The best disc brake rims

Emails we send often include links to blog posts. Less often, emails we send become blog posts. I'd warned Colin in my response to his inquiry ("what are the best disc rims?") that my response was going to be long, since I was warming up a blog post on the same topic. A lot of that email is contained below. There is also something of an appendix in the middle, describing to you what I didn't describe to Colin, which is how exactly we grade and evaluate carbon rims. It's in italics. I should also note that the only carbon option Colin asked about was RCG. They are more in line with the cost of alloy than carbon, so it's logical the way that fault line cracks. Here goes:

<<Great question. The disc break development has thrown a big curve into the whole thing. Now that manufacturers are actually making disc specific rims that don't suffer the hindrances of chemistry that's trying to avoid turning into goo above 250*c or whatever, the rims are getting really nice. In the last week I've built carbon wheels from each of the brands we offer, and Enve's the only one that's as well built as an RCG. I grade this on a whole lot of parameters*. So this becomes me saying that if you have the budget, RCGs seem unbelievably rugged (they won't get the full "are rugged" until a broader and deeper experience), set up tubeless perfectly, work perfectly with tube tires, are the lightest of the options, feel really nice to ride (I don't trust myself to avoid confirmation bias here, so take this with a huge grain of salt), may be somewhat faster than the others though probably by some miniscule amount (as miniscule an amount as any other rim in its general class - the differences here these days are TINY), and I think represent a wonderful value proposition given their price. And that's the rub - they do nice stuff that I think merits and earns back some higher cost, but if that cost is 2x (or 4x, which it can be) the equivalent alloy setup, then it's a hard pass. At somewhere around a 15- to 25% premium over our alloy pricing, recognizing that our alloy pricing is pretty freaking fashionable in the first place, I think it's a hit. 
*We've seen a ton of carbon wheels over the years, and though I often question whether having done our own molds was a smart move (short answer - on balance, if we wanted to make the most money and grow the business most quickly, no), there's no question that it provided an education that few others possess. You have experiences, you have successes and failures and get bloody noses and are required to spend countless hours dealing with a thing, and you learn a thing or seven. Here are some of those things.
The spoke hole in this rim is at a funky angle. We call this a "drifted" spoke hole, because the underlying spoke bed in the rim has had layers drift away from where they're meant to be. Whether this will be a long term problem or not, I can't say. Complicating this is that this was a BYO rim build. Had we been the rim supplier, near certainly I would have rejected this rim for this. Whether or not the rim vendor accommodated that would be a huge tell for me. I believe we handled this well with the customer and the exact details of that are immaterial here. In any case, in as many rims as we've seen from the RCG vendor, none of these have occurred. This happened sometimes with the Rail vendor (which is what I'm calling the manufacturer in all instances here) and we once rejected a big shipment because this was too evident. If it doesn't cause a problem for the rim, it at least stresses the nipple, and it shouldn't happen. 
We de-stress the living bejesus out of builds. I mean we torture them. A lot of times, you will hear some amount of noise coming from the rim as you do this, and it's a simple "why?" Uncompacted carbon laminate gives way and then settles into a compacted state. These are like tiny little fractures in the laminate. While they aren't necessarily fatal, or even necessarily harmful for a long term quality build, let's just say they don't make anything better. They're not a feature. We hear these with pretty much all carbon rims, except I haven't heard one yet from a rim from the RCG vendor. 
Well molded carbon rims can be pretty crazily round and straight. We've talked about construction of alloy and carbon innumerable times, but this post from 2014 gives good backstory on it. For the most part, rims only need to hold a certain tolerance and anything beyond that is gravy. And you have to be pretty &$^%ing good at building wheels to see within those tolerances, but they are a tell, a proxy for how good the processes are. When you see waviness or any kind of settling, either the molds or being cycled too hard or the molds aren't good or the heating curves aren't being adhered to or some other thing that's not going to make the rims better is happening. This carries over to how regular the width between the brake tracks (or the "not brake tracks") is, how flat the tire bed is, how consistent the ERD is, etc. The RCG vendor's rims are at least at par with any other rims we've seen (and we've seen all of them). 
Weights should be consistent. Resin ratio should be held to within 2% (so the resin ratio should be in the ~35 to 37% range, depending on what your laminate engineers and material suppliers spec). Resin starved or resin rich laminates will suck. A rim much lighter than spec is not a happy surprise, it's a rim that's likely to fall apart because there's not enough glue holding it together. We've seen like a 5g range in the RCG vendor's rims, which at least implies that the resin ratio is well (well) within that 2% range.
A drum that we've beaten for a while is that high temp resins are more finicky to work with, harder to mold, and are less resilient than lower temp resins. That is why our interest in carbon rims extends only to disc rims that are specifically made as disc rims from the chemistry on up. No switch hitters. 
None of this is to say that we think the RCG rims are the best rims on the planet, or that their vendor is the best rim maker on the planet. I do, however, think that they are in a VERY elite vendor strata, and that the RCG rims are the equal of anything out there for the task. They may not be the right design or specs for you, but we prioritized construction really highly in selecting these, and their construction is ridiculous. 
Then it boils down to a price. At 4x the price of one of our very reasonably priced and very high quality alloy builds, does their benefit bear out the premium? No, quite simply no we do not think it does. Neither at 3x or even 2x. But at somewhere around 1.25 to 1.4x does it? I think it certainly makes a nice case for itself. 
HED Belgium+ is becoming my standard "if not RCG, then..." answer. It used to be the standard answer. They're great and we've been building them for just about 4 years and have yet to see one that's not first class or failed to make the owner happy. Slightly higher cost than others but far from extravagant.
Al33 disc is just about to filter in. It should be good, but I've only seen a sample set from a while ago, not a production one. Our enthusiasm for this one is going to depend on cost and build quality. If pricing is in line with their current machined sidewall rim brake rims (which would make sense) then they'd better be as nice as HEDs because that's what they'll cost. For a non-road racing use case at cost parity, I give the nod to the HED in that comparison to date. 
Wanderlust is really nice. They haven't built up a ton of demand, and we're limited in how much demand we can create. We only get enough reps to build real familarity with rims through sales, which is a function of demand. The ones we've seen to date have been great, and they've been good to their word on fixing the joint deal I noted in my review on them, but we'd really like to build them in volume before professing undying love for them.
The sleeper hit is Boyd Altamont Lite. Reasonable price, lighter than all except RCG, well made, good specs, full drilling option range, nice shape. The only sticking point (to me, and I think to a lot of others) is the graphics. Too much. I hate to write as many emails with "if you can take the graphics" as I do, but apart from that man I really like them. >>

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  • Dave on

    Colin – Secure fit in mounting (meaning good technique needed with using center channel, perhaps you’ll want to use a lever for the last bit of second bead), and then floor pump easy inflate. This also applies to Donnelly Explore MSO (AWESOME mixed terrain tire, handles super well on road and off), Schwalbe G-One, Schwalbe X-One, and WTB Cross Boss. Those are all the tubeless tires we’ve yet used, and they all behave just about the same as far as mounting and inflation.

  • Colin on

    Thanks Dave. Interesting. Any experience yet at how easy Schwalbe Pro Ones are to initially seat on the RCG 36 rims?

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