How to Ace Fixing a Bike Flat; a "Pro" lesson

Waiting by the side of the road for rescue is no longer your fate, as you tackle flat repairs with confidence.

This detailed lesson takes longer to read than the actual repair will if you practice. You can do it!

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Spare tube of correct size and type.
• Bicycle pump
• Tire Levers
• Wrench for bolt-on axles, if necessary
• Patch kit

1. STOP BIKE SAFELY AND FIND A PLACE TO WORK: Get yourself well off the trail or road. You need to focus on fixing your flat without hindering other cyclists and drivers. Keep in mind how unexpected your presence is to them. Be courteous, and safe.

2. PREPARE THE DRIVETRAIN FOR REAR WHEEL REMOVAL: Here's a "pro" tip for removing the dreaded rear wheel on derailleur bikes: You first need to get the chain onto the tiniest sprocket on the rear wheel, otherwise derailleur tension will be greater, and later it will be harder to reinsert the wheel. Stand on the left--the non-drivetrain side--and lift the bike by its seat a few inches off the ground so the rear wheel can spin. Pedal the chain forward with one foot, while shifting the right shift lever into a "higher" gear. Most all right shift levers get into "high" (=the hardest) gear by twisting or rotating clockwise. Just try shifting, and if it doesn't go toward the tiny sprocket, go the other way: observe what the chain does. Do this a few kicks at a time, and a few shifts at a time, until the chain sits on the smallest-sized rear sprocket. This makes it 100% easier to get the wheel extricated from the chain and derailleur. If you have a friend along, have them pedal while you lift and shift. But you can do this alone, too. Just don't turn the bike upside down! (Read why under "Tips.") This trick works for getting into an easy gear before you ride off again, as well.

3. REMOVE THE WHEEL: You may need to open up the brakes to get some wheels out, especially those with large tires such as mountain bikes. This can be done without tools in most all cases. Find where the cable end attaches to each set of brakes down near the wheel. There should be a knobby cable end that slips into a slotted hook. Squeeze the brake arms together, and slip the knob out of the slot. For road bikes, there is either a rotating release down at the brake, or a bullet pin to push at the brake/shift levers. Now you can loosen the wheel. For a bicycle with quick-release axles: flip the lever open to loosen it. Some bicycles have "safety bumps" that don't allow even opened quick releases to escape from the frame where they clamp onto the front fork. In this case you need to not only flip the quick release open, but then spin the lever counter-clockwise while holding the smooth nut on its opposite side. Spin just enough to get past the bumps. (Don't need to disassemble the quick release entirely; and don't want to lose small parts, either.)
   
   Note that the 'QR' as it's sometimes called, is NOT a wrench. Spinning won't easily open it, and spinning it will NOT tighten the wheel effectively. It is much too short to have the leverage of an actual wrench handle. Instead, it relies on the compressive force of a cam inside the 'QR' device to clamp a wheel safely. Adjusted properly, you will need to apply strong pressure with your entire hand in order to close it. It shouldn't be easy to open or close the 'QR' with just one finger. Some with small or weak hands may need to use both palms to close it.
   
   Even though we are just removing the wheel in this step, you must understand how a quick release works. And though you may not intentionally change it's adjustment, it may spin a little while off the bike, so expect to adjust it to a satisfactory pressure when you reattach the wheel.
   
   If your bicycle has solid axles with hex-shaped nuts, you need to have a good wrench in your seat bag; use it to turn the nuts counter-clockwise in order to loosen them. Don't spin them all the way off the axles. Now pull the wheel out of the frame or fork, and lay the bicycle on it's side with derailleurs and chainrings facing up. (don't grind your drivetrain into the ground.)

