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How to Fix A Flat Tire

 

By John Andersen

Unless you live next door to a bike store or have a significant other who loves bike maintenance it's a good idea to know how to fix a flat tire on a bike.  If you get a flat on the way to work or while running an errand, you will usually be late.  Fixing a flat is a skill you should learn sooner, rather than later.  Just a tiny bit of planning can make the difference between arriving late, or not at all.

Fortunately, the problem of fixing a flat tire is not a very serious one.  You will find that it takes about half an hour when you are not used to doing it frequently, and 15 minutes when you do it often (such as when you have several children who get flats seemingly on the same ride).  Fortunately a 10 year old can be taught to fix a flat. 

Required Tools

Patience - this page has a lot of graphics...Pump.gif (6895 bytes)

To fix a flat on the road, you need the small handful of supplies pictured above, you should be able to get all of them for under $30.  If you bicycle as a family, not every bike needs a complete kit, but if you use your bike for errands or commuting be sure not to leave home without these items.

Four items are essential: 1) a good lightweight air pump, 2) a set of tire levers, also sometimes called tire "irons" (usually made of plastic), 3) a patch kit, most preferably one designed for bicycle tires, and 4) a spare tube.  

If your bike does not have quick releases on the wheels, 5) a wrench that fits the axle nuts may be necessary.  Sometimes you can get some very cool tools (some are even named "Cool Tool") that combines the wrench and several other bike tools in a single package.

Why are the patch kit and the spare tube both necessary?  I've found it's sometimes quicker to patch a tube than replace it, especially when you can find the damaged portion and patch the tube without removing it from the wheel.

However, other times a tube can not be patched due to a torn seam, multiple holes, or a damaged valve, or large cuts.  Occasionally, (all too often actually)  your glue will have dried up.  Dried glue is the bane of a cyclists existence.  Occasionally you will see tubes of glue on sale separately from the rest of the patch kit.  Snap them up.  Once a tube of glue is opened, it is more likely to dry out, as it is no longer perfectly sealed.  After a few months, it will be useless.

Types of Flats

Sometimes the flat will happen overnight or while the bike is parked. This usually happens when it's time to go home, and it's dark and raining.  This is your indication that you have not pleased the bicycle gods, and you have not been riding enough.  What ever you do, don't take it as a sign you should ride less.

At other times, you will become aware of the tire is getting flat when riding.  Your steering may get squishy (sorry, that's as technical a definition as I can come up with). Or you may just notice it's hard to pedal.

Occasionally, the tire will deflate very quickly, perhaps even blow out.  Usually you will know exactly what caused the problem because it will still be protruding from your tire. 

The hardest leak to fix is a very slow small one because locating the tiny hole can be difficult.  These are usually caused by small pieces of glass just barely protruding thru the tire into the tube.  

Inspecting the Tire

BikeUpsideDown.jpg (35683 bytes)When you get a flat on the road, first get the bike well off of the road and in a safe and comfortable location, and look to see if you can find the hole from the outside of the tire.

Sometimes it helps  to turn the bike upside down and stand it on its seat and handlebars.  The wheel can be slowly turned while looking for signs of a puncture, or protruding glass etc.

Quick Repair

TireLeversInUse.jpg (36313 bytes)If the puncture is found by visual inspection and is not too close to the valve, it's often possible to repair the injury without taking the wheel off of the bike. (If the puncture is near the valve this is harder because the valve stem will get in the way).

First, take two of the tire levers and insert them (both on the same side of the tire) between the tire and the rim about two to inches on either side of the puncture.  Use the thin end of the tire lever for this. The tire levers will be sticking out beyond the tire initially, but in the next step we will pry the tire over the rim and it will end up looking as pictured above.

Prying with both of the levers at once you can pop the edge of the tire off of the rim. Then you can slide the levers farther apart (first one side than the other) to pull just enough tire off of the rim to reach in and pull out the damaged part of the tube.  Don't lose track of the puncture. Some tire levers have hooks on the end for hooking into a spoke, as shown above.  This gives you a free hand.   

