Tyre Puncture Repairs
One of the last sights drivers want to see when they are getting ready to drive their vehicle is a flat tyre. They realize that in addition to the immediate inconvenience of having to install their spare wheel tyre (should they have a spare wheel tyre), they will have to get the punctured tyre repaired immediately to minimize potential long term deterioration started by the puncture or driving without a spare wheel.
Some tyre manufacturers "allow" a tyre to retain its speed rating if a specified multi-step repair procedure is followed exactly; however most tyre manufacturers reason that since they have no control over the damage caused by the puncture or the quality of the repair, they cannot confirm that the tyre has retained its high speed capability. Therefore, their policy is that a punctured and repaired tyre no longer retains its speed rating and should be treated as a non-speed rated tyre.
Guidelines allow the repair of punctures in a tyre's tread area of a hole up to 6mm in diameter. Repair of larger tread punctures and of punctures to the tyre's shoulder and sidewall areas are not recommended.
There are three primary considerations when repairing a punctured tyre. You need to evaluate the damage the object caused as it punctured the tyre, reestablish an airtight seal of the tyre's innerliner, and completely fill the path the object took through the tyre. Typically a mushroom-shaped patch and plug combination repair is considered to be the best method of repairing a punctured steel belted radial. Before starting any repair check if it is technically safe and economically viable to repair the tyre. Also check the whole tyre for very small injuries and further hidden damage and examine the tyre taking in to account also its general state outside the repair area.
Any repair attempted without removing the tyre from the wheel is improper. Without inspecting the inside of the tyre for hidden damage comes the risk of returning a weakened tyre to service. Punctures in the tread area that looked repairable have revealed upon further investigation that the object that punctured the tyre had been long enough to cut the tyre's sidewall from the inside. Without dismounting the tyre, the hidden damage would have been missed.
Simply plugging a tyre from the outside without removing the tyre from the wheel is improper. (If a tyre is punctured while off-roading far away from civilization and a spare tyre isn't available, a “string repair” plug may serve as a temporary low speed solution that must be replaced with a proper repair as soon as possible upon returning to the road.) This “string repair” plug method is improper as the fact that the tyre is not removed from the rim, and the inside of the tyre is not inspected for hidden damages.
Additionally, any repair that doesn't completely fill the path the object took through the tyre is incomplete. While a patch on the inside of the tyre reseals the innerliner, it does not fill the path of the puncture. This will allow moisture to reach the steel belts and/or the casing cords causing them to rust or deteriorate.
Once punctured, the innerliner must be cleaned, buffed, cemented, patched and coated to assure its ability to retain air has been restored. Since this can only be done from inside the tyre, it's another reason that a plug-only repair is improper.
How do you know which procedures a tyre dealer uses? Ask them! But be aware that if they say they can repair a tyre in 10 minutes for under R50.00 without removing it from the wheel, they aren't following the Rubber Manufacturer's Association procedures. A correctly done flat repair that follows the multi-step repair procedures will take approximately 30 minutes and probably cost around R100.00. Driving on an improperly repaired tyre is dangerous because it can further damage the tyre and/or allow its strength to deteriorate over time. An improperly repaired tyre driven at high speeds may suddenly fail, causing loss of vehicle control. Additionally, the use of an innertube as a substitute for a proper repair generates additional heat and should not be considered.
NO REPAIRS MAY BE MADE IN/ON THE SIDEWALL OF THE TYRE OF PASSENGER AND LIGHT COMMERCIAL AND TAXI VEHICLES