4. LOCATE THE CAUSE: Examine your tire while it is still on the rim. Can you see what caused your flat? Sometimes the culprit is a thorn, a piece of glass, or a nail. Don't pull it out until you can mark or otherwise note the hole's location on the tube itself. Also check for deep cuts or gashes. (These usually announce themselves with a loud hiss at the moment they occur.) The first choice when possible is to quickly swap out a punctured tube for a good spare to save time and continue riding. But if you've already used up your spare tube, you'll be forced to locate the hole (or holes!) in order perform a patch job in the field. By noting the culprit(s), and keeping the tire and tube in relation to each other, it will be faster to locate the puncture. A crayon or pen in your patch kit can be handy to mark the tube. You may want to do this even if you will be patching the tube later. (Sometimes I merely knot the tube in such a way as to mark the hole.)

5. REMOVE THE TIRE: Before you can do anything about the tube, you have to get the tire off, and the tube out of the tire. Another "pro" tip: even punctured tubes tend to have a bit of air left in them. This can make it hard to remove the tire. Let air out from the valve, while "milking" the tire all around. Many seasoned flat fixers don't need to use tire levers after they do this. But you should have and expect to use tire levers in most cases for the removal phase. Get at least 2 tire levers, and start work on just one side of the wheel. Start anywhere except next to the valve. Pinch the tire's sidewalls together, and peer between the rim's inside edge and the tire's nearest bead. Insert the lever vertically here, just barely catching one bead. Don't pry at both beads of the tire, and don't pinch or jab the tube itself. Pry outward, lifting the bead. Lay this first pried lever flat against the rim and hang onto it so you don't lose ground. (Hooking the lever on a spoke is a waste of time; just hold it.) The tire won't want to come off yet; take the 2nd lever, and go 1 hand-span away from the first. Insert vertically but not too deep, pry outward, and gain some more ground. Use the hand that was holding the first lever to now mash the bead and the fabric of the tire down onto the rim, keeping the partially pried bead free. One last leap-frog with a lever along the bead, and it will stop trying to pop back onto the rim. Now gently slide a lever around the remaining bead and get one entire side off the rim. (Don't slide finger; some tires have a sharp fin at bead that can cut you, especially if old and dried out.) Then pull bead up and away; the rest of the tire, together with the tube, will come off. Use care not to tear the tube at the valve, or bend the valve, as it comes out of the rim. Look at the inside of the rim now. If you see bare spoke heads, or uncovered holes, you need a rim strip to protect the tube from damage. Also, if the tube you just removed is found to have a "snake bite" pattern, it means you didn't have enough air pressure and the rim was allowed to sink down and make 2 parallel gashes in the tube. This is entirely avoidable if you pump your tires regularly. Tubes are the same as those balloons your kids get: eventually they can be found deflated in the corner of the room. Did they have a puncture? No. But they are porous, and soon the air escapes. With thick bike tubes it takes longer, but they also lose air.

6. CLEAR THE TIRE OF CULPRITS: Set the tube aside for the moment. Friends along can speed things up by pumping air in a tube to be patched, or it's to be saved for later, by rolling it up for you. Now examine the tire inside and out for "sharps." Most rookies skip this step and regret it. Start at the label or some mark on the tire. You have to do a full 360 degree check, and it's easy to quit too soon without a mark. Look closely at the outside tread, at the same time overlap the fingers of both hands deep inside the casing. Feel gently with your fingertips for any hidden culprits. Pick out all thorns and glass. You will have an instant repeat puncture if you don't do this step. If you find a gash or cut, don't worry. You can "boot" the gash with a folded dollar bill slid over the partially inflated tube, and it will do a great job of holding back the inner tube from the gash. It's a tried and true emergency fix. But replace the tire when you get home.

