Flat rims look pretty cool. GW photo.
Wide, light, stiff carbon wheels with fast hub engagement and excellent trail dampening: long the dream of mountain bike rider and designer alike. And the Atomik Chubby 43's come pretty close to that nirvana.
While there are always some tradeoffs with wheel design (width for weight, stiffness for compliance and dampening), the Atomik Chubby 43's clever technology and design balance those features very well. Of course, at $540 per rim, you'll still have to pay handsomely for them (that tradeoff isn't going away anytime soon).
27.5" rim diameter
12K carbon weave
43-millimeter external width
36-millimeter inner width
15-millimeter rim depth
470 gram rim weight
hookless 3.5-millimeter sidewall
i9 hubs (boost tested) with 3-degree engagement
Symmetrical 32-spoke drilling
$535 msrp per hoop
$2110 wheel set as tested. But available in a variety of builds including a more affordable $1,660 with DT Swiss 350 hubs.
The wheels came with rim tape and a valve installed, neither of which leaked. GW photo.
I mounted the Chubby 43 wheels on a Specialized 6Fattie FSR Stumpjumper and tested them with two sets of tires: supple, light, low knob-profile Vittoria Bomboloni 3.0's and monster-knob Maxxis Minion 2.8 DH tires.
I inflated both sets onto the hookless rim with an air compressor before removing the valve core and adding about 3.5 ounces of Stan’s through the stem. It was pretty easy, though I’m not sure the Maxxis tires would have seated without a compressor.
This brings us to the first nice feature of these wheels: The beadlock shelf.
The beadlock shelf. Atomik illustration.
The shelf is an intermediary shoulder where the tire bead sits before it’s completely locked into the stout 3.5mm rim sidewall. This allows you to easily add extra sealant (if you don’t feel like removing the valve core) and re-inflate the tire with only a floor pump.
Using an aerospace foam core wrapped in a composite layer (their "Koretek" technology), Atomik achieves an astonishingly low 15-millimeter rim profile. They appear nearly flat. To be clear, there’s no air or negative space inside these rims, it’s all foam. The foam’s density allows Atomik to match the rigidity other wheels get by using a deeper, more triangular cross-section. It also has the added bonus of better noise and vibration dampening. I’ve never really seen this anywhere else.
Really flat. Only 15mm deep, with a foam core. Atomik illustration.
Once you flatten rims this much, you’d think they'd have too much vertical flex (like a diving board), but the foam core and thick 3.5mm sidewalls make the Atomik Chubby as vertically stiff as traditional 30-millimeter depth double wall carbon designs.
The thicker-than-normal 3.5mm rim sidewalls. Atomik illustration.
At 470g, the Chubby 43's rim weight is comparable to its competitors; about 10g heavier than Enve's 60 plus and about 25g heavier than the Ibis 742. It’s important to note that a carbon rim's weight varies +/- 15g through manufacturing, so these are all pretty close to margin-of-error differences.
But I think the foam-core, stout sidewall and shallow profile is far-and-away worth the few extra grams.
Atomik also claims narrow rims help reduce hits and damage from rocks. I guess this makes sense—the less sticks out, the less gets hit. The wheels I used were ridden hard, yet remained true and undamaged through the fall and winter.
The width offers plenty of support for a supple tire like the Bomboloni. GW photo.
When TGR tested the Reynolds' Enduro Black wheel, we were impressed with its stiffness and strength but noted their merciless trail feedback. The wider-rimmed Chubby 43, however, immediately quiet trail chatter and feel plusher than other wheels in the category.
The Chubby's wider, hooklesss rims offer great support for the tires' sidewall. Even running low-profile, supple Vittoria Bomboloni rubber, sidewall roll was reduced or eliminated. So you can run lower pressure than you would on narrower rims. And you still get that wonderful, quick acceleration of carbon wheels.
Mounting the Maxxis DHF and DHR 2.8s tires to the wheels created one of the best setups I’ve ever run on any bike. Incredibly aggressive knobs, slightly firmer, shorter sidewalls and a more squared-off profile made for a take-no-prisoners monster ride. Fast, stiff and beefy.
The Minion DHRII on the 135mm Stumpjumper 6fattie rear. GW photo.
Leaning the Chubby 43's hard into a corner produced no discernible lateral flex, and climbing plus-tires on wide rims is phenomenal. So much grip. If you buy these, bid your excuses goodbye.
The knobby DHF/DHRII combo on trail. GW photo.
The wheels can fit most 29er as well as dedicated 27.5+ frames (though you should check tire clearance). Also, if you mount these on a 29er frame and run a tire with a short sidewall, your BB height will drop a bit.
True to marketing copy, the low-profile design didn't scuff or get dinged during multiple days charging through rock gardens. While rocks will always get kicked up and ding spokes, keeping debris from damaging pricey carbon hoops is a big bonus.
And who could forget these hubs? GW photo.
The Chubby 43's steep top-model price does get you arguably the best hubs on the market. 3 degrees of engagement, that wonderful i9 sound... you know the deal. You can buy them on on
Atomik's site and, as noted above, knock $500 bucks off by choosing DT Swiss hubs (which are also a fine choice). Add a set of Maxxis Ikon/
Though I’m still a fan of