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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 10-09-10, 08:17 AM   #1
bike manhattan
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Motionless Flats!

I have had about 10 flats, in the last 2 or so months after getting a DP18 wheel rear wheel. I have replaced my tire, rim tape (velox), etc. No luck. A few of these flats have comes from "nothing". Last night I was hanging out in my living room watching TV and all of a sudden I hear my tube deflate. What could cause this? I'd say 3-4 out of the 10 flats have been like this.
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Old 10-09-10, 08:21 AM   #2
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Locate the hole in the tube, then match it to the wheel and the tire.
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Old 10-09-10, 08:27 AM   #3
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yea done that a bunch. most of the holes have been kinda close to the tube stem. i have checked the rim extensively. lightly sanded rough spots. carefully applied velox rim cloth, etc. there is honestly nothing but i keep getting flats and sometimes not even from riding. this is getting very frustrating.
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Old 10-09-10, 08:31 AM   #4
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There could be something like a little pices of glass in your tire.
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Old 10-09-10, 08:45 AM   #5
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I have had 53 flats on the road, only one was a complete mystery.

Something must be wrong with your rear wheel somewhere?

Moving the valves when pumping can causes tears in the tube.
Do you use a floor pump?
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Old 10-09-10, 09:09 AM   #6
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Wounded Knee recently had this problem with his DP18s. It ended up having something to do with his rim tape.
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Old 10-09-10, 09:21 AM   #7
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In my opinion the best rim tape is just plain duct tape. I have only had 6 flats in my entire life.
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Old 10-09-10, 09:27 AM   #8
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OP - Are you using a presta valve tube in a rim drilled for larger schrader valves?
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Old 10-09-10, 09:47 AM   #9
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well i took the tire off and matched the hole. same spot it usually is. there is a defect with my dp18. there are a total of 8 small holes on the side of the rim. not spoke holes, just these little pointless holes that the rim tape has a hard time covering. i put some electrical tape over them and then reapplied velox. hopefully that does it. i was aware of the holes and tried to solve this before but part of the velox was not covering a tiny tiny portion of one of these defect holes still. hopefully the electrical tape/velox combo works. the bad news is i just broke my axle spacers when putting my wheel back on. i have some awfully weird bike karma.
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Old 10-09-10, 10:08 AM   #10
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I know what your problem is.

I had the same problem on the same wheels a while back. The holes kept appearing around the valve stem, at random times. Took me a while to figure it out.

Anyway, what's happening is that when you inflate your tubes, part of the tube gets "pulled under" itself around the valve stem (the abrupt change in thickness of the tube results in it happening at this specific point) and the pressure/friction ends up punching holes into the tube. Here's a rough illustration in MS Paint, the red circles are where the flats occur:



In order to prevent this from happening, you simply need to use the little nut for the valve stem that everyone generally throws away. Before you inflate your tires, tighten the nut onto the stem just enough to give it some preload. Then inflate the tires. After they are fully inflated, tighten the nut the rest of the way so that it is tight against the rim but don't overdo it. The nut will keep the tube, on the inside of the rim, tight against the rim so it doesn't flop over on itself.

Try this, let me know. I went through countless tubes before I figured this out, it was the worst.
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Old 10-09-10, 10:12 AM   #11
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i also wanted to add i just ordered some 22mm velox. i have the 17mm on there now. the electrical tape is a temp fix until the 22mm stuff arrives. but yea, this is a total defect with dp18's. there are 4 groups of 2 tiny holes on the farthest edge of the bottom of the rim right before the side. 2 sets of 2 on either side of the valve hole and than 2 sets of two where the rim seam is opposite side of the stem hole. completely ridiculous to have holes in a rim that are not spokes holes or a valve hole. plus the location makes it so that you need to use extra wide rim tape to cover them.
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Old 10-09-10, 10:14 AM   #12
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mrville, thanks for your response. i have been using the valve nut as you described. almost 100% the problem is these tiny little holes as i described above. the tube is getting punctured right where these holes are about 1 inch away from the stem.
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Old 10-09-10, 10:17 AM   #13
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Quote:
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i also wanted to add i just ordered some 22mm velox. i have the 17mm on there now. the electrical tape is a temp fix until the 22mm stuff arrives. but yea, this is a total defect with dp18's. there are 4 groups of 2 tiny holes on the farthest edge of the bottom of the rim right before the side. 2 sets of 2 on either side of the valve hole and than 2 sets of two where the rim seam is opposite side of the stem hole. completely ridiculous to have holes in a rim that are not spokes holes or a valve hole. plus the location makes it so that you need to use extra wide rim tape to cover them.
Those holes are drain holes, they are there for a reason.