7. MOUNT THE TUBE & TIRE: (If you must patch your tube, see tips below.) Put the tire back on the rim halfway. That means one entire bead is over the rim, the other still free. Pump up your spare or patched tube with just enough air to give it shape--too much causes trouble. Bend the tire back from the "open" side and insert valve into hole. Now tuck the tube into the open tire cavity. Don't try to get the final bead of the tire popped onto the rim yet.(Alternatively, some folks tuck the tube fully into the tire before they get anywhere near the rim, and then proceed to mount it and 1st bead.) With tube fully cupped inside the half-open tire, work to get the tube sitting over the rim now, but not the final bead yet. When done, you can't see any tube showing, but you still have to mount the final bead. If not done right, you'll see tube oozing between the tire's bead and the rim. You could pinch your tube if so when you mount the tire. Now begin mounting the final bead right at the valve. This is the thickest part of the tube and best to get it out of the way first. If the bead wants to sit on the valve reinforcement, push the valve up into the rim. The bead will pop down where it belongs. Working your hands away from each other, squeeze and pull the fabric of the tire to get the last bead over. You should only use tire levers as a last resort; best if you never use levers at this point. If you weary of pushing the bead, turn the wheel around and pull at the tire for a bit. The last 6 inches is the hardest part. Here you do best to work right where the bead is hanging up on the rim. Don't try to push the bead from the middle of the 6 inch final area, it will just flex and fight you. Focus on the transition areas. Instead of digging at the bead with your fingertips, palm the entire fabric of the tire to get a grip on it, and pull it over the rim. It will go! If you do resort to levers, watch out for pinching your new tube. If you're mounting a tube and tire at home, consider putting the tube into a plastic bag with some talcum powder to coat it prior to mounting it to really make an easy job of things.

8. PUMP IT UP: I suggest fully inflating the wheel before putting back in frame. Then if there's a hitch you don't have to take wheel back out. While pumping with a hand pump, avoid bending or damaging the valve, it's easy to tear the valve right off. Brace the valve area securely with your hand. Keep eyes on the valve so you know you're not "working it." Pause halfway through, to rest, and to eyeball the wheel--you shouldn't see any lifting of the bead or bubbling tube anywhere. If you do, quickly let air back out and massage tube back to where it belongs. No bead should be sitting on the tube. Now pump as much as you can, you don't want a "pinch flat" from riding a too-soft tire. This takes effort with an emergency pump, keep at it. If you are using a compressor at home or at a gas station, only inflate the tire in spurts. Do NOT apply the inflation chuck and gaze off into the distance--the next sound you hear will be like a gunshot! There is very little volume in a bike tire, and before the count of "3" you will exceed that with a gas station compressor. The trick is to accurately line up the chuck over the valve, and jab down with it in spurts. If your aim is good it may only take 3 to 5 "jabs." This also applies to CO2 cartridges--ones without a control valve can blast pressure into the tube too fast, a problem if the tube is pinched under a bead. Check early for correct seating of the bead before you inflate tire fully: make a full lap around the wheel with your eyes.

9. BOLT IT IN: Put the wheel back in the bike. For a rear wheel, hold the bike up high enough to roll the wheel in from the rear & slightly from the left on an angle. Make sure to aim the group of sprockets into the circle made by the main loop of chain. Some have trouble here when they simply rest the lowest loop of chain on top of the sprocket assembly and then can't get things to go right. If the chain fell off of the front sprockets, fix that first. It will be easier to see the loop I'm talking about. Rest the uppermost loop of chain onto the smallest rear sprocket. Then slide the axle ends into the frame's "dropouts." You may have to swing the derailleur back a bit to get the axle into place. While trying to insert the wheel, if it's hanging up somewhere, look at the brake area--the tire often hits here before the wheel is in proper position. Eyeball that the wheel is straight in the frame or fork before clamping the quick release, or tightening the bolts. Look both at the brake pad area, and any other part of the frame that the wheel could rub on. For a quick release axle, adjust it if needed for proper clamping force. For bolt-on wheels, tighten the nuts a little at a time, swapping the wrench back and forth from left to right to tighten the wheel. If you tighten one side down all at once, the axle nuts may creep along the dropout, and make it hard to bolt wheel in straight. Re-attach any brake cables if you undid them. If you like, "kick-shift" the bike into a good starting gear before climbing back on. You're done!