If you are able to find the puncture by this method, you probably don't have to remove the tire completely, so you can now jump down to "Patching the Tube."

Removing the Wheel

RotateDerailureRearward.jpg (16725 bytes)If the puncture can't be spotted by visual inspection, or, you decide to replace the tube,  it is necessary to completely remove the tube from the tire.  

The first step is to remove the wheel from the bike.  If it is the rear wheel, shifting the chain onto the smallest rear sprocket will give you some chain slack to work with. 

Either pop open the quick releases or use your wrench to loosen the nuts.   A rear tire may have to be pushed towards the front of the bike before it will lift off. 

Note the arrow in the picture at right, above.  Grab the derailer body and swing it toward the rear of the bike.  Don't try to move the lower pulley (which is at the top-right of the photo because the bike is upside down).  Instead, look for the upper pulley, and grasp there, and swing that joint toward the rear of the bike.  You will see that this will pull the chain out of the way so you can lift the wheel directly out (and stay cleaner in the process).  Remember this trick when it comes time to re-install the wheel.

The front wheel will comer right off once you have opened the quick release or removed the nuts with a wrench.

Getting the Tube Out

Once the wheel is off the bike, remove the tire following the directions under Quick Repair, above.  It's easier if you begin opposite the valve with the tire irons. Completely loosen the one side of the tire all the way around.  Leave the other side of the tire alone.

Then pull the tube completely out. The valve stem sometimes is difficult to remove, but by pulling open the tire you should be able to get it out.

Before you remove it, take note of the orientation of the tube in the tire.  This may save time finding the leak in the tube if you discover the source of the puncture in the next step, inspecting the casing.  

Inspecting the Tire Casing

CheckingTireCasing.jpg (37374 bytes)Before doing anything else, use your fingers to inspect the inside of the tire casing. (Be careful for sharp objects protruding from the tire casing).  Carefully and slowly run your fingers around the inside of the tire feeling for anything that does not belong there.

Sometimes you will quickly find a staple or nail, or shard of glass that caused the flat. Other times, the object that punctured the tire will be gone.  If you do find anything, pull or dig it out from the tread side of the tire, not the inside.  

But it's important to always inspect the casing anyway because if you skip this step, you will very often have another flat within a very few miles. 

Finding the hole by Inflation

If you can't find the hole by visual inspection, try inflating the tube a bit with your pump. The tube should inflate in spite of its leaks.  If not, it is probably too damaged to be repaired.

Pump the tube until it is larger than its original diameter (somewhat stretched). Then hold it near your ear and listen for a hiss as you rotate the tire past your ear.  If the puncture is large enough, you may be able to feel the air rushing out if you hold it near your face. However, if the puncture is tiny, I may need to splash some water on the tube or hold the tube under water to find the leak.

gash.jpg (13661 bytes)Sometimes, you will find a long or deep cut in the casing. Very often patching the tube and continuing to use a gashed casing will result in another flat, quite probably in less than a mile.   Often you can apply your largest patches to the inside of the tire casing, and thereby get hundreds of more miles out of the tire.  Other times, gashed tires are too far gone to be salvaged.  To get home, a favorite cyclists trick is to place a dollar bill, folded in half or quarters between the tube and the tire, so that it covers the gash in the tire.  Paper money has very high bursting resistance.

If the leak is very tiny, only an occasional bubble will escape when the tube is held under water, but then this type of leak seldom forces a repair on the road.  You could just pump it up and ride home.  Being observed giving your inner-tubes a bath in the ditch seldom does much to enhance your image as a cyclist.

MarkingTheDamage.jpg (34774 bytes)Once the puncture is found, be careful not to lose sight of its location. Some patch kits include a piece of chalk or pencil to mark the spot, some cyclists carry a ball point pen to circle the hole, and make a mark on the tire in the corresponding position for careful inspection when done patching.

