Repairing A Flat Tire
To be technically correct, you don't have a flat tire - you have a flat inner tube, which is inside the tire itself. This tube will have to be patched and reinflated, then reinserted in the tire. To do this, you first have to get into the tire.
You should always have a tool kit with you when you ride which has (at the very minimum) pump, tire levers, spare tube and patch kit. Your patch kit will include several patches, a tube of glue and a scraper or piece of sandpaper (see Riding Tool Kit).
Release the Brake Cable Tension
The most convenient way to deal with the mechanics of removing the wheel is to flip the bike over onto its seat and handle bars. Make sure in doing this you don't damage any items on the bar. You may also want to cover your saddle. Before you flip the bike, release the brake cable tension on the wheel which is flat. To get the tire out past the brake pads, the brake cable tension must first be disengaged by opening the brake cable releases on the brake pad arms. This is the point at the top of the brake arms where a metal yoke attached to one arm catches a ball or hook on the cable to engage pressure on the brakes. Different bikes use slightly different devices, so you should make yourself familiar with yours before ride. If you can't figure out how to release the brake cables, fully deflate the tube before you remove the wheel and put the wheel back on again before you reinflate the tube.
Loosen the Wheel
Most newer bikes have quick-release handles on the axle for easy removal of the wheel. Flip this lever to release tension on the fork and unscrew it enough to get the wheel out of the slots at the end of the fork (called "dropouts"). Lift the wheel out of the fork.
If Your Bike Doesn't Have Quick-Release Levers
If you have an older bike you'll need to find a wrench which fits the axle nuts. Loosen the axle nut until you can remove the wheel easily. You should probably practice taking wheels off at home before you ride. Make sure you put the wrench in your riding tool kit!
Rear Wheel Flats
If your flat is on the rear wheel, you will first have to get the chain out of the way. Don't remove the chain, but slip it over the smallest rear sprocket - this will give you a little slack to work with. Grab the rear derailleur (at the top, now that the bike is upside down) and pull it toward the rear of the bike. This will allow you to lift the wheel out cleanly.
Loosen the Tire
Once the wheel is off, deflate the tube all the way - this will make it easier to remove the tire. One edge of the tire needs to be pulled until it is completely outside the rim. This can be done by hand if you have strong hands, but most people use two or three tire levers, which provide the leverage without the pain. The first lever is inserted between the rim and the tire, then worked under the edge (bead) of the tire. Be gentle in doing this to avoid pinching the tube and causing another puncture. The lever is then flipped to bring that section of the tire outside of the rim. Without removing the lever from its wedged position, the other end is locked to a spoke to hold that section of tire in place.
Additional Tire Levers
The second lever is then wedged between the tire and rim several inches away and the flipping process repeated. A third lever can be used the same way, then the middle lever can be removed and moved to the front of the line, where the process is again repeated. Go all the way around the tire until one edge is completely outside the rim. The tire does not need to be completely removed - just one side.
Remove the Tube
Find the valve stem and work it loose from the rim. Then simply pull the tube out under the open edge of the tire. Take note of the orientation of the tube in the tire - if you find the damage in the tire casing quickly, you can locate the leak in the tube more easily (or
Find the Leak in the Tube
Pump the tube up part way and listen or feel for the air leaking from the tube. Mark the leak with a wax pencil or other tool. Then deflate the tube again.
Find the Source of the Damage on the Tire
Examine the tire to find the cause of the damage and remove it. Run a piece of cloth around the inside and outside of the tire casing. It will snag if it catches on a sharp object. Be careful not to cut your hand by running it around the tire unprotected. This is important - otherwise the same piece of glass or metal may just blow the tube in the same spot again. If you need to dig to remove the object, do this from the outer (tread) side of the casing. On very rare occasions, the tire may be badly cut and not support the tube properly. In this case you need to insert a "boot" for support between the tube and the cut area of the tire. A dollar bill actually makes an effective boot. Many bikers carry a cut piece of old plastic or other waterproof material for this purpose. You can also buy a packaged boot at a bike shop.
