closely butted together as they currently are, you are good to go.