29+ Tubeless Conversion (split tube method)

I recently hand built a couple of 29+ wheels based on Surly 29″ Rabbit Hole rims and Halo 170mm & 150mm hubs. I will use the wheels on a Surly Wednesday fatbike. I wanted to convert them to tubeless.

Is tubeless for you?

On plus and fat bikes tubeless makes sense for one main reason: you can lower the pressure as low as 5-7 psi without worrying about snake bites ( or pinch flats ). In other words if you “kiss” the rim against an obstacle you won’t pinch the tube since there is no tube.  Be aware anyway that if you ride so aggressively and crash the rim against a rock, a flat should not be your only concern.

Tubeless allows you to run lower pressures, which is desirable on some terrain to gain more traction, more suspension and fun. Tubeless is also a tad lighter. If shaving a few grams won’t make any real difference, it is anyway a welcome feature. 

The widespread opinion that tubeless almost completely eliminates flats is true but it doesn’t tell you the whole story: you can put sealant liquid into an inner tube also and obtain the same level of puncture protection, except for the snake bites mentioned before.

The downsides of tubeless are:

  1. You have to set it up and mess around with the specific tools. It requires time and ordering some items from the internet
  2. You cannot conveniently change tires often. If you own one bike only, this can be an issue. Also you cannot easily swap front and rear tires to balance wear
  3. If you break a spoke/nipple couple, it is likely that you have to undo the tubeless system to replace the nipple
  4. An accurate truing of the wheel can be more difficult. On most truing stands, the feelers won’t reach the rim edge if a plus or fat tire is mounted on
  5. Gorilla tape method is prone to burp air out of the beads

To sum it up, if you want more performance from your bike and if you are confident with basic repairing, go tubeless without too much hesitation.

For bikepacking and longer trips in remote places, the decision can be a bit more complex, especially due to downsides #2 and #3.

Personally I’d go tubeless without worrying too much if, at some point, I’d have to reverse everything and continue my trip with inner tubes (with sealant inside).

Finally, if you are pretty happy with your current setup and don’t feel intrigued by the advantages, you could simply use sealant in the existent inner tubes to eliminate most of the flats.

Ghetto or Gorilla Tape

I chose ghetto tubeless  (or split tube method) option over Gorilla tape solution for a number of reasons:

  1. Reliability. Ghetto tubeless are more reliable and lot easier to inflate even on the trail. This is paramount for longer bikepacking adventures.
  2. They’re virtually “burpless”. Sealant will seal tire and split tube creating a sort of tubular tire. It will not burp air in most conditions.
  3. Ghetto tubeless is easy and you don’t need a compressor to initially inflate and seal the tire beads.
  4. You generally get the work correctly done at your first attempt.
  5. It is cleaner: the sealant is enclosed between the split tube and the interior of the tire. Rim will stay almost completely clean.
  6. It is negligible heavier than Gorilla / duct tape solution. Just a few grams will not make any real difference.

I personally cannot find any real downside to split tube.

Schrader or Presta valve

I chose Schrader valve over Presta.

Pros

  1. Reliability. Schrader valve is reliable.  Valve core is inside the stem and you cannot break it easily with a pump nozzle.
  2. Compatibility. A rim drilled for Schrader can easily accept a Presta valve, but not the other way around.
  3. Compatibility, again. Schrader is used for car tires. This is one of the few worldwide standards reusable in the bike world.
  4. Versatility. Valve core is always removable. You don’t need to check for it. If it is a Schrader, you can disassemble it and pour in sealant.
  5. Easy to use. The larger diameter of a Schrader valve means more air flow and a faster inflation. This is particularly useful for tubeless first setup.
  6. Easy to use, again. Presta valve often blocks itself if the nozzle is not well latched. I never learned how to properly latch a pump to a Presta and make it “click” at the first pump stroke. Schrader doesn’t blocks so easily and never gives you the impression that you are breaking the valve during latching/unlatching.

(minor) Cons.

  1. You have to drill your rim, if it has a smaller hole.
  2. It is not recommended on road bike rims, since they are too narrow and a larger hole will likely weaken the structure.
  3. For deflating you need something pointed like a little stick to press the valve pin.
  4. If you have other Presta wheels, you may have to swap often pump nozzle adapters.

Prepare the rim for a Schrader valve:

Drill a hole with a 8mm (or 21/64″) drill bit for metal. Once done, remove any aluminum alloy shards with a fine or you risk to puncture the split tube later.

If you ever want to use again a Presta valve, be sure to use an adapter (a simple rubber grommet) to avoid “hernia” popping out from the excess room. In our case, since we’ll work with very low pressures (6-20 psi) you could simply use an additional stem nut in the inside of the rim.

drill a hole for Schrader valve on rim

Once done, we are ready to set up the rim strip. I used the Surly specific ones. Just pay attention to mount it precisely centered. Double check centering later also, when finished installing the tire. Failing to find an acceptable centering may produce, under pressure,  split tube “hernias” through the rim holes.

Rim strip 29+ rabbit hole

Installing the split tube

Find a suitable inner tube. I went for a 24″ 1.50-2.40, Schrader. A 26″ should be fine, also, but don’t go narrower: a 1.0-1.5 will be insufficient to cover the rim surface.  Avoid DH (downhill) as they’re thicker and heavier, but we don’t really need any added strength. Just use freeride / regular MTB type. The tube should weight around 170 grams before splitting and cutting the excess flaps away.

