Surly ExtraTerrestrial Tires: First Ride Impressions

compose Cass Gilbert
time Oct 19, 2015
comment 16

We’re not quite sure how they do it, but Surly appear to draw from an inexhaustible well of awesome product names. The latest in name calling greatness is their ExtraTerrestrial tire, which is, appropriately enough, designed for lands far away. Also synonymous with the brand is size; as such, the ET is pretty much the biggest volume, dirt road touring tire on the market, at 2.5in in width.

Tread wise, its unidirectional design is not dissimilar to Schwalbe’s celebrated Marathon series, with extra side knobs to add more bite when cornering off road. Quoting from their press release, Surly claim “a Kevlar cap between the treads for puncture protection, a nylon breaker in the sidewall for cut protection, a pattern molded into the sidewall to help prevent cut propagation, as well as a file tread between the main tread blocks for additional puncture protection.” All of which should help prolong its life as a heavy duty, multi use touring tire with dirt road aspirations.

But how do they perform on Earth? While we can’t say we’ve had a massive amount of time with the tires so far, at least relative to their intended use, what we’ve experienced has been very positive. To get a better idea of how they’ll fare after a few more thousand miles on the clock, we’ve sent a set to long distance tourer Nick Gault, currently riding dirt roads across South America on his Surly Troll. Touring tires are all about long haul durability, so check back for a long term review.

In terms of initial impressions though, the tires roll quickly and quietly on pavement, and handle dirt roads with surefooted assurance. The larger volume certainly helps boost comfort levels on a rigid bike, and given how big tires opens up possibilities for lower pressures, there’s good opportunities for optimizing grip. Flats are the bane of tourers and commuters; so far, the tires have proved puncture free, both on bikepacking trips in the UK, a short portion the GDMBR in Colorado, and desert rides around New Mexico. Not wishing to tempt fate, they’ve even been unusually resistant to the goatheads that mine Santa Fe’s city roads.

No doubt Surly will release a typically detailed blog post listing the intricacies of running such tires on various frames. As far as our testing has revealed, they play fine with a Troll set up with a standard triple and average-width rims (Rhyno Lites, in our case). Note that if you have aspirations of fitting them to 26in Rabbit Hole rims, you’ll need to change out your triple for one of Surly’s nifty O.D. crankset – which pushes the chain line further out, by displacing the middle cog with the smallest, and sacrificing the largest. You’ll also need to position the wheel further back in the dropout (though anyone running a Rohloff Speedhub shouldn’t have any such issues). If fat tires on longtails are your thing, we also noticed a slight grazing of the chain on the tire sidewall in the largest cog on Surly’s Big Dummy when running a triple. It’s not a safety issue, more of an annoyance, and luckily there’s a workaround: place a 4.5 spacer behind the cassette and ditch a cog.

Surly suggest running the ET with rim widths in the 24-50mm range. If you want numbers, they quote an overall diameter of 688mm, a max casing width of 63.5mm, and a max knob width of 64mm. The tires use a 60 tpi casing; a nice surprise is that they’re officially tubeless compatible too.

There’s no confirmed weight until the first production batch arrive, but expect them to tip the scales at comfortably less than 1kg a piece, which seems perfectly reasonable considering their size and intended use. Tires should be landing in the US this winter, and spring for rest of the world. Price is set at $60. Oh, and there’s rumour of a 29+ version somewhere in the Surly pipeline…

Surly ExtraTerrestrial Tire Specs

• Size: 26 x 2.5″
• ETRTO: 559mm
• Casing: 60tpi
• Suggested Rim Width: 24-50mm outer dimension. 19-45mm inner width.
• Tubeless Ready Bead: Intended to interface with bead hook on Surly / Whisky rims.
• MSRP: $60
• Estimated US Instock: Winter 2015/16

Nov 13, 2015 update:

Surly have released a cross sectional diagram detailing the guts of the new ExtraTerrestrial. And we’ve heard back from our tester Nicholas Gault, currently pedaling the Trans Ecuador Mountain Bike Route: “Tires are awesome, so is the route!! Quick email to say both the tires finally arrived a couple of weeks ago and they are freaking awesome. They’re doubled my enjoyment of the trip.”