[Ken Kifer's Bike Pages]
ARTICLE: How to Fix a Flat
Being able to fix a flat tire on a bicycle is a simple but necessary skill for the cyclist who wants to feel free to travel and to commute, especially since filling stations won't inflate bicycle tires any more, let alone inflate them.
Questions How long does it take to fix a flat? What tools are required? What are tire irons? Why is both a patch kit and a spare tube necessary? What are the different kinds of flats? What kind of leak is the hardest to repair? What task should be performed before removing the tire from the bike? How is a quick repair possible? How are tire levers used? How does one remove the wheels? How is the tube removed? Why is the tire casing inspected? Why is the tube inflated after it is removed? What precautions must be followed in patching a tube? Should one use glueless patches? How is the tube reinstalled? How is the tire put back on? What problems can be discovered after the tire is back on? How do quick releases change how the tire is put back on? How can the rear wheel go back on incorrectly? Why should you check the brakes? How can a properly patched tire go flat?


Bike Pages Home Page

The Cyclist Lifestyle

Bike Commuting and Transportation

Bicycle Camping and Touring

Cycling Health and Fitness

Bicycling Advocacy

Bicycle Traffic Safety

Basic Skills for Cyclists

Cycling Humor and Tales

Bicycling Surveys and Statistics

Links to Other Cycling Sites

Comments on This Page

How to Fix A Flat Tire on a Bicycle

NOTE: For a humorous version, see Zen and the Art of Fixing a Flat Tire

On several occasions when I have been talking about one of my bike tours, I have been interrupted by a frantic question of "How many flats did you have?" Although this seemed like a rude and unimportant question to me, it may have seemed quite necessary to the asker. After all, if you can't fix a flat tire, it's impossible to depend on a bicycle for transportation, especially in these days when gas station attendants won't pump gas, let alone tires. Fortunately, the problem of fixing a flat tire is not a very serious one. I can usually fix a tire and be riding again within five to ten minutes. Here are the directions for doing so. I would recommend that you pretend you have a flat in order to first practice the procedure at home rather than on the road.

Required Tools

Four or five items are needed to fix a flat: 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. The tube of glue is sealed with foil inside the plastic cap, so it's a good idea to add a toothpick to your patch kit for this purpose. The toothpick can also serve to mark the location of the hole.

You may ask, "Why are the patch kit and the spare tube both necessary?" It's usually quicker to patch a tube than replace it; however, sometimes a tube can not be patched due to a torn seam, multiple holes, or a damaged valve. Occasionally, you will not be able to find the leak, the glue will have dried up, or rain will prevent the application of a new patch (which must go on dry).

Types of Flats

Flats belong to different types depending on how they occur. Some happen overnight or while the bike is parked. At other times, you will become aware of the flat when riding because the tire starts bumping on the ground. Occasionally, the tire will deflate very quickly, perhaps even blow out. In the case of a flat while riding, stop immediately to prevent further damage to the tire, tube, and rim.

Those who have never repaired a bike tire think that a small leak is better than a large one, but the opposite is usually true. The easiest puncture to fix is a large piece of glass or nail stuck in the tire. In these cases, I don't have to even take the wheel off of the bike. The hardest leak to fix is a very slow one because locating a tiny hole can be difficult. If I have a slow leak, one that causes the tire to deflate only after a long stop or overnight, I usually just inflate the tire and continue using it, as a slow leak is very difficult to locate. Or, if I prefer to solve the problem immediately, I usually replace the tube rather than trying to find such a small leak.

Inspecting the Tire

The first task, after getting the bike well off of the road and in a safe and comfortable location (out of the sun during the summer), is to visually inspect the tire. One common method is 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. Some people use their fingers to feel for a piece of glass or a nail while rotating the tire, but this method involves the risk of getting cut, so go slowly.

A Possible Quick Repair

If the puncture is found by this method and is not too close to the valve, it's often possible to repair the injury without taking the wheel off of the bike. I rotate the wheel so that the puncture is upward. Then I 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.

Looking at a tire lever from the side, it's easy to see that one end is curved and thinner to make easy insertion and better prying possible. Prying with both of the levers at once and pulling them apart at the same time, I pop the edge of the tire off of the rim. Then I work the levers farther apart until I have room to pull the tube out, which I do carefully, so I don't lose track of the puncture.

NOTE: Having complete this step, you can jump to "Patching the Tube"

Slow Repair

If the puncture can't be spotted by visual inspection, it is necessary to completely remove the tube from the tire. To do so, the wheel must be removed from the bike. If a flat is on the front wheel, I might pull the wheel off of the bike without turning the bike upside down, but my usual practice is to balance the bike on its handlebars and seat.

