5:33 PM

Zipp Fix Pt. 1

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Awhile back I purchased a set of Zipp 303’s to see what the big fuss is about with tubular carbon rims.  I was immediately blown away by the lightness, acceleration, and feel of the whole setup.  Sadly though, after having only gotten a few rides on it I discovered a small hairline crack forming on the rear rim.  I didn’t want to risk it so I hung it up for awhile.  A few months lather a friend decided he wanted to take the risk and bought it off me.  He rode the hell out of it and gave them back to me after the squeezed every last mile out of it.  Now the crack is bigger and its definitely time to replace the rim. 
 
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Instead of simply paying someone to do it I decided this is a good project to learn from.  Conveniently  I also found a local selling a carbon tubular generic Chinese rim with the same number of holes. 
 
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The Chinese rim has a 50mm section instead of the original 38mm Zipp 303 rim.  It also has internal nipples which are supposed to be a stronger design for carbon rims but a pain in the butt in other aspects.  The rim alone comes in at 530 grams…. I may be new to this wheel building thing but i still know that’s QUITE HEAVY.  It makes up for it in rigidity though.  The walls are stiff as opposed to the Zipp rim that could be squeezed with minimal effort. 
 
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First order of business is to free the hub from the old rim.  This means prying the tire off the rim.
 
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The crack has moved about halfway across the rim cross-section.
 
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For reference later, the full 303 setup weighs a nice 697.1 grams.
 
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The rim itself its BEAUTIFULLY light. 300 grams on the dot! 
 
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Next order of business is to measure the ERD or effective rim diameter of the new rim.  This number will be used in determining the new spoke lengths.  There are several ways to do this but I chose to use the spoke method.  Take two straight long spokes and two nipples.

More info and a calculator can be found here :  SAPIM SPOKE CALCULATOR
 
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But the curved ends and file them so they’re not sharp and easier to measure.  It’ll make it simpler if you cut the spokes to the same length.
 
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Some people use Loctite but I chose to go with some Teflon tape to make sure the nipples don’t move around and mess up your measurement once you thread them on.
 
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The nipples are on backwards because I have an internal setup.  Otherwise they’d go the other way.
 
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Measure the length of the spoke from the end that you’ve cut to where the nipple starts. Lets call this value A
 
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Insert them in opposite holes.
 
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Measure the overlap.  Call this value B

ERD= 2A-B

Now you can measure the hub dimensions and enter all of that into the calculator.  I didn’t have to because the Zipp website provided everything for me. WIN!

if you have an internal nipple setup then you’d need to add 10-12mm to the length of the spokes to compensate.

Will be adding more and changing this as more is learned and tested!  Email me if you have any suggestions.