Originally Posted by
well biked
You said, I've read and reread sheldon Brown's method. It just doesn't seem like a good way to do it.
As has been pointed out, it's a fine way to do it. You are mistaken in your original statement. If you want to use a different method, that's fine, too. At least you are acknowledging the importance of bending one side at a time and taking measurments to insure good alignment.
This hits the nail on the head. The only thing wrong with the OP is that it implies that Sheldon Brown's method is somehow lacking, which isn't the case. However, Sheldon Brown never claimed that it's the only method for doing the job, it's just one of many possible ways.
If working with only a frame it's easy to fixture by the bottom bracket, and many frame builders do just that. OTOH there's no need to do it that way as long as you have a method to control and monitor which side of the triangle bends and how far.
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For those who think you can simply insert a jack into the dropouts and assume that equally strong stays will bend equally, here's a heads up.
There's a fundamental difference between how things flex and how they bend. Flexing occurs within the elastic range and is proportional to both the bending moment (force and distance) and strength (inverse proportion) of the parts, so nearly equally strong sides of the rear triangle will flex out about equally when jacked.
But bending (cold setting) occurs only when the elastic limit is exceeded, and since the stays are not exactly equal in strength once the weaker side begins to bend, in accordance with Newton's 3rd Law of Motion, there will never be sufficient force for the stronger side to bend also, so all bending will occur on the weaker member, rather than a proportional response. That's why it's so important to control the process and bend each side separately.