Bicycle Mechanics - constantly getting rear wheel punctures... somebody please help !!
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06-11-10, 12:03 PM
I have been riding for over a year now, and have covered some good distances recently. However, I feel as though I am suddenly marrooned at home, as everytime I take the bike out, my rear tire goes instantly flat everytime I hit any kind of pot hole or bump. Something is obviously wrong somewhere, and it is costing me a fortune in innertubes. it's now at the stage where I am on the bike less than five minutes and it happens. I am totally bewildered as to why this has started to happen, but it must be into double figures now, and innertubes being 5 quid a piece, I am stuck at home and skint to boot.
Any help and or advice on this matter would be greatly appreciated. TIA
06-11-10, 12:32 PM
1) Take the tire and tube off the bike and inspect the rim tape on the rim. If there's a hole or cut in the rim tape, the tube will bubble up into the spoke holes and blow the tire when you hit a bump. If there's a hole in the rim tape, replace it.
2)The next step would be to completely inspect your rear tire for any holes in the sidewall where the tube might bubble out of the tire. If that's the case, replace the rear tire.
3) If your rim is damaged or the wires of the tire are damaged, then the tire won't seat well on the rim. That would allow the inner tube to sneak out of the tire and get pinched. Replace tire or rim if they're dinged up.
4) Make sure the tire is pumped up to recommended pressure. Otherwise you could get a "pinch" flat by bottoming out the rim on a bump.
Sounds like it's #1 or #2 - those are easy fixes.
06-11-10, 12:35 PM
First, learn to patch a tube. Patch kits are about a pound and will allow to to make numerous repairs.
Second, when you make a repair, figure where the hole is. Is it on the rim side of the tube? Then the rim strip could be the issue. Is it on the tire side? Examine the tire closely to see if a piece of glass or wire are still in the tire. Is it snakebit (two small holes close to each other)? You are running the tire at too low of a pressure.
When mounting a tire, always allign the label with the valve stem to make it easier to determine where to look. Also, make sure the tube isn't trapped between the tire and rim.
What tires are you currently running?
Any chance you're pinching the tube between the tire and rim each time you fix them? I had a similar problem for a while, solved it by making absolutely sure that the tube was tucked all the way into the tire before inflating it, by going around both sides of the tire and peeking between the tire and rim before putting any air in.
You mention potholes and bumps leading to flats too... Are you getting a "snake-eyes" flat, with a double-puncture? If so, that's a sign of underinflation, make sure you're putting enough air in.
06-11-10, 12:48 PM
Probably this christian is putting too much air also.
06-11-10, 12:51 PM
By now you must have a good idea of where the punctures are occuring. At least I HOPE you do. If not then the trick is to align the tire's name patch with your tube stem. And when you first pull out the tube keep it aligned and blow it up. Find the leak and note how far it is from the stem. Then very carefully check the tire for any embedded shard of stone, glass, metal wire or thorn at that point in the tire. If you don't find the cause of the flat then it's likely that the thing that poked the first tube is still in there. Finding the leak in the flat tube and checking the tire carefully is highly important. The thing that caused your flat in the first place almost never just pokes through and then stays behind. It typically comes along for the ride and stays hidden in the tire carcase. Sometimes you need to find the hole in the tire and flex the carcase a lot to expose the Dastardly Device of Doom and Destruction.....:D
The other thought is that you're allowing your tire pressure to get way too low for your area. This can cause something called pinch flats or snake bites. THis is where the tire mashes down at the edge of a pothole and pinches the tube between the tire and the rim. It often produces two holes about the rim width apart. Or sometimes one hole and an obvious mark of an almost second hole. The way to fix this is to fill the tires to a higher pressure. If you have been using a guage and you're getting pinch flats despite supposedly being up to pressure according to the guage then it's time to get a new guage.
Hopefully you have not thrown out those tubes. A patch kit and some time will restore them to full usefulness. Most of us don't retire a tube until it's got about 6 to 10 patches on it.
