This week we’ll tackle what is, without a doubt, the most common maintenance procedure that you'll do on a bike. It may even be the ONLY one you do, although this series is intended to change that!

The number one thing that will stop you from finishing, or at least cost you lots of time, in your event is if you have a bike problem and the most common problem will be a tyre problem. We are going to tackle this in the comfort of the workshop with a full set of tools but the reality is that you generally do it by the side of the road... ...in the rain! The processes are the same and it's well worth practicing in the comfort of the home environment so you know what to expect when it happens for real.

You'll need some or all of the following tools and parts:

• Work stand
• Tyre levers
• Patch kit
• Air pump or hand pump or air compressor
• 14 or 15 mm spanner for non-quick-release type wheels that use outer axle nuts

The wheel must first be removed in order to replace the tube and tyre -- we have seen people try to do it without, honest!! If possible, begin by mounting your bike in a stand. Out on the road no stand will available and so the bike should be laid on its left (non-derailleur) side when the rear wheel is removed.

Removing the wheel

Taking a front wheel out is easy, just release the brakes and the quick release, undo the skewer a couple of turns if required to clear the "lawyers lips" (those little metal stubs designed to stop the wheel falling out when you forget to do up the quick release) and the wheel just drops out. Rear wheels, on the other hand, have all the drive train to get around first:

• Change the gears to the inner chain ring (front) and smallest (rear) sprocket. This makes it easy to get the chain off and on.
• Release the brake pads. On a Shimano-equipped bike this will be a lever on the brake calipers, on a Campagnolo-equipped bike it’s a little pin on the shift/brake levers.
• Release wheel quick-release by pulling the release lever outward. If necessary, loosen the quick release adjusting nut.
• For wheels with axle nuts, loosen both nuts with your 14/15 mm spanner outside of the dropouts.
• For rear wheels, pull back on the rear derailleur to allow the sprockets to clear the chain. Lower the wheel, guiding it down through brake pads and forward to clear the chain and gears.

Removing the tyre and tube

Tyres can be tightly fitted to the rim. Use tyre levers to remove the tyre from the rim. Do not use a screwdriver, knife, or other sharp object as this might damage the tyre or the rim. Fully threaded valves may have a locking nut next to rim, this will need to be removed before you can removing the tube.

• Deflate the tyre completely. Even a small amount of air left in the tube can make it more difficult to get the tyre off. For best results, press downward on wheel while depressing the valve.
• Push one bead of tyre toward rim centre. The tyre bead will be pressed tight against rim. Pushing it inwards loosens the bead from the rim. Repeat on other bead.
• Start opposite the valve and engage one tyre lever under the bead of the tyre. Engage the second lever ½" (25-50mm) from first lever then pull both levers toward spokes to lift the bead off the rim. Disengage one lever. Move it two inches (5cm) along the rim and engage lever in the bead. Pull the lever to lift the next section of bead off rim. (1)
• Repeat engaging the lever until the bead loosens. Then slide the lever along the rim under the bead. (2 & 3)
• Starting opposite the valve, pull inner tube from tyre. Lift the valve from valve hole and remove the tube from the wheel. (You can also inflate the tube at this point and see if you can find the puncture and then check the tyre at this spot.)
• Remove the tyre from the rim, so you can fully inspect the tube and tyre, it is best to remove both completely. (4 & 5)

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Checking the inner tube

When repairing a flat tyre, always inspect the tyre and tube carefully to locate the cause of failure. This will help prevent future flats from the same cause.

• Inflate inner tube if possible.
• Inspect for air leaks by holding tube close to the sensitive skin of your lips or by holding tube near your ear to hear leaks. Move the tube around its circumference. If these steps do not work, submerge tube in water and watch for bubbles at the hole.
• If you plan to repair the inner tube, use a marking pen to mark hole. Make four marks, one to each side of hole. Do not mark close to hole, as the mark may be sanded off.

The type of cut or hole in the tube will help determine the cause of the flat. Common causes of tyre and tube failures are:

• Cut at valve core, commonly from misalignment of tube in rim or riding with low pressure. Be sure tube is mounted straight in rim and check pressure before rides.
• Blow out causing a large shredded hole. These are usually not repairable. Check tyre and rim as well for damage.
• Hole on inside edge of tube indicates a problem inside the rim, such as from rim strip failure, a protruding spoke or other sharp object inside the rim.
• A long cut or rip may indicate a tyre blow out. Typically this is not repairable. Use care when seating tyre during installation.
• A single puncture or small hole is commonly from a thorn, wire, or small nail. These may be repairable. Check tyre as well for thorn, etc.
• Double slits, often called a "snake bite" are commonly from a rim pinch. The tube was pinched between the rim and an object in road/trail. Increase air pressure or use wider tyres.
• V-shaped slits may be from nails or glass.

Checking the tyre

It is important to always inspect the tyre as well as the inner tube. The cause of the flat, such as a nail or piece of glass may still be embedded in the tyre or tread. Inspect both the outside of the rubber tread and the inside of the casing.

• Inspect outside of tread for protruding nails, pieces of glass, thorns, or other objects, or damage Squeeze any cut to look inside for objects such as slivers of glass. (1)
• Visually inspect inside of tyre casing for nails, glass or debris. Carefully feel inside with fingers for any items.
• Inspect sidewall for rips, holes, or damaged rubber and casing. (2 & 3)
• Inspect wire or fabric tyre bead for damage.
• Check the rim and rim tape for any damage.

