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Aluminium rim repair... splitting at the rim joint


RLucas
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Why you paying school fees?

It's my first MTB, so there's a lot I didn't know about old vs newer tech, e.g. straight vs tapered steerer tubes, QR vs thru-axle, what's more available in the market (new or used) and what to look out for when buying a 2nd-hand MTB (esp a cheapie). It's been a good learning experience though... researching and asking around... repairing and upgrading what I can. I've tried to do everything on a tight budget, but things add up rather quickly

Tons of fun though!... at least until I have to explain the budget to the wife  :wacko:  :lol:  :lol:  :lol:

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Ride it until it is shot. As Jobst Brandt puts it in "the Bicycle Wheel" it does not really matter if the rim is plugged, pinned, welded or simply lined up.

 

RIM JOINT

Rims are formed from straight material that is rolled into a hoop and joined.

Many solid-section rims have welded joints, as do some hollow aluminum rims.

For hollow rims, however, welding is not only difficult and expensive, but also

unnecessary because the joint as well as the rest of the rim of a properly tensioned

wheel is always under compression. Most hollow rims are joined with a close-

fitting plug. Welding generally produces poorer alignment than a plug joint,

and it has no strength advantage because there is no tension at the joint, only

compression. When unspoked, plug joined rims can be pulled apart by hand if

the insert does not fit too tight.

Plug joints sometimes separate in a crash, but only after the wheel has collapsed

and has lost its spoke tension, and then only if the destructive force is near the

joint. In fact, a wheel could be built from a rim of 36 segments not held together

at all except during assembly. Such a wheel would perform normally except that

if several adjacent spokes were cut, the rim would explode into 36 pieces,

whereas a one-piece rim would develop a radial hump.

A concern has been expressed that, unless the two spokes adjacent to the joint

cross on the way to the hub, the joint will separate in use. This concern ignores

that the tension of all the spokes is supported by the rim as an arch in

compression, a load of about a half ton for a 36-spoke wheel. To facilitate

engaging a tire pump, wheels are usually spoked so that the spokes adjacent to

the valve stem "pull apart" (are parallel). With this standard arrangement the

spoke pair at the rim joint does not cross in radial wheels or those whose number

of spokes is evenly divisible by eight (24, 32, 40, 48). That these spokes do not

cross has no effect on the integrity of the rim joint.

 

 

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Jip, removed decal on the one side and it was indeed dried sealant, will keep an eye on the joint.

The wheel is fine. You're not going to have a problem. Ride and be happy. Hollow butt joined rims are (usually) incredibly strong. Sometimes it takes a little bit of effort to get the joint sealed the first time you go tubeless with them but that's about it. FWIW, I have a set of enduro rims built this way. They're practically indestructible.
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The wheel is fine. You're not going to have a problem. Ride and be happy. Hollow butt joined rims are (usually) incredibly strong. Sometimes it takes a little bit of effort to get the joint sealed the first time you go tubeless with them but that's about it. FWIW, I have a set of enduro rims built this way. They're practically indestructible.

Cool, thank you very much for the input and advice.

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