Working definition
The bead breaker separates the tire bead from the wheel seat so it can move into the drop center.
01
Fully deflate first.
02
Keep the blade away from rim flange and sensor.
03
Work around the circumference.
04
Inspect bead and sidewall while separating.
Blade position
Place the blade close to the bead but clear of the rim flange. Start away from the valve and sensor.
Breaking the full bead
Use multiple controlled presses around the circumference. Add approved lubricant and time rather than extreme force.
What the bead reveals
Watch for corrosion, rubber tearing, sealant, damaged bead and wheel cracks as separation progresses.
Diagnostic reference
| Finding | Possible meaning | Next check |
|---|---|---|
| Blade contacts rim | Wrong position | Reposition |
| Bead resists strongly | Corrosion or incomplete deflation | Work around and inspect |
| Sensor damage | Started near valve | Plan position |
Workshop procedure
- Remove valve core.
- Confirm zero pressure.
- Locate sensor.
- Position blade near bead.
- Press at multiple locations.
- Repeat opposite side.
Frequently asked questions
Why must pressure be zero?
A pressurized assembly can release energy violently.
Where is the sensor?
Often near the valve, but verify the design.
Should the blade contact the rim?
No.
Technical review edition · Published 17 July 2026.