Seating a Tire Bead with WD-40, Starting Fluid or Fire: Why Tire Makers Prohibit It

The situation behind the search

A bead hangs, and videos show two shortcuts: spray something slippery on the bead, or spray something flammable into the tire and light it. This page explains why the tire makers prohibit both. It gives no instructions for them.

Two different ideas, two prohibitions

The association's Tire Information Service Bulletin Vol. 41, No. 4 addresses each idea separately.

WD-40 on the bead

The bulletin gives three reasons why silicone, petroleum and solvent-based lubricants are ruled out. They may cause the tire to slip on the rim. They may have a harmful effect on the tire, tube, flap or rim. And they may create explosive mixtures of air and vapors in the tire, which may result in serious injury or death.

That WD-40 belongs in this group is not our assumption. The safety data sheet for the U.S. aerosol, prepared by WD-40 Company in November 2024, lists the ingredients: 45 to 50 percent of a low-vapor-pressure aliphatic hydrocarbon, less than 35 percent petroleum base oil, a further 10 to less than 25 percent aliphatic hydrocarbon classified as a flammable liquid, and carbon dioxide as propellant. The sheet classifies the product as an Aerosol Category 1 with the label wording extremely flammable aerosol, and gives a flash point of 138 °F for the liquid.

The bulletin also says what a bead lubricant should do after the job: when dry, it should not remain slippery.

Starting fluid, brake cleaner and fire

Here the bulletin leaves no room: introducing a flammable substance into a tire is prohibited under any circumstance. Beyond the explosion itself, it names a second danger: the practice may result in undetected damage to the tire or rim that could lead to failure of the tire in service.

The association's motorcycle bulletin repeats the rule in its list of nevers: never use a flammable or volatile substance, bead sealer, aerosol inflator or rubber donut to aid bead seating.

What to do instead

A bead that will not seat has a cause, and neither shortcut removes it. The tire makers name three main factors: the tire was installed over the rim flanges improperly, tire and rim are not properly lubricated, or the beads are not centered. The page tire bead won't seat goes through them; the fix is this sequence.

1. Completely deflate the assembly

   Let all the air out before anything else.

2. Relubricate with a bead lubricant

   Use a commercially available lubricant made for bead seating on both beads and on the rim's humps, bead seats and flange tops.

3. Reposition and center the tire

   Push the beads into the rim well, then rotate and center the tire on the rim.

4. Restrain the wheel and stand back

   If the machine has no positive lock-down device that holds the wheel, inflate in a safety cage or other restraining device. Never stand, lean or reach over the assembly.

5. Reinflate, never beyond 40 psi

   If both beads are not seated at 40 psi, repeat the sequence: deflate completely, reposition, relubricate, reinflate. If repeated attempts fail, contact the wheel or tire manufacturer.

More on the permitted products is on the page about tire mounting lube. The complete seating procedure is under how to seat a tire bead, and the pressure rule on its own under how much air pressure to seat a bead.

Air-blast tanks, which use compressed air only, are not described in the bulletins we read; they are covered under tire bead seaters. A tank does not change the 40 psi limit for the tire.

If a flammable product is already in the tire

For tires that may contain a flammable sealant or inflator, the bulletin lists precautions, and they are the minimum for a tire someone has sprayed into: keep it away from heat, flame and sparks; use tire irons and hammers with caution to avoid sparks; in a well-ventilated area, with the tire secured to a vehicle, a mounting machine or another restraining device, remove the valve core and deflate completely; then reinflate and deflate a few times to expel the vapor.

If the substance was ignited, the tire and the rim belong in front of a tire dealer before they go back on the road, because of the undetected damage the bulletin warns about.

When to hand the job over

Stop after two careful attempts with fresh lubricant, and at once if a bead shows a cut or the rim is bent, cracked or corroded at the bead seat; the signs are described under tire bead damage. Stiff, low-profile tires are a case for a shop from the start. The rules for the inflation step are under tire mounting safety, and the manual tire changer overview shows which tool is specified for which wheel.