Test the tube. New tubes sometimes fail before you even throw them in. Just inflate some air, not to much, and wait half a hour to see if it holds air properly.

I Cut the tube with scissors just all along the centerline opposed to the valve. Clean talc from the inside, wash with water and let the rubber dry.

Gently install the tube on the rim. Pay attention not to pinch it.

Split tube ghetto tubeless on 29+

Installing the Tire

I chose Surly knards 29″ 3.0″ 27 tpi. But any other similar model should be ok. Install one edge at a time. Check if the tire has a rotation direction, search for a small arrow stamped on the wall. The Knards 29″ 3.0″ have a symmetrical design, so there’s no preferred direction. It is a good practice anyway, to position max pressure recommendation found on the sidewall, in correspondence of the valve.

Squeeze the tire beads towards the center of the rim to help them to slide over the rim edge. Use then cargo tape all around the tire to, turn after turn, progressively compress and squash the rubber and make the beads splay and touch the rim edges.

Now, while the system is obviously not yet sealed, if you are quick enough pumping with a floor pump, you should be able to slowly increase the pressure and make the beads sit on rim edges. Before starting, check for visible openings between beads and split tube.

tire installation on ghetto tubeless on knard 29

If you are out of  luck and you don’t see any pressure variation on the pump gauge, double check for larger open seams and try to reduce them by further compressing the tread down.

If everything fails, before you get frustrated, there’s a shortcut:  try with a single and sudden burst of CO2: a 16 grams cartridge should inflate a 29+ tire up to around 20psi, enough to sit the beads in place and dry seal the system. Just sharply open the valve and let the CO2 make the rest. The cartridge shell will suddenly chill as in the photo.

Be aware anyway that if you did not really close as much as possible any possible open slots, even the CO2 will completely burp out of the tire.

CO2 cartridge compressor pump tubeless

Continue pumping and reach around 25-30psi to make sure the beads fully sit. At this point you will probably hear some air leaking somewhere along the beads. This is normal, continue pumping until the max tire pressure. By then, any evident air leak should stop. Anyway, as we don’t have used any sealant yet and the system as it is will hold air for no more than 15-30 minutes. If, after the tire completely deflates, the beads don’t shrink and stay sit on the rim edges,  you are victorious!

Remove the cargo tape, put it aside and reuse it later for the other wheel.

Pour sealant in

Remove the core valve with a valve key. Shake very well the liquid before using it. I used Stan’s notube (also marketed as Schwalbe Doc Blue). Pour around 120 ml / 4 oz of sealant. Reinstall the valve and inflate again to 30 psi.

fill up with stans notubes for tubeless

Spin the wheel, bounce it on the floor. Repeat. It is possible that a minimum quantity of sealant will leak out from the beads. Just let it dry and seal.

tubeless setup leaking from beads

The tire will likely lose pressure in a matter of half an hour. If it deflates completely, just inflate it again to 30 psi, shake it and spin the wheel horizontally on both sides for a minute or so.  If necessary repeat a third time. After that everything should be sealed completely and holding air at max pressure. You’re done!

Cut the excess flaps, leaving a reasonable margin.

NOTE: If you still experiment some weeping of liquid and pressure loss, the most probable cause is that Stans still requires shaking. The best solution is to ride the bike. In my experience, problematic weeping Knards will definitely seal in around 40 kms of mixed terrain.

Maintenance

Shake the wheel up and down, you should hear the sealant inside splashing around. Check for this sound every 2-3 months – more often during summer in hot climates. If the liquid dried, refill it!

Repair

A tubeless system should hold very well. Most kind of punctures will be sealed rapidly. Anyway tubeless won’t save you from major gashes and tears on the tire. You should always carry both a tubeless repair kit, a couple of spare inner tubes and, if you’re backpacking, add also 200 grams of sealant.

Use a repair kit with butyl plugs to seal medium sized holes. Carry a small tube of rubber cement and “boots” also. Boots are bigger patches used to cover gashes. Dental floss and a strong curved needle can be used to sew longer tears on the tire walls.

Spare tubes become useful in case the tubeless tire completely fails. As they are only used in the worst scenario, I carry just a couple of lighter tubes, instead of the specific Surly ones which weight a ton (440 grams). As you can see from the picture the alternative Conti tubes are a bit under spec’d (narrower) but they just work inside a knard 29″ 3″ and they weight just 240 grams.

When mounting a tube remember to check the interior of the tire for shards and any other sharp object.  I also carry a glueless tube patch kit, just in case.

inner tube surly weight

inner tube mtb conti

 

UPDATE

I rode now about 1000 km, almost 90% off road, mostly technical singletrack rooty and rocky terrain. I did some reckless descents and I smashed the rim once on a rock.

The rear wheel initially tended to lose air and weep sealant, requiring to pump new air every about 48 hours. After about 200 km and 10 days, both wheels stopped weeping. As a precaution I poured some fresh sealant (80 grams per wheel). From that point on, any air and sealant leakage stopped. At 1000 km, still both tires are super stable and don’t leak anything out.

I didn’t had any flat, or at least, I did not notice any puncture that could have instantly auto repaired thanks to the sealant.

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