How to Change Your Mountain Bike Rear Inner Tube

Last Updated on October 4, 2026 by Md Arifur rahman

Changing your rear mountain bike inner tube is a repair you can totally do yourself. You’ll need a few tools, but the process is straightforward once you know the steps. Don’t let a flat tire ruin your ride – fixing it is simpler than you think!

We found that knowing how to do this basic bike maintenance can save you time and money. It’s a skill every rider should have in their toolkit. Plus, it gives you a better understanding of your bike’s mechanics. You’ll feel more confident on the trails.

• Get your tools ready: tire levers, pump, new tube.
• Let the air out of the old tube completely.
• Carefully remove the tire from the wheel rim.
• Replace the old tube with the new one.
• Re-seat the tire and inflate it.

Let’s walk through exactly how to swap out that flat rear inner tube step by step, so you can get back to riding as quickly as possible.

Tackling a Flat: How to Change Your Mountain Bike’s Rear Inner Tube

Don’t let a pesky flat tire bring your mountain biking adventure to a screeching halt! We know it can seem a bit daunting at first, but changing your rear inner tube is a really manageable repair. It’s a skill that will serve you well on the trails and save you precious riding time. Let’s get you back rolling!

Getting Prepared: Your Essential Toolkit

Before you dive in, let’s make sure you have everything you need. Having the right tools makes the job go much smoother. Think of it like packing for a trip; you wouldn’t leave home without the essentials, right?

What You’ll Need

• Tire levers: Usually, you’ll need two or three.
• New inner tube: Make sure it’s the correct size for your tire. Check the sidewall of your tire for the size.
• Pump: A floor pump is ideal for home use, but a good portable hand pump will work on the trail.
• Patch kit (optional but recommended): For future repairs.
• Gloves (optional): To keep your hands clean.
• Rag (optional): For wiping things down.

Many seasoned riders also carry a small multi-tool, which can be super handy for various bike adjustments. But for just the tube change, the core items are levers, a new tube, and a pump. We found that keeping these items in a small saddlebag is a great way to be prepared for trailside emergencies.

Step-by-Step Guide to Swapping Your Inner Tube

Now that you’re geared up, let’s get down to business. This process is designed to be clear and easy to follow, even if you’ve never done it before.

Step 1: Remove the Rear Wheel

This is your first main hurdle. On most modern mountain bikes, you’ll have what’s called a “thru-axle” or a “quick-release” skewer. You’ll need to open it up to get the wheel off.

Thru-Axle Bikes

If you have a thru-axle, you’ll likely need to unscrew it. Some axles have a lever you can flip, while others require a hex wrench (often a 5mm or 6mm Allen key). Just turn it counter-clockwise until it comes out. Don’t lose that axle!

Quick-Release (QR) Skewers

For QR skewers, simply flip the lever open. You might need to unscrew the nut on the opposite side a few turns. The wheel should then slide out. Be careful not to lose the little springs inside the skewer.

You’ll also need to deal with your gears. For the rear wheel, you’ll need to shift your chain onto the smallest cog (the highest gear) before you start. This makes it easier to pull the derailleur back when you remove the wheel.

Step 2: Deflate the Old Tube

Even if the tube is flat, there might be a little residual air. Find the valve stem on your wheel rim. You’ll see either a Presta or Schrader valve.

Schrader Valves

These look like car tire valves. You’ll need to push down on the little pin in the center to let the air out. You can use a small object like a key or the tip of a tire lever. Press it until all the air hisses out.

Presta Valves

These have a small nut on top. You need to unscrew this nut first. Just turn it counter-clockwise. Then, gently push down on the very tip of the valve stem to release the air. Unscrew it all the way.

Make sure all the air is completely gone. This makes the tire much easier to get off the rim. We found that taking an extra moment here really pays off.

Step 3: Remove the Tire from the Rim

This is where your tire levers come in handy. Start opposite the valve stem.

Using Tire Levers

Tuck the curved end of one tire lever under the bead (the edge) of the tire. Pry it up and over the rim. Hook this lever onto a spoke if it has a notch. Then, take a second lever and slide it along the rim, about 4-6 inches away from the first. This will lift the rest of the tire bead off. Sometimes, you can get the whole side off with just two levers.

If it’s stubborn, you might need a third lever. Once one side of the tire bead is completely off the rim, you can reach inside and pull out the old inner tube. Start by pulling the valve stem out last.

Step 4: Inspect for the Cause of the Flat

Before you put in the new tube, it’s super important to figure out what caused the flat. You don’t want your new tube to go flat immediately!

Checking the Tire and Rim

Carefully run your fingers along the inside of the tire. Feel for any sharp objects like thorns, glass shards, or even tiny pieces of wire. They can be very small! Also, check the rim tape inside the rim to make sure it’s not damaged or moved, as this can expose spoke holes. Many experts suggest this check is crucial (National Institute for Occupational Safety and Health).

