Post by tomac on Nov 10, 2003 23:01:20 GMT 10
How to fix a trialsin flat.
This post has more detail than most people need, just catering to the newest common denominator.
flat tyres are pretty much all the same - your tube just doesn't have air in it any more. In trials the reason for getting a flat is generally a pinch flat or snakebite. This is where an object (generally the corner of a wall, a pointy rock edge, a rail or anything thin) compresses the tyre in a small area, pushing the tyre right down to the rim and "pinching" the tube in this fold of tyre, generally puncturing it on both sides (hence the term snakebite, it looks like two fangs have punctured the tube). Anyway the long and short of it is pinchflats are better than normal flats because they normally don't damage your tyre with pokey things like glass, thorns etc that you have to first locate, and then dig out of, your tyre casing.
To fix this you will need to take your wheel out of the bike (unless you pinch your front tyre using a telescopic fork like a cannondale lefty or USE alien - but nobody uses those anyway). This should be easy enough to do, trials riders are notorious for making it difficult for themselves though. You may have to derail the chain off your chainring and fiddle with your rear derailleur to get it out. After you do this you will normally need to find at least one tyre lever. These can be made out of plastic, which can't damage your tyre/rim but are often not strong enough for big beaded DH/trials tyres and may break. Conversely, you can use metal ones, which can be found in some cheap tube repair kits from kmart/target etc. You will need to put the lever underneath the bead of the tyre (which runs around the inside of the rim, the lowest point being called the "well" of the rim) and lever it over the rim sidewall (you have to do this at the seam of the rim, which is always opposite the valve hole - don't try and pull a tyre off at the valve). make sure that the tyre bead is as close as possible to the rim sidewall to reduce the pressure being put on the rim and the tyre lever. Once you have one point of the tyre over the edge of the rim make sure you hold it there and don't let it snap back into the rim. Using another tyre lever lift another point of the tyre over the rim a couple of inches from the first point, keep going around like this until you can take an entire half of the tyre off with your hands. Some people will run the tyre lever around after lifting off one point, pulling the rest out like a car tyre remover. This is something I definitely don't recommend as it rips up the tyre bead, often exposing and damaging it, as well as scraping the rim sidewall pretty badly. You only need to take off half the tyre in order to get the tube out. Once you have half the tyre off you can pull the dud tube out, run your fingers around the inside of the tyre checking for anything that might re-puncture the tyre, as well as shaking out any grit or gravel in there. Either put in a new tube of the right size or repair the old tube using a patch kit (which will come with instructions, these vary slightly with different kits so follow those provided) and put the tyre back on, starting from the valve and finishing at the seam. Be careful that the tube stays completely inside the tyre (putting a tiny bit of air into the new one first can help shape it into the tyre) and doesn't get pinched between the tyre and rim. You may be able to put the tyre back on with your hands, which is recommended, or just use a tyre lever again, popping the tyre back on a little at a time. Trials riders would be best putting the wheel back in before re-inflating it, given brake clearance etc etc. Inflate the tyre a little at first, then check that the tyre is seated evenly on the bead and that no tube is showing, before fully inflating the tyre.
there you go - now nobody can complain that they don't know.
- Joel
This post has more detail than most people need, just catering to the newest common denominator.
flat tyres are pretty much all the same - your tube just doesn't have air in it any more. In trials the reason for getting a flat is generally a pinch flat or snakebite. This is where an object (generally the corner of a wall, a pointy rock edge, a rail or anything thin) compresses the tyre in a small area, pushing the tyre right down to the rim and "pinching" the tube in this fold of tyre, generally puncturing it on both sides (hence the term snakebite, it looks like two fangs have punctured the tube). Anyway the long and short of it is pinchflats are better than normal flats because they normally don't damage your tyre with pokey things like glass, thorns etc that you have to first locate, and then dig out of, your tyre casing.
To fix this you will need to take your wheel out of the bike (unless you pinch your front tyre using a telescopic fork like a cannondale lefty or USE alien - but nobody uses those anyway). This should be easy enough to do, trials riders are notorious for making it difficult for themselves though. You may have to derail the chain off your chainring and fiddle with your rear derailleur to get it out. After you do this you will normally need to find at least one tyre lever. These can be made out of plastic, which can't damage your tyre/rim but are often not strong enough for big beaded DH/trials tyres and may break. Conversely, you can use metal ones, which can be found in some cheap tube repair kits from kmart/target etc. You will need to put the lever underneath the bead of the tyre (which runs around the inside of the rim, the lowest point being called the "well" of the rim) and lever it over the rim sidewall (you have to do this at the seam of the rim, which is always opposite the valve hole - don't try and pull a tyre off at the valve). make sure that the tyre bead is as close as possible to the rim sidewall to reduce the pressure being put on the rim and the tyre lever. Once you have one point of the tyre over the edge of the rim make sure you hold it there and don't let it snap back into the rim. Using another tyre lever lift another point of the tyre over the rim a couple of inches from the first point, keep going around like this until you can take an entire half of the tyre off with your hands. Some people will run the tyre lever around after lifting off one point, pulling the rest out like a car tyre remover. This is something I definitely don't recommend as it rips up the tyre bead, often exposing and damaging it, as well as scraping the rim sidewall pretty badly. You only need to take off half the tyre in order to get the tube out. Once you have half the tyre off you can pull the dud tube out, run your fingers around the inside of the tyre checking for anything that might re-puncture the tyre, as well as shaking out any grit or gravel in there. Either put in a new tube of the right size or repair the old tube using a patch kit (which will come with instructions, these vary slightly with different kits so follow those provided) and put the tyre back on, starting from the valve and finishing at the seam. Be careful that the tube stays completely inside the tyre (putting a tiny bit of air into the new one first can help shape it into the tyre) and doesn't get pinched between the tyre and rim. You may be able to put the tyre back on with your hands, which is recommended, or just use a tyre lever again, popping the tyre back on a little at a time. Trials riders would be best putting the wheel back in before re-inflating it, given brake clearance etc etc. Inflate the tyre a little at first, then check that the tyre is seated evenly on the bead and that no tube is showing, before fully inflating the tyre.
there you go - now nobody can complain that they don't know.
- Joel
