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Tyre Repair Guide

General Considerations in Tyre Puncture Repair

Methods for repairing punctures in tyres have been available since before the turn of the century. They have covered a wide range of materials and devices for preventing air leaks and filling voids in tyre casings and tubes. Repair methods for punctures of tubeless tyres have been available since the early 1950's. This article describes important considerations for the repair of tubeless tyres and may be of use to professionals who operate service centers or to the serious do-it-yourself repairman.

There is much misinformation about the repair of tyre punctures. Some companies insist that a tyre must be removed from the rim and repaired from the inside out with a patch to be effective. Others claim that one must ream the puncture site and insert a large plug with glue. Some use a combination of a plug in the hole and a patch on the inside. There is available a plug-patch combination that can be pulled into the puncture from the inside and there are a variety of string type repairs and slotted or eyelet type tools for inserting the repairs into the hole. The strings are made of a variety of materials and are impregnated with a variety of vulcanizing or non-vulcanizing rubbers or other sealants, and some require glue and some do not.

Recommendations for puncture repair:

NEVER stretch the hole excessively. When a puncture occurs, the tyre integrity is already compromised. This integrity should not be further compromised by stretching or tearing the hole more than necessary. Stretching a nail hole to more than about 3/16" causes additional tearing of rubber between the cords and distortion of the cords such that the area of damage is greatly increased and the repair site is further weakened. NEVER enlarge hole with a rasp type reamer to accommodate a larger plug. Rasp type reamers can grab steel cord or synthetic cord and literally rip them out of the tyre or at the least severely damage them. They also leave a ragged hole which is more difficult to seal. Good commercial service centers have special equipment for smoothly removing broken cord from ragged holes. This process cannot be accomplished with a rasp type reamer. If a hole has gravel or other debris in it, use a smooth object like an awl to remove it. Do not use sharp objects that can cut the cord or rubber.

Avoid vulcanizing type plugs or solid rubber plugs used with glue. Vulcanizing type plugs and glue, dry out, harden and eventually break loose from the tyre. Although plugs of any type rarely come out of the hole when they are properly applied, plugs which harden or dry out or do not mold perfectly to the shape of the perforation, will soon begin to leak.

The material and method of choice for puncture repair depends on the size and location of the puncture. Michelin Corporation has determined that about 97% of automotive tyre punctures in vehicles disabled along the roadside were caused by objects that are about 3/16" or less in diameter. For holes this size and smaller, non-vulcanizing, viscoelastic, and permanently self-adhesive rubber plugs reinforced with cord, as used with Dynaplug®, has decisive advantages over other types of repair. This material flows slightly under pressure and fills all voids. It seals the entyre hole from inner to outer surface, and flexes with the tyre. It never breaks loose from the tyre. The best blend of viscoelastic rubbers does not bond well with synthetic string type repair cord and is usually supplied reinforced with cotton cord. This combination works well in many cases. However, when repairing steel belted tyres this material may be cut by the fine sharp steel wires of the steel belt making it difficult in these tyres to get intact plugs properly in place. The solution is to use this superior repair material with complete shielding of the plug to prevent damage to the plug on insertion. At the present time Dynaplug® is the only product on the market that efficiently accomplishes this function.

Important functions in tyre puncture repair include:

Inspect puncture to determine if it is repairable. 97% of on-the-road punctures are round or oval and made by objects less than 3/16" diameter. These normally cause little or no cord damage and the holes are completely repairable. Holes caused by large blunt objects are large and ragged and usually have many broken cords. tyres with these large holes with exposed cord should always be removed and inspected on the inside to help determine the extent of tyre damage.

The most important function of a repair is to make an air tight seal with the inner surface of casing. This is the obvious intent of all repairs. It is important to prevent air from leaking at the inner surface not only to keep from losing air but to prevent air from leaking into small voids around the puncture site and causing a bubble to develop between the casing and tread.

It is also important for the repair material to fill the hole and make a seal at the outer surface to permanently prevent water and other debris from entering the hole from the outside. Water, road salt, stones and other material cause corrosion and eventual failure of steel cord and abrasion of the rubber and synthetic cord which may eventually lead to substantial weakening or tyre failure.

Advanced tyre Puncture Repair

A significant advance was made in the process of tyre puncture repair with the introduction of the Dynaplug® tyre Puncture Repair System. Since its introduction at the US National Hardware Show, Dynaplug® has become known as an extremely effective, simple, fast and easy to use system for the repair of punctures in tubeless tyres. Initially Dynaplug® was designed for the do-it-yourself industry, but it is so effective for the majority of punctures that it is now being used in commercial repair shops. It is effective in about 97% of punctures and has been regarded by those who use it as the best and easiest to use tyre puncture repair system on the market. The ease of use and speed of application that make it attractive to the do-it-yourself industry also make it attractive to the commercial user. It requires no glue, so there is no need to maintain a supply of this volatile material. The special visoelastic rubber of the plug flows slightly when the tyre squeezes it and it seeps into every small crack and void around the puncture, and then stays put. The only parts required with Dynaplug® are the insertion tool and a supply of plugs. There is no glue and no reamer required. Plugs have a very long shelf life and require no specialized storage. In fact, many plugs store in the cavity handle of the Dynaplug® tool. The Dynaplug® tool is made of impact plastic and stainless steel and is very durable. The handle has a broad base for comfort when pushing it into difficult-to-repair small holes in steel radials.

There is a common misconception that repair plugs must be large in order to work. According to research by Michelin cited in Automobile Magazine (April 1990, p. 45-47), 97.5% of crown punctures in auto tyres are made by objects 4.6mm (about 3/16") or less in diameter. Because of the elastic recoil of the tyre when the puncture object is removed, the remaining hole closes almost completely leaving only a small void in the rubber matrix and no defect in the cord. It is therefore necessary only to replace the puncture object with appropriate sealing material of about the same size. This is precisely the function of Dynaplug®.

Many have had the experience of watching a service station attendant enlarge a small hole with a reamer so he could get a plug into it. They wonder why a small hole in their new steel radial should be made into a large hole so it can be repaired. The repair may work, but there is a substantial cost in customer satisfaction, the time it takes to ream and prepare the hole, and the additional tyre damage caused by reaming. According to one major marketing firm, Dynaplug® is destined to become the standard of tyre puncture repair, and now we see that this is not only true for the do-it-yourself industry, but for the commercial industry as well. It isn't necessary to use over kill when repairing punctures at the risk of causing more tyre damage than was present when the tyre was brought in for repair. There is substantial peace of mind for the repairman when he doesn't have to guess if the plug is properly in place or if it has been partially cut during insertion. Dynaplug® always leaves the plug neatly and precisely in place because it is 100% protected from being cut by the steel cord.

Please consider the regulations that apply in your country of residence regardless of our recommendations.

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