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Image from Road Cycling Tips

In this Skill Builder piece, guest contributor and mountain biker Chris Nodder (author of Bike Boo Boos) outlines how to deal with punctures on both tube and tubeless bicycle tires. – Gareth

Puncture – Regular Tube Tires


This repair assumes you are patching your tube. Use regular tire repair patches and glue. The peel-and-stick patches don’t conform well to the shape of tubes and tend to come unstuck as the tube is re-inflated inside the tire. They are also a very temporary repair that can fail on subsequent rides. Regular patches are good for the life of the tube, if applied correctly.

Preparation
Clean as much dirt from the tire and rim before you start your repair. Remove the wheel from the bike (remember to release rim brakes first) and deflate the tube completely if it still has air in it.

Tire and Tube Removal
Push the tire towards the center of the rim all the way around on one side. This allows the tire bead to sit in the middle of the rim, giving you more room to pull or lever it over the rim. Start trying to remove this side of the tire by “rolling” it off the rim with your (gloved) hands. If this doesn’t work, find your plastic tire levers, and insert two of them under the tire bead (which is still sitting in the center of the rim).

Using lever tools on a bike rim. Image from bikehero.com

Lift both tire levers up at the same time so that the bead clears the rim. Now hold one lever still, and slide the other one around the rim to pop the bead over the rim all the way around. Once one tire bead is completely clear of the rim, you can remove the tube. Before you do so though, check to see if you can find the source of the puncture through the tire. This makes it easier to locate the place you need to repair on the tube. If you can’t find the source, remove the tube but keep it in the same orientation as the tire.

Finding the Puncture Hole
Now, inflate the tube to find the hole. Holding the inflated tube up to your face will allow you to feel where air is leaking. Water (or spit) will bubble when placed on the hole. Look on the same location on the tire for any remnants of the thing that caused the puncture. Also run your (gloved) hand carefully around the inside of the entire tire to find and remove any other spikes. The last thing you want to do is to have the same object puncture your repaired or replaced tube.

Gee, where do you think the puncture could be? From Willybikes.com.

If you find a hole or pair of holes on the side of the tube, it is most likely a “snake bite puncture” caused by the rim pinching the tube against a rock you rolled over. Run a higher pressure to prevent this kind of puncture from occurring again.

Puncture Repair
Clean and roughen the area around the puncture hole on the tube, making sure it’s completely dry. Then put a layer of tube patch glue on it, slightly larger than the size of the patch. Wait for the glue to become cloudy and dry to the touch. It is impact adhesive, so it won’t work unless it’s dry.

Peel the foil off of the patch but leave the clear plastic bit on the other side. Now place the patch on the glue (rubber side down, clear plastic side up) and press hard for about 30 seconds. Don’t try removing and re-placing the patch once it’s touched the glue — this won’t work.

Leave the tube for another five minutes for the glue to set (longer in cold climates), then inflate it just slightly. With one bead of the tire on the rim, replace the tube in the rim, starting at the valve stem.
Start the second tire bead back on the rim at the side away from the valve. Put it way down in the center of the rim to give you more “play” once you have worked the rest of the bead on to the rim. Rest this piece against your belly, and use both hands at the same time to hook the bead back over the rim all the way round to the valve. You should not need to use the tire levers to put the tire back on. Use your (gloved) hands to roll the bead on. Using the tire levers will most likely pinch the tube and cause it to puncture.

1. Roughen 2. Glue (let Dry) 3. Press Hard. Photos from Repairing a Flat Tire on BikeToledo.net

Once the tire is back on (yes, it’s hard sometimes, but it came off, so it can go back on), ensure that the tube is not trapped at any point under the tire bead, then inflate to 10-15psi (very soft). Now run your hands around the tire, squeezing it as you go. This allows the tube to seat within the tire, and ensures that it is not pinched anywhere. Now continue to inflate the tube. For a newly repaired tube, inflate the tire to 45-50psi (hard) or higher if your tire suggests. This uses the tire to press the patch securely against the tube.
Re-insert the wheel, re-attach your brake cable (rim brakes) and ride!

Tip: Out on the trail, you probably want to replace the tube using the spare you carry rather than patching it. Still check around the inside of the tire for spikes before using the new tube, or you’ll be patching that one too.

Puncture – Tubeless Tires

Tubeless tires use a thicker tread area and sidewall to prevent punctures. This allows riders to run lower pressures for more grip. The lack of tube also creates lower rolling resistance. Tubeless rims are also specially designed to form an airtight seal with the tire.

The tires typically have a soft compound rubber on the inside of the tire to “grip” thorns that do penetrate, thus not allowing air to pass out.

Avoiding Punctures with Tubeless Tires
Regardless of the thicker construction and soft compound lining, these tires do sometimes get a puncture that causes them to lose air.
The best way to avoid this situation is to use a tire sealant such as Stan’s NoTubes (notubes.com). A small amount of this sealant will prevent even large holes from becoming an issue. You may need to re-inflate the tire after a major puncture, but no other repair is required.

Tubeless tires also sometimes “roll” off the rim because of the lower pressures used, causing them to burp air. This can lead to dirt getting between the sidewall and the rim, preventing a good seal. Sealant will sometimes turn this goop to glue, but not always. If you are not using sealant, you have got dirt in the bead/rim interface, or the tire has a major gash in it, you may have to “tube” the tubeless tire.

Putting a Tube in Tubeless Tires
The procedure for tubing tubeless tires is the same as for regular tires. However, before you can put a tube in you must remove the valve stem by unscrewing the retaining nut from the outside of the stem and then pushing the whole valve unit into the rim from the outside. This will unseat the valve seal from the rim and allow you to pull the valve out. Keep the valve safe, as you will want to replace it later.
With the tubeless valve removed, you can place a tube in the rim in much the same way as a regular tire. You will most likely have more difficulty getting the tire bead back over the rim. Make sure that the tire’s bead is sitting in the lowermost indentation in the middle of the rim, and work the bead round, pushing it away from you with both hands until you get to the far side of the rim. At this point, it should be possible to roll the last portion of tire bead over the rim. If you really must use plastic tire levers, do so very carefully so that you do not pinch the tube between the lever and the rim.

Re-inflation of Tubeless Tires
Tubeless tire beads tend to “snap” on to their rim. Ideally, you should inflate the tube to 50 PSI and listen for the tire making cracking noises as it seats in the rim. If you can’t reach 50 PSI because of a poor pump, be prepared for cracking noises that sound almost like a spoke breaking as you ride along.

Tip: If you find yourself on the trail with a pump that seems to be sucking more than it blows, try taking it apart and dropping oil on the plunger washer. This creates a better seal.

More:

Gareth Branwyn

Gareth Branwyn is a freelancer writer and the former Editorial Director of Maker Media. He is the author or editor of a dozen books on technology, DIY, and geek culture, including the first book about the web (Mosaic Quick Tour) and the Absolute Beginner’s Guide to Building Robots. He is currently working on a best-of collection of his writing, called Borg Like Me.


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