Tips & Warnings

• WHY NOT WORK WITH THE BIKE UPSIDE DOWN? First, it damages the shift and brake cables by mashing them (and the levers) into the ground. Second, the chain usually tangles itself around the rear derailleur while you perform the flat repair. Third, it is difficult to bolt the axle properly in its place unless gravity is helping to push the rear frame or front fork down onto the axles. Don't work upside down, and don't let helpful strangers do it, either.
• HOW TO PATCH A TUBE: Find the hole by pumping air into the tube. If don't have a bucket of water or a sink to submerge it in (you can see the bubbles), then pass the tube past your face, feeling for puffs of air. Your upper lip is very sensitive. Out on the road you won't be able to hear hissing very well.
• Mark a "bullseye" around the holes you find. I like a ball point pen or a white china marking pencil. Don't mark right at the hole. You need to be able to see the marks after you apply glue. I do a "cross" pattern, one at 3, 6, 9, and 12 o'clock.
• Take the sandpaper from the patch kit, and buff the tube in an area just a bit larger than the patch. This removes oil and talc that may hinder adhesion. You don't need to overdo this step.
• If you are using "quick" style patches that are good for emergency repairs, carefully peel off the backing and apply patch over the hole. Burnish it down with a tire lever a bit, it's now ready to put in your tire. These patches are fast and easy. But don't over-inflate a tube with one of these while it is out of the tire. The material doesn't stretch the same way "vulcanized" permanent patches do. They work well, but do rely more on being contained inside of a tire to really perform their best.
• For permanent or "self-vulcanizing" patches, the main mistake is applying the patch while the glue is still wet. The vulcanizing glue is like contact cement; you must let the cement dry first. The colored back of the patch will react with the "dry" cement and bond completely. Be patient.
• Be sure to spread a wide enough pond of glue onto the tube. Never apply glue to the patch itself. Don't paint a tiny circle, you want the patch to land completely on cement. However, you must make a thin veneer of cement. After painting a good circle, immediately brush the (non-oily) back of your finger across the pond of cement on the tube to make a very thin layer. If not thin, the glue layer will be dry on the surface, and still wet beneath. If you apply the patch in this state it will not bond well. Most failed patches are because of this.
• Use permanent patches for your "snake pit" of punctured tubes at home. You can patch and roll up a whole stockpile of recycled tubes. These will be as good as new and in fact you can put a dozen patches on one tube with confidence if you do it right. Try stretching the tubes the next day, and see how well the vulcanized patches conform to the tube. Much better than emergency patches over the long haul.
• Know what kind of tubes you need for your bike. There are two basic valve types: Presta, or Schrader. A Schrader valve, also seen on autos, is too fat to fit into a rim drilled for Presta. But you can slip a skinny Presta valve into a Schrader drilled rim in an emergency. (If you are a ride leader, carry Presta tubes for this reason.) The main thing is to have a pump that will fit your valves. Some have dual purpose heads which is ideal. Read the label on your tire to see what diameter and section of tube you need. A typical mountain bike tube might be marked "26" x 1.90" The first number is the diameter, and the second is the overall section or width of the tube.
• If you are unsure about proper quick release axle operation go to your friendly bicycle shop and the staff will be happy to give you a hands-on demonstration. Be sure to participate by actually closing the lever yourself, to judge what constitutes tight enough. Never spin the lever like a wrench, except to make minute adjustments before actually closing the lever; it is too short to be a wrench handle. Instead, swing it closed. The curved "claw" of the lever should cup itself toward the frame.

[wisemcternan]

on 3/4/2009 forwarding this to my husband. Thanks for the tips

[ewrite]

on 1/18/2009 Thanks, redhoss. Don't know how many actual flat fixes in the count, but it's been over 30 years of bike mechanic mania. This includes some couple of decades of wielding a wrench professionally. (btw, it's not that important to me, but you got the chromosome wrong...["a man."]...but hey, we're all 'hu-man'.) Thanks again.

[redhoss]

on 1/18/2009 Obviously written by a man who has done it many times.

[torque63]

on 11/8/2008 very thorough tube repair!