Nothing too far out there (and sorry for the iphone picture), but I felt like sharing....
The rim is an Open Pro (though this post is absolutely not a dig on Mavic!) on a rear wheel. The dark line through the braking surface is a crack- above the crack, the rim is bulging out.
It started six months ago or so, loaded with weight on a bike tour, when my tire flatted out, and I hit a pothole. This caused the rim to bend inward very slightly right at the impact. I carefully bent the rim back into shape with a crescent wrench, but it was never like new again. The hit also put a slight flat spot in the wheel, and spoke tension has been a constant-but-manageable issue.
~3000 miles later, I've got this crack.
Luckily, I've already got the parts for my new wheelset, and a spare bike as well, so no worries
'''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
From the picture it seems the rim is pretty badly worn all around the brake track and the crack occured when the metal got thin enough. The earlier damage and the crescent wrench repair probably didn't help but I don't think it was the ultimate cause.
I've had two rims fail similarly from brake track wear and, fortunately, neither failure was severe enough to strand me.
1986 Alan Record Carbonio, 1985 Vitus Plus Carbone 7, 1984 Peugeot PSV, 1972 Line Seeker, 1986(est.) Medici Aerodynamic (Project), 1985(est.) Peugeot PY10FC (Project)
Looks more like an Open crack Pro rim ??
I guess the bottom line is the rim is worn out. None of them last forever and the fact that this rim might be designed more for lighteness(racing?), the MTBF will be much lower than a more robust "touring" or off-road type of rim.
Just wondering, what kind of brake pads are you using on those rims?? Could they be Modolo's "Sinterized" brake pads??, which I heard are rough on rim surfaces.