If the flat is on the rear wheel of a derailleur bike, the next step is to shift the chain to the smallest rear cog. I do this before turning the bike upside down by holding the rear wheel off of the ground and shifting while turning the crank, but this is awkward without practice. Less difficult is to shift while the bike is upside down, being careful that you are moving the correct lever.

Then open the quick release or use a wrench to loosen the wheel nuts. A rear tire may have to be pushed towards the front of the bike before it will lift off, and the derailleur can be pulled to the rear to clear it.

The front tire will lift right off unless your bike is equipped with lawyer lips: these contraptions are designed to keep the wheel from falling off in case the quick releases are not locked. You usually have to unscrew the quick release a bit more to get past these.

Getting the Tube Out

Once the wheel is off, remove the tire following the directions under Quick Repair above, except begin on the part of the wheel furthest from the valve and completely loosen the one side of the tire all the way around. Then pull the tube completely out. The valve stem is sometimes difficult to remove, so removing the tire is sometimes necessary. It's important to preserve the orientation of the tire and tube, as sometimes an inspection of the inside of the tire will discover the cause of the leak.

Inspecting the Tire Casing

Before doing anything else, use your fingers to carefully trace the inside of the tire casing to feel for any piece of glass or wire or perhaps a thorn that may have punctured the tube. If such a object is there and is not found, it will quickly puncture the tube again. If such an object is found, its location will indicate the location of the leak in the tube. Any pieces of material inside the casing must be removed as they could cause further punctures.

Please note that a rare flat is caused by the spokes being too long and puncturing the tube from the side next to the rim. If you have tightened your spokes recently, feel the rim tape or check under the rim tape at this point but, even if a protruding spoke is found, don't assume a spoke caused the flat until you inspect the tube as well.

Inflating the Tube for Inspection

Now that the tube is off out of the tire, inflate it with the hand pump. If the tube can't be inflated, it is probably too damaged to be repaired. The tube might have a torn seam, a leaking valve stem, or multiple punctures. In these cases, the spare tube is essential. In other cases, pumping a little air into the tube might quickly locate the hole. Otherwise, I pump the tube up until it is much larger than normal size, which provides extra pressure to help me locate the leak.

Then I listen to and feel around the tube. If the puncture is large enough, I can feel the air rushing out. Often if I hold it near my face, I will feel it on my lips. 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. If the leak is very tiny, only an occasional bubble will escape when the tube is held under water, so I never try to repair the very slow leak while on the road. Instead, I will pump in more air and keep going, or use my spare tube.

Once the puncture is found, it is easy to lose sight of its location. Some patch kits include a piece of crayon to mark the spot, but I have never found it useful. I sometimes mark the spot by just tightly placing my fingernail on it, but this does not always work either because I sometimes have to move around. For this reason, I suggest carrying a toothpick with the patch kit. It can be used to punch a hole in the foil top of the glue bottle, and by sticking it into the hole, it can mark the location, so the leak can be easily found. A ballpoint pen can also be used to mark the hole.

On very rare occasions, it is possible that there may be two punctures. Patching one and not the other accomplishes nothing of course, so it pays to check if there is any reason to be suspicious.

Patching the Tube

When patching the tube, the following precautions must be observed. First, the tube must be dry, as 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. Third, unless you are using glueless patches, you must apply and spread a little glue -- just enough to get the surface wet -- and wait until it almost dries. This glue must cover an area slightly larger than the patch. Then add and spread a little additional glue, and allow it to dry a little. Unpeel the patch, and place it on top of the drying glue, and press it down strongly with your thumb. I like to use the tire lever to press it down even harder. Before putting the tube back into the tire, I inspect the patch carefully to see that it has sealed all the way around. If it has not, the tube will leak.

Glueless Patches

As an option, one can purchase some clear plastic patches which have their own glue. The advantage is that they go on a little quicker; the disadvantage is that they have a poorer reputation for holding. I have used some without any problem, and then I purchased some Bell patches, and they wouldn't hold long enough for me to inflate the tire. If you're in a hurry, it might be best just to put in a new tube.

Putting the Tube Back On

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 reinflate 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. I find a tube with 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, I first put one side of the tire on the rim, all the way around. Then I hold the tube with the valve between my fingers and my thumb behind, and I maneuver the valve up under the tire and into the valve hole. After making sure the valve is correctly in the hole, I then 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 be slightly too long: these longer tubes are the hardest to install. I often use 26" tubes with 27" tires for this reason.