On some occasions, it is possible that there may be two punctures. This is especially true if you run into a curb or stone.  This is called a snake bite, because side of the rim will pinch the tire leaving two holes that look like a snake bit the tire.

If you find one leak, don't assume that's the end of it. Further, patching a tube and sticking it back into a tire that still has a foreign object embedded in it will result in another flat almost immediately.

Patching the Tube

When patching the tube, the following precautions must be observed. First, the tube must be clean and dry; water and glue don't mix.

Second, the tube must be roughed up a little, using a little tool included in the patch kit; the glue won't bond well to a smooth or dusty tube.  Just use the bit of sand paper or the mini-file to scuff up the area around the puncture.  Scuff an area slightly larger than the patch you intend to apply.  Don't get crazy with the scuffing.

SandingTheTube.jpg (24895 bytes)

Unless you are using  the newer glueless patches (see below), you must apply and spread a little glue - just enough to get the surface wet -- and wait until it almost dries. This glue spot must cover an area slightly larger than the patch. 

It's important to rub the glue around in a little circle just bigger than the patch.  This gives the glue a chance to mix with the rubber, and form a layer of softened rubber that will bond with the patch.  This is how the glue works, it just softens the rubber so that it can stick to another piece of rubber.  The glue itself is not really an adhesive.  This process is called vulcanization.

ApplyingGlue2.jpg (27369 bytes)
If it does not seem tacky enough, you may want to add and spread a little additional glue, and allow it to dry a little. Patching with the glue too wet and runny leads to poor quality patch jobs.  

Note that the patches pictured have a clear plastic backing and a thicker plastic covering the glue side. Peel the thick plastic from the patch, and place the patch on top of the drying glue.  (Sometimes it's a good idea to apply a drop of glue to the glue side of the patch and rub it around and let it get tacky).

GlueAreaLargerThanPatch.jpg (20264 bytes)
Two patches showing glue spot just a bit bigger than the patch.
As soon as you apply the patch press it down strongly with your thumb and HOLD it tightly for a minute.  It is not necessary to remove the thin plastic backing plastic from the patch.  In fact, it is better to leave it on, as shown here, because it keeps the edges of the patch from sticking to your fingers.

Remember, the pressure is important, you are actually driving the molecules of softened rubber of the tube and the patch into, around, and between each other.  The tighter you press the better the patch will hold.

Before putting the tube back onto the wheel,  inspect the patch carefully to see that it has sealed all the way around.  If a gap is found that is not sealed a small drop of glue can be used to seal it tight.

PressPatchTight.jpg (25319 bytes)
Click here for a larger image of a finished patch.
 

wpe27.jpg (10196 bytes)Glueless patches: 

There are several brands of glueless patches, the best are by "Park".   These still require cleaning and roughening the tube surface, but there is no glue to spread. 

Simply peel off the backing, and apply as described above.  These do require an absolutely dry tube.  Don't try to patch in the rain.  Glueless patches work better on mountain bike tires than on high pressure road bike tires.  They look like a thin piece of clear plastic, but they do work quite well.  They are not usually as long-lasting as other patches, but some cyclists have gotten hundreds of miles out of these patches.

Putting the Tube Back In the Tire

If you are doing the quick repair, stuff the tube back into the tire, making sure it's not twisted or unduly stretched, use the tire levers to pop the tire back into place, and re-inflate the tire. Some of the directions below may be necessary, however.

If you have had to remove the entire tube, the task is somewhat more difficult.  Often a tube with just a little air in it to be easier to install than a completely empty tube, especially when installing a new tube.  If the tire is not still partially on the wheel, first put one side of the tire one the rim, all the way around.  Then maneuver the valve stem between the rim and the tire and into the valve hole.  Be sure to do this FIRST, or it will be difficult to get the valve stem into the hole. ReseatingTheValveStem.jpg (32602 bytes)
After making sure the valve is correctly in the hole, start tucking the tube into the tire all the way around, keeping it from getting twisted.  Some tubes will have to be stretched slightly to fit; others will seem slightly too long.  Just distribute the tube evenly around the tire. It's very important to avoid kinks, folds, and twists. Tucking TubeInTire2.jpg (38705 bytes)

Putting the Tire Back On the Rim

PryingTireBackOn.jpg (50526 bytes)Now that the tube is in, it's time to finish putting the tire on.   Sometimes it helps to put the wheel in your lap, (unless the tire is dirty).  Or you may find it easier  to hold the wheel with the valve up and opposite end against the ground.  