Fitting the inner tube and tyre

Re-fitting the tyre and inner tube can be a hard job if you don’t follow some key points.

• After you have check the tyre for any problems or damage re-fit one edge of the tyre beading back onto the rim. If you look at your tyre you will find a makers logo or some other information printed on the tyre. For a faster fitting, and as a way of being able to refer a puncture location on the tube to the corresponding place on the tyre, place the tyre maker’s information over the valve hole on the rim. Remember also to check the tyre for a rotation arrow which will indicate which way the wheel should rotate when fitted as not all tread patterns work properly the wrong way round. (1)
• Using your hand pump or just blow into the valve to inflate the new inner tube with just a little air to give it some shape. (2)
• Fit the inner tube valve into the rim looking for the tyre maker’s information to find your valve hole. (3)
• Seat the partly inflated tube into the tyre so you have it located under the tyre all the way round.
• Now you have one side of the tyre and the tube located over the rim with just the other side of the tyre left to be fitted back on the rim.
• The next step is key for your tyre fitting. Push the valve up in the rim to compress the tube inside it which will help you to locate the bead back into the rim. Ref-fit the bead for 5cm each side of the valve hole. If you have a valve with a locking ring fit this just finger tight at this point as will hold the tyre in place at the valve hole and help keep it on the rim. (4 & 5)
• From the valve, work round the rim holding the top of the tyre and pushing the tyre bead back into place until you come to the last 10 or 15 cm. (6)
• At this point it helps to have strong hands. You need to push the top of the tyre with both thumbs pushing the tyre on by 2cm on each side of the rim. If you find that this is too hard on your hands let the air out of the inner tube which will help you roll the tyre on the rim. (7 / 8 / 9)
• Don’t use your tyre levers to re-fit the tyre as you will have a much higher chance of puncturing the inner tube with the lever.
• Now you have the tyre fitted to the rim partly re-inflate the tyre and work your way round it making sure the bead is properly located in the rim all the way around. (10)
• Fully inflate the tyre to the maker’s maximum pressure marked on the side off the tyre.

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Re fitting the wheels

Now the tyre is back on it’s time to fit the wheel back into the frame.

• Hold the frame from the rear of the bike with your left hand and slot the wheel back into the rear stays.
• You will now have the chain over the rear cassette. Slot the chain over the cassette so the low chain is under the cassette and the upper part of the chain is sitting on the small cog on the rear cassette. (1)
• If we have the rear gear set in the middle of the rear cassette at this point it is much harder to re line the back wheel into the drop outs and fully fit the wheel. (2)
• Now line the wheel up with the rear brake and lower the frame down by pushing down on the rear gear cage. (3)
• Now the wheel is back in the drop out, line the wheel up in the frame so you’re not hitting the rear chain stays and start to tighten the quick release and then lock the lever closed. The quick release lever has an 'open' and 'closed' marked on the lever so make sure you push it in so that it is showing 'closed'.
• Now the wheel is back in and working remember to reset the brake quick release and change up a few gears before you set off.

Valve types

There are two common types of valve stems on bikes, the Schrader (car or MTB type) and the Presta (road type). A Schrader valve core can be removed if necessary. This is rarely required, but a valve can become stuck and cause a slow leak. A loose core can also be the source of a slow leak. A special tool is required to remove or tighten the core.

The Presta valve is common on road bikes and on higher priced MTBs. Presta stems are nominally 6mm (¼”) diameter, thinner than Schrader valves. At the top of the valve stem is a small locknut, which must be undone before air can enter the tube. To deflate the inner tube, unthread the locknut and epress the valve stem to deflate. To inflate the tube, unthread the locknut and tap the valve to ensure it is not stuck before inflating. Always remember to do the locknut up! Presta valve inner tubes come with different length valves, the deeper your rims the longer valve stems you'll need.

Repairing an inner tube

Simply replacing the punctured inner tube with a new tube is always the safest and most reliable procedure. However, it is possible in some cases to repair a small hole in an inner tube. If the hole is quite large, it may not be possible to repair. When in doubt, replace the tube.

• The Park Tool Super Patch Kit uses pre-glue patches. There is no tube of glue to leak or dry up and the Super Patch is much smaller then a repair kit from old.
• Check for a punctured inner tube when you find the puncture make the spot with a pen.
• Sand down the spot on the tube with the puncture with sand paper this will help the patch take hold.
• Give the patch some time to stick and then inflate the tube to check the patch is working fully. You now have a fixed tube.

Road side tools and spares

For any trip out on the road you should have the following items with you so that you can at least deal with a puncture. This should apply regardless of whether it’s a training ride or race day.

• Two inner tubes (check you have the right size and valve type to mach your wheel...)
• Two yre levers
• Small puncture repair kit or patch set
• Multi-tool with allen keys and a chain tool
• Valve extenders (if you have deep aero rim wheel)
• Two CO2 gas cartridges or a mini pump.

Other items you could also have in the rear seat pack would be the following.

• Latex gloves (keeps your hands and kit clean)
• Money (for food or a call home for help)
• Nutrition (gels or bars also carbohydrate or electrolyte powder or tablets)

Kevin Worster owns and runs a mobile bike service and support unit called The Cycle Doctor. An experienced bike mechanic with over 20 years in the cycle industry, Kevin ran the Cannons professional cycle team and has been mechanic to members of Britain's Olympic triathlon team. For more information about the services he provides, see his website: www.cycledoctor.co.uk