Bicycle Flat Tire Changing Clinic
At some point, you will have a flat tire. Learning to change a flat tire will help you feel more confident while out on the road and the skill may allow you avoid making a call for taxi service.
Tool & Supply List
- Spare tube –in a plastic bag with a small amount of baby powder
- 2 Tire levers
- Small hand pump
- Dollar bill
- Hand wipes
- Air cartridges and applicator (optional)
- Patch kit (optional)
- Bag to carry it in
Spare Tube – Be sure to carry a tube that is specifically sized to your bike’s wheels and has the appropriate valve type; almost all road bikes use the Presta type valve, not the Schraeder. Also note valves come short or long; the shape of your wheel will determine which length you need. If you’re not sure, ask your bike shop mechanic.
Give this vital item some extra protection by storing it in sturdy zip lock bag (the heavier type) and make it easier to install by squirting a small amount of baby powder into the bag before putting the tube in. The powder-y tube will mount into the tire far easier than one just out of the factory box it came in.
Tire Levers – You’ll need only two, even though they come in sets of three. Look for nylon, sturdy models and leave the metal type at home in your shop, no need for the weight.
Small Pump – We usually mount these to our frames, but some prefer to carry in a pack. Our favorite right now is the Lezyne which is light, and most importantly, can produce the high pressures we need. Most road bikes will do best with a pressure of 100 to 120 psi (more on this in a moment).
When you select a pump, be sure to verify that it will go that high – not all do (mountain bikes, for instance, never run with pressures this high). Also be sure the pump fits your type of tube valve – Presta or Schrader.
Dollar Bill – or a 4” x 6” scrap of tyvek, or similar very thin but super tough, flexible material (dollar bills are manufactured to put up with rough handling and survive). We’ll explain how to use this later.
Handwipes – Although back in the day, wet grass was the best alternative to cleaning up the grease and grime from changing a tube, we now have access to cheap, individually packaged handwipes… buy a box, and keep 2-3 of these little envelopes in your tube-changing kit.
Air Cartridges — We have found the air cartridges can easily malfunction, and don’t fully inflate the tire… and small hand pumps are now available at nearly the same weight. And optimal flat repair calls for the ability to partially inflate the tube to check for leaks, before installing a new tube, and that’s hard (if not impossible) to do with a cartridge.
But this is a matter of personal preference, and because you could be pumping that small hand pump for as long as 10 minutes to get the tire to full inflation (it is a very small chamber in the pump) some riders choose to carry both a pump and the cartridges.
If you do decide to carry air cartridges, don’t wait for a “tire emergency” to learn how to use them. Plan to “waste” several, learning how to use them at home, to minimize malfunctions on the road.
Patch Kit — We haven’t “repaired” a patch on a tube on the side of the road in years – a tricky business under the best of conditions. So we don’t carry a patch kit on the bike, but we do bring one on multi-day rides, along with extra spare tubes usually carried in a vehicle. We may repair tubes at night, to increase the number of spare tubes.
Bag – Most road and mountain bikers will carry their tire repair tools and supplies in a “wedge” style bag under their seat. The rationale is simple: it’s always there, ready when you need it.
If you use this bag only for your tire repair gear, and a micro tool (a micro tool is vital to making other adjustments on the bike, but isn’t used in changing a tube), it can be quite small.
Some riders however prefer a larger bag, so that food, car keys and other items can be stored conveniently. But beware – storing other items in the bag can puncture the tube. And getting in and out of the bag all the time might cause you to drop a lever or the dollar bill, leaving you underprepared for a quick tube change. So you might consider using your wedge bag exclusively for repair items. Just sayin’.
Get Off the Road
Stop riding as quickly as possible when you realize that you have a flat tire. Find a safe place to work on your bike and get out of the road…completely.
As you fix the flat, you will become preoccupied with the task at hand… and remember that it will not be possible to “jump out of the way” fast enough if a vehicle sideswipes your position.
About 350 workers (on foot) are hit and killed every year in the U.S. by vehicles mowing them down on highways and roads (CDC & NIOSH). And they were wearing mandatory high-viz vests and had the benefit of warning signs, cones, and flashing lights on their vehicles. Nevertheless, they were hit.
You are even more vulnerable given that you may not have a Lime Green vest, don’t have a big dump truck to protect you and don’t have high-powered flashing lights. You too can become a fatality if you’re on the edge of the road.
Please move completely off the road, not like the people in this picture… they’re on the wrong side of the guard rail!
