Fixing A Bike Flat

Fixing a Flat
Without Silicon

The tools you will need to fix a flat differ between doing it on the trail or at home. For instance, the tools in the above photo are adequate for fixing a flat on the trail. At home, you should be able to use more robust tools such as a floor pump, and a drill with a wire brush to speed up the process. The wheel removal tools at home can be more robust as well.

The first thing you need to do is remove your wheel from the bike. That being said, I have heard of and seen bikers fix a flat on the trail without removing the wheel. It can be done this way if you know precisely where the leak is. You do the same thing to fix the flat as if the wheel was off in regards to liberating the tube in order to repair it. The only difference is, you have to work around the wheel being mounted. This is not impossible to do, just more difficult.

Wheel release lever engaged.

Wheel release lever "released."

Rotate the release nut on the opposite side, counter clockwise just to the point of being able to lift the axle off of the bike. DO NOT REMOVE THIS NUT or the release axle.

To remove the rear wheel on a bike with a derailleur and rim brakes, first release the rim brakes in order to allow the tire to be pulled off from between the brake pads. If you have disk brakes, there is nothing to do. Once the rim brakes are released, release the wheel axle holding lever. Once the lever is released, reach over to the other side of the axle and unscrew the thumb nut to the point of being able to release the wheel from the bikes frame. DO NOT REMOVE THE NUT. Once you get the axle loose, you can grab the wheel and lift it up and off of the bike. In order to successfully do this, you will also have to grab the derailleur and pull it out of the way so that the rear sprockets can clear the derailleur.

Grabbing the derailleur.

Pulling it back to clear the rear sprockets.

After you have removed the wheel from your bike, the first thing you need to do when fixing a flat, is to make sure as much air is out of the tube as is possible. If you have a Shrader valve (Presta shown) it helps a lot to remove the inner valve first to ensure as little air is left in the tube as possible.

<----This is what a Shrader valve tool looks like. Insert the slotted end into the valve until it mates with the valve stem and then turn it CCW until you can remove the valve stem. If the tube is still pressurized, it should be pushed out by the air pressure. If you have a Presta valve, unscrew it until it stops and then hold your finger against it to release any remaining air.

Once enough air has been removed from the tube, insert your first tire removal lever as shown and hook it on a spoke as shown. The next tire lever should be inserted about 4 to 6 inches away from the first and again the tire should be levered over the rim. Repeat until one entire side of the tire is free of the rim. Note that it does not matter where on the tire rim you start this tire removal lever process nor does it matter which side. The only object is to remove the tire from one side only, completely, so that the tube can be removed.

Once a side of the tire is free of the rim, then starting with the tire valve, remove the tube from the wheel. If it is a Presta valve, remove the nut holding the Presta valve to the rim as well.

Now the fun part, locating the leak(s.)

The standard way to find a leak is to pump up the tube until it is slightly over inflated and a tiny bit distended. Then hold and rotate the outer part of the tube next to your face and lips or cheek, to detect any leaks. This is best accomplished when it is quiet out with a great deal of concentration. Quiet helps to hear a leak and concentration allows you to be patient and keep looking till the leak is evident. Alternately, if water is available, hold the tube under water and watch for bubbles to appear as you drown one section of the tube and then another.

Once the leak(s) is (are) discovered, mark it (them) with a big X over the exact center of the leak. The idea is to make the X large enough such that when you buff an area large enough for the patch you intend to use, parts of the X are still evident to allow you to center the patch properly after the glue is applied. Do not stop when you find one leak. Insist on surveying the entire tube until you are satisfied that all leaks have been found.

Buff the area of the leak with sandpaper (provided in most repair kits) if you are on the trail or with a drill and wire brush if you are at home. Apply a small amount of rubber cement making sure it covers the entire buffed area which is also larger then the patch you intend to use. Scrape off any excess glue and allow to dry for approximately 15 to 30 seconds. This is contact cement and drying is necessary in order for the patch to properly adhere to the tube. Remove the protective cover from the underside of the patch and apply the patch centered over the leak. Seat the patch firmly with finger pressure and set aside.

Go back to the tire and remove any thorn or object which may have caused the leak. You can usually find the cause of the leak by carefully running you finger tips over the entire inner surface of the tire concentrating on the area of the tire that the patched part of the tube was sitting in. If nothing is evident then inspect the outside of the tire as well for any lodged thorns or objects that could cause a flat. This is an important part of the flat fix as if you put a patched tube back in your tire and you have not removed the cause of the leak, you will have another flat tire and you will have to repeat this process all over again. Double and triple check for the cause of the leak before reinstalling the repaired tube in the tire. It is not unusual for the cause of the leak to be gone, just be really sure that is the case.

Install the tube valve first and if it is a Presta valve apply the nut to the stem as well. Work the tube into the tire making sure there are no folds. it helps to have the tiniest bit of pressure in the tube while doing this. A tube that is completely flat will not conform to the tire properly when you lever the tire back over the rim.

After you have stuffed and poked and herded the tube back inside the tire, pick a point on the tire and start inserting the tire back onto the inside of the rim. You can usually do this by hand except for the last six or nine inches. If you can, force the tire over the outside rim with your thumbs. If that is not possible then carefully use a tire lever to lever the last few inches over the outside rim and into the inside rim. If you have to use a tire lever, be aware that it is very easy for your lever to catch an edge of the tube, pinching it against the rim and causing a leak. You wont know that you caused this leak until after you try to pump up the tire and you hear the ominous hissing of air escaping from your leak.

After the tire is seated, inspect it to make sure the tire bead is below the rim at all points on both sides of the wheel. It is not unusual for the tire bead to be above the rim if something is blocking it for instance. The tire valve is the most common reason for this. If the tire valve is causing it, physically push the valve up into the tire until the tire bead seats and then pull the valve back down. If the tire bead is not seated in any one place on either side of the rim when you pump the tire up, the tube will sneak out and literally blow up. It may do this right away or after you have jumped on your bike and have gone down the road.

Pump up the tire and reinstall the wheel on your bike reversing the take off procedure. Remember that the derailleur will be the first thing in the way and you will have to physically pull it back in order to clear the sprockets. Retighten the lever. First tighten the thumb screw opposite of the lever until you feel the lever working when you apply it. Be sure it is reasonably difficult to push the lever closed as this is what holds the wheel to your bike. If the lever is loosely applied, your wheel will become loose while riding.

If you have rim brakes, reinstall the brake cable and test the brakes before using them.

Can you avoid flats in the first place? Usually no. There are precautions you can take such as not riding off trail for instance as the unfettered existence of thorns and sharp objects are more likely found "off" trail. There is also a goop called "Slime" that you can buy and is guaranteed to stop leaks. I have seen this stuff in action, actually stopping a leak caused by running over glass. There was a horrific noise of lost air followed by silence and the ability to continue riding on just a slightly deflated tire. The only distraction is the necessity to get this "Slime" stuff inside the tube. Difficult to do with a shrader valve, almost impossible to do with a presta valve.

There are also thorn resistant tubes and tires and tire liners designed for additional leak protection. Everything works to a varying degree but at a cost of weight and additional riding effort. Since the odd flat doesn't happen that frequently, I usually just trust the original setup. If you lack the confidence of fixing a flat on the trail, then maybe one or more of these leak resistant solutions will work for you, forestalling the eventual flat tire.

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