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How to fix a flat bike tire

Sooner or later every cyclist gets a flat. Knowing how to fix a flat tire is a super useful bike repair skill that can save your ride (or save the ride of any stranded cyclist you might come across). It’s relatively easy and doesn’t require many tools.

Bike tools you’ll need

Video: How to fix a flat bike tire

Steps to fix a flat bike tire

First up: a few simple terms to know for beginners:

  • Tire: Outer rubber part of your wheel that touches the ground when you’re riding.
  • Inner tube: Fits inside the tire; the source of the flat.
  • Rim: Outer edge of the wheel that the spokes attach to.
  • Tire bead: The stiff part of the tire that fits inside the rim edge to hold the tire in place.

Alright, now for the good stuff:

Part 1: Remove the wheel

  1. If you have a V-brake or cantilever brake, disconnect the brake cable from the brake arms.

  2. If it’s your back tire, use your gears to shift the chain to the smallest sprocket.

  3. Loosen the quick release to free the wheel, or use a crescent wrench if the wheel is attached with nuts. Never used your quick release before? Ask a bike buddy who knows how it works to make sure you take it off – and more importantly, put it back on – properly.

  4. Pull the wheel out. If it’s the back wheel, hold the derailleur down as you pull the wheel out.

  5. For bikes with disc brakes: once the wheel’s off, make sure you don’t touch the brake levers or you may have trouble getting your wheel back on. If you can’t trust yourself, slip a piece of cardboard between the pads.

Part 2: Remove the inner tube

Removing the inner tube from a bike tire
  1. Open the valve and deflate the inner tube all the way. If you have a Presta valve, you’ll need to unscrew the tip of the valve before you press it down with your finger to deflate the tube.

  2. Next up: get one side of the tire bead off the rim. Start by pushing the tire all the way around to help loosen it from the rim.

  3. If the tire’s tight, tire levers will help. Insert a tire lever between the tire bead and the rim edge (make sure to do this at least 10cm away from the valve area). Use leverage to flip the tire lever over and hook the tire lever onto a spoke to lock it in place.

  4. Insert another lever a few centimetres from the first.

  5. Push down on one lever, then the other, to free the tire from the rim. Work all the way around the tire until one edge of the tire is off the rim.

  6. Reach inside the tire and pull the inner tube out. When you get to the valve, gently pull it through the rim. If there’s a circular nut on the valve, unscrew it to remove the inner tube (put it somewhere safe since you’ll need it later).

Presta and Schraeder bike valves
Presta valve (left) and Schrader valve (right).

Part 3: Find the problem

Tire with sharp object stuck in it
  1. With the old inner tube out of the tire, use your bike pump to inflate the old tube fully.

  2. Detective time: you need to find the source of the leak. Hold the tube near your cheek and move the tube past your face to feel for escaping air.

  3. If you can’t feel escaping air, another method to find a slow leak is to submerge the half-inflated tube in a tub of water. Look for bubbles – that’s where the puncture is.

  4. When you’ve figured out where the hole is, circle it with a pen or marker so it’s easy to find where the corresponding spot is on the tire (also useful if you’re patching the tube).

  5. Inspect the part of the tire or the rim where the hole is to find the source of the leak. Is there something stuck in the tire or rim? Remove it, otherwise another flat is inevitable.

“Patching a tube is easy, it’s way cheaper than a new tube and it cuts down on waste. Plus, you’ll feel super good about it. If you don’t have time on the go, pack it in your bag to fix it at home later.” – MEC staff tip

Part 4: Patch the tube

If you have a new tube, skip to part 5.

Note: If you have several leaks, a giant slash or you notice that leaks are coming from old patches, it may be time to consider replacing your inner tube completely.

  1. Deflate the tube and get out your patch kit. Make sure the tube is dry before you move on.

  2. Follow the instructions in your patch kit. If the instructions are long-gone, here are some steps to try.

  3. Use the sandpaper in the patch kit to roughen a patch-sized section around the puncture.

  4. Clean the sanded area (rubbing alcohol works great, but a corner of your t-shirt will do) and apply a thin layer of glue around the puncture that’s big enough for the patch. Wait a few minutes for the glue to cure before you apply the patch; the glue should be tacky to the touch. Note: some patches are pre-glued, so you don’t need this step.

  5. Peel the foil side from the patch and apply it over the puncture with strong pressure for at least 30 seconds. Make sure the edges stick.

  6. Leave the plastic sheet in place and keep applying pressure for a few minutes to let the patch bond.

“Ideas to upcycle old inner tubes: make tie-down straps (with buckles if you want to get fancy), chainstay protectors, resistance bands for physio exercises, or a crafty wallet.” – MEC staff tip

Part 5: Insert tube and replace tire

Checking bike tire
  1. Use your bike pump to inflate the new or patched tube about 50% to give it structure and shape.

  2. Push the inner tube valve through the hole in the rim. Make sure it’s not crooked.

  3. Starting from the valve, work the inner tube into the tire so it’s completely tucked in and not twisted.

  4. Once the tube’s inside, it’s time to get the tire back into place. Use your hands to work the tire bead over the rim. Make sure you don’t pinch the tube between the tire and the rim (you can let out a bit of air if needed).

  5. The last few centimetres of the tire takes a bit of oomph and patience. Grab the tire with both hands and use the meaty part of your hand to work the sides back onto the rim; work one side, then the other. You can also use tire levers. If you use tire levers, make sure you don’t snag the tube.

  6. Check both sides of the wheel and make sure the tire’s sitting nicely all around the rim, and that the valve didn’t shift around or tilt during the process.

  7. Inflate the tire to the recommended psi, and tighten the valve nut and replace the valve cap.

  8. Once it’s inflated, check the tire one more time. If it’s sitting nicely and there aren’t any weird bulges, you’re almost done!

Part 6: Reinstall the wheel

Replacing the back wheel of a bicycle
  1. Get ready to put the wheel back in place. Pull the derailleur down and make sure the chain wraps around the cassette. Align the disc brake rotor with the space between the brake pads, and ensure the axle is in the dropouts.

  2. Insert into the dropouts and properly tighten the quick release lever (ask a knowledgeable bike buddy if you’re not sure, since a loose quick release is dangerous). Once there’s enough tension, push the quick release lever back into position and check that it’s solid.

  3. If your bike has rim brakes, remount the brakes. For all bikes, check that your brakes are working.

Nice work! You’re ready to ride.

How to prevent flat bike tires

There’s only one thing more frustrating than a flat tire – a flat tire that keeps happening. By following a few simple steps, though, you can avoid being delayed (or stranded) on your next ride. If flats keep coming, here are some common reasons why:

  • Something stuck in the tire: Small sharp stuff like slivers of glass or metal can cause recurring flats. Give your tire a close look and remove sharp bits with pliers or tweezers.
  • Protruding or sharp spoke heads: Get your bike shop to replace the spoke or to cut the existing spoke to the right length and replace the rim tape.
  • Hole in the tire: If the inner tube is bulging out through the tire, that’s a problem. In this case, you need to replace your tire and inner tube. For a temporary fix to get you home, you can use a folded energy wrapper or a folded $5 bill: