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29 May 2012 2 comments

The Definitive Guide to Puncture Repair

Uncategorized Bicycles Urban Cycling
By Alasdair
The Definitive Guide to Puncture Repair
[caption id="attachment_7777" align="alignleft" width="640" caption="Oh man, what a let down!"][/caption] Ppssssssssssssssscchhhhhhhhhttttt. Darn. Sooner or later every cyclist is likely to experience an unplanned tyre deflation episode. Whether due to a lack of dilligence and subsequent navigation through a patch of broken glass, or even a wanton stab through the sidewall from an irate property owner whose fence you've adorned regardless of signs to the contrary, the outcome is equally irksome. No need to bestride your bike before reinflation has been achieved. Granted, it is possible to ride on a flat tyre, but this is likely to lead to further damage to the bike, and quite possibly even the rider. Given the unlikelihood of experiencing a puncture outside a friendly bicycle shop during opening hours, you're going to have to get your hands dirty. Or at least, as dirty as your bicycle wheel. If your steed is a filthy neglected object, your mitts will get just as grimy. A clean bike is easier to repair just as it is more pleasant to ride. Your mood now will be dependent upon your state of preparedness. If you lack a spare inner tube or a puncture kit, and in the absence of a pump, you're learning a salutary lesson. During the long trudge home, reflect on the importance of foresight and resolve to obtain either, both or all items forthwith, and always to keep them about your person on future cycle rides. [caption id="attachment_7778" align="alignleft" width="640" caption="puncture kit contents and mini pump"]puncture kit contents and mini pump[/caption] If you have the aforementioned items handy, congratulate yourself. Now you just need to know how to use them properly. Get off the street, out of the way of traffic. It is probably raining, so look for a dry doorway or bus shelter to get you and ideally your bike out of the wind and the downpour. Identify which wheel has suffered the flat. If both have expelled all air, you may now curse loudly. If you thought you were clever because you have a spare inner tube in your tricot pocket, now would be the time to consider carrying a pair. Your road bike is equipped with tubulars? Downer, but alas yours is a predicament for another article. If you've got a spare tube handy, you probably know how to fit it and get on your way, so get off with you. The following notes are intended for those with puncture kit, pump, and the will to repair their own puncture. Look for debris sticking out of the tyre. If you see a nail, tack or similar, you've probably found the culprit. Note the location before removing it, so as to be better able to precisely pinpoint the hole(s) in the inner tube. If the front tyre is flat it might be easier to remove the wheel from the fork and repair it off the bike. A flat rear might be more complicated, and if you lack sufficient skill to perhaps disengage a hub gear and/or back-pedal brake linkage, you might well be better off attempting to fix the flat with the wheel in situ. If your axles are fastened with axle nuts, you will need an appropriate spanner or wrench. If you have quick release skewers, loosen it/both but do not fully remove and dismantle. The little conical coil springs that locate the skewer centrally have a habit of pinging off into the gutter or undergrowth. [caption id="attachment_7780" align="alignleft" width="640" caption="Opening a quick release front wheel skewer"]Opening a quick release front wheel skewer[/caption] You will probably need a pair or more of tyre levers to get one bead of the tyre sidewall off one side of the wheel rim. Teaspoon handles may serve if you're improvising. Better tyre levers feature a notch with which to locate the first one securely over a spoke. Inspect the inner underside of the tyre and sidewalls for debris. A fingertip feel around the inner carcass might help to locate strands of wire or protruding shards or embedded glass, but be careful not to cut or stab your pinkys. [caption id="attachment_7781" align="alignleft" width="640" caption="Using tyre levers, lift one tyre bead off the rim adjacent to the puncture"]Using tyre levers, lift one tyre bead off the rim adjacent to the puncture[/caption] [caption id="attachment_7779" align="alignleft" width="640" caption="Find and remove sharp objects protruding into the tyre, such as this staple"]Find and remove sharp objects protruding into the tyre, such as this staple[/caption] Pump air into the tube whilst looking and listening for the puncture. (It helps to be away from noisy traffic when you do this) Once you've located it, hold the tube between finger and thumb just adjacent to that spot, and don't lose it! If you have a ballpoint pen, mark the spot. [caption id="attachment_7783" align="alignleft" width="640" caption="Mark the spot where the tube is punctured"]Mark the spot where the tube is punctured[/caption] Match your patch to the size of hole you need to repair. Better puncture repair kits contain