How to Replace an Inner Tube
First off, make sure you have the right equipment at hand. To fit a new Inner-Tube, you will need:
- Repair Stand (optional – but makes the job a lot simpler)
- 2-3 Tyre Levers
- Air Pump (either Presta or Shrader valve – or both! Depending on what valve you are dealing with)
- Wrench – (For non-quick-release wheels)
Removing the Wheel from the Bike
To start the repair- you must first remove the wheel from the bike. If possible, begin with putting the bike in a bike stand. If no stand is available, being careful with the bike, turn it upside down, and put it on its Saddle and Handlebars.
1. Shift derailleurs into smallest gears (inner gear on front derailleur, and outer gear on rear derailleur) This will make the chain as slack as possible, which makes it a lot easier when removing the rear wheel
2. If you have rim brakes, release them, to allow the wheel to fit through.
Release the quick-release lever by pulling it outward from the wheel. If necessary, turn anti-clockwise a few revolutions, while holding the other side of the skewer, to allow more movement of the wheel. For wheels with axle nuts, loosen both nuts outside of dropouts.
If removing the front wheel: Guide wheel down and out of the fork (or up, depedning on which way up the bike is)
If removing the rear wheel: Pull back on the rear derailleur to allow cogs to clear chain. Lower wheel, guiding it wheel down, through brake pads and forward, to clear chain and derailleur. (Again, do the opposite of lowering if the bike is upside-down)
Before attempting to remove the tyre from the rim, make sure you have fully deflated the tube inside.
Do not use any kind of sharp object E.g. screwdriver, knife etc, as this could damage the tyre or rim. Fully threaded Presta valves may have a locking nut on them, securing it to the rim. Loosen and remove locking nut before deflating.
Removing the Tyre from the Rim
1.Push the tyre bead to the centre of the rim, this will loosen the tyre from the rim, repeat this process for the other side.
2.Insert one tyre lever under the bead of the tyre, so it lifts the bead above the rim. Insert the second lever 2-3” away from the first lever.
3.Once both levers are holding the tyre above the sidewall of the rim, remove the first lever, and move further down the bead a few inches again. Repeat this process until you have successfully gone round the entire rim.
4.Push the valve up through the rim, and pull it out of the tyre. Then working your way round the wheel, remove the entire inner tube from the wheel.
5.When repairing a flat tyre, it is always best to fully inspect the tyre and rim for any obvious signs of puncture causes, to prevent the same issue re-occurring. To do this, it is best to remove the tyre from the rim completely.
This can be done by holding the wheel and rim separately, and pulling the remaining tyre bead over the sidewall of the rim, until the tyre is completely removed from the rim.
Inspecting the Inner Tube
1.Once you have the tube out of the wheel, inflate it until it is twice its normal width.
2.Inspect for air leaks by holding tube close to the sensitive skin of 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.
4.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.
•Leaky valve core, tighten with a valve core tool. More common with Schrader type valves, but also possible on some Presta valves.
•Blow causing a large shredded hole. These are usually not repairable. Check tire 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 tire blow out. Typically this is not repairable. Use care when seating tire during installation.
•A single puncture or small hole is commonly from a thorn, wire, or small nail. These may be repairable. Check tire as well for thorn, etc.
•Double slits are commonly from a rim pinch. The tube was pinched between rim and object in road/trail. Increase air pressure or use wider tires.
•V-shaped slits may be from nails or glass.
Inspecting the Tire
As well as inspecting the inner tube, it is also important to check the tyre as well. The course could just be a nail, or glass, which is no longer in the wheel. But often, small bits of glass or thorns can get embedded in the tread, which need to be removed before fitting a new inner tube. So inspect carefully, both the outside of the rubber tread and the inside of the casing.
1.Inspect outside of tread for protruding nails, pieces of glass, thorns, or other objects. Squeeze any cut to look inside for objects such as slivers of glass.
2.Visually inspect inside of tire casing for nails, glass or debris. Wipe inside of casing with a rag, or something that will protect your hand from sharp objects. Also Inspect sidewall for rips, holes, or damaged rubber and casing.
4.Inspect wire or fabric tire bead for damage.
Rim Strip and Rim Cavity
To form the wheel rim, there are spoke nipples, which hold the spokes in place. Inside the rim you will see a strip of tape circulating around it. The strip protects the inner tube from sharp edges in the base of the rim and from spoke ends and nipples that might puncture the tube when inflated.
This tape can eventually perish, causing the nipples to be exposed to the inner tube. To repair this, you can either buy new rim tape, or use electrical tape as a budget alternative.
