Setting up tubeless tires

Preparing the rim bed

A successful tubeless conversion begins with a thoroughly cleaned surface. Remove any old rim tape and use a clean rag soaked in 91% isopropyl alcohol to wipe away residual adhesive, manufacturing oils, and dirt from the rim channel. Let the metal or carbon dry completely for five minutes before applying the new tape. Choosing the correct tape width is critical for an airtight seal. For example, a rim with a 21-millimeter internal width requires a 23-millimeter tape to cover the drop center properly and extend slightly up the bead shelves.

Apply the tape starting two spoke holes past the valve stem hole. Pull the tape with significant, steady tension as you press it into the center channel, smoothing out any air bubbles with your thumb as you progress. Maintain this tension for the entire circumference of the wheel. Overlap the tape by four inches once you reach the starting point, then cut it cleanly with sharp scissors. Instead of using a knife to poke the valve hole — which can cause the tape to split under pressure — heat a small metal poker or an old spoke with a lighter and push it through the tape to melt a neat, round opening.

Mounting the casing

Installing a tubeless bead requires patience and strong thumbs. Push the first side of the casing completely into the central drop channel of the rim; this channel has a smaller diameter, which provides the slack needed to slip the bead over the outer edge. Work your way around the rim, finishing at the valve stem. A senior mechanic once told me, “if you are forcing it with metal tools, you are doing it wrong,” and that holds true for tight beads. If you must use a tool, use a plastic tire jack to avoid scratching the aluminum or carbon hook.

Insert the tubeless valve through the melted hole in the rim tape. Push the rubber cone firmly into the rim bed and thread the locknut onto the stem by hand. Tighten it only finger-tight; using pliers can easily over-tighten the nut and strip the thread or destroy the rubber grommet, causing a slow leak later. While some minor mechanical noises, like a persistent bottom bracket creak, can distract you during a ride, a leaking valve stem will make itself known immediately through a steady hiss of escaping air.

Adding the liquid sealant

Before mounting the second bead completely, you must add liquid sealant to coat the inside of the casing and plug any microscopic pores. For a standard 29 by 2.3-inch mountain bike tire, 90 milliliters of latex-based sealant is ideal, while a 700 by 40-millimeter gravel tire generally requires about 60 milliliters. You can pour this directly into the open side of the partially mounted casing, or you can mount the bead fully and inject the fluid through the valve stem using a plastic syringe.

Injecting the liquid through the valve stem is usually cleaner and less prone to spilling. Use a small brass tool to unthread and remove the valve core before attaching the syringe. This is a straightforward task, much quicker than diagnosing a loose headset adjustment on a modern carbon bike, and it ensures that the sticky fluid bypasses the delicate sealing surfaces of the core itself. Keep a damp paper towel nearby to wipe up any accidental drips from the rim edge.

Seating and final inflation

To seat the beads against the rim hooks, you need a rapid volume of air. Remove the valve core if you have not already done so, as this maximizes airflow into the chamber. Connect a high-volume floor pump or a dedicated pressure chamber pump. Pump vigorously until you hear two distinct, loud pops… these sharp noises indicate that the beads have snapped securely onto the shoulders of the rim. Once you hear these pops, check the thin alignment line printed on the casing to ensure it is evenly spaced around the entire rim.

Reinstall the valve core quickly to retain the air, then pump the wheel up to 30 pounds per square inch to help the beads settle. Shake and spin the wheel horizontally in a figure-eight motion to distribute the liquid sealant across the entire inner surface. Now that your wheels are airtight and rolling smoothly, you can turn your attention to other small tasks like derailleur indexing or wiping down the frame before your next ride.