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concluded 135mm must be the right size, because most of the 130mm rear hubs they offered were labeled as "road", "track", or "internal-gear" hubs, whereas the hubs I wanted (Shimano Deore XT) were always 135mm. Not sure why you'd think any stretching is necessary to fit a hub that size; they drop right into place on my bike.
Don't be such an engineer;
some might try and spread a frame to fit a rear hub. A 150mm rear hub is only 7.5mm wider per side than a 135mm rear hub
Did you read any of Sheldon's words of wisdom from this link? http://sheldonbrown.com/frame-spacing.html 130mm is considered a road bike spacing now, but wasn't always. Older bikes often have narrower OLDs (Over Locknut Dimension). http://sheldonbrown.com/gloss_n-o.html#old