Rim Joining: The Process and the Mystery

Wheel nerds take the details of their hoops seriously. We should know. We’re some of them. So, when it comes to details such as how rims are joined, we take these decisions seriously. Afterall, we’re in this to make the best possible rims. That’s why we brought production in-house. Perfectionists demand total control.

Now, not all of you are wheel nuts. We get that. So, before we go too far, we’ll cover some basics. Like – “What the heck is rim joining?”

In our experience, most people haven’t really thought about where aluminum rims come from or how they’re made until they see it happen. Then the light goes on, and they realize why these details all matter so much.  

Rims start off as compact logs of aluminum forced through a tool making it into the shape of a rim profile. This is called an extrusion (think of an old playdough toy making spaghetti). They’re then run through a special machine that rolls them into wheel-shaped circles and cut in order to be the right diameter. The precision of the rolling is imperative. When done right, the cut ends should just kiss each other at rest – if there is much gap or overlap between the cut faces, you’ll have something that looks like a high-quality rim until you build, true and tension it. Then you end up with a real crap-wheel. We can’t abide by that - but we’re skipping a lot of steps. We’ll get back to that in another post.  

Up until this point, there’s little difference in opinion in the process. But then it gets interesting. After it’s cut, the two cut faces need to be attached to each other. This is called “joining.”

There are three ways to achieve this goal. You can attach the ends with pins, weld them together, or use inserted sleeves. Done correctly, all three joining methods are safe. Once a wheel is built, the spoke tension forces the faces of the rim together. But there are performance differences that make the difference between “functional” and “awesome.” We’re shooting for awesome.  

First, let’s discuss pinning. This uses two steel dowels jammed into each end of the rim to hold it together. This option is inexpensive, but yields unreliable results and too often causes noise in the brake pads when you brake. This is because the pins allow a tiny amount of play between the two rim faces. It holds them together, so it’s still safe, but far for from precision-crafted. can’t keep the two faces from shifting relative to each other. Generally speaking, only the cheapest rims use this method. No one would claim it’s the best, so obviously we don’t do it. You’re not surprised.  

The next option is welding the rim. This approach was designed as a superior alternative to pinning – and it is. If done correctly, it can make a great rim, because it naturally yields a smooth face where the two pieces were fused. However, it does have some downsides.

Most importantly, the flash welding process generates an enormous amount of heat. That’s just the nature of welding. However, this heat-affected zone degrades the heat-treatment of the rim surrounding the joint, making that part of the rim weaker than anywhere else. So, while the joint is sound, the finished product is now less strong. As perfectionists, that’s a tradeoff that we’re not quite willing to make.

The last option is called sleeving. Although we own the equipment to weld rims, we further invested in the equipment to sleeve join as we’ve found that it yields the best over-all quality. Like anything in life, it has its pros and cons, but when done correctly, the results are impressive.

Sleeve joining uses a form fitted sleeve in the shape of the inner cavity of the rim to span the joint. That sleeve is slotted into one side of the inner rim, then the other to hold them together in a similar way to how Legos stick. Except that this is press-fit making it incredibly tight-tolerance. Even better, the sleeve does double duty as a strength-reinforcement piece, making the joint the strongest section of the rim – the opposite scenario as with welding.

Now, here, some of our favorite wheel fanatics will point out that with sleeve joining you can end up with a braking surface (on rim brake models, anyway) that isn’t completely smooth. They’re not wrong – that can happen if it’s not done right. We machine the rim after joining to ensure that the faces are clean and there is not a noise-generating step in the brake track. By doing it in house we can ensure our process and guarantee it.  And when we say guarantee, we mean it – every rim and wheel we make is backed by our certainty program which promises that you’ll love what you buy.

With over 15 years of wheel production in our pocket you’d better believe that if we had to back that up very often, we wouldn’t be around.

It’s worth mentioning that when it comes to building rims, our bar is high. Afterall, we designed the process for our sister brand Rolf Prima’s wheel systems. In that model, the paired-spokes touch the rim at larger intervals between spokes than a traditional wheel. They build, true and repair just like any other wheel, but in order to work its magic that rim has to be totally, one-hundred percent, undeniably round and flat from the get go. There’s no faking it with uneven spoke tension the way higher spoke count other wheels can (but shouldn’t).

We take this seriously, because we love what we do, and are in it to ensure that you do too. We want your every ride to be enhanced by riding bomber, precision-built product made right here, by people that care.

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