Punctures

Punctures are inevitable. The pressure inside the tyre is higher than the pressure outside, and the world is full of sharp things. Don’t worry if you’ve never fixed a flat before though; it’s not as difficult as people make out. And, like learning to tie your shoelaces, it gets easier with practice.

There are ways to reduce the number of punctures you get. Occasionally you pick up a sharp object that cuts straight through tyre and tube and causes a flat, but often objects take a while to work their way through the casing of the tyre. Before you set out, check both tyres: raise each wheel off the ground in turn, spin each slowly and pick out foreign objects. Maximum and minimum pressures are printed or stamped on the tyre sidewall. Make sure the tyre is inflated to at least the minimum suggested pressure to reduce the chance of snakebite flats (caused when pressure from, say, a rock edge, squeezes two symmetrical holes in the tube against the sides of the rim). If you like running at very low pressure, choose a tyre designed to take it. These tyres have a thicker sidewall, which won’t fold over itself and pinch the tube.

Problems with punctures at or around the valve can also be caused by low tyre pressures. If there isn’t enough air in the tyre, it won’t sit firmly against the inside of the rim. The tyre will creep gradually around the rim, dragging the tube with it. The valve is held in place in the valve hole, so the tube around it becomes stretched and tears easily, ripping the valve out of the tube. Check your tyres regularly for large cuts as well – under pressure, the tube will bulge out of these cuts and burst instantly.

Some people suffer from punctures more than others. If you feel unfairly blighted, consider investing in puncture-resistant tyres. These have an extra layer of tough material incorporated into the carcass of the tyre under the tread, which helps to stop sharp things working their way through. They do make the tyre a little heavier, but it’s worth it if you find punctures irritating. Also, think twice before buying tyres that proudly proclaim their weight on the packet – there will always be a compromise between weight and puncture-resistance.

Fixing a puncture by fitting a new tube in a standard tyre

We prefer to carry a spare tube as well as a puncture kit. It’s much quicker than messing about waiting for the glue to dry or hoping that a glueless patch will hold. They don’t weigh much or take up much room. Don’t forget to check your tyre carefully before you fit the new tube and to remove whatever caused the flat in the first place. Take the punctured tube home with you, repair the puncture in the comfort of your own home and carry the tube around as your new spare. Once a tube has five or six patches, it’s time to retire it.

If you’re out and about, try to calculate how quickly your tyre is going down. Maybe, if you’re on your way home, you could pump it up and get there. Doesn’t work that way very often, though! More likely, you’re going to have to fix it.

Punctures (1)

Step 1 : If you have rim brakes, you need to release them to get the tyre out easily. For V-brakes, pull the black rubber boot off the end of the noodle, squeeze the brake units together and pull the noodle out and then up to release it from its nest. For cantilever brakes, squeeze the brake units together and push the cable nipple down and out of the slot in the unit. For calliper brakes, turn the release knob, then remove the wheel.

Punctures (2)

Step 2 : Turn the bicycle upside down. Undo quick-release skewer. Unless you have a fancy skewer set, do this by folding (not turning) the handle over the axle. If you’re unsure how to use quick-releases safely, read the section on them before you go any further. For the front wheel, undo the nut on the opposite side of the wheel several turns to get past the lawyer tabs (which stop the wheel falling out of the dropout slots if the skewer comes loose).

Punctures (3)

Step 3 : The rear wheel is a little trickier to remove than the front. Stand behind the bike. With your left hand, pull the body of the derailleur backwards with your fingers and push the cage forwards with your thumb, as shown. This creates a clear path, so that you can lift the rear wheel up and forward, without getting tangled up
in the chain.

Punctures (4)

Step 4 : Inspect the outside of the tyre before you go any further to see if you can work out what caused the puncture. There may be nothing – you may have had a snakebite puncture or the escaping air may have ejected whatever caused the puncture. If you find something sharp, prise it out. (Later you also need to examine the inside of the tyre)

Punctures (5)

Step 5 : If there’s any air left in the tyre, expel it. Remove the valve cap. For Presta valves (long and thin), undo the little thumb nut on top of the valve and press it down. For Schraeder valves (car-tyre type), use something like a key, to push down the pin in the middle of the valve. Stand the wheel upright on the ground, push down and massage the tyre. The more air you get out now, the easier it is to get the tyre off.

Punctures (6)

Step 6 : Each side of the tyre is held on by an internal wire, or Kevlar hoop, called the bead. This is smaller than the outside of the rim so the tyre stays on when you pump it up. To remove the tyre, lift enough of the bead over the sidewall of the rim. With care, this can be done by hand. Hold the wheel upright facing you. Work around the tyre, pushing the side closest to you into the dip in the middle of the rim. This will give you enough
slack to pull the bead off.

Punctures (7)

Step 7 : With the wheel still upright and facing you, pinch a 10cm (4 inch) section of the side of the tyre nearest you with both hands. Lift this section up and over the rim, towards you. Hold it in place with one hand and work around the tyre with the other gradually, easing the bead over the rim. Once you’ve got about a third of the tyre off, the rest will come away easily.

Punctures (8)

Step 8 : If you can’t get the tyre off by hand, you need to use tyre levers. Starting opposite the valve, tuck one tyre-lever under the bead in line with the spokes. Fold it back and hook the tyrelever under the spoke to hold it in place. Move along two spokes and repeat with a second tyre lever, then repeat with a third tyre lever. Remove the middle tyre lever, leapfrog one of the others and repeat, continuing until you can pull that side of the tyre off with your hands.

Punctures (9)

Step 9 : If the valve has a little nut screwing it to the rim, undo it. Reach inside the tyre and pull out the tube. Leave the other side of the tyre in place.

Toolbox

  • Spare tube – check that the valve matches the tubes on your bike
  • Puncture kit – backup in case you get more than one puncture
  • Pump – make sure it works on your valve type. A pressure gauge is useful
  • Tyre levers – two is standard, take three if you’re not confident
  • Spanners – any spanners you need to remove your wheels
  • Tool pack – carry these separately, so you can find them in a hurry
  • Warm clothes – a hat to put on to keep you warm while you fix your bike – you can get cold quickly when you stop riding

Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES