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Old 03-22-19, 02:21 PM
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Join Date: Apr 2012
Location: Saratoga, CA
Posts: 270

Bikes: 2005 Trek T2000; 2005 Co-motion Speedster Co-pilot; various non-tandem road and mountain bikes

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Cracks in Spinergy tandem rim

I happened to notice some hairline fracture lines emanating from several spoke holes on our rear Spinergy Z-lite tandem rim the other day. Not sure how long they have been there, the wheel still was perfectly round and true. The wheels are just over 2 years old with a bit less than 4,000 miles of use. We are a 128 year-old team weighing about 310 lbs riding in hilly terrain. The wheel has an Arai drum plus rim brakes, 9 speed cassette, symmetrically laced with 2-crossed round spokes (no dish). I have been lately running a 32 mm Continental 4-seasons tire on it at 90 psi. The braking surface has not worn down to the thickness indicator and still looks good.

The good news is that Spinergy was great about immediately sending me a new rim with no hassle. They would have replaced the rim had I sent it to them also, but I preferred to do the job myself.

I wondered if the cracks were due to too much spoke tension, but if anything the average tension was a bit low at less than 80 kgf whereas Spinergy recommends greater than 100 kgf. After removing the tire I could also see cracks around the valve stem and access holes which are not subjected to spoke tension. So perhaps the tension was too low allowing the rim to flex excessively? Or maybe it was a bad alloy or extrusion? I would expect many more miles and years normally.

If if you are running Spinergy tandem wheels I would advise you to closely inspect the rim surface for cracks near the spoke holes periodically.

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