Putting the Tire Back On

Now that the tube is in, it's time to finish putting the tire on. I like to put the wheel in my lap, with the valve away from me, unless the tire is dirty or I have nice clothes on. In those cases, I hold the wheel with the valve up and opposite end against the ground. I always seat the tire at the valve first, lifting the valve a little (pushing the valve stem back into the valve hole) to allow the tire to fit under it. Then I start seating the tire around the rim, using both hands -- and not the tire levers -- to pop the tire onto rim. However, at some point -- depending on the tightness of the tire -- if the job begins to be difficult, I start using the tire levers again, sliding them around when I can and levering the tire at other times.

When the tire finally pops back into place, I adjust it somewhat to make sure it is evenly on the wheel; otherwise the wheel will be slightly out-of-round (the thump-thump-thump as you ride, though, comes from not putting the tube in correctly). A trick to remove the thumping is to completely empty and then reinflate the tube several times. This may allow the tube to relax into position if it is not twisted.

One caution that I have always read is to carefully inspect to make sure that none of the tube is pinched between the rim and the tire. After doing so for years and never finding a problem, I decided that this is a worthless step and forgot about it. However, I use small diameter tires, and I have heard that it is a real problem with fat tires.

Reinflating the Tire and Reinstalling the Wheel

In inflating a tire, I put a little air into the tire and then check to see if the line along the side of the tire and the rim line up all the way around. If not, I let out some air and use my hands and sometimes the tire irons to readjust the tire.

It's often easiest to go ahead and fully inflate the tire off of the bike. However, if your bicycle lacks quick releases for the brakes, the brakes may block the tire from going back on. The simple solution here is to fully inflate the tire only after it is back on the bike.

Be sure to carefully bolt the wheel back on or to lock the quick releases. You may also have to reattach the lawyer's lips on the front wheel. On the rear wheel, make sure the chain is on the smallest sprocket and not in the gap, and make sure the tire is lined up correctly and is not too far forward or rearward (on bikes with fenders, rear tire can rub on the bolts inside the fenders which will quickly ruin it or it can rub against the fender braces). A common problem after reinstalling a tire and riding away is for the rear wheel to quickly start rubbing against the right-hand stay. This indicates either that the wheel is not on tightly enough or that it was installed crooked. Therefore, be careful that the rear wheel is aligned properly and that the quick releases or wheel bolts are very tight.

After all has been completed, but before you get back on the road, check your brakes to make sure that their quick releases or cables have not been loosened, even if you didn't loosen them. My simple trick is to push the bike forward and apply each brake in turn. In fact, it's not a bad idea to have the habit of checking the brakes after every occasion when the bike has been worked on, stored for a period of time, or carried in a vehicle.

Watching for Further Problems

After installing a tire and riding away, watch it carefully for a while. Two problems are likely: 1) the just-mentioned rubbing of the tire, and 2) the tire becoming flat. In the case of the second, do not immediately assume that the leak was not patched correctly. Sometimes air is trapped between the tire and tube, and this air leaks out after you begin riding, giving you a flat tire again. Instead, stop and pump up the tire one more time, and then proceed. I would like to be able to say that a successful patch is possible 100% of the time, but alas! I have not had that kind of success. However, with a little care, a success rate above 90% is readily obtainable.

What causes the failures? One corner of the patch has not sealed properly. Since applying the patch is the easiest part of the repair job, being very careful to clean and rough-up the area, to allow the glue to partially but not completely dry, and to press the patch down into the glue, and to inspect the patch afterwards are all important procedures. If you can't get the patch to seal properly, it makes no sense to proceed. Instead, use your spare tube.

Washing the Hands

A little water from the water bottle and some vigorous hand rubbing will get most -- but not all -- of the dirt off of your hands. A little dishwashing liquid in a tiny bottle makes an excellent hand cleaner. I like to lather with a few drops before adding any water.

Using Your Mastery Wisely

Only when you can patch a tube and continue on your trip are you truly the Zen master of the bicycle. Now crossing high mountains, arid deserts, eerie swamps, and foggy slums will no longer disturb your tranquility. But heed one final warning! On a club ride, especially one with dozens or hundreds of cyclists, never, never, never, admit that you know how to patch a tire, or you will find yourself elected to the job for perpetuity.


Zen and the Art of Fixing a Flat Tire  A humorous look at the same problem.


How to Fix a Flat Tire on a Bicycle  Somewhat different directions for solving the same problem.

Comments | SECTIONS: | The New World | Writing | Thoreau | Home | Bike Pages |
DIRECTORIES: | Lifestyle | Commuting | Touring | Health | Advocacy | Traffic | Skills |Humor |Survey | Links |
IN SKILLS: | Bike Repair | Fix a Flat | True a Wheel |. Mistakes | Climb Uphill |Descend Downhill |
http://www.kenkifer.com/bikepages/skills/fixflat.htm | Copyright © 2001 Ken Kifer | September 24, 2001