a selection of different sized patches. Smaller patches are for individual holes, and are especially suitable for use on narrow inner tubes such as those fitted to road racing bicycles. The larger patches are to repair longer slits rather than individual pinprick holes. Use the smallest patch you can to properly cover the whole hole. [caption id="attachment_7784" align="alignleft" width="640" caption="Big patch for gashed tube, medium patches for medium tubes, and small patch for road bike tubes"]Big patch for gashed tube, medium patches for medium tubes, and small patch for road bike tubes[/caption] Your puncture kit should also contain a small piece of sandpaper and/or a small round metal grater. The latter is not for grating mini-cheese onto small salads, rather it is for suitably abrading the tube. Roughen the inner tube at the spot where you will be attaching your patch. Your roughened area should be the same size as the patch you will be fitting there. Slightly stretch the tube over your forefinger and pull it taut with adjacent finger and thumb, and sand/grate until the surface of the inner tube is roughened and coarse. Obviously, don't abrade right through and worsen the hole. Your objective is to provide a coarse surface area for maximum adhesion of the patch. Abrasion increases the available surface area and thus strengthens the bond between tube and patch. [caption id="attachment_7785" align="alignleft" width="640" caption="Stretch the tube over the forefinger and abrade with sandpaper"]Stretch the tube over the forefinger and abrade with sandpaper[/caption] [caption id="attachment_7786" align="alignleft" width="640" caption="Roughened area the size of the patch to be applied"]Roughened area the size of the patch to be applied[/caption] Apply enough of the vulcanising solution (contrary to popular misconception, it actually isn't glue) to retain the patch properly. Too little or too much will prohibit correct adhesion. A pea-sized blob is enough for a small patch the size of a €1,- coin. Spread the vulcanising solution evenly, and quickly, leaving no big blobs or bare areas where you want the patch to stick. [caption id="attachment_7787" align="alignleft" width="640" caption="Pea-sized blob of vulcanising solution, enough for a small patch"]Pea-sized blob of vulcanising solution, enough for a small patch[/caption] [caption id="attachment_7788" align="alignleft" width="640" caption="Spread the solution to cover an area the whole size of the patch you want to apply"]Spread the solution to cover an area the whole size of the patch you want to apply[/caption] If you use too much there is the likelihood of the tube glueing itself to the inner tyre carcass on re-fitting, which you really don't want to have happen. Use just enough goo (no really, it isn't glue!). If you do squidge too much vulcanising solution out of the tube, look for a little rubber tube in your puncture kit. In addition to allegedly being necessary to inflate some sort of arcane French tyre valve the likes of which I have never encountered, if you roll this little 1cm long rubber pipe back and forth across the firmly affixed patch it will magically lift excess vulcanising solution from around the adjacent area. Now wait for the solution to 'cure' or 'go off'. Don't succumb to the temptation to affix your patch straight away. Patience will reward you. The ideal length of time to pause before applying the patch is approximately that required to enjoy a cigarette. A habit I cannot recommend. The small area of vulcanising solution should cease to glisten and gain a dull filmy quality. Firmly and squarely press the appropriately sized repair patch you've selected over the puncture point, whilst holding the inner tube in the same ever-so-slightly stretched state rolled over the forefinger and held by ring finger and thumb. Press firmly from the middle of the patch out towards the edges. [caption id="attachment_7789" align="alignleft" width="640" caption="Firmly apply the patch, again stretching the tube slightly across the forefinger"]Firmly apply the patch, again stretching the tube slightly across the forefinger[/caption] The finest repair patches have a 'feathered' outer edge, often orange in colour, and a thicker darker middle section. They are backed with a square of thin transparent carrying film. Stretch the tube and patch to split this film in the middle of the patch, and peel it in two halves away from the centre out toward the joggled edges. Don't try and lift off the transparent film from the outer edge, this will lift the feathered edge and in all probablity render the patch useless, requiring you to start from square one. Last patch in the puncture kit? Definitely don't lift the backing from the edge, remember to crack and peel from the middle! Or just leave the backing film there, nobody will ever see it. [caption id="attachment_7790" align="alignleft" width="640" caption="Split the carrier film in the middle and peel outwards toward the feathered edge"]Split the carrier film in the middle and peel outwards toward the feathered edge[/caption] [caption id="attachment_7793" align="alignleft" width="640" caption="This is a pretty good patch job. Not 100% at the top edge, but not bad."]This is a pretty good patch job. Not 100% at the top edge, but not bad.