Puncture

How to fix a puncture on a wheel utilizing an inner tube

Tools needed

• Sandpaper -- Patch kits include it, but I recommend replacing those with a durable textile based good one, in 2x5cm size (better handling)
• Patch(es) -- You can buy them in bulk quantity in bicycle shops. My favourite brand is Rema Tip Top
• Rubber "glue" (cement) -- Any brand will work
• Permanent or ball pen
• (Optional) Wrench or other keys for wheel removal
• (Optional) Tyre levers -- can be substituted by a pair of teaspoons with blunt edges - Never ever use a screwdriver!
• (Optional) A piece of wire or a similar pointed object -- I use a paperclip with a straightened end
• (Optional) Nail scissors
• (Optional) Access to water
• +Spare tube -- It never hurts to carry one, and it's still faster to replace than to patch...

Situations

• Puncture
• Cut or tear - Repairable only below 1cm and is not recommended to be kept for a long period
• Material defect - Goto new tube.
• Valve failure - This is not covered here. Goto new tube.

Procedure

1. Find a spot for the repair. A clean solid flat surface is recommended (desk, bench, fence or at least a safe curb side).
2. Locate and remember the location of the puncture while the wheel is in the bicycle, if possible.
3. Always check for further punctures!
4. Remove foreign objects if possible (thorns, nails etc)
5. Undo rim brakes and shift to the smallest gear in the rear if applicable
6. [Wrench] Remove wheel, remembering how the chain was routed etc. Don't lose any of the bolts, washers etc.!
7. Lay the bike down, making sure parts like brakes or drivetrain don't touch the ground.
8. Remove valve cap and ring and put them in a safe place.
9. Deflate wheel completely.
10. [Tyre levers] Unhook tyre from the rim on one side. You should be able to do it by hand if the edges of the tyre are seated in the deepest part (middle) of the rim.
11. Remove tube by remembering puncture location if it has been identified before.
12. Check the inner surface of the empty tyre with your fingers for foreign objects carefully so you don't hurt yourself. Most of these tend to pierce the tyre in the center area where the most pressure is put on the ground. Thorns can hide in the material.
13. [Piece of wire] Push thorns through the tyre until you can pull them out by hand.
14. If you are sure the tyre is clean, preceed to fixing the flat.
15. [Pen] Mark visible puncture on the tube (if you don't have a pen, mark it with your nails, for example - this is crucial) with a cross so that it extends beyond the place of the patch
16. When the puncture is not apparent or you suspect more, inflate the tube completely, making it swell wider than the tyre itself. If there's enough pressure, the puncture will start letting air out, no matter how small the hole is. If you can't find it, slowly pull the tube in front of your nose/mouth until you sense the escaping air. When you find one, seal it with a finger put on it and continue looking for more until you went completely around.
17. [Water] As a last resort, you can examine the tube under water and watch for escaping bubbles, but it makes a mess.
18. [Scissors] If there's a cut, it is advisable to rounden the ends of the cut to prevent tear, and stick something into the tube to prevent the two sides sticking together.
19. [Sandpaper] Roughen/sand up the area around the puncture. The prepared area should be larger than the patch itself and velvety black. Make sure you blow/shake off rubber dust.
20. [Cement] Put a drop of "glue" on the puncture and spread it across the prepared area with the nose or the tail of the glue tube in a circular motion.
21. Wait for the cement to dry up (1 minute)
22. [Patch] Pull the metal foil from the patch and put it carefully on the cement. Lay the tube like a ribbon on the clean flat surface and apply pressure on the patch, making sure the complete patch is pressed down like a stamp. Hold it down for a minute.
23. Immediately after applying the patch, carefully peel the upper foil from the patch. The patch may want to come off, so be very careful and slow, try to start peeling on a spot that seems to be glued perfectly.
24. Push back the edge if it starts to come off. You can apply a bit more cement there. If the whole patch wants to come off, it is better to discard it and start it over.
25. Apply the rest of the patches if necessary.
26. Inflate the tube now, only slightly until it gets a round shape. Check for escaping air and re-do the patches if necessary.
27. Put it back into the tyre, starting from the valve.
28. Hook the tyre into the rim, starting from the valve and avoiding pinching the tube between the rim and tyre.
29. Inflate the tyre until it finds its place in the rim - make sure it is centered properly. When it's half inflated (still a bit soft, at 1 bar), rotate the wheel and keep pushing/tilting the tyre sideways to ensure proper seating.
30. Put the wheel back in the frame and inflate it to the desired riding pressure. (I assume you arrange the chain, derailleurs and brakes afterwards.)

Methods for avoiding punctures

• Use higher pressure
• Avoid thorns by keeping an eye on the road
• Don't ride through roadside debris
• Use a sealant like Stans Notubes
• Choose a tyre with a good puncture resistance (refer to tests/forums)
• Choose a tyre with an advertised anti-puncture feature, but bear in mind that it has a weight penalty
• Switch to tubeless + sealant combination (common practice on MTB, but needs rim compatibility and/or conversion kit)