How to Fix a Flat Tire (Tube + Tubeless): Step-by-Step, Plus Common Mistakes to Avoid

Learn how to fix a flat bicycle tire whether you run inner tubes or tubeless sealant. This guide covers the exact steps, what to carry, how to find the cause fast, and the most common mistakes that lead to repeat flats.

Are you dry on the basics? Here’s a summary:

• Flat from a tube (puncture) → remove wheel → remove one tire bead → pull tube → find the cause → cover it or replace the tube → carefully reinstall (no pinches) → inflate slowly and make sure the bead is seated all the way around the rim.
• Flat from a tubeless tire with sealant (puncture) → find leak in the tire → rotate the wheel to get sealant to pool at the hole → inflate and shake/roll the wheel to try to help sealant plug it → if it won’t plug, use a plug → reinflate and re-check → if the cut in the carcass is large or located in the sidewall, install a tube to get home and expect to replace the tire.

Most of repeat flats succeed from skipping the “find the cause” step, leaving debris in the tire, pinching the tube with the lever, and/or riding on a bead that is not seated and/or with low pressure. An almost flat tire can flatted again quickly because the rubber doesn’t want to seal at the rim, it will bulge enough for the tube inside to push right out through an unseated bead. More minor, tires might have a small flat spot caused by the bead not being properly seated.

A flat tire is almost always an easy fix—if you treat it like a little quick investigation and not merely a swap of parts as-is. Your goal is not just to get air back in the tire! You also want it not to suffer the same puncture (or, the same installation mistake) twice running to get to a new trailhead this afternoon.

## First: Know What You’re Riding On! (Tube vs. Tubeless)

Inner tube setup: There’s an inflatable tube inside the tire. Flats require tube change or patch. Tubeless setup: There is not a tube in there. The tire seals to the rim (the rim tape + the tubeless valve are usually necessary), and a liquid sealant inside plugs or seals small holes and gaps while you ride. Not sure?

Now let out the remaining air and squish the tire sidewalls together; on tubeless, you may even hear the slosh of sealant inside and you’ll often see a tubeless valve with a removable core. If you pull off one tire bead and there’s a tube, then it’s a tube setup.

What to Carry (Minimal vs. “I Don’t Want to Walk” Kit)

A practical flat-fix kit for most riders

Item	Tube setup (recommended)	Tubeless setup (recommended)	Why it matters
Tire levers (2)	Yes	Sometimes	To remove/install tight of ink bed, without killing your hands.
Pump or CO2 inflator	Yes	Yes	You can’t check you’ve fixed the flat without putting air in it.
Spare tube (correct size + valve type hardtail z2 dirt 1 e mountain)	Yes (1–2)	Yes (1)	Even tubeless riders must sometimes “throw in a tube” to get home.
Patch kit	Yes	Optional	Saves a ride if you get multiple flats and/or run out of tubes. Park Tool and REI outline how to do. (parktool.com)
Tubeless plug kit	No	Yes	Plugs bigger punctures that sealant won’t seal.

Device/Item	Requires carrying?	Strongly recommended for this use?	Notes
Valve core tool	Optional	Strongly recommended	Removing the valve core can help seat tubeless tires and inject sealant; also helps fix clogged/slow valves. (stans.com)
Tire boot (or emergency boot material)	Yes	Yes	Gets you home when the tire casing is cut (especially sidewalls). REI mentions emergency boot ideas. (rei.com)
Small rag + nitrile gloves	Nice to have	Nice to have	Sealant and roadside grime can make everything slippery.

How to Fix a Flat Tire with an inner tube (Step-by-Step)

If you’re fixing a tube flat out in the field, replacing the tube is often going to be faster than patching. You can patch the punctured tube a few days later in the comforts of home (or patch immediately if you’ve only got one tube). REI and Park Tool both emphasize checking your tire/tube carefully so you don’t flat again right away. (rei.com)

1. Shift to the smallest rear cog (rim rear flats): This makes removing the wheel easier and relieves chain tension.
2. Remove wheel: Open the quick release (or loosen the thru-axle). If you have rim brakes, open the brake quick release so the tire can pass through. (Checking bike specifics for exact steps)
3. Fully deflate tire: Even if mostly flat, press on the valve to let out remaining air. REI shows Presta vs. Schader. [how to remove and apply sealant/install tube]. (rei.com)
4. Unseat one bead of tire: Work your hands around the rim to push the bead into the center channel.
   Use tire levers only if needed; start across from the valve to reduce the chance you’ll damage it. (rei.com)
5. Remove the tube: Pull the valve out first, then pull the tube out. Don’t yank the valve out of the tube at an angle or you may pull the valve out or tear the tube at the base of the valve. (rei.com)
6. Find the cause (don’t skip this):
   • Look for glass/thorns it may have picked up in the tread.
   • Cautiously feel the inside of the tire for sharp debris.
   • Check the rim bed/tape for any exposed spoke holes or sharp edges.