You can also use the old tubes to find out which type of flats you've gotten and maybe fix the tire before another flat happens. Even if you didn't line up the tire if you only lift one side to swap tubes then the tire doesn't often move. Find the holes in the old tubes and note how far they are from the stem. Check the tire for embedded shards, glass, etc in that area very carefully, FOlding the tire to stretch any holes in the carcase open and hopefully expose the cause. Or if you always remove the tire all the way and don't replace it with the same alignment all the time then there's nothing to do other than go over the entire inside of the tire extremley carefully with a good light looking for signs of penetration. Each such spot must be checked for any embedded stuff.
What happens is that the stuff in the tire sits inside and only pokes out as the tire comes around to the bottom and is flexed by your weight. This poking at the tube is what produces the new hole after only a few minutes.
I always align the tire with the decal on the drive side, mounted at the valve stem. So if I have a flat, I know pretty much exactly where it is in regards to the tire. Its a simple step, but very helpful in diagnosing a problem. It really doesn't take any longer to do it this way.
Notice how the stem on both tires is centered between the words "Hutchinson" and "Nitro"?
I would try a different wheel. Either there is a wheel or tire defect you are not seeing, or your tube changing technique is flawed.
06-16-10, 09:51 AM
thanks to each and all for the quick and insightfull information. It seems my latest flat was due to not inflating the tires to the correct pressure, as I found a "snake-bite" on the side of the tube. I am sure some of my previous ones were also down to the tire not sitting fully outside the tube.
Thanks for the many tips that I will certainly be bearing in mind each time I next need to put a new tube on.
06-16-10, 11:05 AM
Remember when installing the tire to inflate the tube enough to keep some shape; that will help keep it from getting pinched between tire/rim. Also, use those tire tools sparingly! You should be able to install even a fairly stiff road tire with hands alone. (sometimes getting an excellent hand and forearm workout in the process!)
06-16-10, 11:09 AM
The first step is to look at the puncture(s). The appearance and location will assist you more than anything else in determining the problem. Given only your description so far my guess is that a foreign object such as a small piece of glass, wire etc. is still in your tire and going over an obstacle drives it back into the tube or a pinch flat from low pressure. So when you remove the tube immediately place it back on the tire in the same orientation as when installed and carefully inspect the tire (or rim/tape area if the puncture is not in the exposed part of the tire) for the cause.
(Sorry - somehow the other posts did not show up, so this is a bit out of date)
06-16-10, 12:04 PM
One trick when reinstalling a tire/tube is to use some very, very dilute dishwashing detergent in a spray bottle. It will lubricate the tire and tube so they will slip over the rim, and not get pinched as readily by the tire tool/levers.
Heavily spray the tube and tire when reinstalling. There should be a "bit" of air in the innertube, so it will tend to form to the tire, but not so much air that it will bulge out and get caught/pinched by the tire/bead as you are levering or thumb pushing the tire bead back on.
Some tire rim combos require tire levers-be careful when levering the tire bead back on-you need 3 levers in some cases- one on either side, and one to lever in the middle.Make sure you push that tube "in"(not too much air in it) before levering that tire bead back on.
Another trick-pump the tire up to maybe 20 psi-then bounce it all the way around a bit to "seat" the tire and bead. Drop the pressure to 10 bounce it carefully , then pump to 40 psi-bounce, 60 psi-bounce.
Make sure that the valve stem is at 90 degrees-not bent.
Make sure the bead is more or less even all the way around-the same amount of tire should be invisible all the way around.
Some folks say detergent is too hard on rims-never noticed that to be a problem. Rinse/hose your rim with water after this(soapy rim is slippery-hurt your braking.
Dan The Man
06-16-10, 12:17 PM
Before you fix or replace a tube, you should always always always always figure out what caused the flat in the first place. If you don't you will only have a repeat of the same incident the next day or sooner.
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