How do I put this? This is not the easiest review to write because while the product is brilliant at what it does, and it has so many great ways to cover your butt in a pinch, it also has the potential to cause a few serious issues if you don't pay attention. I should make it clear though - the trouble is NOT caused by the product - it's caused by the sense of 'set and forget' that this product can create in the driver. OK... I'm going to have to explain this carefully... let's start with what makes this stuff THE must-have motoring product in my mind.

A short while ago, I was driving over a local bridge that was getting some work done on it. In typical style, the workers had left bits of offcut metal, screws, bolts and even some tools lying around. Most were on the sidewalk or in the gutter, but there must have been at least one screw on the roadway itself, because it ended up in one of my car tyres. Cursing myself for a fool, I realised that I had taken the car jack out of the boot to use in the garage briefly earlier in the day, and had forgotten to put it back, so I had no choice but to drive home listening to my tyre fapping away to itself for the 1.8km journey home.

I got home and changed tyres to my half-wide spare, then took the busted tyre to the repair bay the next day to get fixed. That's when I decided I had to get some of this stuff for review - so I did, at the Fieldays Expo that weekend. With the able assistance of my local mechanic - who kindly offered to assist me in installing this into my tyres, mainly because he was really curious about it too - we pulled the wheels off the car one by one, ran them through the wheel balancer, removed the tyre's valve, let the air out, squirted about 100ml of this into each tyre, replaced the valve and reinflated the tyres. I then took the car on a 5km road trip to make sure this stuff was evenly distributed around the entire inner surface.

I still had 100mls left over in the bottle, and since I didn't want to risk my tyres, we decided to put an older tyre on to a rim, throw this last portion in, run it through the wheel balancer to spin the wheel in a manner consistent with a small road trip, then go to town on it with a nail gun and other assorted "typical tyre hazards" to see what happened. To say that I was impressed is pretty bang-on, mainly because I had seen this stuff in action at the Fieldays expo the previous year. However, the mechanic was having mixed feelings. "It's pretty amazing at patching holes that's for sure," he said "but if the driver isn't aware he has something in the wheel, he could keep driving on it long distance and [cause extreme damage to] the steel belts right up." And upon some thought, I had to agree.

This stuff will seal any small to medium sized puncture. It'll even seal a large hole, if the puncturing object stays in the hole. But the problem with that is that the driver may not hear any difference in the road noise - especially with modern cars that have superior soundproofing - and that can mean the damage just keeps getting progressively worse over time, eventually causing a catastrophic blow-out. This is really a serious issue - a bit like a glass splinter in your finger - pull it out quickly, and you have a small, fresh wound that will heal in a few hours to a few days. Ignore it, and with every flex of your finger it will slice the wound a little more, eventually ending up with a visit to the doc for antibiotics, or worse.

So, the practical side of this product is this - chances are, you won't get caught on the side of the road in the rain and the dark, having to deal with a flat tyre. But it also means that you need to be extra vigilant about checking your tyres regularly to see if there are any embedded objects in there that need to be removed, and possibly have a puncture repair done if it's serious enough that this sealant won't be able to lock it down.

Overall, I'm still sold on it, to the point where I plan to buy some more to put in my son's bike tyres. Teenagers can be so hard on a bike. But I am also now far more aware of the road-noise as I drive, and even the slightest hint of a cyclic noise that matches the rotation period of the wheels has me pulling over and checking for stones, nails, whatever. So far, so good. Fingers crossed. The only installation issue the mechanic raised was that it was hard to squeeze the goop into the tyre because there was nowhere for the displaced air to vent. We overcame the issue by having me sit on the edge of the tyre until he was ready to squirt the TyreShield into the valve stem, then I hopped off, creating a small partial vacuum, which meant there was no extra air to displace. Thank You MacGyver, for always teaching me how to problem solve! I should also add that in the month since I had this stuff put in my tyres, repeated pressure checks have shown no loss of tyre pressure, thanks to the extra layer of sealant inside the wheels.