Tech: Emergency tyre repair
Stuck by the roadside with a flat tyre and no suitable spare? You might just be able to carry out an emergency repair. Here's how.
Of course, the trick is to realise that you have a tyre problem before the tyre is reduced to a sad bag of rubber and canvas flailing around, although it can be difficult to assess just as the tyre is punctured.
It’s rare for a tubeless tyre to suddenly, catastrophically fail after a puncture. That’s why it’s important to do regular visual checks of tyres when on tour so you can discover any damage or punctures in the safety of a roadside rest area or town car park.
There are a few ways to avoid getting punctures in the first place. The first is to set off with new tyres, or tyres with at least 80 per cent of tread remaining. This will give sharp stones and other road debris less opportunity to puncture the tyre.
The next is to buy a more rugged tyre, which is relatively easy if your tow rig is a 4WD, but unfortunately not possible if it’s a passenger car. Many 4WDs are able to run on the more rugged all-terrain offroad tyres (or the more aggressive mud-terrains, but that’s probably overkill) which, depending on the tyre, will typically offer marginally less road grip, be slightly noisier and not ride quite as well as highway terrain tyres but will provide a stronger, more puncture-resistant carcass and better grip offroad.
When you face even ‘only’ 5000km of travel, it pays to have reasonably fresh tyres on your rig. Setting off with a set of tyres that are worn to near the tread wear indicator is inviting trouble, including punctures and less wet weather grip. Broken or missing valve caps should also be replaced, as grime getting into valves can cause air leaks.
If the worst happens and you have a puncture, try to find somewhere safe to stop. Once you’re satisfied that you’ve got the best spot possible, find where the tyre is leaking. Hopefully it’ll be obvious, with a screw or nail stuck into the tyre, but if not, try to listen to where the air is escaping and mark the spot with a piece of chalk, or a small stick from the roadside if you have nothing else.
If the puncture is in the tread area, and is a neat hole rather than a tear, you should be able to plug the tyre and continue on until you can have the tyre inspected and either patched from the inside or replaced.
If the puncture is in the shoulder of the tyre or part-way up the sidewall, then you should replace the tyre with a spare tyre if you can – don’t try plugging it. If there’s no other option, then you might want to give it a go with plugs but you are taking a huge risk. Delamination and tread separation occur with repairs done in this area, so drive very slowly until you can stop and organise a replacement – treat this as a tyre ready to burst.
If you have a slow-leak puncture (most on-road failures of tubeless tyres are) and have been driving on the tyre for a while with low inflation pressures, it may be damaged beyond repair. Sidewall plies do not take well to such abuse (unintentional as it may be) and if the tyre is repaired and used as normal, the tyre may blow out. If you see feathering on the sidewall when plugging a tyre, drive at as low a speed as is safe until you can get to a good tyre shop to check for sidewall damage.
PLUGGING A TYRE
Get out all the gear you require so that you can spend minimal time at the tyre itself – important if it’s on the traffic side of the road. Prepare the tyre compressor to re-inflate the tyre, and get the plug kit set up and ready. You may want to hook up the compressor now, too.
Take a pair of pliers to clear the puncture of any foreign objects such as a nail or screw (pic 1). Once you pull out the cause of the puncture, the tyre pressure can drop fairly quickly if it’s a large puncture, so if you hear air rushing out, try to act quickly because if the tyre is completely deflated it may be difficult to get it to reseal on the rim. This is where it helps to have the compressor ready.
Get the probe tool to check that the puncture hole is clear of debris (pic 2). Then wipe some lube on the probe tool and wipe it in the puncture area, and keep the dirty jokes to yourself (pic 3). Then, with a plug threaded into the insertion tool (pic 4), push the plug into the puncture site with about half the length you’ve inserted remaining visible (pic 5). Cut off excess plug material with a razor blade if it’s hanging out well past the tread blocks. Then pull the T-piece handle up, releasing the plug, and take out the insertion tool (pic 6). Inflate the tyre to maximum tyre placard pressure (pic 7).
You should know by this point if the plug is going to hold, or if the hole is too big and requires another plug inserted. Listen for air leaking and check the pressure a few times as you’re packing up (pic 8). If the pressure drops, unpack the gear and prepare to plug again.
Don’t rely on a plug repair alone: it should also be patched internally at the first opportunity by a tyre shop to ensure a complete seal, as plugs are known to leak.
WHAT YOU’LL NEED
To repair a tyre puncture out on the road with a wheel still fitted to the vehicle, you’ll need a tyre plug puncture repair kit. This should include at least 10 self-vulcanising plugs (which you won’t need all at once, but you don’t want to run out if you have more than one puncture or botch your first effort), a probe tool, insertion tool, razor blade and lube. You’ll also need a 12V tyre compressor to re-inflate the tyre.
Include a pair of pliers to extract nails or screws, a torch in case you’re stuck doing this in the dark, and last but not least, some safety gear: a high-visibility vest and a warning triangle.
Source: Caravan World Sep 2009