For those who aren’t familiar with the brand, Duro is a Taiwanese tire manufacturer with a surprisingly broad range of road, BMX, commuting, and mountain bike tires. Their Crux tire has long had a cult following amongst plus-tire bikers, and interestingly, unicyclists too! The trouble is, they’ve often been somewhat hard to track down. The good news is that the 3.25″ Duro Crux is now back in circulation in both 29 and 27.5″ wheel sizes, and it has a relatively assured future.

The Duro Crux comes up almost true to size on a rim measuring 45-50mm internally.

Being a goliath 3.25″ in width, this tire will best suit rims with a minimum internal measurement of 45mm, especially if you intend to run the kind of low tire pressures that get the most out of Plus bikes. If your wheelset has significantly narrower rims, you’ll risk losing out on side knob grip and you’ll have to pump them up to ensure sidewall stability, losing out on the inherent advantages of a Plus bike.

Duro Crux 27.5 on the left, 29 on the right. Ours came out about on par for the listed weights.

Given that the Duro Crux is such a wide tire, there is an inevitable weight penalty to pay, so don’t expect to be the fastest in a sprint from the traffic lights. Still, it’s not much heavier than any similarly aggressive, plus-size tire. It’s just the nature of the plus tire beast.

Side knob placement and the overall rounded shape of the carcass lend themselves well to cornering grip.

Over the last few months, I’ve been testing a set of pre-productions Duro Crux 29 x 3.25″ samples (the non-branded tires you see in these images), and have been really impressed, especially with the amount of cornering grip they offer, how well they roll, and their overall durability. The extra width and ensuing volume offer a noticeable improvement in riding comfort at low pressures, particularly if you’re aboard a fully rigid mountain bike and riding burly trails, which we have no shortage of here in Oaxaca.

Aside from using them on trails, I’ve also taken them bikepacking on tours that include a bit of everything – from soft loam to sharp rocks, from pavement to pine needles, and from cobbles to corrugation. Again, great all round performance. Only a lack of rain has meant that I can’t comment on how they ride in mud. In my experience though, I tend to prefer a narrower tire in gloopy, wintry conditions for added bite, frame clearance, and so my chain stays cleaner with a 1x drivetrain.

This image shows the 29 x 3.25″ Crux on a rim measuring 45mm internal. The front tire is a sample, and the rear tire is the production version with branding.

Still, anyone who owns a Jonus Plus or the newer LWB and SWB models will be pleased to know there’s ample space to fit them in both the front and back of the frameset – just bear in mind that chain-to-tire clearance could be an issue in muddy conditions, depending on your drivetrain and resulting chainline. For this reason, I imagine the Duro Crux tire will work especially well with the likes of a Tumbleweed Prospector (in the 27.5+ version), thanks to the Rohloff hub’s 54cm chainline. Surly’s Krampus and Karate Monkey, as well as various Stooge offerings, jump out as good contenders too, and I bet the Crux would be a fun option for a summer wheelset on a fat bike. In terms of whether your bike can fit them, we measured the axle length of the 27.5in version at around 365mm and the 29+ version to be about 398mm, and in terms of width, the tire comes up true to size on a 45mm rim. Note too that this tire will raise your bottom bracket height by 10mm or more, at least compared to Plus tires that are 3″ in width.

Jeff Jones discusses the history of the Duro Crux and his work to develop the latest tubeless version.

Although the Crux has been around for a number of year, the previous generation of Duro Crux wasn’t officially tubeless compatible, even if this didn’t stop riders from running them without tubes – you can hear more about that in the video linked above. This version is, and mine were quick and easy to set up tubeless on both alloy and carbon rims using my Specialized Blast and a generic floor pump.

Durability has been very good so far, both in the tread pattern and the overall robustness of the sidewalls. I’ve had no cuts or plugs to report, nor has the sealant wept out of the sidewalls a couple of months in. Prior to that, the only 3.25″ tire I’ve run is the Vee Rubber Bulldozer, and although it rolls more quietly on pavement, the Duro Crux offers considerably more cornering grip, along with a more hardwearing tread. If you’re going big with your 29+ tires, it’s definitely my favourite of the two.

Duro Crux 29 x 3.25″ on Jones C-Rims during testing.

As mentioned, choosing a rim wide enough to provide sidewall support at low pressures is particularly important, as that’s where plus-size tires become worth their extra weight – which is considerable, in the case of the Crux. My wheelsets measure 45mm and 49mm internally (Jones Alloy and C-rims respectively), allowing me to get the most out of such a large volume tire. As pickings for wide rims are a little slim these days, you’d likely be fine with 40mm internals too, but it’s probably best not to go narrower than that.

In fact, although the recommended psi range is 15-35psi, I typically run mine at 9-12psi, depending on the terrain I’m riding and how much I’m carrying (for reference sake, I weigh 72kg). Presumably, this 15psi suggestion is a ballpark figure, so the tire doesn’t roll too much to the side when mounted to rims that are narrower than optimal.

More recently, Emma has fitted a production version of the 27.5″ Crux to the front of her Jones SWB and also noted a distinct improvement in riding confidence compared to the now discontinued 27.5 x 3″ Nobby Nics she was running before. When we took some measurements, the height of the Nobby Nick came in at around 710mm and the Duro Crux at around 735mm, making a 25mm difference – which is very evident in the photos below photos. Tire pressure-wise, 9psi felt about right for general use (she weighs 59kg), be it riding across town or tackling trails, with no disconverting sense of self-steer.

Over the time I’ve had my pre-production tires, I’ve also tried a 29″ Duro Crux up front, paired with a 29 x 2.6″ Specialized Butcher in the frame, as this is an affordable tire that’s readily available here in Mexico. Although this setup does lift the front of the bike up and slacken the head angle a little, it offers a good balance between weight, budget, and performance.

The overall height and volume of the Duro Crux 27.5 x 3.25″ dwarfs that of the 27.5 x 3″ Schwalbe Nobby Nic.

Speaking of price, I’d actually consider the Crux to be surprisingly good value, at least for such a speciality tire and for how durable they’ve proved to be – over the years, I’ve been a big fan of WTB’s comparatively priced Rangers, but they do tend to wear quickly and they’re no longer available in the Tough casing. Although this latest round of Duro Cruxs isn’t exclusive to Jones, the tire is currently available through its website for $80 apiece.

Models Tested: Duro Crux 29, Duro Crux 27.5
Actual Weight (27.5): 1,219 grams
Actual Weight (29): 1,316 grams
Place of Manufacture: Taiwan
Price: $80 at Jones Bikes
Manufacturer’s Details: Duro.com.tw

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