If you find the culprit, remove it. If you don’t find anything, the puncture might have been caused by a pinch flat (hitting an obstacle hard with insufficient tire pressure).

Step 5: Install the New Inner Tube

Now for the fresh start! Take your new tube and inflate it just enough to give it some shape. This makes it easier to handle and less likely to get pinched.

Placement is Key

Start by inserting the valve stem of the new tube through the valve hole in the rim. Then, gently tuck the rest of the slightly inflated tube inside the tire, working your way around the wheel. Make sure the tube isn’t twisted.

Step 6: Re-seat the Tire on the Rim

This is the part that can sometimes be tricky, especially with tight-fitting tires.

Using Your Hands First

Try to push the tire bead back onto the rim with your hands. Start at the valve stem and work your way around. Often, you can get most of it on without tools. Make sure the tube isn’t caught between the tire bead and the rim.

Tire Lever Finesse

If the last section is too tight, use your tire levers carefully. Try to push the remaining bead up and over the rim. Be extremely careful not to pinch the new tube with the levers. We’ve all been there, and it’s frustrating to pinch a brand-new tube!

Once the tire is fully on the rim, go around the entire wheel, pushing the tire bead towards the center of the rim. This helps ensure the tube isn’t caught anywhere and that the tire is seated evenly. You want to see an even gap all the way around.

Step 7: Inflate the Tire

Time for some air! Attach your pump to the valve stem. If you have Presta valves, make sure you screw the little nut down before pumping.

Pumping Up Your Tire

Start pumping. As you inflate, keep an eye on the tire to make sure it’s seating evenly on both sides of the rim. If you see any bulges or uneven spots, stop, deflate a bit, and adjust the tire.

Inflate to the pressure recommended on the sidewall of your tire. Mountain bike tire pressure can vary quite a bit depending on your weight, the terrain, and your tire size. Many riders experiment to find their sweet spot.

Step 8: Reinstall the Rear Wheel

Now, reverse the process of removing the wheel. Make sure your chain is still on the smallest cog. Guide the wheel back into the dropouts. You’ll need to pull the derailleur back slightly to make room for the cassette. Ensure the wheel is straight and fully seated.

If you have a thru-axle, thread it back in and tighten it according to your manufacturer’s recommendations. For quick-release skewers, close the lever firmly. It should feel snug but not impossible to close. We found that a good QR lever closure will leave an imprint on your palm.

Give your wheel a spin to make sure it rotates freely and doesn’t rub against the frame or brakes. You’ve done it!

Your Flat Tire Repair Checklist

Did you cover all the bases? Here’s a quick rundown:

• Tools gathered: levers, new tube, pump.
• Old tube fully deflated.
• Tire bead removed from rim.
• Cause of flat inspected and removed.
• New tube installed and not pinched.
• Tire bead seated evenly on rim.
• New tube inflated to correct pressure.
• Wheel reinstalled securely.

Conclusion

You’ve successfully learned how to change your mountain bike’s rear inner tube! We know it might have seemed a bit intimidating at first, but by following these steps, you’ve tackled a common trailside issue. Remember, preparation with the right tools is key, and taking a moment to inspect your tire for the cause of the flat will save you headaches later. This skill is a fantastic confidence booster. Now, go out there and enjoy your rides, knowing you’re ready for whatever the trail throws at you!

Frequently Asked Questions

How do I know which size inner tube to buy?

You’ll find the correct size printed on the sidewall of your mountain bike tire. Look for numbers like “29 x 2.3” or “27.5 x 2.1”. Your new inner tube needs to match these dimensions closely, especially the diameter (e.g., 29 or 27.5) and the width range.

What if I can’t get the tire bead off the rim?

Sometimes, tire beads can be quite tight. Try pressing down on the tire all around the rim to loosen it. If it’s still stubborn, you can carefully use a third tire lever, but be very cautious not to pinch the new tube when you’re putting it back on.

My new tube went flat again immediately. What did I do wrong?

This often happens if the new tube was pinched between the tire bead and the rim during installation. Also, double-check that you completely removed the sharp object that caused the original flat from your tire and that your rim strip is covering all spoke holes.

How much air pressure should I put in my mountain bike tires?

Tire pressure recommendations are usually found on your tire’s sidewall, but for mountain biking, it’s often lower than road biking. Factors like your weight, tire size, and the trail conditions will influence your ideal pressure. Many riders experiment to find what feels best for grip and comfort.

Can I use a patch kit instead of a new tube?

Yes, you can! A patch kit is a great backup to carry on rides. For a trailside fix, patching the old tube is a good temporary solution. However, we generally recommend installing a new tube if possible, as a patch might not hold as reliably long-term, especially under high pressure or stress.