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Old 09-02-2020, 05:36 PM   #20
BRENT in 10-uh-C
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Join Date: May 2010
Location: Eastern Tennessee
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Default Re: Tighten the 21" rims straight

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Originally Posted by daveymc29 View Post
Talked to an engineer friend about shrinking spokes to straighten wheels. He's not much of a fan of putting uneven heat on wheels. He assured me that it will work, but feels it is not the best solution. He rather straighten them cold and is concerned that heating and quenching will make the metal brittle, which was also my concern. His thought was more along the line of heating the entire wheel and let it cool slowly, like in powder coating and use the best wheels on the front. Any other thoughts along those lines?
Respectfully, your friend needs to study up on metallurgy first. To begin with, the wheel components were made from a low carbon steel so that it could be welded during assembly. The higher the carbon content, the easier to embrittle with heat. Secondly, when straightening spokes or wheel rims, the intent is not to make the spoke 'cherry red'. Instead, it is to heat the spoke enough where steam is generated when water is added to cool it. That is all it takes to shrink a spoke. And thirdly, with metal you only do three things, ...you stretch it, you shrink it, and you bend it. Originally each spoke was put into tension as the spoke weld cooled. The only way the tension is lost is if the contact points are broken, -or if the spoke is stretched (due to trauma). If it is stretched, it will never return to tension unless the metal is shrunk the same amount it was stretched. All cold bending does is rearrange the metal shape. Cold straightened rims will lose their shape if there is not an adequate method of holding the rim into the correct position. The only way to hold that position is to have tension pulling from multiple directions.
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