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Tkart magazine

How To | How to repair a tyre that is leaking air

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16 July 2016
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There are several reasons why you might find yourself with tyres that are leaking air between the shoulder and the rim. Usually, this is a result of incorrect fitting or removal of rims, but sometimes it can also be caused by imperfections in the tyre itself or by its losing shape due to wear. Whatever the reason, there is no need to despair: there is a simple method and generally successful way to solve the problem.


Tyres are typically fitted on rims by hand and, once in place, are made to “pop” using a compressor. The process allows the tyre to expand and properly adhere the edge of the two shoulders (inner and outer) to the profile of the rim, thereby creating, among other things, a seal that does not allow air to leak out. Latest generation kart rims have so-called “screws”, i.e. 3 screws per rim, positioned close to the outer edge, that ensure greater safety by avoiding tyre unbeading, that can occur especially when using very low inflation pressures. Care must be taken to sufficiently loosen the screws, so that the tips are inside the threaded seats, because if that is not the case, during the tyre removal process using a tyre changer, or when you “pop” the tyres, the screws themselves can damage the edge of the outer shoulder, thereby compromising the seal.


The system to check an air leak on a tyre is quite simple and well known: use some water, preferably soapy water, and pour it on the edges between the tyre and the rim, as well as on the beading security screws. In fact, these are the critical points where air can leak out. Soapy water, compared to normal water, produces more noticeable bubbles in the event of an air leak.


If a check reveals there is a leak where the screws are, usually the problem is the O-ring, which should be replaced. In other cases, the seat may be ruined, which means it needs to be re-threaded. The quickest solution, although temporary, is to use sealing paste, generally known as “red paste” (although it can also be black). However, you must always remember not to over-tighten the screws: the bottom seat of the screw head is flat, while the inner seat of the rim is curved. Therefore, the seal is squeezed between two different shaped surfaces and can become damaged or cut due to over-tightening.


You can use sealing paste even if an air leak is located between the profile of a tyre’s shoulder and the rim. Perhaps it is just where the screws are located. To do so, you need to deflate and remove the tyre using a tyre changer. Rotate the tyre while it is still on the rim so as to misalign the damaged areas with the location of the screws. Then, put a generous amount of sealing paste on the rim and on the edge of the tyre. Wait 5 minutes and then “pop” the tyres, being careful not to let the paste squirt over you. Wait another 5 minutes until the paste is dry, then adjusts the tyre pressure to the desired value and spread the excess paste on the edge of the tyre. At this point, you’ve done it. All that’s left to do is to repeat the checks using soapy water and re-fit the rims on the kart.

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