Fixing a puncture

This article, first published exactly ten years ago in Newsletter 13, is one of the most popular on our website, with almost 10 000 hits to date, and at the time of writing is fourth in Google’s results for this subject.

Given the huge increase in membership over the last ten years, we reproduce this article by popular demand.

This how-to picture story is aimed at anyone who struggles to fix a flat tyre, or who always takes the bike to the shop. It may be a bit tedious, but everyone should be able to fix their own.

A Tools

Pump, replacement inner tube, tyre levers, spanner or whatever you need to take off the wheel, and a patch kit with at least one patch, some glue which hasn’t dried up yet, and a bit of emery paper.

Tools (8k)

B Take off the wheel

For a hub gear, you need to disconnect the cable and take out the delicate indicator rod first. For derailleur gears, select top gear (chain on smallest sprocket). Front wheels are much easier.

Take off the wheel (14k)

C Remove the valve cap

and locknut

Remove the valve cap (7k)

D Get all three tyre levers…

under the bead of the tyre opposite the valve, lined up so that the levers can be hooked on to spokes. On a back tyre, use the face of the wheel away from the gears – it’s cleaner.

Get the three tyre leavers under the bead of the tyre (9k)

E Lift the middle tyre lever first

Hook it onto its spoke to stay put, then use each of the other levers in turn. Then take out the middle lever, and put it further round the tyre to extend the part levered off.

Lift the middle leaver first (8k)

F Slide the lever round…

to finish lifting off the edge of the tyre once it is loosened a bit. Now coax the inner tube out from inside the tyre.

Slide the lever round (7k)

G To find the hole

Usually all you have to do is inflate the tube to twice its natural diameter. The hole stretches with the tube, and even a quite small puncture gives a jet of air strong enough to feel and hear. Only the very slowest leaks need a bowl of water to locate.

Find the hole (13k)

H Find the cause

Line up the hole in the inner tube with the tyre and the wheel. Feel carefully to find the sharp object, if it is still there.

Find the cause (9k)

I Pick out all the broken glass

Check the whole tyre for glass or worse things stuck in it.

Pick out the broken glass (6k)

J Fit the new inner tube

Fit the new inner tube (9k)

Don’t try to patch the old one, yet. Put just enough air into the good tube to make it keep its shape, and fit the valve back into the rim. Feed the tube gently into place all round, and make sure it isn’t crumpled, and the valve isn’t pulling sideways. Start at the valve, and settle the tyre bead over the edge of the rim. Work evenly away from there, and you’ll get more than half way before the tyre seems too tough to keep pushing with your thumbs. Don’t use a tyre lever, though, or you risk poking a new hole in your good tube. Push on the end of the valve stem to make sure the tube isn’t trapped under the bead of the tyre.

K Push the tyre back onto the rim

Push the tyre back onto the rim (6k)

Start again at the valve, and settle the part you’ve already done as far into the well of the rim as you can. Then push at one side of the stuck part with both hands, as in this picture. You’ll gain a few millimetres. Push at the other stuck section. Start again at the valve… until after a few goes, the work gets easier and the tyre settles into place. Check that the tyre has fitted evenly all round, with no bumps or squirming sideways.

L Put the wheel back,

pump up the tyre, and replace the lock nut and valve dust cap.

Put the wheel back (12k)

M Line up the gears

Line up the gears (7k)

For a 3-speed hub, you need to put back and adjust the gear linkage. This means screwing in the delicate indicator rod, connecting the gear cable to it, and selecting second (‘Normal’) gear. Now use the adjusting barrel to line up the end of the plain section of the indicator rod with the end of the wheel’s axle. You can just see both through the hole in the side of the special nut.

N Patch the tube later

Patch the tube later (9k)

Locate the hole again, clean the tube, and roughen, roughen, roughen an area which looks a good bit bigger than your patch. You have to take off all the original smooth surface, because it’s coated with a release agent, to stop the new inner tube sticking to its mould in the factory. The release agent also helps defeat most glues.

O Spread a thin layer of glue…

Spread a thin layer of glue (6k)

over the roughened area. You don’t need much glue, but you do need enough to cover the whole area. Let it dry for a few minutes. Peel off the foil from a patch, and press it hard over the hole in the middle of the prepared area. It should stick firmly and immediately.

P The plastic or paper backing

on the new patch is easier to pull off from the middle outwards. Fold the patch sharply to split the paper. Now let your patched tube’s glue cure for at least a few hours before you use that tube again. Full tyre pressure under a new patch is a good way to make it peel off again.

Remove the plastic or paper backing (6k)

Mark Irving