Originally Posted by
cyccommute
They don't have machined brake surfaces so they can have an annoying bump at the joint but that's typical of many nonmachined rims.
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Where did you come up with this nonsense? Obviously you never owned a joined rim!!
Only the cheapest of the cheapest joined rim would have a joint that would "bump" you. I've never owned a machined rim in my life untill the Mercian, but previous to that ALL my rims were joined and NONE ever "bumped" actually you mean grabbed the brakes pads as they went by or made the brakes squeal. This is one of those old bike tales.
Prior to more accurate machining of jointed rims and prior to machined rims, all a person had to do was take a piece of emery paper and smooth the joint down so it wouldn't grab; this was a ritual all cyclists went through with new rims back in the day (prior to about 75). But once more accurate machining techniques came along...and still prior to machined rims...we no longer had to sand our rims down.
A machined rim by the way is not any better then a joined rim; a machined rim the hoop is welded together then it's put through a machine that grinds the entire wheel until the weld and the hoop look like one continuous loop, whereas the joined rim is joined by a series of pins or filler pieces that go into hollow areas that were drilled into the rim.
For more detailed info see
http://sheldonbrown.com/brandt/machined-rims.html