It's often been said that tire repair is an art that takes finesse, attention to detail, and care. However, unlike art, creativity is not the requirement of a good tire repair technician.
On the contrary, following correct procedures is vital to making good quality tire repairs that will last the life of the tire.
There are some facts that all good tire repair people should know:
* A repair unit must be used in all permanent tire repairs.
* Never mix product brands of cements, repair units, pre-buff cleaner etc., since they may not be compatible and may not produce adequate adhesion.
* Nail hole repairs are made in the crown only of a radial truck tire and are 3/8 inch in diameter or less. (The crown area is 1.5 inches from either side of the tread edge.)
* A section repair is required for any injury larger than 3/8 inch in the crown area as well as any injury, other than cosmetic, in the shoulder and sidewall.
* The size of the area that must be removed from the tire must not exceed the repair limitations set by the tire repair material manufacturer.
* It is impossible to lick your elbow.
Experience is essential
Not everyone, no matter how much training they receive, makes a good tire repair person. Some people just never get it.
However, the more experience they have, the better most people become. The problem is that experience is something you don't get until just after you need it.
There are many very common mistakes that tire repair people make that result in tire repair failures, which often lead to a tire's demise.
Perhaps by bringing them to your attention, you will acquire successful and beneficial experience sooner.
A very common mistake that especially rookie tire repair people make is mis-drilling the injury hole and creating a second hole.
Often only one of the two holes is filled, which results in a dimpled or cracked repair unit and rust in and around the unfilled nail hole.
In the retread process this leads to a lifted repair unit and possibly a retread separation. To avoid this predicament, be sure to probe the injury hole to determine its angle.
Also, if the angle of the injury allows, drill nail holes from the inside of the tire. This will ensure that there is only one hole through the innerliner of the tire.
Enlarging or elongating the injury hole is another goof that is commonly made, especially by rookies. It is really important that the injury hole shape and diameter is round and not too large.
If a stem is used for the injury fill, either a hole too large for the stem or an irregular-shaped hole will result in space around the fill stem.
This will lead to ``gassing,'' patch lifting in the retread process and ``falling out'' in the process of running down the road.
To avoid this situation, be sure not to elongate the hole as it is being drilled by wobbling the carbide burr tool in the injury.
Another very common mistake is not using pre-buff cleaner prior to buffing the innerliner for the repair unit.
The purpose of this step is to remove contaminants such as silicone (which is used to help prevent adhesion and release the tire from the mold during the manufacturing process), dirt, bead lubricant, etc., from the tire liner.
These materials will reduce adhesion of the repair unit and remain on the buffing stone or brush and con-taminate the next tire buffed.
If this step is omitted, the repair unit may not adhere to the tire, and the repaired area will not be reinforced and sealed from air. Air will migrate into the casing and separate the tire.
Some tire repair material manufacturers recommend that after the liner is buffed that pre-buff cleaner be used again to clean the buffed surface. Others recommend that pre-buff cleaner not be used after buffing at all.
You should check with your tire repair material manufacturer for its policy on this step. If it recommends that pre-buff cleaner be used again, keep in mind that the adhesion of the repair unit could be harmed if the pre-buff cleaner is not allowed to dry completely before applying the cement.
Often a penetrating object such as a nail may cause a split in the rubber under the innerliner. A good repair person knows to closely inspect the injury for this condition.
These splits radiate from the injury and can be detected by either probing or inspecting the area after using a small ball burr, encapsulated brush or other tool to remove the liner around the injury.
All splits and separations must be removed or a repair failure will result. In the retread process, the repair unit will bubble up, and a tread lift may result as well.
Probably the most common repair goof is failure to remove all of the injury. It is essential that all rust, broken cords/wild wires and separated areas around the injury be removed and cut back to solid material.
If loose wires are allowed to remain, they will cut the rubber fill material or stems while the tire runs and allow air into the casing, resulting in separation at the repair.
Rusty and separated areas left in the tire will trap air that will fail the repair and the casing as well. These failures usually appear as a split or crack that extends from under the repair unit.
The repair unit may also be torn loose or be missing. On the outside of the tire, you'll see tire components that are separated leaving rusty, loose cords. These repair failures are remarkably ugly. To prevent this condition, take time to stop and probe the injury periodically as you clean it out to make sure all the damage is removed.
Another mistake often made by rookies as well as by field technicians eager to get a trucker back on the road is treating injuries larger than 3/8 inch in diameter as nail hole repairs.
We all know that any injury larger than 3/8 inch in diameter after being cleaned out must be treated as a section repair, but sometimes it's faster or easier to install a nail hole repair and get on to the next event.
When this occurs, the stem used in the field repair fails to seal the injury since the injury is larger than the stem.
The stem can fall out or the loose wires will cut it or the rubber fill material used in the retread process. Separation will occur, and tire and repair failure is guaranteed. The failed tire will look much like the one described above for failing to remove all the injury.
Use the right tools
A quite popular goof that I see frequently is using improper tools for tire repair. Stones, brushes and carbide cutters are matched with air tools that have the wrong rpms or are used on the wrong parts of the tire.
You can readily see this when you inspect repair tools since they usually will be scorched and covered with black, reverted rubber.
Billows of smoke will be coming out of tires being worked on, and high-pitched screams can be heard coming from the tires themselves that have been given no anesthesia prior to this torture.
It is critical that carbide burr tools be used only with a low rpm (maximum 1,200 rpm) drill and used only to ream out penetrating holes.
Grinding stones should always be mounted in a high-speed (minimum 20,000 rpm) air tool and used to remove only steel. Tungsten carbide rasps are used only to remove rubber and should always be mounted in a slow speed (maximum 5,000 rpm) air buffer.
Mixing these various attachments in the drill and air buffers, using one medium speed air tool for all applications or using the wrong attachment for the material being removed is a formula for disaster.
Rubber will be scorched and reverted, which will prevent adhesion of the fill material, create separation and result in repair and possibly tire failure.
Making good truck tire repairs may be an art, but it's not rocket science. Just follow the rules and apply some finesse, attention to detail and care, and you will most likely be a great tire repair technician.
Oh, one last fact you should know: At least 75 percent of the people who read this will try to lick their elbow.