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.  

Tubeless Knard/Rabbit Hole Explorations

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One of two wheels is built for my Surly ECR, composed of a SRAM X7 hub and a Surly Rabbit Hole rim.  The 50mm wide Rabbit Hole rim is one of several options in the 29+ genre, alongside several conventional doublewall rims in excess of 30mm.  Choices include two Velocity rims, the Blunt 35 (35mm) and the Dually (45mm), both of which claim to be ‘tubeless ready’, but some have called Velocity’s tubeless claims into question.  The 47mm Northpaw rim is a true singlewall rim (with cutouts), and is available from Schlick Cycles.  A 52mm Stan’s rim is rumoured to be coming this season, bringing Stan’s surefire tubeless features to bike with big tires.  Currently, the Rabbit Hole is the widest 29+ rim available, engineered like other Surly fatbike rims as a combined singlewall and doublewall extrusion with cutouts in the center singlewall section.  For winter riding, wider is better.  

Considering that my ECR is doing work alongside real fatbikes here in Anchorage, it is important to give myself the widest footprint possible, to ensure the best flotation and traction in tough and changing conditions.  For this winter, at least, there will be two bikes in the stable– the Salsa Mukluk 3 and the Surly ECR.  Come spring and summer, the bikes will dual for my attention as we set off traveling.  Until then, the bikes will remain as two distinct concepts, with unique specialties.

From past experiences, a tubeless system promises less rolling weight and a more supple tire system, in addition to eliminating flats.  I hoped to install the Knard tire onto the Rabbit Hole rim, tubeless, with no more than a few layers of duct tape to seal the rim and build up the rim bed.  The tire fit nicely on the rim with only the Surly tape installed (it was not loose, like some older Surly fatbike tires), and when inflated with a tube, I sensed a strong bead lock.  It would be easy, I figured.  

The SRAM X7 hub is my new favorite inexpensive quality hub.  For $50 or less (I grabbed this one for $33 online at Tree Fork Bikes), the hub features sealed cartridge bearings, a nice machined finish, and a quality three-pawl freehub system which is visibly packed with grease when new.  Lael and I used these hubs all summer and they never missed a beat.  The bearings in both hubs feel almost new.  The closest competitors are Shimano’s Deore and XT loose ball bearing hubs.  While the manufacturing quality is good, the design of these Shimano disc hubs has proven to loosen prematurely, resulting in an unnecessary amount of hub maintenance and a premature death.  With a sealed cartridge bearing, no matter how much the bearing surfaces are ruined by neglect and harsh conditions, the hub body is never compromised.  I really do wish Surly would stop speccing all of their bikes with Deore disc hubs; SRAM X7 hubs please!

Surly Rabbit Hole rim and SRAM X7 hub, laced with straight gauge spokes on the drive side and butted spokes on the disc side, due to a limited availability of butted spokes.

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Install a layer of hi-visibility reflective ribbon inside the rim cutouts, backed with a layer of clear packing tape.  The flexible nature of duct tape may work better as a backing to conform to the rim and create an airtight seal in the first layer of tape.  With a blast of air from a small compressor, the tire does not seat, but it seems close.

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The valve has begged for attention for some time.  I forced the knurled nut off the stem and cleared a blockage of Stan’s latex sealant.  It is best to remove the core from the valve when seating a tubeless tire that requires a lot of air (but not the brass stem).  The larger passageway allows more air to enter the tire at once.   

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With two layers of duct tape, in addition to the reflective ribbon and one layer of clear packing tape, the tire easily pops into place,  Without sealant in the system, the tire loses air in less than a minute, not entirely uncommon when seating tubeless tires.  However, some tires hold air overnight without liquid sealant.  

Hoping that sealant will coagulate in the zones of air leakage, I inject 2 oz. of Stan’s into the tire.  The system sputters from the junction of the tire bead and rim.  Two more ounces of Stan’s helps to seal the tire.  However, any additional handling unsettles the system, and the sidewall begins to spit again.  Adding air to the system breaks the seal, removing air breaks the seal, and I predict that low pressure riding on soft snow will certainly break the seal.

This is my first tubeless horror story.  

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Refinements to the system may be possible.  Building up the rim with more material may create a tighter bead lock and a more reliable system, but engineering a patchwork inside of a rim to be run tubeless at low pressures in freezing temperatures is a greater risk than I am willing to accept, especially as a surefire solution is so close at hand.  The full-insurance approach is the split tube method, historically referred to as “ghetto tubeless”.  With a small weight gain, I know the system will seal.   

