Originally Posted by
Slightspeed
I had similar cracks on the rear rim of my 2006 Roubais. These were 10 year old Mavic Open Sport rims. Someone said incorrect spoke tension, but since the wheels always stayed true, I never checked for that. There were two cracks on adjacent spokes, so I don't think they were drive side specific. I noticed it while cleaning the bike after a gear cable change. No idea how long they were broken, since the bike rode fine. I got a deal on a set of Reynolds Stratus Elites, so the cracked rim and it's partner are hanging on the garage wall. The Mavics are double wall construction, and might have been safe to ride but why chance it?
Yes, the cracking is due to incorrect spoke tension but not necessarily “incorrect” in the way that most people think. Cracks can form from both low and high tension. Low tension allows the spoke bed to flex constantly which leads to cracking. High tension stresses the aluminum of the rim and leads to cracking. Two different mechanisms but the same result.
If your wheels (and CoogansBluff’s) are OEM wheels, I would suspect that the tension is too low. I regularly run across OEM wheels on bikes that are improperly tensioned at my local co-op. Oddly, I run across a large number of OEM wheels that aren’t dished properly. I’m even seeing a lot of front disc wheels that haven’t been dished properly.