[/caption] Test inflate the tube before refitting the tyre, to ensure that the patch has repaired the puncture. Repeat the above process as often as necessary to regain the air retaining integrity of your inner tube. Do not attempt to refit the tyre with a fully inflated tube. A little air in the inner tube, rather than a floppy and totally shapeless absence thereof, can make refitting the tyre somewhat easier. You want the tyre bead to be firmly and evenly re-fitted to the rim, without pinching the inner tube and creating a new puncture in the process. Work the sidewall with your thumbs around the entire circumference to seat the tube and tyre properly, and without any pinch spots where the tube becomes trapped between the sidewall and the wheel rim. Ensure that the tyre valve is emerging perpendicular to the rim, which is to say not protruding at an angle, which would most likely lead to irreparable damage to the tube itself around the base of the valve. [caption id="attachment_7791" align="alignleft" width="640" caption="Refit the tyre bead over the rim, and ensure the tube is not pinched in between"]Refit the tyre bead over the rim, and ensure the tube is not pinched in between[/caption] [caption id="attachment_7792" align="alignleft" width="640" caption="Two strong thumbs are preferable to tyre levers, which can pinch the tube and cause another puncture"]Two strong thumbs are preferable to tyre levers, which can pinch the tube and cause another puncture[/caption] Reinflate, without exceeding the maximum pressure as stated on the tyre sidewall. Or as hard as you generally like your tyre to be. Remember that using an air compressor, such as those at your local filling station, at which the pressure guage is more than likely not to be trusted, is at your own discretion. Stop before the easily overinflated tube bursts with a shocking and deafening explosion. [caption id="attachment_7802" align="alignleft" width="640" caption="If, having packed away your puncture paraphenalia, the tyre still looks like the image on the right, you may now cycle on"]If, having packed away your puncture paraphenalia, the tyre still looks like the image on the right, you may now cycle on[/caption] Refit the wheel to the bike frame if you had to remove it, ensuring it is straight and does not foul against the frame or fork. Tighten securely. If you have quick release levers, ensure you close them correctly, with the ear tucked in alongside the fork tube or frame tube, and pointing neither down at the road or out into thin air, either of which positions can lead to involuntary and of course dangerous opening of the lever by obstacles. Finally, having fixed your puncture and packed up all your puncture repair paraphernalia, you're probably going to have grubby mitts. Time for some waterless hand cleaner, by the manufacturer of the best puncture kits. Great fun, simply squeeze a bit onto your palm and rub. It lifts the dirt out of the skin creases and leaves your hands feeling moisturized. [caption id="attachment_7799" align="alignleft" width="640" caption="Waterless hand cleaner, from the people who make the better puncture repair kits"]Waterless hand cleaner, from the people who make the better puncture repair kits[/caption] [caption id="attachment_7801" align="alignleft" width="640" caption="Hey presto, clean(er) hands, no need for water or towels, great stuff!"]Hey presto, clean(er) hands, no need for water or towels, great stuff![/caption] If you seem to be suffering a spate of punctures your tyres have very possibly seen enough mileage and thus worn too thin. Puncture resistant tyres incorporating protective Kevlar reinforcement are ever more flexible and no longer the uncompliant and unresponsive disappointment of yesteryear. Never-the-less, regard bold marketing claims of 'total puncture resistance' with scepticism, and be advised it is probably smart to carry your puncture kit and pump with you anyway. As a final note, sometimes puncture kits used to contain a small cube of hard compacted chalk, that in my experience was neither useful for marking the spot where the air is escaping from the tube, nor for dusting over excess vulcanising solution to prevent the tube adhering to the tyre. So what the heck was it for? Why haven't I had one in recent puncture kit purchases? Answers gratefully received. Ride on.
Comments
"..an unplanned tyre deflation episode". What a great euphemism!
Al. 23 May 2016 at 16:31
It is my understanding that the chalk is provided to prevent any vulcanising fluid from adhering to the inside of the tyre thereby causing the inner tube to rip under load.
The biggest problem is identify the source of the puncture. You can try listening. You can try immersing the tyre in water when partially inflated to spot the air bubbles or you can feel your way round the partially inflated tyre in the hope of detecting an air leak in that way. You need to mark puncture position quite clearly.
Tom Lavin 23 May 2016 at 16:31