Home » Bike Maintenance » Basic tools and repairs » Patching UST tubeless tyres

Patching UST tubeless tyres

Although flats are less likely with UST tyres, they do happen. If you’re out riding, often the easiest thing to do is to stick an ordinary tube into the tyre and fix it when you get home.

Once you get home, patch the tyre. Tyres are expensive, and patches work, so it’s worth the effort. Finding the hole can be the tricky bit! Pump as much air as you can into the tyre and listen for hissing from the hole. Look carefully for a thorn or other spiky object sticking out of the carcass; you may also spot sealant bubbling out of the hole. Sometimes the hole is tiny and hard to locate, and you have to submerge the inflated wheel in water to look for the bubbles. This is much more awkward than doing the same process with a tube!

Once you’ve located the hole, mark it carefully or you will lose the place! I usually draw a circle in ballpoint around the hole, then draw an arrow pointing to it on the sidewall of the tyre where it’s easy to see. Undo the thumbnut on the valve and let all the air out of the tyre. It’s important to do this next stage carefully. Both sides of the tyre have an airtight seal against the rim. It’s much, much easier to refit the tyre if you only break one of the seals. If the hole is nearer one side of the tyre, start with that side. Push the sidewall of the tyre in and away from the rim. It will resist at first because the seal is tight, but once it’s released the rest will pull off easily.

Sometimes the seal is very tight. If all else fails, lay the wheel on the ground and stand carefully on the sidewall of the tyre, as close to the rim as you can get. Don’t stand on the rim – you’ll bend it. Pull off the released side of the tyre all the way around and locate your hole from the inside. Pull out whatever it was that caused the puncture.

While you’re in there, feel carefully around the inside of the tyre for anything else sharp there may be more than one intruder. Use clean sandpaper to roughen up the area of the tyre around the hole. If you’re used to patching tubes, don’t underestimate this part you need to make an area bigger than the patch much rougher than you would with a tube. Follow up by cleaning with solvent.

Spread the special UST glue around the hole. Start directly over the hole and work outward in a spiral, so that the patch ends up centred over the hole. Make the area of glue much bigger than the size of the patch. Then leave the glue to dry. Don’t touch it or poke it, just leave it. It needs five to ten minutes – if it’s cold, give it the full ten minutes.

The next stage

You’ll find that your patch is now trapped between two layers of plastic, or a layer of plastic and a layer of foil. Peel off one layer, but don’t touch the surface of the patch with your fingers at all or it won’t stick. Use the other layer of packaging to hold it. Lay it carefully onto the glue. Don’t move it about at all, just put it on. With the packaging still on there, press the patch firmly onto the tyre. A tyre lever is perfect for this, or the flat side of a spanner, or a spoon.

You can peel the backing off the patch now, but I usually leave it there – it doesn’t weigh much, and you risk pulling off your carefully fitted patch if you try to remove it. Starting opposite the valve, refit the tyre onto the rim. The tyres are unwieldy, and it can feel like you need three hands, but once you’ve got most of the tyre on, it stays in place.

This last part is harder. Don’t be tempted to use tyre-levers because if you do your tyre will leak forever. Fold the tyre onto the rim with your thumbs. Aim to finish at the valve. If it gets tough, return to the opposite side of the rim and massage the bead of the tyre into the well at the centre of the rim to gain enough slack to pop it on at the top. Once it’s in, ensure that the bead of the tyre sits beside the valve, not on it, and pump it up. Be very vigorous at first to seal the tyre and keep pumping until it pops into place.

Sometimes, if the tyre is really tight, a bit of warm soapy water will help. Work in very small sections, lifting a 10–20mm (3⁄8–3⁄4 inch) length of tyre at a time over the rim. The last bit will be a struggle and will pop into place just as you are about to give up. Urban myths to ignore include pouring lighter fluid on the tyre and applying a match. Don’t do this. Tyres are expensive, and this is not a time when setting something alight helps.

Big workshop track pumps are better at getting the initial volume of air in fast enough; very small mini-pumps can make hard work of this. Air canisters can be hit-and-miss. If the tyre seals straight away, they’re quick enough; if it doesn’t, you waste the canister. It definitely helps when reinflating tyres if you can keep one side of the bead locked onto the rim. Fitting new tyres is particularly frustrating; they’re usually packed folded up and the kinks that result from their being folded usually make for air gaps. Take new tyres out of the packet as soon as you buy them and store them unfolded until you come to fit them.

Even if you run very low pressures, it’s worth pumping the tyre up really hard to seal it properly – check on the sidewall to see how high it will go, then pump it up to that pressure before letting it down again to however low you want to run it.

Sealant dilemmas

Sealants make the tyre very slightly heavier and do a fantastic job of plugging the small- and medium-sized cuts and tears. However, they’ll make it very much more difficult to persuade a patch to stick to the tyre.