Originally Posted by
pdlamb
Well-built wheels don't have cracked spoke holes unless they've been abused. As-built stock wheels are built on a machine, and the spokes won't be overtensioned unless somebody at the factory was angry and/or hung over. That leaves bad rims. My guess, they weren't checked for proper annealing and hardening on receipt, and the poorly tempered aluminum cracked under a much lower load than they should have. Might be a design flaw, if the rims weren't specified correctly, but I'd still bet on poor quality control in manufacturing.
Of course, since mass produced bikes are bought in thousands, that may have been "normal" for one year's production. It still should have been caught and corrected after a year. If you've got the receipt for the bike, you might want to file a warranty claim.
I've had cracks at spoke holes, that's the primary failure mode, on road bike wheels on smooth roads. But 35 miles a day, 8 months of the year, for 3 years, that's a lot of miles. Wore out the factory set and a new set, each 3 years. Aluminum has no "fatigue limit". Steel does; Below a certain stress level, you can stress steel forever in fatigue and it won't break. Aluminum has no such limit, eventually it will fail by fatigue with enough stress cycles. But, put double sockets at the spoke holes to spread the load between both inner and outer walls, and a very wide surface area on the outer, and stress levels due to the spokes are slashed immensely. That's the LAST set of wheels I put on that bike, and it's now retired in favor of a townie, but I have little doubt that had I been riding that bike all these years since, those rims will still outlive me, though in this much more hilly environment, the sidewalls would eventually succumb to rim brake wear, my townie wheels are almost at that point after 10 years.