OK, summer’s technically over, and both cyclocross and winter are coming, so I’m reminded of the titanium Chiru fast bike that we previewed earlier in the year. Fat bikes aren’t really only for deep winter riding, but this is a fairly unique adventure-ready bike that really excels when the snow starts to pile up. It’s still warm out for the most part, even where I live in the Czech mountains, so I’m going to keep this brief as I still am hitting the roads & trails on much skinnier tires.

(Photos/Cory Benson)

But if you dream of making winter plans heading further off the beaten track, consider this a teaser of snow biking to come…

Chiru Nanulak longtail titanium adventure fat bike

(Photos/Cory Benson)

Attentive readers might have noticed the Chiru Nanulak back in February with the release of Old Man Mountain’s FLiP Cage system. We didn’t get any real advance notice of when this bike would launch (even though we had one of just a couple in existence to test out) when there still was snow on the ground for that story, other than that the Nanulak would be ready for next winter. But Chiru founder Pierre Arnaud Le Magnan also didn’t say we couldn’t tease it in the wild a bit early, so I did get some proper snow riding in late last winter.

Now that the bike is officially out there, and is available to buy, I figured it was time to think about the winter to come.

So what is the Nanulak?

Willy Mulonia on tour (Photo/Chiru)

Chiru describes their new Nanulak as a fat bike “for the most extreme adventure”. That’s not a big surprise, as all of their titanium bikes have a distinct adventure leaning, and this one was specifically developed for Willy Mulonia of PA Cycling to take on the Iditarod Trail Invitational in Alaska – aka Iditabike. Mulonia went on to win the ITI race on this bike in March, in a 7-way-tie show of camaraderie, as they all rolled in after riding the final 4 days of the brutal 17-day race in intense winds together.

(Photo/Chiru)

But while this one was built to thrive in snow & ice, it’s equally capable in soft sand, loose rock, or swampy mud. And it is definitely the fattest tires Chiru has ever put on a bike.

The general concept could be broken down into a few core ideas:

• massive tire clearance, no matter if you choose 26″, 27.5″, or even 29″ wheels
• extended geometry for unmatched traction in the loosest terrain and stable handling while fully loaded
• expedition-ready titanium durability and maximum carrying capacity

Willy Mulonia’s expedition-ready setup (Photo/Chiru)

The bike takes its name from the native Alaskan Inuktitut language, where Nanulak is the “hybrid breed” between polar and grizzly bears, a symbol of ‘ecosystem clash’ as the planet warms and the arctic bears’ habitat disappears. But that hybrid name is fitting, because Chiru’s Nanulak is a fully capable fat bike – with classic fat axle spacing – but it features a much narrower MTB bottom bracket spacing that lets users run a much narrower and more comfortable low-Q-factor crankset if you aren’t fully maxing out rear tire width.

“Titanium is still the best material to achieve the optimal balance between comfort, lightness, and power transfer. That makes it the ultimate material for a reliable bike that can withstand the hardship of bikepacking or ultra-distance challenges, and to top it off, it’s a low-impact environmental material.”

– Pierre Arnaud Le Magnan, Chiru Founder & CEO

Key Tech Details

• custom 3Al/2.5V grade 9 butted titanium tubeset
• max 26 x 5″, 27.5 x 4.5″ or 29 x 3.0″ tires (min 4″, 4″, or 2.6″, respectively)
• sh!t tons of bikepacking mounts: 1x standard seattube bottle cage, 4x 3-pack mounts, a top tube bag, fender & rear rack mounts, plus bolt-on front triangle & longtail frame bag mounts

• tapered headtube for 1.5″ tapered steerers, suspension corrected for a 100mm fork
• 1x specific mechanical or electronic with ultra-long chainstays (2 chains required)
• 83mm BSA threaded bottom bracket for narrow MTB or wide fatbike cranks
• guided internal cable routing, including for a 31.6mm dropper post and rear dynamo light
• sliding 20mm adjustable rear dropouts with UDH for 12x197mm thru-axle and 180mm post mount brake
• ultra-long, slackish geometry with 600+mm chainstays & 68.5° head angle
• 3 frame sizes available (S, M, L)

Note: My build with 100mm fork travel (~525mm a-c) slackened the head angle out to 67° & seat angle to 72.4° for a very long feel on the bike, even as it shortened Reach by 5mm.

First Look & First Impressions

We got an early look at the new Chiru Nanulak, just at the tail end of last winter’s snow.

I was frankly a bit scared of the ultra-long rear end, as our home snow biking tends to include more steep terrain and tight singletrack than the wide open landscapes of Iditabike. My worries of slow handling never really materialized – snow biking is generally slower anyway to start with, compared to regular mountain bike trail riding.

And the long rear end turned out to be pretty magic feeling – both on the steep climbs and in soft snow. Since the rear wheel was so far behind the saddle, there was a sense that all of your weight was always being put down into the rear wheel. Never could the front wheel lift, and rarely would the rear wheel spin. But when the rear wheel did slip in loose snow (then slush, and later mud), it didn’t really matter. The long wheelbase remained stable, you could keep spinning the cranks, and the rear wheel eventually found grip again.

Look, this thing isn’t really magic. It feels more like driving a monster truck crossed with a tractor-trailer. This bike doesn’t change direction quickly. It doesn’t do anything all that quickly. But it finds traction and stability in soft terrain that is usually unrideable. Yes, it feels pretty slow. But it also feels fun – whether you are slowly climbing a loose, slushy mountain at the edge of winter or rolling over endless roots and soft pine forest trails in the summer.

If you aren’t in a giant hurry, it’s a really fun bike to ride.

Chiru Nanulak – Pricing, options & availability

They sell the new titanium Nanulak fat bike as a frame-only from 2890€, with no complete bikes on offer. But you can also opt for a Chiru Nanulak frameset, picking either an Enve carbon fork for proper fat tire widths at 3470€, or a sleek welded titanium Chiru fork intended for up to 29×3″ tires for 3755€. Chiru will also sell you a ti stem, to or carbon seatpost, ti or carbon handlebar, or titanium bottle cages to start out your bike build. They will also set you up with an Old Man Mountain Divide Fat rack pre-mounted if you have expeditions in mind.

Frame lead-time is about two weeks from the time you order, and then it is up to you to figure out how you want to complete your new Nanulak custom build. We built up a 2349g size Large frame, set up with a 100-120mm Manitou Mastodon fork, 27.5 wheels with either 3.8″ or 4.5″ tires (depending on conditions), adjustable spindle width Race Face cranks, a BikeYoke Revive dropper, a narrow handlebar setup, and a Wheeltop EDS OX wireless shifting setup. Complete bike weight was generally around 16.1kg, depending on some variables, with several cages & a Tailfin toptube bag mounted, plus old school Crankbrothers Mallet pedals.

Are you ready for winter adventures?

ChiruBikes.com

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