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Repurposing a well-loved 26″ tube from Lael’s Surly LHT, I mount the tube to the rim and cut it along the outside seam.  Anyone interested in a a nicely appointed 50cm Long Haul Trucker?  

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It fits nicely over the rim, although a 24″ tube would be even easier to work with, and would result in a slightly lighter system.

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Mount the tire and pull it into position as best as possible.

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Air from a floor pump is nearly enough to seat the tire.  A compressor quickly does the job, and with an extra puff of air, it snaps into place and is seated roundly onto the rim.

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Before installing sealant into the system, spin the wheel to verify there aren’t any high or low spots in the tire.  Now is the time to rectify any issues.  Finally, trim the excess rubber.  I’ve seen some people leave some of the excess tube to assist in reseating the tire in the future.  In my experience, this system is so reliable that I hope not to be reseating the tire for a long time.  I will, however, carry a tube as a precaution.

So far, in one week of riding, the system hasn’t lost any air, and has been reliable down to about 8psi.  Past experiences with tubeless Knard tires on Marge Lite rims have also been reliable.

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Knard dimensions

The 3.0″ Knard tires take on a different profile when mounted to Rabbit Hole rims.  On the left, a fresh Knard is shown on a 29.1mm Stan’s Flow EX rim.  On the right, the tire is mated to a Rabbit Hole, as it is intended.  Not only does the tire become wider, but a flatter profile puts more knobs to the ground, and it gains a larger internal volume.  On narrow rims, the bike looks and feels like a big-boned 29er.  On Rabbit Holes, it is more like a lightweight fatbike.  In the snow, the Rabbit Holes make a difference.

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Casing diameter of Knard on Stan’s Flow EX: 70.0mm.

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Outer knob diameter of Knard on Stan’s Flow EX: 75.5mm.

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Casing diameter of Knard on Rabbit Hole: 75.8mm.

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Outer knob diameter of Knard on Rabbit Hole: 77.1mm.  

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Note: These dimensions are measured on a worn 27tpi Knard, and a new 120tpi folding Knard.  

Does it work?

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Update: Check out my updated Tubeless Fatbike Guide for information on the non-split tube tubeless method.  The method used here is still relevant, and may be more reliable in situations where bead retention is of greatest concern, such as on rough rocky trails.  The non-split tube method described in the guide mentioned above is a little lighter.  For the most reliable tubeless system, consider adhering the split-tube to the tire bead to create an airtight unit, much like a tubular tire. (2/16/2014)

Does our home-brew tubeless fatbike system work, as on this tubeless Moonlander? These are goatheads.  These are tubeless fatbike tires: 4.7″ Surly Big Fat Larry tires to 100mm Clownshoe rims.  These two wheels are entirely cluttered with spiny goathead thorns– perhaps 500 in total.  This is no match for a tubeless system and some Stan’s liquid sealant.  Ride on.

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Thanks to Two Wheel Drive for the demo Moonlander for the weekend.  Live near ABQ and want to ride a fatbike?  Come find me at TWD on Tuesdays.

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Overnight.

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A few days away, finally.  Three, now only two days out of town.  Overnight– on a very familiar bike.  Since last time, the Pugsley has a new chain and cassette, tubeless tires, and a full luggage system from Revelate Designs.  I use a large Carradice Camper saddlebag for longer tours as it offers twice the capacity of the Revelate Viscacha seat bag, and also fits my MacBook Air.  But this seat bag rides nicely, and is lighter.  Up front, I typically us a compression dry bag for my sleeping gear, but I opted to try this large handlebar stuff sack called the Sweet Roll, paired with my Revelate Pocket accessory bag.  The Pocket makes a great mini-messenger bag when not attached to the bike.  The included shoulder strap is always attached, and provides daily use over the shoulder.  I bought all of these bags last May directly from Eric in Anchorage expecting that Lael would use them over the summer, but she didn’t have enough gear to necessitate so much space.  Mostly, she used the seat bag and Gas Tank top tube bag on her Hooligan.  Without a computer, I could easily pack for long distance excursions with these bags alone– another nail in the coffin of racks and panniers.

