There was a time when carbon mountain bike wheels were the sole domain of the cross-country crowd, a place where the narrow and often delicate hoops were less likely to be hucked into rock gardens or repeatedly slapped into corners. That's no longer the case, and the last few years have seen a massive influx of wider-rimmed carbon wheels hit the market that are aimed at the all-mountain crowd. Not one to sit idly by the sidelines, Bontrager is joining in with their new Line XXX wheelset that's built to withstand the punishments doled out by professional enduro racers and weekend warriors alike. With an an internal rim width of 29mm, the wheels hit that wide-but-not-too-wide sweet spot that allows for 2.3” tires to be run without negatively affecting the tire profile, and for even wider tires to easily be mounted up as well.
Line XXX Details
• Size: 27.5" or 29"
• Intended use: all-mountain, enduro race
• Internal width: 29mm
• Rim material: carbon fiber
• 28 straight pull spokes
• Boost hub spacing
• Weight (29" with TLR rim strips and valves): 1760 grams. Front: 840 grams, Rear: 920 grams
• MSRP: $2,500 USD
The carbon rims are made in-house at Bontrager's Waterloo, Wisconsin facility, which is part of the reason the retail price for the set is an eye-watering $2,500. According to Bontrager's Alex Applegate, “Simply put, the Line XXX as it is today would not be as good if made overseas, and we aren’t just saying that, we have tested and proven it. We did not want to compromise with this wheel and the best way to build it was down the hall from where it was designed.”
There are a number of carbon rims on the market that use a hookless rim profile, a design that's easier, and thus less expensive, to manufacture. Bontrager went a slightly different route, creating a tiny hook at the top of each rim that works in conjunction with their TLR plastic rim strips. Once installed, the strips are just about the same width as that tiny hook, and at first glance it makes it appear as if the rims are in fact hookless. Those strips make it easy to set the wheels up tubeless, and there's no need to worry about them ripping or tearing while installing a tire.
When it came time to decide what hubs to lace those carbon rims to, Bontrager chose DT Swiss' ultra-reliable 240s hubs, which use a 54-tooth star ratchet system in the rear hub for a quick 6.6 degrees between engagement points. Both wheels use 28 straight pull spokes that thread into nipples that can be accessed without removing the tire, a feature that's not always present on higher end carbon wheels, even though it should be.
A tiny bead hook on each rim is designed to accommodate the TLR rim strips.
DT Swiss' 240s hub uses a 54-tooth star ratchet system.
The carbon rims measure 29mm internally and 34mm externally.
I've only just begun to test the Line XXX wheels, and three rides isn't nearly enough time to comment on durability and strength, but the initial setup was completely hassle-free. I was able to get a set of Bontrager SE5 tires seated and sealed with a regular floor pump, and they popped securely into place right around 40 psi.
At 1760 grams the Line XXX wheelset isn't going to set the hearts of weight weenies aflutter (Bontrager's recently announced 1390 gram Kovee XXX cross-country wheelset takes care of that), but the weight is still very reasonable number, especially if Bontrager's claims of just how tough these rims are prove to be true. I will say that they feel lighter on the trail than the number that shows up on the scale, and even though there was barely a weight difference between the wheels and the alloy wheelset they replaced, I would have sworn they weighed significantly less. There's a very enjoyable snappiness to their handling, with a lively, stiff feeling that doesn't waver no matter how hard they're pushed into tight berms. Cornering was where the wheels' stiffness was the most noticeable - they made the bike feel like it wanted to leap forward, springing out of one corner and then diving into the next with just as much energy.
The big question is, are they worth it? Bontrager have their work cut out for them, especially given the increasing number of less expensive options on the market. The USA-made tag is commendable, and sky high pricing don't seem to have kept other US companies from making their presence known in the carbon wheel world, but it'll really come down to how much of an improvement they make out on the trail. Keep in mind that this is the top tier offering in their carbon wheel line - there are more economical options on the way. Look for a full review one we put more in more hard miles to see exactly what they can handle.