Tire Bead Damage from Mounting: Causes, What Is Scrap and How to Avoid It

The symptom: what mounting damage looks like

The bead is the stiff inner edge of the tire, built around a hoop of steel wire, that seals against the rim. Its parts are explained on the page what is a tire bead.

According to the U.S. Tire Manufacturers Association (USTMA), the most common form of mounting damage is a cut on the inside of the bead, located above the toe or on the bead seat. The toe is the inner edge of the bead; the bead seat, also called sole or face, is the surface that rests on the rim. The bulletin shows two examples: damage on the inside of the bead and damage at the bead sole.

Searchers also ask about a torn bead and a kinked bead. The bulletins we read do not use those two words, so we do not define them from a source. The warning below covers any bead that is cut, torn or deformed.

The most likely causes

The tire makers name three main factors that contribute to damaging a bead during mounting:

1. The tire was installed over the rim flange improperly. In practice: the bead was levered or driven over the flange while its opposite side sat up on the bead seat instead of down in the rim well, the drop center. That stretches the bead.
2. Tire and rim were not properly lubricated. A dry bead drags on the tool and on the flange. The owner's manual of the reference manual changer, which we read as the copy on ManualsLib, says the same from the tool side: lubricate when removing a tire from a rim, or the tire may be damaged.
3. The beads were not centered on the rim before inflation.

Their bulletin on bead damage adds causes that belong to the machine: the increased power of machines that clamp the rim from underneath, a machine that has gone out of alignment, and a mount/demount head in the wrong position. A fourth point is the rim itself. On most rims the narrow ledge and the deep part of the well sit toward the outboard side, and that side has to face the mounting tool. On reverse-mount rims it is the other way around, so the wheel goes on the machine face down.

One more cause comes after mounting: too much air. Seating pressure in excess of 40 psi puts extreme stress on beads that are forced onto the flange in a distorted manner.

What is scrap, and who decides

• A cut, torn or deformed bead: take the tire out of use. The industry repair procedure for passenger and light truck tires limits repairs to the tread area, with the tire off the rim. The bead is not part of that area.
• A scuff in the rubber with no cut: this is the case nobody can judge from a description. USTMA publishes no measure for it in the bulletins we read. Show the tire, off the rim, to a tire dealer, or ask the tire maker.
• A bead that never seated although it looks fine: deflate completely, reposition the tire, relubricate, reinflate, and never go beyond 40 psi. If repeated attempts fail, the tire makers say to contact the wheel or tire manufacturer. The checks are on the page tire bead won't seat.
• A bent or cracked rim: the tire makers say it should be destroyed and replaced.

Whether a tire maker's warranty covers a bead damaged during mounting is a question for that maker; the bulletins we read say nothing about it. Count the risk of losing a new tire into the decision for or against mounting tires at home.

How to avoid it, step by step

1. Clean and inspect the rim

   Remove corrosion and dirt from the bead seats, and check the rim for bends and cracks.

2. Lubricate both beads and the rim

   Use commercially available lubricant made for mounting tires. On the tire, apply it from the mounting guide ring around the bead toe. On the rim, cover the humps, the bead seating surfaces and the top of the flange. If the product is diluted, follow its maker: an over-diluted mix dries too fast and acts as if no lubricant had been used.

3. Put the right side of the rim toward the tool

   The narrow ledge and the deep part of the well go toward the mount head or bar.

4. Keep the bead in the rim well

   Mount the bottom bead first. While the top bead goes over the flange, keep pressure on the sidewall opposite the tool so that this part of the bead stays in the well. The tire makers call this very important, and more so the lower the profile of the tire.

5. Watch the bead while you work

   Stop when the bead binds on the tool or the flange. Back off, push the opposite side into the well, add lubricant, and start again. More force is the wrong answer.

6. Inspect before inflating, then respect the limit

   Look at both beads all the way around. Center the tire on the rim, then inflate: never more than 40 psi to seat beads, and if they are not seated at 40 psi, deflate completely, reposition, relubricate and reinflate.

The full mounting sequence is in how to mount a tire on a rim, and inflation is covered in how to seat a tire bead.

The one product that addresses the main cause

Which lubricants the tire makers allow and rule out is explained on the page about tire mounting lube. A plastic rim protector can also help reduce tire and rim damage, according to the same bulletin.

When to hand the job to a shop

Low-profile and high-performance tires have stiff sidewalls, and the tire makers ask for equipment designed for them. If the bead of such a tire will not go over the flange with moderate force on a manual tool, stopping costs a mounting fee; going on can cost the tire. The limits of hand tools are sorted on the manual tire changer overview.