Originally Posted by
AlbertaBeef
Keep in mind there IS the risk without cold-setting that only one side of your stays move, or one side moves more than the other, changing your chainline, impairing shifting and causing faster wear of the drivetrain components. It's rare, but I've seen it happen.
I find it's best to cold-set just to avoid these issues, but it's obviously not always necessary.
The chainstay has to flex way more than 2mm for any cold-setting to occur, and up to that point of yield the flex is completely elastic and thus will be symmetrical between the two chainstays.
The problem with one chainstay going out further than the other chainstay occurs when the two chainstays are forced apart against one another during a deliberate cold-setting operation. In this case, one of the chainstays will almost always reach the yield point before the other, and so the spread-out chainstays would now be centered off of the frame's centerline.
One other concern about simply forcing a wider axle into a frame is that since the left and right chainstays are now pre-loaded to the left and right sides, respectively, any large side-force applied to the wheel will stress the same-side chainstay significantly more than the opposite-side (of the applied force's direction) chainstay, and thus is more likely to exceed the yield strength of the chainstay and thus go out of alignment.
Possibly this what AlbertaBeef experienced after a forced-in wheel was ridden for a while.
Yes, this can happen. Essentially, it is as if your frame's yield strength is reduced.
Small increases in hub width are no big deal though.
I use a custom axle with 124mm locknut spacing to allow a 7-speed rear wheel on my 121.5mm PX10LE's frame, and Shimano even designed special "ramped" (semi-conical) locknuts that allowed their first 8-speed, 130mm Dura-Ace freehub to wedge more easily into the 126mm and 128mm frame spacings of that era.