It's easier to seat the tire at the valve first, pushing the valve stem back into the valve hole just a little ways, to allow the tire to fit between the stiff base of the valve stem and the rim.  Then you can pull the valve back out of the valve hole and the stiff base of the valve will hold the tire in place as you seat the rest of the tire working your way around the wheel.

Start seating the tire around the rim, using both hands -- and not the tire levers -- to pop the bead of the tire (the lip) into the cavity of the rim.

With many mountain bike tires, you may never need tire levers to re-install a tire.  You can often do it all by hand, pushing the last segment with both thumbs. It's recommend you try it this way first, as using tire levers can actually cause punctures if you pinch the tube with them.

However, you will often have to use the levers to re-install the tire if the job begins to be difficult.  Start using the tire levers again, inserting them where the tire is properly in the rim, and sliding them around the tire so that the un-seated bead gets smaller.  Eventually you will end up with a small segment (as pictured above) where the last little bit of tire remains outside the rim.  This is the most difficult part.  You need the tire levers here.

Warning:  Watch those tire levers.  You can easily "pry" a hole into your newly patched tube.  Be very careful not to allow the tip of the tire lever to apply any pressure against the tube.  This is tricky, because you can't always see what is happening inside the tire. 

Finally, before pumping air into the tire, go all the way around the wheel, pinching the tire from both sides.

Peek into the gap between the rim and the tire. Looking for places where the tube is sticking out between the bead of the tire and the rim.  You must poke the tube back into the tire if you can see it in the gap.   Often two or three strokes of the pump will  assist in this task by adding just enough air to give the tube some shape.  If you let the tube stay between the tire bead and the rim, sooner or later you will have the most spectacular blow-out (it can sound like a gun shot) and your tube will be totally unsalvageable with a long rip.

Pumping it Up

PumpUp,NotDown.jpg (68000 bytes)Now it's time to re-inflate the tire. Before you start, see if you can figure out how too release your brake cable tension.  There are many different kinds of brake cable releases and we can't show all of them here.  If you can't find your brake release or if it requires tools to release the brake tension, then follow the steps under "Attaching the Wheel" BEFORE you pump it up.  Reason: The tire may be too fat to fit between the brakes when inflated.

First pump enough air back in to get the tire slightly firm, usually no more than 8 or 9 strokes of the hand pump. Then look where the tire meets the rim, and follow the rim all the way around the tire.

Is the tire evenly seated on the rim?  Does it seem to be deeper in the rim in some spots than others? (This is easy to tell if your sidewalls are a different color as shown in the picture above).  If it's not even, readjust the tire by pulling it sideways slightly, first to one side then the, other. Push with your thumbs against the side wall and pull with your fingers over the top of the tread. If this fails to even out the depth to which the tire sits in the rim, let some air out and try again. When the rim is next to the bead all the way around the tire it's time to fully inflate the tire.

Be careful with hand pumps like the one shown here.  You should not put too much force on the valve stem, as you can sheer it off.  It's best to "hang" the tire on the pump as shown in this picture, then hold the pump only, never applying force to the tire, just let it hang there with its valve stem pointing DOWN into the pump.

LuxuryofAFloorPump.jpg (30964 bytes)If working at home, you may have the luxury of a floor pump.  This makes the work much faster, and many have a built in gauge.

Remember to read the inflation pressure from the side of the tire and inflate to no more than that pressure. (Well, if the truth were known, many cyclists use a little more pressure than the sidewall says because it reduces rolling resistance.  You should never be tempted to go above 110% over the side wall rating, and even then, only on fairly new tires.)

