How to Fix a Puncture on a Mountain Bike — Step-by-Step Guide

You're mid-ride on the Longdendale Trail, the tyre goes soft, and you're miles from anywhere. Don't panic — changing an inner tube is a skill every mountain biker needs, and once you've done it once, it takes less than ten minutes. Here's exactly what to do.

What You'll Need

Before you head out, make sure you're carrying:

• A spare inner tube (the right size for your wheel — see below)
• Tyre levers (2-3 plastic ones)
• A pump or CO2 inflator — the Zefal EZ Max FC CO2 Pump is compact enough to fit in a jersey pocket
• Optional: a puncture repair patch kit as backup

The most important thing is having the correct tube size. Check your tyre sidewall — you'll see something like 26 x 1.95 or 27.5 x 2.10. The first number is the wheel diameter, the second is the tyre width. Our Impac 26" Inner Tube fits 26 x 1.75–2.35, and the Impac 27.5" Inner Tube fits 27.5 x 1.75–2.35 — both with a 40mm Schrader valve, the standard for mountain bikes.

Not sure which size you need? Read our guide: What Size Inner Tube Do I Need?

Step 1 — Remove the Wheel

Rear wheel: Shift to the smallest sprocket before you stop — this makes refitting much easier. Release the quick release lever or undo the thru-axle, then lift the chain off the cassette as you pull the wheel free.

Front wheel: Simply release the quick release or thru-axle and drop the wheel out.

Step 2 — Remove the Tyre and Old Tube

Let any remaining air out by pressing the valve core. For a Schrader valve (the chunky one, like a car tyre), press the pin in the centre. For Presta (the thin one with a brass collar), unscrew the collar first. Not sure which you have? Here's how to tell.

Hook a tyre lever under the bead of the tyre (the edge that sits in the rim) and lever it over. Clip the lever to a spoke to hold it, then work a second lever around the rim until one side of the tyre is off. Pull out the old tube.

Step 3 — Find What Caused the Puncture

Before fitting the new tube, run your fingers carefully around the inside of the tyre to feel for whatever caused the puncture — a thorn, piece of glass, or sharp flint. If you skip this step, you'll puncture the new tube immediately. Check the rim tape too — an exposed spoke hole can cause pinch flats.

Step 4 — Fit the New Inner Tube

Put a small amount of air into the new tube — just enough to give it shape. This stops it folding and getting pinched when you fit the tyre.

Push the valve through the valve hole in the rim, then tuck the tube inside the tyre all the way around. Starting at the valve, push the tyre bead back onto the rim with your thumbs, working around both sides simultaneously. The last section is always the tightest — use your palms to roll the bead over rather than a tyre lever, which can pinch the tube.

Check the valve is sitting straight and the tube isn't visible anywhere between the tyre and rim.

Step 5 — Inflate and Refit

Inflate to the recommended pressure — for MTB trail riding, typically 25–35 PSI depending on your weight and terrain. Lower pressure gives more grip on loose ground; higher pressure reduces pinch flat risk on rocky trails.

Refit the wheel, making sure the disc rotor slots cleanly into the brake calliper. Tighten the quick release or thru-axle firmly, click through the gears to check the chain is seated correctly, and you're ready to roll.

Should I Patch or Replace?

For trail riding, always replace with a fresh tube if you have one. Patches work, but they take time and can fail under pressure on rough terrain. Keep a patch kit as an emergency backup only — if you've already used your spare tube and puncture again, a patch gets you home.

FAQs

Can I fix a puncture without tyre levers?
Technically yes — some experienced riders can remove tyres by hand — but tyre levers make it much easier and reduce the risk of damaging the rim tape. Always carry two.

How long does it take?
Once you've done it a few times, 5–8 minutes. Your first time might take 15–20 minutes — that's completely normal.

What causes punctures on MTB trails?
The most common causes are thorns and flint (especially on Peak District limestone trails), pinch flats from hitting rocks at low tyre pressure, and rim tape failure on older wheels.

What's the difference between a 26" and 27.5" tube?
The numbers refer to wheel diameter — they're not interchangeable. A 26" tube will not fit a 27.5" wheel. Always check your tyre sidewall before buying. See our full guide: What Size Inner Tube Do I Need?

Stock Up Before Your Next Ride

A spare inner tube weighs almost nothing and takes up minimal space in a pack or jersey pocket — there's no reason to be caught out. We stock Impac inner tubes in 26" and 27.5", available with free UK delivery or collect in person from our shop in Hadfield, on the edge of the Peak District.