How To Fix Your Flat Tire
Your wheel consists of a metal (or carbon) rim, connected by spokes to the axle. A tire is mounted on the rim, held in place by two very rigid “edges” of the tire, called beads. Inside the tire is a tube.
(there are other types of bicycle wheels, such as tubeless tires, but that is beyond the scope of this document – if you have a different type of set up, learn the specific requirements of repairing flats to your wheel).
When you notice your tire is flat, think about what might cause it – because that might affect how successful your repair will be. Possibilities for causing flats include:
- Tire pressure too low (resulting in a pinch or “snake bite” puncture to the tube); if the inflated tire changes shape when you put your weight on the bike… it is low enough to be vulnerable. We recommend restoring tire pressure at the start of every ride.
- Cracked/damaged tube at the junction with the valve stem, sometimes due to age and usually indicated by a visually bent and/or loose stem, and the tire frequently found with low pressure at the start of every ride.
- Glass or other sharp object cutting through the tire, and into the tube, often apparent immediately (sometimes with a bang!). This may cause catastrophic failure of the tire, as well as the tube.
- Glass or other sharp object picked up miles ago, and eventually working through the tire, not visible on the outside of the tire and causing a tiny puncture in the tube that may leak slowly.
- Tube damaged during the tube-changing process. Usually realized with loud audible noises made by the cyclist.
The following procedures can be followed anytime you get a flat. We recommend you go slow, and be methodical, because if you skip a step… or get clumsy because you’re in a hurry… you may have another flat just a little bit farther down the road, and have to do it all over again. Yuck.
1. Getting Ready
You don’t have to flip the bike over upside down in order to work on the wheels, in fact that may damage any computer, lights, bell or other equipment mounted on your bar… and scuff up that seat you love.
We recommend keeping the bike upright, but out of dirt/dust/sand. Lean it up against a fence, mailbox, or guardrail is just fine – but be sure you’re well off the road. And if you’re using the guardrail, position the bike on the opposite side.
If you’re taking off the front wheel (see Step #2) then take extra care not to bend or damage the ends of the front forks – set it down gently.
If you’re taking off the rear wheel (see Step #3) then take care not to get the rear derailleur in dirt (it has grease, which attracts dirt and sand) and do not rest the weight of the bike on the derailleur, as that could bend it or change the adjustment, which would affect shifting.
If we have enough people, we usually ask one of them to hold the bike up, especially when it is a rear wheel repair.
2. Take the Wheel Off The Bike – FRONT
Open up the brake shoes, which on most modern road bikes is a little thumb lever on the side of the brake arms, that opens brakes wider – pulling the brake shoes away from the wheel rim.
Do this now, even though you could probably take the front wheel off without doing it when the tire is flat – because you won’t get the wheel back on without these open (the inflated, repaired tire will be too wide to fit between the brake shoes).
Open the quick-release lever on the wheel’s axle. The lever is always on the left side of the bike (“Left” from the rider’s perspective sitting in the saddle).
Then loosen it further with counter-clockwise turns, so that the axle can come out of the fork. Note that all modern bikes have forks that will not allow the axle to be removed merely by only opening the quick-release lever – you have to loosen it further.
Go to Step #4.
3. Take the Wheel Off The Bike – REAR
Before you take the wheel off, hold the bike off the ground enough that you can spin turn the pedals – and adjust your gears so that you’re on the small ring in the front, and the smallest ring in the rear. This is not a “legal” gear combination when riding (also called a “cross up”) but it puts as much chain slack as possible in your transmission system… before removing the wheel. This is going to make everything easier.
Open up the brake shoes, using the little thumb lever on the side of the brake arms, that opens brakes wider – pulling the brake shoes away from the wheel rim.
Do this now, because you won’t get the wheel with inflated tire back on without these open.
Open the quick-release lever on the wheel’s axle. The rear lever is also always on the left side of the bike (because the derailleur is always on the right side, and there isn’t room for the lever next to the derailleur).
Then like the front wheel, loosen it further with counter-clockwise turns, so that the axle can come out of the rear dropouts. You don’t usually have to do this as much as with the front axle.
Finally, gently push the rear derailleur back (in the direction away from the pedals) with one hand, while maneuvering the axle slightly forward, and down, out of the rear dropouts. With the chain loose, and the derailleur out of the way, this should be easy!
4. Look for the Culprit
Now that you have the wheel away from the bike, slow down a moment… turn the wheel in your hands slowly and carefully, and examine the tire closely to see if you can see what caused the flat.