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Charlie at Two Wheel Drive is an invaluable resource for local route planning.  Over that past decades he has ridden everything in this part of New Mexico, and beyond.  Over the past few weeks, TWD has become the fatbike shop in NM.  Coming soon, monthly fatbike rides– arroyos, snow, forested trails, and the moon!

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Tubeless Moonlander

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Update: Check out my updated Tubeless Fatbike Guide for the non-split tube method.  The method shown below is still relevant, and may be more reliable in situations where bead retention is of greatest concern, such as on rough rocky trails.  The non-split tube method described in the guide mentioned above is a little lighter.  For the most reliable tubeless system, consider adhering the split-tube to the tire bead to create an airtight unit, much like a tubular tire. (2/16/2014)

My tubeless Pugsley has been a blessing in the land of cacti and goatheads– no pinches, punctures, or burping.  Burping is modernspeak for a tubeless tire rolling away from the rim, momentarily, losing a little pressure and sealant.  Two Surly Moonlanders are rolling out of Two Wheel Drive this week here in Albuquerque, NM.  Their owners will never know the annoyance of slow leaks in 4.8″ tires, nor the weight of supersized tubes.  Even in temperate zones without thorns, tubeless fatbike wheels are the way to.  Surely, it is the cheapest way to lose almost a full pound on the bike, especially out of the wheels.

Over the past few weeks, Two Wheel Drive has become the premiere fatbike shop in Albuquerque, perhaps even the entire state.  Out the door– two Moonlanders this week, a white Pugsley last month, and a Neck Romancer Pugsley in the next month.  Jeff and I are well versed in tubeless systems for wide rims and tires, and I can heartily attest that these bikes are for much more than riding on snow. Here’s what we have learned in converting six fat wheels to tubeless:

All fatbike rims have deep rim channels, and most fatbike tires fit loosely which means that any air injected into the tire will escape from under the bead.  The solution is to build up the rim bed for a tighter fit.  My solution is to use thin foam, a strip of duct tape, and then a rubber rimstrip made from a repurposed tube.  Twenty inch (20″) tubes work best on 26″ fatbike rims, as the tube fits tight to the rim and makes tire mounting easier.  Look for 20×2.75-3.0″ tubes; 24×2.75-3.0″ tubes also work.  It is necessary to use a Presta valve with a removable core (Q-tubes, from QBP are all removable cores), or a standard Schraeder valve which all have removable cores.

Our first effort used a narrow foam strip.  The tire mounted onto the rim easily and nearly seated with air from the compressor.  Still, it remained limp.  Try again.

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A second time, with a wider strip of foam.  For reference, we cut the foam about the same width as the cutouts in the rim.

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A layer of duct tape secures the foam, and adds a little bulk near the edge of the foam to ensure a tight fit when seating the tire.  The foam used was a cheap camping pad from Sports Authority, about 5-8mm thick.  We have also used foam pipe insulation front the hardware store.  Punch a hole for the valve.

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Cut a 20×2.75-3.0″ tube along the outside seam, opposite the valve, to create the airtight rimstrip.  It may be possible to do a tubeless fatbike system without the rubber rimstrip, but Jeff and I reckon this method is less likely to burp and the tire is less likely to “walk” along the rim at low pressures.  Our system is refined, but not yet perfect.  We strive to develop a simple, replicable system of cheap lightweight parts.

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This Moonlander receives some more aggressive tires.  A Lou replaces the Big Fat Larry in back, and a Bud will do the steering up front.  All tires are 4.7-4.8″, but the Bud and Lou borrow a taller, more aggressive tread from the Nate.

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Fit the tire over both sides of the rim to start.  Pull one bead up and over the rim, taking care to keep the rubber rimstrip between the tire and the rim.  This will ultimately provide a tight seal and an airtight junction.  Try to do all of this by hand, to avoid pinching a hole in the tube.  If necessary to use a tire lever, pull the damaged rimstrip outward so that it will eventually be trimmed away.

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Both sides mounted, inflated.  Remove the valve core, deflate, inject about 6 oz. of Stan’s sealant through the valve.  Re-install core, inflate, shake the wheel to allow sealant to contact all internal surfaces.

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Trim the excess rubber for a clean look, and to shed some grams.

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Lou– fat and mean.

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The giant cardboard box in which “Lou” arrived will be the basis for a Halloween costume ten months from now.  Painted yellow with a cylindrical yellow dot on top, Jeff plans to be the Lego Man next Hallow’s Eve.