How to repair a puncture - video
By Hilary Stone and BikeRadar |
Monday, April 7, 2014 7.30am
Knowing how to repair a puncture is an essential skill that every cyclist needs to master. It can be daunting for the inexperienced but only takes a few minutes once you know what you're doing.
In this video, BikeRadar's James Tennant explains how to carry out the task in a step-by-step walkthough, which demonstrates the procedure on a mountain bike.
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Need to stock up on tools before you start? You can purchase Park Tools used in the video at a number of dealers across the UK and internationally.
Here's written instructions for those who prefer them to visual demos.
1 Find the puncture
Starting at the valve, check all the way around the tyre’s tread to ﬁnd the cause of the puncture. Remove any glass or grit that you spot. Even if you ﬁnd one possible cause, continue checking the tyre until you get back to the valve.
2 Remove the tube
Let the air out of the inner tube and push the valve up into the tyre – unscrewing and retaining the valve ring, if ﬁtted. On the side of the wheel opposite the valve, slip a tyre lever under the tyre’s bead and a further tyre lever about 5cm away. Pull the nearer tyre lever (available from all good bike shops) towards you, lifting the tyre’s bead over the edge of the rim.
Continue until one bead of the tyre is completely free of the rim. Pull the tube out. Remove the tyre completely from the rim – with most tyres this can be done by hand unless exceptionally tight.
Note: it's not always essential to remove the tube from the tyre, as the video above demonstrates.
3 Inflate the punctured tube
Inﬂate the tube and listen for air escaping. Passing the surface of the tube over the lips is a favourite trick of mine. If the hole still can't be found, re-inﬂate the tube and pass it through a bowl of water until you spot escaping bubbles. Then dry the tube before proceeding to the next step.
Take care – do not twist a push-fit pump on the valve. The pump should be pushed on straight and pulled off with a single straight pull. The stem nut can easily be broken off if the pump is twisted sideways.
4 Prepare the tube
Select the correct size of patch – use a bigger rather than a smaller patch if in doubt. Roughen the surface of the tube around the hole with emery paper. Ensure that any moulding marks are ﬂattened completely. Apply one drop of tyre cement and spread it thinly with your ﬁnger over a 2cm circle around the hole. Allow to dry. Apply a second thin layer similarly. Once again, allow to dry – the rubber cement will change from shiny to matt.
5 Patch the tube
Inﬂate the tube slightly – this will help to highlight the position of the hole. Firmly press the patch into place after removing the backing foil. If there’s a thin cellophane backing on the patch, it can be left on. Dust the repair with chalk, talcum powder or road dust to prevent it sticking to the tyre casing.
6 Check the casing
Before reﬁtting the tube, double-check the tyre casing from inside for the cause of your puncture. On one occasion after riding a canal towpath with hedge clippings, I found over half a dozen thorns! Placing the tube over the tyre will help to you to discover the position of the puncture. Run your ﬁngertips carefully around the inside of the tyre to feel for the cause of the puncture and remove.
7 Refit the tyre
After repairing the tube and checking the tyre for glass, thorns or any other sharp debris, reﬁt one bead to the rim. Slightly inﬂate the tube and reﬁt it to the rim, putting the valve through its hole ﬁrst. Starting at the opposite side of the rim to the valve, use your thumbs to lift the tyre’s bead (the part of the tyre that connects the rim to the wheel) over the rim. Work around the rim until there’s just one small section of tyre left. Push the valve up into the tyre and then, using your thumbs, ease the remaining section of the tyre’s bead over the edge of the rim.
8 Make final checks
Check that the tube isn't trapped between the rim and the tyre bead. Inﬂate to the point where the tyre feels soft but has maintained its shape. Check that the moulding mark around the tyre follows the rim evenly all the way around. If not, deﬂate a little and ease any high spots down and pull low spots up until the bead is ﬁtted evenly.
Inﬂate to the recommended pressure and check once again that the tyre’s bead is still seated evenly and that the tyre isn't lifting off the rim at any point. Finally, check that the tread is running reasonably straight by spinning the wheel. If not, deﬂate the tyre and start again from the beginning of this step.
Puncture fixing tips
- When taking the tube out of the tyre, note which way the tube was around in the wheel. This will help identify the position of the hole in the tube once the position of the object in the tyre causing the puncture has been found.
- With a ballpoint pen, mark the hole with a cross so you can pinpoint it accurately.
If you don't have any emery paper, roughen the tube by rubbing it against a stone or the road surface.
- For tyres that blow off easily: ﬁt a thicker rim tape or a second rim tape – this prevents the tyre bead sinking into the rim well and blowing off the opposite side.
- For tight tyres: ﬁt a thinner rim tape if possible – this will make your tyres easier to ﬁt and remove.
- Be very particular with your technique. The last section of the tyre to be ﬁtted to the rim should be at the valve. Make sure that the tyre’s bead is pushed as far as possible into the well of the rim. Some very tight-ﬁtting tyres may need tyre levers to ﬁt them. Using VAR 425 special tyre levers will help to prevent puncturing the innertube when reﬁtting the tyre.
Two small holes in a tube placed fairly close together indicate a pinch puncture. This is caused by the tube getting trapped between the tyre and the rim when riding over a sharp object. Tyres not inﬂated hard enough are a frequent cause of this. Check that the tyre’s sidewall isn't cut. If it is, you may need to use an emergency repair – see the ‘Emergency tyre repairs’ section below.
A hole on the inner side of the tube indicates that the puncture was caused by a spoke head. Check around the inside of the rim to ensure that the rim tape properly covers the spoke holes and no spoke end protrudes above the inner surface of the rim. If this happens it'll need ﬁling down.
A less common cause of a puncture is a rough edge to the valve hole rim. The puncture will be at the base of the valve and will not be repairable.
Create your own puncture kit
- Feather edge patches
- Rubber solution
- Pair of plastic tyre levers
- Piece of ﬁne emery paper
- Small adjustable spanner, if using wheels with hex nuts
- Allen key if using Allen-bolt-ﬁtting wheels
- Reliable pump
- Keyring LED – useful if you’re riding in the dark with a dynamo
- Always carry a spare tube too.
Pump aside, all this should pack in an underseat bag.
Check your tyres for cuts in the tread, swelling in the sidewall, or serious wear. Tyres with cuts, swelling or casing visible through the tread must be replaced. Remove any grit or glass embedded in the tread. Check your tyre pressures with a proper gauge. Tyres inﬂated to the correct tyre pressure will have fewer punctures and a longer life. The recommended pressures are normally marked on the sidewall of the tyre.
Use your spare
Repairing a puncture is very difﬁcult in the rain as the patch will not stick to the tube. Instead, ﬁt the spare tube that you always carry! The spare tube is also essential if a tyre blows off a rim, or if the tube is cut by the valve hole.
Emergency tyre repairs
Double over a largish section of heavy duty polythene. Trim off a piece 10cm wider than the gash and 5cm wider than the tyre. Remove the tyre from the rim. Wrap the double layer of the patch around the inside of the tyre casing centred on the slit or cut. With the patch overlapping each side of the casing, reﬁt the ﬁrst tyre bead, trapping the emergency patch.
Fit a new tube if necessary and inﬂate it a tad. Reﬁt the second tyre bead with the patched section last. Check that the patch is trapped at both sides. Reinﬂate the tyre and trim off any excess patch. The patch will be held in place miraculously by the tyre’s air pressure.
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