Bicycle Mechanics - Regarding install of new tube
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07-31-08, 09:25 PM
Hi. Thanks for the replies to my previous post regarding introductory repair manuals. I'll put some on order through the library in town. In the meantime, I need assistance regarding the install of a new tube. I never have any luck with the process. They always seem to lose air within days. I installed a new tube on the rear tire of my girlfriend's mountain bike (yesterday) and tonight I found it totally deflated. The bike was stored upside-down in the garage. The rims are 26" and call for Presto valves (that's the small one, right?). Are there mistakes that are commonly made when installing new tubes? I inflated the tube a bit in order to give it some shape, put it inside the tire, fit one bead in the rim, fit the other bead in the other side of the rim, and then inflated the tube to the recommended pressure (I think in this case it was 65 but I only really went as high as 55). Again, maybe there are some common errors I'm making when doing this. Any help would be appreciated and thanks for taking the time to read and respond to such a basic inquiry.
07-31-08, 09:41 PM
Did you check inside the tire for what ever caused the flat? Also be sure not to pinch the tube when installing the tire.
As stated, check the inside of the tire and rim for debris. Check the rim tape to make sure all the spoke nipples are covered. Try to align the label on the tire with the valve stem, that way when you do flat, you can find the leak in the tube and know where to look on the rim or tire.
I put just a tiny amout of air in the tube when I put it in the tire, to make sure it does not kink. After I get the tire started back on the rim, I let the air out.
After the tire is back on the rim, I start inflating but stop after I get a little pressure in the tube to make sure the tire is seated all the way around on both sides. If it is, I take the tire to full pressure.
I do not like using the valve stem nut, and I never use a frame pump unless I am forced to do so. Try to always use a floor pump and be careful not to pull on the valve stem when removing the pump head from the valve.
07-31-08, 10:40 PM
Are you tightening the knurled nut on the valve so it's closed tightly by hand after inflating? Odd that a new tube would leak after a few days. I second the inspection of your existing tire. I've found things like thorns in my tire.
I got a flat on the trail last night from what appeared to be a 1/2" of some kinda animal quill... that one was hard to miss inside my tire along with the 10" long puddle of slime in my tire. :D
Side tip - buy a container of baby powder and throw it into your bike tool box. When changing tubes, I always make sure the inside of the tire and the tube itself have a good dusting of baby powder. Helps against pinch flats since the tube can slide around the inside of the tire a little.
08-01-08, 01:44 AM
Don't use hand pumps, floor pumps only.
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