If you choose to use electrical don’t patch the rim where the exposed nipple is. Instead, tightly wrap the tape around the rim, in the same way the rim tape lays. Do this a 2-3 times for added protection.
The rim strip should be wide enough to cover the bottom of the rim, but not so wide it interferes with the seating of the tire bead.
Inspect the rim strip whenever changing a tire or inner tube. Look for tares and rips, and make sure rim strip is centred over the nipple holes. (Refer to the image above for correctly placed Rim Tape)
Generally, there are two types of valves that will appear of bicycle wheels; Schrader and Presta. The Schrader valve is common on cars and motorcycles; it is also found on many bicycles. Schrader valves have a small pin inside the valve, which is on a spring. When pressed, the valve will open, and the inner tube will deflate. TO press this, you will need something thin such as a small Allen key. Schrader compatible pump fittings press on the internal stem with a plunger, allowing the tube to be filled.
The 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 will remove and or tighten the core.
Presta valves are more commonly found on higher-priced bicycles. Presta valves are noticeably different in shape, as they are a lot thinner, and longer than Schrader valves. At the top of the valve, there is a tiny screw-nut, which has to be loosened before air can enter the tube.
To deflate the inner tube, unthread the locknut, and press it in; you can do this with your finger.
To inflate the tube, unthread the locknut and tap the valve to insure it is not stuck, and then attach the Presta-headed pump, then the tyre can be inflated.
Presta valve tubes come with different length valves. The longer valve stems are needed for the deeper aerodynamic rims.
The rim valve hole should match the valve of the tube. It is possible to use the smaller Presta valve in a rim intended for the larger Schrader by using an adapter sleeve.
Installing Tyre and Tube on Wheel
1.Look on the size wall of the tyre for directional arrows. Some tread patterns have specified rolling directions for maximum rolling resistance. Other tyres, including slicks generally have no actual rolling direction, so these can be placed any way on the rim.
2.Inflate the inner tube, with a small amount of air, just so it holds its shape.
3.Install one bead of the tyre onto rim, working it on with your hands, taking note of the direction of the tyre.
4.Install the inner tube inside the tyre and rim, starting by inserting the valve it to the rim valve hole.
5.Once the tube is correctly placed inside the tyre, begin to install the remaining tyre bead back onto the rim. Try to avoid using tyre levers for this stage, as you can end up trapping the inner tube between the tyre and rim.
6.Once the tyre is completely on the rim, push the valve up, in to the rim, leaving just enough to grab hold of, and then pull it back down again. This makes sure that there is no area of the valve trapped inside the tyre bead. Then attach the pump head to the Valve
7.Slowly begin to inflate the tyre to the recommended PSI, which will be written on the size of the tyre wall. Look for a small molding line above bead. This line should run consistently above rim.
8.Inflate to full pressure and check with pressure gauge. For fully threaded valve shafts, re-install the locking nut, if any. Do not use wrench or pliers to tighten nut. Tighten finger tight.
9.Inspect both sides of tire for bead seating and for any sign of the inner tube sticking out. Re-install if necessary.
Installing Wheel on Bike
The wheels must be properly mounted to the bicycle frame. Misalignment can result in problems with shifting and bike handling. If the wheel is not securely mounted in the dropouts, it may come out when the bike is ridden, possibly causing injury to the rider.
Quick release wheels use a hollow hub axle fitted with a shaft, a lever that operates a cam mechanism, and an adjusting nut. The cam puts tension on the shaft and pulls both the cam and the adjusting nut tight against the dropouts. This tension is what holds the wheel securely to the frame.
The adjusting nut determines the amount of tension on the quick release lever and cam. Lubricate the cam mechanism if it appears sticky or dry.
The quick release is fitted with two conical shaped springs. The small end of the spring faces the axle, and the large end faces outward. These springs make the wheel easier to install. If one or both springs become twisted or damaged they may be removed. The springs serve no purpose once the wheel is tight on the bike.
Disc Brake Note
Bicycles using disc brakes at the hub need special attention to skewer use. Rim brake systems (Dual Pivot, Linear Pull, Cantilever, Sidepull, etc.) tend not to apply significant pressure on the axle. Disc brake systems are mounted on the fork and apply a load on the rotor, which is attached to the hub. There is an outward load on the hub axle that tends to push the axle out of the dropout.
It is especially critical the skewer is properly and fully secure on forks with disc brake systems.
Thanks for reading this guide. We hope it's helped you to resove your issue of a flat tyre.