   REI and Park Tool both recommend systematically checking the tire, tube, and rim. (rei.com)

7. Decide: patch it or replace it:
   • Replace the tube if it has a torn valve, a long slit, or multiple holes.
   • Patch it if it has a small puncture and the tube is good otherwise. (rei.com)
8. If patching: rough it up, glue it, and patch it properly:
   • Mark the hole.
   • Roughen it up.
   • Coat it with vulcanizing fluid and let it set until tacky.
   • Apply the patch and press it.

   Park Tool lays this out and notes that you don’t patch tubeless tires with tube patches. (parktool.com)

9. Reinstall the tube without pinching it:
   • Put one bead of the tire all the way onto the rim (if it came off).
   • Soak up a little air to inflate the tube just enough to hold its shape.
   • Put it in the rim with the hole for the valve straight through the hole in the rim and then tuck the tube into the tire all the way around.
   • Finally, put the second bead on starting across from the valve.
   • Before inflating, press on the sides and walk the tire around, checking both sides that the tube is not trapped under the bead. REI calls this out specifically as a must-do check. (rei.com)
10. Inflate slowly, watching and verifying that the bead is seated. Inflate at low pressure and check both sides that the bead is seated evenly. Park Tool specifically calls out checking the bead seat line (that molded line near the bead) for consistent presence around the rim. (parktool.com)
11. Reinstall the wheel and do a quick function check before you ride away: axle is seated and not going to fall out of the frame, your quick release/thru-axle are locked in securely and the brake is working fine. REI lists out a pretty nice quick rear-wheel-reinstall checklist. (rei.com)

That hole in your tube:

What shape says about the culprit

Single small hole in the tread area: Generally glass/remains of thorn or wire. Find and remove whatever makes that shape from the tire tread.
Two holes in parallel (“snakebite”): Classic pinch flat, often from low-pressure or hitting an edge (like a pothole or curb). Must pump up the tire more and/or look for a wider tire.
Close to valve hole: Generally crooked valve or a tube tugged into such shape by low pressure, or perhaps sharpstice all by a hole in the edge of the rim with jagged edges. (and be reminded, a crooked throatle can bring on flats later.) (parktool.com)
Long split: Old tube, pinched tube during install, thorough battering honest of beat/ or bump in edge.

### Finally! Modern Approaches to Fixing Tubeless Flat Tires (Step-By-Step)

Tubeless flats fall into three categories: (1) a small puncture that the sealant can handle, (2) a puncture that may need a “plug,” or (3) too much damage for the tire and thus it (or the bike) requires a tube. Stan’s explains basic tubeless setup/troubleshooting and offers up how they do plugs for a repair. (stans.com)

Maker Warning(s): Some tire makers suggest against DIY repairs. For instance Continental says if their sealants don’t reliably seal the damage, change the tire. They further state they don’t recommend repairs whatsoever. So it’s wise to follow the guidance of your tire and rim makers on your specific model. (continental-tires.com)

Find the leak: Listen for hissing/spray. Note where it is in relation to the bottom of the rim. If you see sealant spraying, stop the wheel so you don’t fling sealant all over (oops).

Try a sealant-first fix (the fastest):
Rotate the wheel so the puncture is at the bottom (this is where the sealant would pool if you stopped moving).
Inflate it fairly well (moderate pressure).
Lightly shake/roll the wheel so that the sealant can strike out towards the hole on the leading edge as the wheel rolls along the pavement.
This is that “do nothing but help the sealant school of fixing.” In many cases, it will seal a hole, especially in a small one.

If it won’t try to plug it:

• Remove the object (thorn, nail) if it’s still in the tire.
• Insert a tubeless plug according to the instructions for that tool. Some are designed to push a rubber plug into the hole and allow the sealant to finish the seal. An example of that style of tool would be something like Park Tool’s TPT-1. (parktool.com)
• Trim some of the excess plug material back if necessary (but only when you’re sure it’s airtight).

4. If the tire won’t hold air:
   • Inspect the rim/tire interface (bead) for a poor seat.
   • Inspect the valve area for leaks (loose valve nut, damaged valve base, or tape problems).
   • If you’re roadside: slide a tube in as a get-home solution (steps below).
5. Get-home: install tube in tubeless:
   • Remove the wheel.
   • Break one bead off the rim.
   • Pull out the tubeless valve stem. (You can’t run a tube when the tubeless valve is in place).
   • If you cut through the casing of the tire, install a tire boot between the tire and tube.
   • Install the tube as you would do for a normal tube, being extra wary of pinching it.
   • Inflate, and ride conservatively until home. Then inspect/replace your tire.

