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Joint gap on new tubeless rim?? pic

Old 07-25-15, 07:12 PM
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Joint gap on new tubeless rim?? pic



So I researched this and everybody seems to agree that joint gaps on pinned rims are no big deal, that they will close once the wheel is built due to the pull of the spokes and the compressive effect of the inflated tire.

However, this is a tubeless rim; and I have not seen this mentioned.

Specifically this is a new Mavic EN423 disc 29er rim. It comes with a fancy rubber strip that you wedge into the valley to prevent air leakage through the spoke holes. I don't know if the strip extends up from the valley (on the sides) far enough to actually meet the tire, so a joint gap may or may not impair the air-tightness.

I'm in the process of preparing a claim since several wheels of this shipment were damaged due to inadequate padding, so I have no qualms at all about rejecting this rim if there is any chance that it will not function properly.

Please share your thoughts. Thank you.
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Old 07-25-15, 07:38 PM
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When built, the gap will close to no wider than a tiny crevice. Between the rim liner and sealant it should be fine.

If you want, you can paint the mating surfaces with gasket sealing compound, so the tiny crevice will seal perfectly airtight.
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Old 07-25-15, 07:49 PM
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That gap looks way too big. Normally it's just toward the top of the rim sidewall and not down in the valley. I'd return it.

- Joel
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Old 07-25-15, 08:11 PM
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Clark

If you want to know if the gap will close before wasting time building it, test it.

Get s strong piece of rope, and a stick. Wind the rope around the rim and knot it off into an oversize loop. Arrange the knot away from the split, and insert the stick and twist as you would a tourniquet. It shouldn't need any great effort to pull the joint closed.

Warning, once closed, opening is can be difficult, so if you plan on using gasket compound, you should do it first.

For my part, I'm so used to pinned rims closing, that I'd just apply compound and build it.
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Old 07-25-15, 09:34 PM
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Originally Posted by FBinNY
Clark

If you want to know if the gap will close before wasting time building it, test it.

Get s strong piece of rope, and a stick. Wind the rope around the rim and knot it off into an oversize loop. Arrange the knot away from the split, and insert the stick and twist as you would a tourniquet. It shouldn't need any great effort to pull the joint closed.

Warning, once closed, opening is can be difficult, so if you plan on using gasket compound, you should do it first.

For my part, I'm so used to pinned rims closing, that I'd just apply compound and build it.

AH, very clever . . . Thanks!
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Old 07-25-15, 11:17 PM
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Maybe this is a dumb question, but on pinned rims, are the pins the only thing holding the rim together? I had had always assumed there was some kind of weld.
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Old 07-25-15, 11:22 PM
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Originally Posted by Gresp15C
Maybe this is a dumb question, but on pinned rims, are the pins the only thing holding the rim together? I had had always assumed there was some kind of weld.
The pins hold the joint positioned, but it's the compression from the spokes that hold it together.
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Old 07-25-15, 11:35 PM
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Here's an interesting article with pictures of the pins
Deconstructed, cheapo rim. | Bicycling Magazine Forums
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Old 07-26-15, 12:37 PM
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Originally Posted by FBinNY
The pins hold the joint positioned, but it's the compression from the spokes that hold it together.
Thanks. I always wondered how they joined rims.
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Old 07-26-15, 01:08 PM
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Originally Posted by Gresp15C
Thanks. I always wondered how they joined rims.
Nobody really thinks about it, but the compression from the cumulative load of the spokes is staggering, at somewhere in the range of 1,200kgf at any point. The added compression from the inflated tire is on to of that and can increase that load by more than half again.

Rims cannot be pulled apart at the joint, but they can buckle to the side.
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Old 07-27-15, 12:52 AM
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Originally Posted by FBinNY;180152l68
Rims cannot be pulled apart at the joint,
.... Under anything remotely resembling normal conditions...
On a de-tensioned wheel or as an unlaced rim, it can happen. All pins and rim extrusions are not created equal.
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