Hi,
as when brazing in the SS bridge pulls dropouts together - I’ve heard, that some people put additional spacers to the axle, so it’s not eg 142 but more so after the whole operation everything is in place. And the question is how thick spacers? Of course the answer is “it depends”, but maybe someone has any comment on that?
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Yes, you’re correct, that usually happens. Depends on the wall thickness of the seatstays and chainstays. I usually get about 2mm “shrinkage”. I’ve been adding a couple of mm to the spacing beforehand to accommodate this. You can minimize the shrinkage by “witch wanding” ie heating up the outside of the seatstay for a few seconds after the bridge is brazed, this equalizes the heating and prevents some of the metal movement.
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I’ve experienced it, but never measured. Thanks for your input. I thought about adding 2mm spacers each side. And eventually changed my mind and will not be adding SS bridge at all to this frame 
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You can also just put your foot in there afterward and fix her up.
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That’s moreless the way I’ve dealt with it before
The old joke is that you adjust it with a custom tool that is so delicate and valuable you keep it in a leather case.
-Walt
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Maybe I should provide a more useful answer:
-If your bridge miters are really tight, expect about 1mm on each side of shrinkage.
-If miters aren’t very tight (which is fine for a bridge in general, so long as you’re not mounting a brake to it) you can end up with 2 or even 3mm on each side.
-Walt
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Is that where Surly’s 132.5mm spacing came from? 
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Thanks for that, I think I’ve got miters pretty tight, but as the frame is disc brake I thought I don’t need the SS bridge.
Yes, you do not need one. I only do them because customers get upset if there isn’t one.
-Walt
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