Do not use your bare hand to feel the tire surface. There may be a sharp piece of glass or metal sticking out of the tire that could cut your hand.
If you find the culprit, mark the spot in some way, or use a landmark on the tire such as sidewall lettering. You’ll be coming back to this nasty bit of business in a moment, once you have the tire off the wheel.
If you can’t find the cause, it may be that it is not visible from the outside. Small pieces of glass and sharp objects can be picked up, and then over time be pushed into the tire by your weight on the bike, and disappear from view. But they’re still in there, and we’ll address that in Step #6.
5. Remove the Tire from the Wheel
If there is any air left in the tube, open the Presta valve, and press the valve pin to release it. You want as much air out of the tube as possible.
Slowly and carefully, slide the rounded end of one tire lever under the bead (the rigid outer edge of the tire), putting the end of the tire lever between the tire and the metal rim. The other end of the lever will be sticking out, away from the center of the wheel. Look carefully to see that you’re not pinching some tube material with the rounded end of the tire lever.
Slowly, flip the tire lever over so that the far end is pointing towards the center of the wheel, which will pry the rigid bead of the tire away from the metal rim. Just the tire, not tire-and-tube, as that will damage the tube, which will make finding the original leak much harder.
Then hook the other end of the tire lever onto a spoke, using the little notch on the end of the tire lever. This will hold the lever in place and keeps the unseated tire from popping back into the rim.
Take the second tire lever, and follow the same procedure, immediately adjacent to the first tire lever. This will be much easier because of the gap between tire bead and metal rim created by the first tire lever. Avoid pinching the tube between the tire lever and the rim.
With both tire levers in position, take the second tire lever and walk it around the tire/rim clockwise until one side of the tire is off the rim. The tube should remain tucked inside the tire.
6. Find the Culprit – Try Again!
If you failed to find the culprit in Step #4, check the tire again by pumping a small amount of air into the tube. Keep the valve stem in place in the wheel, and do not shift the position of the tire while you perform this check — you want to be able to align the leak in the tube with a specific location on the tire. Put your ear close to the tire, and listen for hissing of escaping air.
Two holes side by side is a pinch-flat–the tube got pinched between the tire and rim. A single hole was most likely caused by a sharp object such as metal or a piece of glass. If you find a single hole in the tube, locate the same position on the tire, and check carefully on the inside of the tire and the outside of the tire for anything that could have caused the puncture in the tube.
If you can’t find an obvious cause, carefully run your fingers along the inside of the tire to make sure the foreign object is no longer there.
If the tube has been punctured because of an object coming through the tire, it is vital to find the object, because if you don’t, it could cause another flat.
If you find a cut in the tire, or an object in the tire, we will address that in Step #8.
7. Remove the Tube
Once you have confirmed the location of the cut, or concluded that the flat was not caused by a cut through the tire, then you can remove the tube from the tire.
If you inflated the tube in the previous Step #5, release that air by again pushing on the pin in the valve stem. When the tube is empty…
Push the valve stem through its hole in the rim, and gently pull the tube away from the inside of the tire, and away from the rim, so that you are holding the tube in one hand… and the rim/tire in the other hand. The tire will be loosely fit over the rim, with one of the two bead edges inside the rim, and the other outside the rim.
8. Handling A Cut Tire
If you do find a cut in the tire, remove the culprit using your lever (rather than your hands, which could be cut) and make sure the inside of the tire (which will be up against the new tube) is clean and smooth.
Then place a dollar bill (or scrap of tyvek fabric) inside the tire over the cut. This will provide a barrier between the tire and the new tube and will help to avoid a second flat.
If you don’t do this, then you run a real risk of the new tube bulging through the cut when filled to high pressure, flatting again and even exploding (in rare circumstances).
9. Installing the New Tube
Take the new tube out of its protective plastic bag, and unfold it gently. Keep it out of the dirt and avoid getting anything on it, especially any form of grit. Inflate it with your pump just enough to hold its shape, and to confirm that it is not leaking from a puncture suffered while stored.
Next, confirm one more time that the tire is clean and smooth of any obstructions, inside and out. It too needs to be kept out of the dirt, and avoiding any foreign objects even tiny ones, from being inside the tire.
Do the same thing with the inside of the rim of the wheel – most rims have a thin but tough belt running around the rim on the inside to protect the tube from the butt ends of the spokes. Feel this with your fingers to be sure it is clean and smooth.
Hint: we recommend storing the tube in the plastic bag with a bit of baby powder, as the powdery tube will be easier to re-install in the tire and onto the rim.