CO2 and tubeless sealant: what to do after you emergency inflated

CO2 will get you rolling in a jiffy, but some sealant makers suggest swapping out the CO2 for regular air after the ride. Stan’s, specifically, suggests CO2 is best for emergencies and that prolonged exposure can reduce sealant life (separation/decreased lifespan). A practical routine is to use CO2 to get you home and then deflate and refill with a floor pump. Soon after you get home, check your
sealant level.(stans.com)Common Mistakes To Avoid (and Which Bring Repeat Flats):

• Skipping the cause check: If you don’t remove the glass/thorn from the tire, your new tube (or new layer of sealant) may go down right away after install. “Both REI and Park Tool make it a point to stress this careful inspection. (see here and here))
• Running your fingers carelessly along the inside of the tire: Bits of sharp glass or thorn can cut you if you vigorously feel around inside the tire.
• Using tire levers aggressively (pinched tube): When you lever the bead on and accidentally trap the tube, it can get cut in the process. Park Tool suggests using your tire levers as a last resort and being extremely careful not to pinch the tube. (see here))
• Starting bead removal / installation at the valve: You increase the chances again of damaging the valve or pinching the tube against the valve stem. “Starting at the valve stem increases the chances of pinching the tube near the stem or cutting the stem itself. When removing the tire using tire levers, start opposite the valve stem,” says REI. (see the full repair process here))
• Inflating before checking to see if tube caught under bead: The #1 “I fixed it and it instantly-popped” scenario is: the tube is caught under the bead. “If that is the case the only way to fix it is to deflate, determine where the tube is caught or pinched, and inflate again,” says REI. (see the full process to repair again here))
• Ignoring the line that indicates the embedded mold line that should fall into the well of the rim. “Inconsistent bead seating can cause wobble, loss of air pressure or even blow-offs at higher pressure. When finished inflating, look closely at the molded line on the tires’ bead seat. It should be easy to see when your bead settles into the rim’s well. “…..When remounting a worn tire, do check that the molded line still matches the rim edge,” says Park Tool. (see here) Bead not seated properly? Inflate until it is, right? Overinflate? Uh-huh. If the bead is not seated then stop inflating, and carefully deflate, delube it with soapy water (not oils/grease) and then try again making sure your second attempt stays within limits. Parent site, Park Tool, suggest soapy water to help seat the bead.
  (parktool.com )
• Patching mistakes (tube setups): Not roughening and/or cleaning the tube as well as not waiting for the glue to get tacky, or touching the glue with grimy fingers compromises patch adhesion. Park Tool covers patch prep. (parktool.com )
• Tubeless plug misuse: Plugging a sidewall cut or deep gash isn’t likely to hold. Sidewalls flex a lot; treat this like a get-home scenario and get prepared to replace the tire.
• Forgetting that tubeless still needs maintenance: Low sealant volume or dried-out sealant makes that “tubeless self-sealing” marketing slogan moot. Stan’s warns that the life of sealant depends on conditions and regularly-packet into the tires . (stans.com )

## Troubleshooting: If It Still Leaks After You ‘Fixed’ It

Fast diagnostics when a flat fix doesn’t hold

Symptom	Most likely cause	What to do next
Tube goes flat right away	Debris still in tire, OR tube pinched breaking bead	Remove one bead again. Carefully inspect inside tire and check tube must for fresh “bite” of the bead.
Slow leak from valve (tube)	Valve base torn, OR angle of valve stem is wrong didn’t ‘seal’	Replace tube; hopes it’s no accident that you won’t reinstall with a crooked valvee of that tire?Park Tool warns that a crooked valve causes trouble you don’t want to face. (parktool.com )
Losing air overnight (tubeless)	Low sealant, leak at the valve, OR problem with rim tape	Tighten valve; top up or refresh sealant; if it still leaks, then roll up your sleeves. Stan’s mentions considering re-taping if tape isn’t sealing they’ve apparently been there too. (stans.com)
Sealant sprays everywhere and won’t stop	Hole too big/ cut in casing	Try a plug. If it’s a sidewall cut or long gash, install a tube + boot to get home, then replace tire.
Tire bead won’t seat (tubeless or tube)	Dry bead/rim, bead stuck in rim channel, or airflow too low	Use a bit of soapy water on bead, remove valve core for more airflow (tubeless), and inflate within safe limits. Stan’s notes removing the valve core can help with difficult seating. (stans.com)

## When to Replace Instead of Repair

• Replace the tube if: the valve is damaged, the puncture is a long split, or you have multiple close-together holes (patches won’t reliably stick). REI suggests replacement when damage is extensive or the valve is damaged. (rei.com)
• Replace the tire if: the casing/sidewall is cut, cords are showing, the tread is worn through, or the bead is damaged.
• For tubeless: if sealant won’t seal and a plug won’t hold, it’s tire replacement territory. Continental explicitly states you should change the tire when sealant doesn’t reliably seal damage. (continental-tires.com)

## A Quick Prevention Checklist (So You Flat Less Often)

1. Check tire pressure before riding. Underinflation leads to pinch flats (tube) and burping/rim strikes (tubeless). Continental recommends checking pressure before every ride. (continental-tires.com)
2. Quick tread glance to see if embedded glass (for example), and pull it out before it works deeper.
3. Refresh sealant periodically (tubeless): Just like with tubes, sealant can dry out over time. Stan’s lists the normal lifespan and explains a variation based on usage conditions. (stans.com)
4. Make sure your rim tape is in good shape (tubeless): If you have repeated slow leaks, it’s often more a tape/valve issue than the tire.