Roughen the Tube
Your patch kit will contain several rubber patches, a tube of glue and a piece of sandpaper or metal scraper. First make sure the tube is clean and dry. Then use the sandpaper or scraper to rough up the surface around the puncture thoroughly, in an area just larger than the patch.
Spread a thin layer of glue over the area around the hole (just larger than the patch) and let it get nearly dry but still tacky. The "glue" is not really glue, but a rubber compound which softens the rubber of the tube enough to adhere to another piece of rubber (the patch). Remove the thick plastic backing from one of the patches - leave the thin plastic cover on the back of the patch in place. You may even want to put a drop of glue on the rubber side (down side) of the patch and spread it around a bit.
Press the Patch Into Place
Press the patch down over the roughened area and hold it firmly in place for about a minute. The tighter you press, the better the hold. Inspect the patch to see that it has adhered well - if you find a gap which has not sealed well, this can be repaired with a drop of glue. Note: once you have opened the glue tube the remaining glue will dry up quickly. Replace the glue tube or get a new patch kit soon.
Replace the Valve Stem
After you have given the glue a few minutes to dry, carefully push the valve stem back through the hole in the rim until it is firmly seated.
Reinsert the Tube
Carefully reinsert the tube into the tire. Be careful to straighten the tube as you replace it and not let it twist, as a twisted tube could lead to pinch flats. You may want to partially inflate the tube first to make this easier.
You should know, however, that there are two different kinds of valves - Presta and Schrader. Schrader valves are thicker and require only the removal of the stem cap. Presta are taller and thinner, and once the stem cap is off, the top of the valve itself must be loosened by screwing counterclockwise. Only then can a pump be used to fill the tube. After filling, the valve top must be screwed down again and the cap replaced. Newer pumps usually work for both kinds of valves, but older pumps may not. Make sure your pump is the appropriate type for your valve or it can completely deflate your tube.
Reseat the Tire
When the tube is fit snugly into the tire, the tire must be reseated inside the rim. If possible, use just your hands to do this. If you need to use the levers, use them as little as possible and gently - it is very easy to pinch another hole in the tube. Go all the way around the tire, inspecting to see that the tube is not caught between the tire casing and the rim. Make sure the casing is seated evenly all around the edge.
Reinflate the Tube
When the tire is securely on the rim, use the pump to refill the tube. Be careful with the pump not to put too much pressure on the valve stem - it can shear off. The best way to fill the tire is to let the tire "rest" on the pump, with the valve stem pointing down into the pump. If you have a pressure gauge, you can use it as a guide to proper pressure. If not, fill it to approximately the same as the other tire (squeeze with your hand to estimate - the tire should give only slightly under firm hand pressure). To avoid some of the road delay of this process, most riders carry extra tubes with them and simply insert a new tube. They then wait to get home to repair the tube and replace it in the pack, ready for the next flat. A patch is actually stronger than the original tube, so tubes can live with many, many patches. Avoid using pumps at gas stations - the gauges are often highly inaccurate and set up for cars and you can blow the tire right off your bike.
Replace the Wheel
Next, slip the wheel back into the dropouts. Spin the wheel to make sure it is straight in the fork, then retighten the quick-release lever. Be very sure this is adequately tightened, or the wheel could come off. Then make sure to reconnect the brake cable release so the brake will work. Spin the wheel again to make sure the wheel is moving freely and not rubbing the brake pads. If it is rubbing, loosen the wheel and repeat the process until the it spins freely. If you have a cyclocomputer, make sure the magnet is on the same side as the counter, or you will lose your readout. Some tires have "directionality" to the tread, so make sure the newly replaced tire is oriented the same way as the other tire. Many tires have the direction labeled on the side.
Flip the bike Upright
There. All finished. Not so hard, was it? Keep the old tube - there are many uses for these. Check that your brakes work before you start riding again and keep an eye on the tire for a while - sometimes the patch can leak, sometimes there is more than one puncture.
© 2010 - 2012 Bob Beach