Seat a stubborn tyre bead on the rim

On a tubeless tyre, the bead must seal against the rim edge before the tyre will hold air. If there is a gap between bead and rim, the pump cannot build pressure. This page covers ways to close that gap. It is an assessment and hand-off for most readers: seating a bead can throw the tyre off the rim with force.

Safety

• Never exceed the maximum inflation or bead-seating pressure printed on the tyre sidewall or the rim. Use the value on your tyre or in your bike's manual.
• Keep your face and body away from the wheel while it seats. Do not lean over the tyre.
• Never use fuel, flammable spray or any fire to seat a bead.
• If the rim is cracked or bent, stop. Do not inflate.

You need

• Clean rim edges and bead seats with no dirt or old sealant.
• Plenty of lubricant on both beads and the rim.
• One of these helpers: a bead expander, a ratchet strap or rope with a lever, a rubber ring that fills the gap, or a pump or tank that can deliver a lot of air very fast.

Steps

1. Remove the valve core so air flows in quickly. Check the rim edges for cracks.
2. Lubricate both beads and the rim well. A dry bead will not slide into place.
3. Make the beads touch the rim. Options: - Wrap a strap or rope round the middle of the tread and tighten it. This squeezes the tyre so the beads move outward. - Fit a bead expander as its maker says. - Fit a rubber ring in the gap to close it while you pump.
4. Pump a lot of air quickly. A tank with a wide hose does this best.
5. When you hear the beads pop onto the rim, remove the strap or tool. Refit the valve core.
6. Inflate to the cold pressure in the manual. The thin moulded line round each sidewall should be the same distance from the rim all the way round.
7. If a bead does not seat, release air, lubricate again and repeat.
8. Finish with soapy water on the bead and valve to look for bubbles.

Check your work

• The line on the sidewall is even on both sides.
• No bubbles from the bead or valve.
• Pressure is the same after an hour.

If it did not fix the problem

• The bead leaks: Air leaking where the tyre meets the rim.
• Rim damage: Rim is dented or cracked.
• If you cannot seat the bead safely, ask a tyre shop. See Replace a tyre.