Without a gauge, how do you tell when there is enough air in the tire?  Feel the firmness of the OTHER tire, and pump the patched one till it's about the same firmness.  If you still can't judge, apply a fair amount of your weight to the top of the Other tire and compare how much it squashes down where it meets the road.  Adjust the repaired tire to match. You can buy a small tire pressure gage at bike stores which is small enough to take along in your bike bag.

 Hand pumps in general are just barely adequate to the task, and it takes a lot of pumping to get the tire inflated.  It is slow going requiring many many strokes, but the smaller the hand pump the less strength it takes. Remember that it's better to spend a few extra minutes than it is to start out with too little air in the tire.  Doing that could cause another snake-bite flat on the first bump you hit.

Attaching the Wheel

ReleasingBrakeCables.jpg (12695 bytes)Remember that above we told you that if you inflated the tire before you mount the wheel on the bike that you may have to loosen your brake cables in order to get it back on.  This is usually accomplished with cable releases on one of the brake pad arms.  Just squeeze the brakes together and pull the brake cable out of the slot with the little tab on the end. There are many different brake release systems, but all usually have a cable release somewhere.  If worse comes to worse, and you can't release your brake tension enough to get the tire back in, just deflate it and pump it up after you mount the wheel.  If you release your brake tension, be sure to restore it before riding.

Some bikes come with bumps where the front wheel attaches (left photo below), others come with metal wheel retainers (right photo).  These are called lawyers lips, or lawyer clips (among other things).  Both systems are designed to prevent the front wheel from falling off of you fail to tighten the front quick-release.  Neither method works well.  Either of these systems make the front wheel more difficult to attach. Higher quality bikes often do not have these features. 

Note that due to these silly inventions, you have to loosen the quick release much more than would otherwise be necessary when removing the wheel, and this sets you up for a mistake when re-installing the wheel.  Make sure you get the quick release above the bumps, or the metal clips fully engaged on the stud before you tighten the quick release.    See "How To use a Quick Release".

LawyerBumps.jpg (4132 bytes) Lawyerclips.jpg (5160 bytes)

On the rear wheel, the chain makes for a more difficult re-installation of  the wheel.  It will be easier if you make sure the chain is on the smallest sprocket as you ease the tire into place.  Remember to rotate the derailer out of the way as was explained above. 

Be sure to carefully bolt the wheel back on or to Properly lock the quick releases.  A common problem after reinstalling a tire is for the rear wheel to start rubbing against the left-side stay. It might look right when you mount it, only to start rubbing after a few pedal strokes.  This is because the rear quick release was not tight enough and your chain pulled the right side of the axel forward, turning the wheel to the left.  You have to get off the bike, loosen the quick release, straighten the wheel and tighten it more firmly.

Before you get back on the road, check your brakes to make sure that the quick releases or cables have been properly reattached. Pickup your tools, and the old tube if you replaced it.  Not only because you don't want to litter, but also because there are several good uses for old bike inner tubes. 

Keeping an Eye On It

After installing a tire and riding away, watch it carefully for a while. Sometimes there is more than one leak, and sometimes you can cause another leak by rough use of the tire levers.  It's disheartening to have to stop and patch all over again, so remember to be careful with the tire levers.  Ride home to your floor pump or to the nearest bike shop and check your tire pressure with a proper gauge.  

Avoid gas station air hoses.  The gauges are seldom accurate.  They are also set for car tires (25 to 30 pounds) which is not usually sufficient for bikes,  - OR - they are set for trucks (125-150 pounds) and will blow the tires right off your bike.  (No, I'm not exaggerating, I've seen this done).

Patching tires is a hassle, and it's dirty work. Once you do it, you will gain two things:  The first is new confidence of being able to handle the situation by yourself.  The second is an uncanny ability to spot broken glass by the little twinkle it reflects while you are JRA.  (Just Riding Along).

One more point:

Before you hit the road, with your new patch kit and pump, you may want to read How to Convert A Pump.

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08/16/11
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