Tubeless Fatbike Guide: Nate to Rolling Darryl

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Living in New Mexico last winter required the adoption of tubeless tire systems.  Arriving in Albuquerque on a Pugsley, I was foiled by goathead punctures on a daily basis.  Naturally, as other mountain bikers in town already knew, “going tubeless” was the answer.  At Two Wheel Drive, we developed a method to bring fatbikes into the tubeless realm using the split-tube method, also known as “ghetto tubeless”.  

For a detailed guide to the split-tube method, check out Fatbike Tubeless, Tubeless Moonlander, and Does it work?.  In short, a 20″ or 24″ tube is split along its outside seam to create an airtight rim strip.  The tire is mounted atop the homemade rimstrip, without a tube, and a blast of air seats the tire.  Finish with liquid sealant, trim the excess rubber from the split tube, and ride.  This method has proven reliable, and may be preferred for anyone concerned about tire burps, such as an aggressive rider on rocky trails.  For a completely burp-free system, it is possible to apply an adhesive between the tire and the split tube to create a permanent seal, also allowing the tire to be moved from wheel to wheel without breaking the tubeless seal.  These two methods typically reduce wheel weight when compared to use of a tube, but not by much.  

The final procedure for converting an existing wheel to a tubeless system is very simple in theory, and is the lightest method.  A layer of tape is applied to the rim to create an airtight seal.  The tire is mounted and seated, and sealant is added.  Finally, sealant is distributed inside the tire to seal the bead and any pores in the tire.  While the concept is simple, there are several challenges.  Seating the tire on the rim can be difficult, especially in the case of a very loose-fitting tire.  Some tire and rim combinations mate better than others, due to inexact tolerances and texture along the tire bead.  Some of the texture designed on the tire bead is intended to improve the bead lock, reducing the risk of the tire walking on the rim at extreme low pressures, but creating some challenge to sealing.   

 The beginning front wheel weight is 7lbs 15oz (3.6kg) for a Salsa Mukluk 135mm hub, custom drilled (1.5″ holes) Surly Rolling Darryl rim, butted spokes and brass nipples, 160mm rotor, stock 26×4.0″ tube, 27tpi Surly Nate tire, and about 75 Grip Studs.  This will not be a super light wheel, but with all the features– studs, aggressive tread, elimination of puncture risk– it will be just right for my needs.  For about $10-$20 per wheel, this is the cheapest way to lighten a fatbike, or any bike.  Of course, wheel weight is always more pronounced than weight on the frame.  Reducing the friction between tube and tire is also a theoretical gain, evidenced by the rubber dust found within the tire from rubbing at low pressure.

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Remove tire, tube, and rimstrip.  The Surly rimstrip weighs about 90g.

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The naked wheel weighs exactly 3 lbs.  The stock tube weighs 15 oz (about 425g)

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I take the opportunity to true the wheel.

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A layer of high-visibility DOT approved reflective tape is applied to the rim, which will be visible through the cutouts, improving safety in traffic.  Similar tape is available in a variety of colors.  Look for safety or sign stores catering to industrial and construction accounts. 

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Finish with a piece of tape.

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Next, a layer of Gorilla Tape is applied tightly to the rim, up to the very edge of the bead shelf, just under the hooked edge of the rim.  Another layer is added to the other side, meeting in the middle to create an airtight seal.  It is theorized that laying the tape right up to the bead helps create a tighter fit at the bead.  It certainly helps to seat the tire initially.  Other sources suggest several layers of tape.

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Mount the tire with a tube to ensure every inch of tape is securely adhered to the rim.  This also allows one bead to be seated, reducing the challenges of seating the tire without the tube.

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Mount the second bead onto the rim.  A cheap 26 ” rubber rimstrip helps to force the tire bead towards the edge of the rim, on the bead shelf, where the tire is most likely to contain air.

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Removing the valve core is essential to a quick burst of air.  A good compressor is also necessary.

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The tire accepts the air on the first attempt, and pops into position.  I deflate the tire and install 4-6oz of Stan’s sealant (more if you want, especially in thorn country, or with even bigger tires) through the valve core, although it is possible to dump sealant into the tire before seating. Spin and shake the tire to ensure a good seal all around.  Bring the tire up to maximum pressure (30psi).  If possible, ride the bike to simulate any disturbances that might arise in real world conditions.  This also helps to distribute sealant.  Some tires may spit sealant from the bead or from under the valve during installation (120tpi Dillingers on Darryls have done this in my experience), but this 27tpi Nate sealed without a drop.  After my experience with Knards on Rabbit Holes, I am amazed.  I will revisit that combination soon.  

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The final weight of the front wheel is 7lbs 5oz.  This is a 10oz (283g) weight reduction.  For greater weight loss, it may be possible to use a lightweight packing tape without the thick reflective tape that I installed.  Wide Stan’s rim tape is unofficially available through Speedway Cycles in Anchorage.

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The final rear wheel weighs in at 9lbs 2oz.

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Time to ride home for the night.  First impressions are that the bike feels like a rocket.  I explore some urban crust on the way home, mounting snowbanks along the roadsides, doing my best to challenge the system.  Anything that makes riding more fun is worth it.  One and a quarter pounds (567g) less weight in the wheels helps a lot!

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In the morning, I go outside for the real test, to see if the tires have held air overnight.  Sometimes, small air leaks are impossible to detect during set-up, but will make themselves apparent by morning.  If the tire is soft in the morning, add air and agitate.  More sealant may help as a failsafe against leaks during initial installation.  If possible, put the bike in a stand or turn it upside down, and spin the wheels every time you walk by.  Thanks to Kevin at Paramount Cycles and Timely at the Trek Store for advice and encouragement.  Thanks to Chris at The Bicycle Shop for assisting the process, and allowing initial explorations on the wheels of his Salsa Beargrease.

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Fun, safe, and lightweight– nothing not to like!

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Future explorations include other rim and tire combinations, lighter weight preparations (for customers, presumably), and testing at extreme low pressures.