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Flat & Tube Patch question(s)
Returning from my road ride, I developed a slow leak in the rear tire.
I decided to pump up the tire and see how long it would last, rather than change the tube on the side of the road. (It was getting close to dusk and I only had 5 or 8 miles to go. I was able to ride a couple of miles before reinflating again. Repeating a couple of times got me home. However, the last turn home caused the tire to slip laterally on the rim (ouch). I later replaced the tube and patched the original to use as a spare. While patching the tube, I found a "snake bite" where the holes were say 2 or 3 mm apart. These were on the road-surface side of the tube 6 inches from the valve stem. I assumed the classic pinch flat snake bite would be much farther apart, about the width of the rim. Q1 - Is that not the case.? While checking the inside of the tire, I could find nothing to account for the original slow leak (assuming the snake bite was caused at the last turn of the ride.) I inflated the tube to about 4 inches diameter and checked the entire tube with a liquid detergent and water. I also checked the valve. No leaks. Q2 - Am I missing something? Will the tube likely be a reliable spare? Q3 - Now that the tube cement has been opened, how long before it "dries up" and is not usable? Other cements and glues I've used always seem to dry in the tube after opening regardless how tightly I recap them. Thank you. TPO |
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Flat & Tube Patch question(s)
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Flat & Tube Patch question(s)
someone writes:
Returning from my road ride, I developed a slow leak in the rear tire. I decided to pump up the tire and see how long it would last, rather than change the tube on the side of the road. (It was getting close to dusk and I only had 5 or 8 miles to go. I was able to ride a couple of miles before re-inflating again. Repeating a couple of times got me home. However, the last turn home caused the tire to slip laterally on the rim (ouch). I later replaced the tube and patched the original to use as a spare. While patching the tube, I found a "snake bite" where the holes were say 2 or 3 mm apart. These were on the road-surface side of the tube 6 inches from the valve stem. I assumed the classic pinch flat snake bite would be much farther apart, about the width of the rim. Q1 - Is that not the case.? That is not the case. Snake bites from bottoming on a road hazard pinch the side of the tube in a manner similar to vertically pinching the cheek. Hole spacing is the length of tube that is contained in that fold. When the tube is flat and in its un-inflated shape, the distance shrinks proportionally to the ratio of flat to inflated minor circumference. It has nothing to do with the width of the rim. The tube never touches the rim. It lies in the fold of the tire casing. While checking the inside of the tire, I could find nothing to account for the original slow leak (assuming the snake bite was caused at the last turn of the ride.) I inflated the tube to about 4 inches diameter and checked the entire tube with a liquid detergent and water. I also checked the valve. No leaks. If the tube was in the tire for a longer time, it bonds with the casing and doesn't leak fast. Of course, if you put plenty of talcum in there, you won't get a slow leak but rather a fast one. That is a saving grace of pinch flats. They go flat slowly if the tube has been in place for a while. Q2 - Am I missing something? Will the tube likely be a reliable spare? What do you believe you are missing. If you gave it a water submersion test, there should be no doubt. By the way, get tubes that barely fit in the tire so they are not stretched to near bursting in use. Weight weenies use 1/2" minor diameter tubes because they weigh less. To make up for that, they puncture more easily and go flat in a hurry. Q3 - Now that the cement tube has been opened, how long before it "dries up" and is not usable? Other cements and glues I've used always seem to dry in the tube after opening regardless how tightly I recap them. Glue tubes with the cap firmly screwed down generally dry up just as fast as ones that have never been opened because the leak is the crimp at the bottom of the tube. Just the same, hold the glue tube vertically squeezing out any air before replacing the cap. That gives the volatile solvent less space into which it can evaporate and escape when the tube is again opened. Why so anonymous? Jobst Brandt |
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Flat & Tube Patch question(s) - 1 more question
Thanks for info.
My new question is this: My LBS sold me an innertube smaller than the tire size I asked for (both circumference and width). When I questioned him, he said it would be fine. If that is the case, why bother with sizing the innertubes? Or did I get bad advice for the sake of a small $ sale? We need to know the size of the tire, as well as the tube, to correctly answer that question. In general you can bump down maybe one size tube if you have to, but I'd generally try to use one that has an indicated range that includes the size of the tire in question. Do keep in mind that there is a range of tire sizes (width) that each tube will acceptably handle. For example, the most-common road tube size is indicated as being a 700 x 18-25c. That tube is going to work fine for either a 700c or 27" tire (either 622 or 630mm as indicated on the sidewall), and a width of 18-25. However, it will be a pretty snug fit in an 18c tire, especially if it's not a "superlight" (thinner) variety. And it will stretch fine to fit up to the 25c size. I wouldn't recommend it for normal use in a 28c though, as you're stretching the walls pretty thin and more likely to see an issue where the valve is attached to the tube. --Mike-- Chain Reaction Bicycles www.ChainReactionBicycles.com |
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Flat & Tube Patch question(s)
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#7
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Flat & Tube Patch question(s)
While patching the tube, I found a "snake bite" where the holes were
say 2 or 3 mm apart. These were on the road-surface side of the tube 6 inches from the valve stem. I assumed the classic pinch flat snake bite would be much farther apart, about the width of the rim. My first (and only) road pinch flat came on a long slight downhill grade doing about 65 km/h. I did not recognize it as a flat, and continued home (another 2 miles or so). I only noticed a slight noise and 'bump' every rotation of the wheel. I elected to continue since I was so close to home (and I *hate* slowing down when travelling at those speeds...there's something strangely validating about keeping up with traffic). I thought it might be a piece of gum stuck to my tire. I got home, spun the rear tire, and found no indication of a drivetrain problem or anything stuck to the tire. I never noticed a flat; the tire held its shape and I was in a rush to get to work. The next day, I discovered that the rear tire was flat. While checking the inside of the tire, I could find nothing to account for the original slow leak (assuming the snake bite was caused at the last turn of the ride.) I inflated the tube to about 4 inches diameter and checked the entire tube with a liquid detergent and water. I also checked the valve. No leaks. I removed the tube and found a diamond-shaped lateral hole, big enough to push an (unsharpened) pencil through. Yowza! I was riding at speed on that thing? Despite the size of the hole, it the tire/tube retained enough air to get me home (and to trick me during the subsequent "inspection"). I checked the rim for damage but couldn't find any. And my tire (Michelin Pro Race 2) came out of the incident unscathed...no punctures. Here's the really confusing part. My tire had been inflated to 110+ lbs just prior to riding that day...so I can't imagine how I got a pinch flat. Q2 - Am I missing something? Will the tube likely be a reliable spare? Heh...with a hole that big, I decided to use the tube as a chainstay protector on my MTB |
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Flat & Tube Patch question(s)
On 25 Nov 2006 20:47:53 -0800, "peter" wrote:
The check described above sounds adequate as long as you rotated the tube through the water slowly enough to be sure to spot any telltale bubbles. In that case I'd assume the snake bite was the cause of the original slow leak. The tube should be fine as a spare after patching the snake bite holes. So far (tempting the p*nct*r* fairy), the only snake-bite flat I've had was NOT a slow leak. Hit the rough pavement (the mayor STILL hasn't fixed that spot!), and I was flat within 50-75 feet. Pat Email address works as is. |
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