Ask a Mechanic aaaaam tubeless1

Published on March 10th, 2016 | by Greg O'Keeffe

Ask a Mechanic: Mountain Bike Tubeless Wheel Set-Up

Jamal asks: “I’ve seen one of your videos on taping tubeless wheels, but can you cover the entire process of going tubeless?”

The benefits of running your mountain bike tires tubeless are irrefutable. Ditch the tubes and you’ll enjoy increased traction, a smoother ride, and fewer flats. Converting to tubeless isn’t complicated and can usually be accomplished without special tools, though a large-volume floor pump, or better yet, a compressor, will make the process much easier for you.

Compatibility between tires and rims is something to be aware of. Tires and rims of the same designation—UST or TCS for example—will be easier to mount together. Compatible rim and tire combos will also experience less “burping.” However, with the proper preparation, any tire and rim can be run tubeless.

UST (Universal Tubeless Standard) certified rims do not need any preparation, as the spoke holes are sealed. Simply mount up the tire of your choice and ride. While UST-certified tires will hold air without sealant, we always recommend adding sealant to heal punctures. Non-UST tires will not hold air without sealant as they lack an extra coating inside the tire to seal tiny holes from the construction process.

For regular, tubeless-ready, and tubeless-compatible rims, the spoke holes will need to be sealed with tape before mounting tubeless. With the tape of your choice, start a few inches above the valve hole and work down around the wheel while holding the end of the tape firmly in place. Keep tension on the tape so it contours to the rim surface, and do two full rotations around the rim. Finish a few inches past the valve hole on the opposite end from which you started. Push your valve stem through the tape and tighten it down.

When it comes to a wider rim where the tape doesn’t reach the edges, you’ll have to change the process slightly. Start above the valve, but favor one side of the rim channel. As you make your way around, stay to that side, still covering the spoke holes in the center. Once you get to the starting point by the valve, transition the tape to the other side of the rim and continue around again. This time, bias the coverage to the side opposite the first rotation, still covering the spoke holes in the center of the rim. Push your valve stem through the tape and tighten it down.

Now mount the tire to the rim, but leave a short section of tire bead unhooked to add sealant.  If you can, either hang the tire vertically or have a friend hold it so the unhooked section of bead is at the bottom of the wheel. Add the proper amount of sealant according to the manufacturer’s guidelines. Keeping it vertical, carefully rotate the wheel until the open section of tire is at the top so you won’t spill sealant, then mount the rest of the tire on the rim.

The key to inflating tubeless tires is to move a large volume of air quickly enough to seat the tire bead all the way around the rim instantly. This is most easily accomplished with an air compressor, but large barrel floor pumps like Lezyne’s Dirt Floor Drive will work on most rim/tire combos.

Still keeping the tire vertical, orient the valve stem at top dead center to minimize sealant splatter. Check that the valve opening is inside the tire; sometimes the tire bead gets stuck on the interior valve gasket, allowing air to flow right past the tire bead. Fit the air chuck of the compressor over the opened valve stem and inflate. If you are using a floor pump, give it your all and try to quickly inflate the tire. Usually, you will hear the tire bead snapping into the rim. If the tire is not seating easily, rapidly slap the tread on opposite sides all around the tire’s circumference as you inflate until it seats. Once the tire is seated and holding air, inflate to about 40 PSI. Shake the tire to coat the entire inside of the sidewalls with sealant. If possible, let the tire sit overnight to seal any tiny leaks. Finally, inflate the tires to your desired pressure and go ride!

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About the Author

After a couple of years as a team mechanic for Highroad Sports, Greg joined the Art's Cyclery crew as our lead mechanic. The only thing Greg loves more than cycling is watching the San Francisco Giants play baseball.



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