Every cyclist gets a flat. It’s not a matter of if — it’s when. The good news is that fixing a flat tire is one of the easiest bike repairs you can learn. While we’re happy to get you sorted at the shop, here’s a quick guide for fixes when out on the road, or at home.

Tools You’ll Need

Gather these before you start. If you ride regularly, keep them in a saddle bag on every ride.

Tire levers (2–3 plastic levers)
Spare inner tube (correct size for your tire)
Portable pump or CO2 inflator
Patch kit (as a backup to the spare tube)

A multi-tool with a wrench is helpful if your wheels use bolt-on axles instead of quick-release skewers.

Step 1: Remove the Wheel

Shift your chain to the smallest cog if you’re removing the rear wheel. This gives you the most slack.

Open the quick-release lever or unthread the thru-axle. For the rear wheel, pull the derailleur back and drop the wheel out. The front wheel lifts straight out.

If you have rim brakes, release the brake quick-release to create clearance for the tire to pass through.

Step 2: Remove the Tire and Tube

Deflate the tube completely by pressing the valve core. Hook a tire lever under the tire bead — the edge that sits in the rim — about 2 inches from the valve. Clip it to a spoke.

Insert a second lever a few inches away and slide it around the rim to unseat one side of the tire. Once one bead is off, pull the tube out starting from the side opposite the valve. Remove the valve last, pushing it through the rim hole.

Step 3: Find the Puncture

Inflate the old tube and listen for hissing. If you can’t hear it, submerge the tube in water and watch for bubbles.

Once you find the hole, inspect the corresponding spot on the inside of the tire. Run your fingers along the inner surface carefully. You’re feeling for the thorn, glass shard, or wire that caused the flat. Remove it. If you skip this step, the new tube will puncture in the same spot within minutes.

Also check the rim tape inside the wheel. Make sure it covers all spoke holes completely. A shifted rim tape is a common cause of mystery flats on the inner side of the tube.

Step 4: Install the New Tube

Slightly inflate the new tube — just enough to give it shape. This prevents it from folding and pinching under the tire.

Insert the valve through the rim hole first. Tuck the rest of the tube into the tire, working your way around both sides from the valve. Make sure the tube isn’t twisted or bunched anywhere.

Step 5: Reseat the Tire

Starting at the valve, push the tire bead back onto the rim using your hands. Work your way around the rim in both directions.

The last section will be tight. Use the heels of your palms and push the bead over the rim edge. Avoid using tire levers to reseat the tire if you can — levers can pinch the new tube and cause another flat immediately.

Before fully inflating, push the valve up into the tire and pull it back down. This ensures the tube isn’t caught under the bead near the valve — a common spot for pinch flats.

Step 6: Inflate and Check

Inflate the tire to the pressure printed on the sidewall. Spin the wheel and watch the tire. It should sit evenly in the rim all the way around. If you see a bulge, deflate and reseat that section.

Reinstall the wheel, close the quick-release or thru-axle, and re-engage your brakes. Give the wheel a spin to make sure the brakes aren’t rubbing.

When to Patch vs. Replace the Tube

A patch kit is lighter than a spare tube and works fine for small punctures. Use a patch as a backup when you’ve already used your spare tube on a ride.

For reliability, carry a fresh tube for your first flat and patch the punctured tube at home as your new spare. Pre-glued patches are convenient but less reliable than traditional vulcanizing patches.

Replace your tube entirely if the puncture is near the valve, if there are multiple holes, or if the rubber is visibly degraded.

Preventing Flats

Run the right tire pressure. Too low and you get pinch flats from hitting bumps. Too high and every piece of glass goes straight through. Check the range on your tire and aim for the middle.

Inspect your tires regularly. Small cuts and embedded debris work their way through the casing over days, not all at once. Pick out anything you find.

Consider flat-resistant tires or tire liners. If you commute on urban streets with glass and debris, tires with a puncture-protection belt (like Schwalbe Marathon or Continental Gatorskin) cut flat frequency dramatically.

When to Get Help

If you keep getting flats in the same spot, something is wrong with your rim tape, tire, or wheel. If your tire won’t seat properly or you’ve damaged the valve, it’s time for a mechanic to take a look.

For tricky repairs — tubeless tire setups, damaged rims, or tires that just won’t cooperate — bring it to Back in Action Bikes in Brookline. We fix flats while you wait.

Frequently Asked Questions

How long does it take to fix a flat tire?

With practice, about 10–15 minutes. Your first time may take 20–30 minutes. The key is having the right tools and a spare tube ready.

Can I ride on a flat tire?

Don’t. Riding on a flat damages the rim, the tire, and the tube beyond repair. Walk the bike to a safe spot and fix it there.

How do I know what size tube to buy?

Check the numbers on your tire sidewall. You’ll see something like “700x28c” or “26x2.1.” Match the tube to those numbers. Tubes stretch to cover a range — a tube labeled 700x25-32c fits any tire in that width range.

Should I switch to tubeless tires?

Tubeless eliminates most puncture flats because the sealant inside plugs small holes automatically. It’s worth it for riders who get frequent flats. The setup is more involved and best done by a shop if you haven’t done it before.