Tire Plug Patches Things Up

Question: I recently had a tire plugged on my 1986 Honda Civic. I had run over a nail and opted for the $6 plug over the $40 tire. Can you please explain exactly how the plug works and how much more life I can expect out of the tire? How often should I check the tire pressure now, and if the plug does not hold, should I buy the same make and model tire?--I.D.

Answer: A simple tire plug is the least costly method of repairing a flat tire. A mechanic usually finds the hole in the tire and then cleans it out. He then spreads some cement in the area and works it into the hole. Using a special hooked tool, a rubber plug that is slightly larger in diameter than the hole is inserted. Some plugs are round, some others are flat pieces of rubber that are twisted into the hole.

A superior method of tire repair involves plug patches, which have a plug attached to a patch. In this case, the tire is removed from the rim, and any debris is cleaned out of the tire cavity. A patch is then applied on the inside of the tire over the hole, and the attached plug fits into the hole.

I have seen repairs like these last a few minutes or last a few years, depending on the severity of damage to the tire and the quality of the repair. If the tire cord body was damaged in any way, then the repair should not be attempted. Initially, you might check the air pressure every few days to see if the plug or patch is leaking. After that, you might check the tire periodically, along with the others.

If you need to replace the tire, you should certainly attempt to find the same make and model tire. If not, then attempt to find the same tire size, the same type (radial or bias ply) and the same tread pattern. If the undamaged tire on the opposite side of the car has substantial wear, you might consider buying two new tires.

Q: I have a 1985 Chrysler New Yorker that has badly cupped rear tires at 28,000 miles. One mechanic blamed the car’s front-wheel drive. Another said it was the tires. Do you have any information about this problem?--J.O.

A: Tires can wear in a cupped pattern because of any number of suspension problems. You should have your rear struts or shocks checked, because weak damping action can cause cupping.

Other things to check include improper tire balance, rear wheel alignment and bent wheels, among other potential problems.

You may also have contributed to the problem by not rotating the tires.

Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.