Also, your tube isn't getting sucked into those holes. When I was dealing with the problem I actually went ahead and plugged the drain holes around the valve stem with epoxy putty, but it didn't fix the problem.

If the DP18 has any issue, it might be a rim diameter tolerance problem, as I think that some of us have slightly smaller rims that result in the tube being a little too long so it will flop over on itself.
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Old 10-09-10, 10:18 AM   #14
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mrville, thanks for your response. i have been using the valve nut as you described. almost 100% the problem is these tiny little holes as i described above. the tube is getting punctured right where these holes are about 1 inch away from the stem.
Okay with this in mind, are the puncture holes happening on the centerline of the tube, or are they offset a little bit? The drain holes in the rim are offset a little, so that'll be an easy way to determine what the problem is.
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Old 10-09-10, 10:40 AM   #15
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Okay with this in mind, are the puncture holes happening on the centerline of the tube, or are they offset a little bit? The drain holes in the rim are offset a little, so that'll be an easy way to determine what the problem is.
i just checked the tube again. the hole is pretty much dead center. it did align perfectly with the drain hole that was partially exposed though. however i took your advice, i just deflated my tube, tightened valve nut (leaving a bit of room), pumped to 110psi and tightened again. i am not entirely sure if that is what the problem was or the "drain holes" being exposed. either way i hope i am good to go. so sick of flats.
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Old 10-09-10, 10:52 AM   #16
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Sounds like it would be a tedious task, but you could always smooth & de-burr the pinholes with a file ? Even the stem hole ?
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Old 10-09-10, 11:02 AM   #17
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Sounds like it would be a tedious task, but you could always smooth & de-burr the pinholes with a file ? Even the stem hole ?
already did this.
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Old 10-09-10, 11:15 AM   #18
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Hmmmmm, the only other thing is that we are closing in on Halloween, Ghosts ?
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Old 11-01-10, 03:04 PM   #19
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I'm having this same problem. Did the valve nut solution work out for you?
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Old 01-21-11, 01:57 PM   #20
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still happening! went 4 months without problem, then one day i am sitting in my living room, where i keep my bike and "psssssssssssssssstttttttttt". another flat, same exact spot. replaced the tube, rode for another week and then last night "psssssssssssttttttttttttttt". going to patch the tube now and really tighten the nut before inflating. **** sucks. i have velox tape on now, i think the problem is def what the poster who drew the ms paint thing said.
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Old 01-21-11, 03:12 PM   #21
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Switch the tire out with a spare. Maybe there's something embedded in the tire that you can't pinpoint. or maybe there's a sharp edge somewhere on the inside portion of the rim that the rim tape isn't covering.
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Old 01-21-11, 03:24 PM   #22
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Quote:
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In my opinion the best rim tape is just plain duct tape.
I use duct tape too! It's basically free compared to rim tape. The only flats I've ever had were due to obvious road hazards like nails. Except for that one time I pinched a tube under the rim and it exploded... I hope to not make that mistake again.
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Old 01-21-11, 10:11 PM   #23
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why not just bite the bullet and get a new rim? i mean so far in tubes it must've gotten close to costing you a new rim anyway, just get a new rim and be done with the headaches
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Old 01-21-11, 11:15 PM   #24
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Yeah man, get your money back from the Dp18 and get a new rim.
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