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Old 03-29-20, 11:28 AM
  #26  
Doug Fattic 
framebuilder
 
Join Date: Dec 2009
Location: Niles, Michigan
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Originally Posted by noglider View Post
There are three measurements that matter. 1. If the two blades are off to one side, that's the easiest to fix, and I have done it successfully.

2. The rakes must be the same. This is the distance forward of the plane formed by the steerer tube. This is harder to get right.

3. The length of the blades must be the same. Sometimes when correcting the rake of one blade (2), you alter the length. This is why I've found fork alignment to be so tricky. When you fix (2) or (3), you worsen the other.
Agree and I would add this fourth measurement using dropout alignment tools to make sure the dropout faces are parallel to each other. It is necessary to go through the other steps 1st because it is possible that the cups match but that the fork is still not in alignment. It is a bit tricky to get all 4 right because as Tom says when you move one it changes another. It is necessary to clear all 4 checks before the fork is really right. Some other observations:

1. I never use a bending assistance tool (except gloves) because I get a better feel for how much to move. It is really easy to over bend. The reality is that a blade won't seem to budge with moderate force and then suddenly with just a little more effort, it gives way and moves a lot.

2. Don't assume any fork or frame was aligned within a millimeter of straight when it was new. The "no hands" test is effected by the frame's alignment too. The best aligned steel frames to come into my shop for painting where Japanese frames, followed by Italian frames after frame making equipment from companies like Bike Machinery became more common (mid to late 80's?). The classic era British frames can often be way out (although a few were spot on).

3. How much a customer noticed the ride improved after an alignment varied on the person. I've aligned hundreds of frames and often asked the owners if they could tell the difference. Some said a lot of difference and some said they couldn't tell at all. I think some are just more sensitive to how their frame feels.

4. Park dropout alignment tools are not accurate enough for me and I recommend to my framebuilding class students not to buy them. The reason is that instead of using washer like spacers for different dropout widths, the cups are threaded to their handles and the slop in the threads are too much variance for me.

5. There should be a little space between the cups otherwise the dropouts might catch on the axle nuts.
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