Insert the valve stem of the tube through the hole in the rim, and make sure it is straight pointing towards the axle. If there is a distinctive mark, word, or logo on the sidewall of the tire, some riders like to position the tire so that this mark is on or near the valve stem (making it easy to find the valve once the wheel is mounted back on the bike).
Carefully tuck the tube into the tire. Use caution not to twist the tube, and using your hands be sure the tube is placed deep in the tire – if this isn’t done correctly you run the risk of pinching the tube in the next step. So don’t rush.
With the valve stem installed straight, work the tire back into the rim with your hands by rolling the bead away from yourself. Start with the portion of the tire that is directly across from the stem. Do not use levers to reseat the tire, as you could puncture the tube.
When tire is almost completely back in place and it is becoming difficult to roll the bead, press the opposite end of the tire into a tree, fence post or the ground to relieve some of the tension (which is caused by the tightly stretched bead). Especially with newer tires, you may need to “massage” the tire, by pressing the palms of your hands against both sides of the tire, while pressing against the tree or post, working the tire towards the tree or post.
The tire should pop into place. If it doesn’t, repeat the “massage” technique.
Before inflating the tube, visually check that the bead is seated correctly and that there are no tube pinches between the tire and the wheel rim.
Inflate the tube, stopping to check for leaks a couple of times before the tube is completely filled.
10.Re-installing The Wheel
To re-install the front wheel, be sure you have the lever on the left side. Pass the tire carefully past the brake shoes – you should not need to force this, and if you do, you may change the alignment of the brake shoes. In an extreme braking situation, mis-aligned brake shoes may cause dramatic problems.
Turn the quick-release lever to tighten onto the axle, then flip the lever.
We recommend the lever be facing backwards, horizontal, although you may have a different preference. Some fork/wheel combinations will only accept the lever in one orientation. Get to know what works best for your bike before you’re on the side of the road.
To re-install the rear wheel, have someone hold the frame up. Use the same procedure (and caution) to pass the inflated tire past the brake shoes.
If you left the chain as recommended in Step #3, you should be able to position the wheel so that the axle is within an inch or two of the dropout notches, and then attempt the somewhat tricky maneuver to put the wheel back on with the chain:
– With one hand, grasp the body of the rear derailleur, and use one finger to push back (away from the pedals) so that the derailleur unfolds and lengthens;
– With the other hand, position the wheel so that the gear cluster on the wheel “hooks” the chain onto the smallest cog of the gear cluster (or cassette);
– Then position the wheel so that the axle drops into the dropout notches; it should pop right in.
Tighten the quick-release lever, first by rotating clockwise, and then by flipping the lever tight.
Some frame/wheel combinations will only permit one orientation of the quick-release lever. In any case, be careful to spin the rear wheel (the frame still held off the ground) and verify it spins smoothly and is centered between the brake shoes. It is sometimes possible to tighten the lever on the axle with a asymmetrical, crooked axle. This may roll on the street, but it won’t shift or brake correctly.
For both Front and Rear wheels, DON’T FORGET TO CLOSE THE BRAKES using the thumb flip lever.
Use your hand wipe to clean chain lube off of your hands – no one wants black grease on their bar tape.
Collect your used tube, any used cartridges, and anything else you brought – and bring it with you to throw away (or repair the tube for future use).
Extra Credit: Patching a Tube
We don’t usually patch tubes – partially because we want a “known good” tube in our wedge bag for next time we flat, and partially because our tires are so tough that we can get as much as 2,000-3,000 miles on a tube… and by then, it needs replacement anyway due to possible rot and wear/tear on the valve stem in the hole of the rim.
But if you like to get every last mile out of a tube, or if the tube was quite new before you flatted, or you’re out on a trip and don’t have access to any more new tubes – you may want to patch your damaged tube.
Using a patch kit to repair a tube:
a) Be absolutely sure you know where the puncture is, by re-inflating and verifying it is leaking at that specific location;
b) Clean the punctured area of the flat tire with an alcohol prep pad;
c) Rough the surface with an emery cloth;
d) For a glueless patch, simply stick it over the hole and press firmly;
e) For a patch that requires glue, apply a thin layer of glue to both the tube and the patch;
Wait for the glue to get tacky, then apply the patch and press firmly until it adheres.
f) Partially inflate, and very carefully check for leaks – it is a bit of an art to patch a tire successfully
Store the tube in baby powder, or immediately install onto the wheel per the previous instructions for a new tube.