298 Tyre sealants Roger Parker mentioned tyre sealants in V8NOTE247 as a way of coping with the removal of a spare tyre to make more room for luggage in an MGV8. (Feb 02) With the wider use of Instant Mobility Systems or IMS in new cars these days, including current MGs, means there is now an option for coping with the removal of the spare wheel. IMS is a can of special sealant and a 12 volt air compressor. The sealant seals the puncture and the pump provides the air to ensure the correct air pressure. Commonly referred to as "pump and goo" systems, they can only be used on steel or alloy wheels and not with wire wheels if they are fitted. A tyre repaired with IMS is regarded as only having a temporary repair and as such is limited to a maximum speed of 80kmph/50mph and suitable only for travelling to a destination from where a permanent repair or replacement is made. Tyre sealants Some car makers supply a tyre sealant and a compressed gas inflator pack instead of a spare wheel. The sealant and compressed gas are injected through the tyre valve. The result will depend on the cause and location of the puncture and how far the tyre has run in a deflated condition. There are two basic types of sealant. Pre-puncture sealants These are put into the tyre as a preventative measure either at the time the tyres are fitted or by injection through the tyre valve. The aim is to prevent air loss if a puncture does occur so the driver can continue the journey without interruption. The seal is pretty much instantaneous after the tyre has been punctured. However the concern is that the driver will have no idea whether there has been a puncture or not. A large screw or nail in the tread of the tyre will cause further damage over time and could lead to more catastrophic failure. Post-puncture sealants These sealants are used following a puncture. The sealant and compressed gas are applied through the valve o re-inflate the tyre. Carrying a can of tyre sealant can bring peace of mind if you regularly drive alone, but it is vitally important that you spot the puncture early and stop quickly - driving on a tyre in a partially or fully deflated condition will cause weakening of the tyre structure and irreparable damage. Permanent or temporary? The British Standard applicable to tyre repairs, BS AU 159, states that tyres should be removed from their rims for a thorough inspection to ascertain their suitability for repair. The standard also defines appropriate repair materials and comments on liquid tyre sealants: "The use of liquid tyre sealants does not meet these criteria and hence cannot be considered suitable as a permanent repair.'" Advice from tyre experts to users of pre-puncture sealants is to inspect the tyres very often - that is every time you use the vehicle. If the pre-puncture sealant has been activated there should be signs of the sealant (usually white latex based) on the outside of the tyre. If there are any signs of this or of an object penetrating the tyre tread, then the tyre must be removed from the rim and properly inspected to see if it is suitable for permanent repair. Acknowledgment: the note and caution above is available on the AA website. (19.3.09) More Copyright reserved by the V8 Register