The problem with the sealant type products is that they effectively make the tyre unrepairable - almost no fitter will plug such a tyre and thus for ANY puncture, a new tyre is required. If the original was a runflat, then, barring a full-on blowout, it can be run up to 50mph to 50 miles, but then has to be thrown away (apparently), and an oridnary tyre would require the sealant, result in another new tyre.

At least with a space-saver spare and no sealant, you stand a chance of being able to have the original repaired if the hole is in the right place and its an ordinary tyre. Besides, how many tyre fitters are open on Sunday afternoons, Bank Holidays or evenings/overnight, or what happens if you're in a very rural area with no fitter nearby?

Personally, I think it should be law that ALL vehicles should have a spare wheel and tyre, and preferably a full sized one. The mpg and CO2 saving from having a space-saver or none, whilst measurable and reasonable over time, pale into nothing to the extra costs of finding and fitting an expensive new tyre, or having an accident after trying to drive normally (as many people seem to do) on the flat runflat tyres or space savers (especially if fitted to the front axle), especially when in poor weather.

You must inspect your tyres regularly to check for foreign object damage that will not cause loss of air because the sealant has sealed the puncture.

As a precaution to reduce the risk of having to stop to change a wheel in a dangerous situation, the hard shoulder of busy motorway for example, it's a good product, but I would still carry a spare if possible.

exactly, and this is where it all falls down, because many plainly do not inspect their tyres properly, some even fail to notice when the inside shoulder is down to the cords or even the whole tread near enough bald.

In some cases these sealing products could lead to worse failures, because an object penetrating and staying in would usually lead to a pressure loss quickly, but if the sealer works you could easily have a 3" nail/screw through the tread and every revolution as the tyre flexes gradually ripping through a section of inside sidewall, itself being re-sealed by the product until eventually its too weak to hold and the sidewall gives way with instant deflation.

Having worked in a tyre repair workshops as a young chap i've seen what foreign objects can do to the inside of tyres, this is not a fit and forget solution.

Edited by gordonbennet on 31/08/2018 at 09:13