Valve Stem Sealing- Mtbr.com
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  1. #1
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    Valve Stem Sealing

    I wanted to start a discussion about valve stems and getting them to seal.
    I just got a new carbon wheelset (BTLOS) to replace my stock Giant XC1 wheels. When I set up the XC1's tubeless I used Stan's tape and didn't have any issues. When setting up my new carbon rims I had heard Stan's sometimes has issues with sticking to the carbon so I went with Kapton tape. I used TruckerCo valves.

    Since I couldn't find the right width for my id30 rims I got 19mm and wrapped twice edge to edge. I poked a round hole with an awl and sealed everything up. It didn't hold air for more than an hour. Thinking it was my wrap job I rewrapped and tried again. I did this a third time with the same results and said screw it and ordered some Stan's 33mm tape.

    When it came (from Amazon) it was a crap roll that was delaminating in the middle so I sent it back.

    I rewrapped again and this time instead of poking a hole, I files out the valve hole completely. This did the trick. Holds air perfectly now.
    Do many others file out the valve hole? I've on'y heard this suggested once (I forget where).

  2. #2
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    I poke a hole through the new tape with a scribe...etc. This can sometimes cause the tape to have a slit that could potentially cause a leak except...I dip the base of the valve in sealant before installing it. Push and hold the valve into the rim firmly with thumb and finger tighten nut. After adding sealant to the tire and inflating it, I shake the wheel so as to splash sealant around valve base. Never had a leak doing dozens of tubeless setups this way.

    I'll add that this is with Stan's tape, Kapton (which is what I use on my own wheels), Gorilla, Orange Seal, Whisky Parts, Sun Ringle, WTB, Zipp and other tapes.
    Do the math.

  3. #3
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    Yup, I always dip the valve end in sealant and never have a problem.
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  4. #4
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    I use a tapered nail punch but heat up first so it melts a perfect hole. So far this has worked every time. But, as said if it seals with sealant I reckon there isn't much difference in how you create the hole.
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  5. #5
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    I usually put a dab of RTV type gasket sealer around the base of the valve or whatever else I have handy, 'seal-all' or similar should work too. +1 on the Truckerco valves. A 22 shell (empty) is about the right size to heat and use to get a nice hole in the tape, if you have any of those handy. Grab it with some vice grips so you don't burn your fingers .
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  6. #6
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    I just use the valve stem with the valve core installed to punch through the tape.
    Don't recall to ever had problems with my tubeless setups leaking at the valve.

  7. #7
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    Didn't have luck with normal holes with the Kapton tape. It tears when punching the hole. I didn't try heating the awl though. But like I said, never had these problems with Stan's tape.

  8. #8
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    Only time I had an issue was when pre-taped carbon rims came what appeared to be a slit rather than a round hole in the rim tape where the valve was pushed through. Mentioned this to the company and was sent a lifetime-esque sized roll of rim tape on the house... now that’s customer service!
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  9. #9
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    Quote Originally Posted by Aglo View Post
    I just use the valve stem with the valve core installed to punch through the tape.
    Don't recall to ever had problems with my tubeless setups leaking at the valve.
    This.
    Best and most reliable technique.
    Tried most of all the other techniques. Some work fine. Other's don't.
    Never had to retape or had a leak from just punching through any tape with the valve stem + valve core combo.

  10. #10
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    Quote Originally Posted by WHALENARD View Post
    I use a tapered nail punch but heat up first so it melts a perfect hole. So far this has worked every time. But, as said if it seals with sealant I reckon there isn't much difference in how you create the hole.
    Good idea, thanks.
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  11. #11
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    Do many others file out the valve hole? I've on'y heard this suggested once (I forget where).
    I use a file on aluminum rims, but I'm afraid to use a file on carbon rims. For Kapton tape, I use an old spoke that I heat up with a lighter to melt a hole in the tape. I use Stan's valves, and I set the valve by firmly pressing on the rubber end while I screw the valve ring down tight with my fingers.

    A few months ago, I built up a rear carbon rim, and I used one layer of Kapton tape. I didn't see any reason to tape edge to edge on my 35mm inner diameter rim, so I just laid one side of the tape against the edge of the rim(the edge closest to the offset spoke holes), and I used the width of the tape to cover the spoke holes. Unfortunately, a few days ago I broke a spoke at the nipple, and I had to remove the tire to replace the nipple, and the Kapton tape was sticking well and no sealant had gotten under the tape.

    In the past, I've noticed that the Kapton tape can be really fragile though, so I don't touch it with a tire lever. Oh yeah, after installing the tape I put a tube in and go for one ride, then I let the wheel sit overnight in order to really seat the tape.

    To get at the broken nipple, I punched a hole in the tape at that spoke hole, and after replacing the nipple I patched over the hole with a 12" piece of Kapton tape that I pressed on by hand. I don't know if sealant will work its way under the patch or not. We'll see.

  12. #12
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    I used stans or wtb tape on my Oxive carbon rims w/o issue. I do however use a heat gun to soften it and work the bubbles out. For the valve stem I use a pick which makes a nice round hole.

  13. #13
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    I use a heated up small Phillips head screwdriver to melt a round hole. Never had an issue.

  14. #14
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    Never had carbon but I've always done fine with Stan's tape and sealant. I take the time to thoroughly clean and inspect entire rim for any burrs (especially valve stem hole and all spoke holes). I dress it up with emery cloth if needed.

    After inflation I always inspect with soapy water for leaks before declaring victory. Sometimes I've had a little leakage around stem but after sloshing things around awhile it always seals up.

    Whale and GRPABT1...Good tip to heat up tool and melt the tape instead of piercing/cutting!
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  15. #15
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    Just a quick update. Since cleaning up the valve stem hole, I haven't lost any pressure at all. I've checked the pressure every week and it's held steady at 24/26psi. This is the first tubeless setup that hasn't needed air ripoffs.

  16. #16
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    +1 on "melting" a hole through the tape. I heat up a small Philips or pointed punch over the flame on my stove, then slide the hot tip through the tape nice and easy to make a smooth, round hole so I don't risk splitting it.

  17. #17
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    I use an exacto knife to cut the tape out in a circle. The rim guides the knife and cuts a perfect, smooth circle.

    Im sure melting works great, but I can cut out two rims before I could heat up a pokey something to burn holes. I hate how melting plastics/adhesives smell.

    I used to dip the valve, but now I don't. We dont put sealant on car stems and its basically the same sealing idea. If your stem happens to be leaking, the sloshing sealant inside the tire will find and seal it.

    Ive been rethinking tape too. All things considered, I dont think your tape actually needs to adhere to the rim at all. It really only needs to stick to itself for the few inches it overlaps. I run full length tape. My tire seals both edges of the tape mechanically. The only potential leak spot with full width tape is the ~30mm long edge where the tape overlaps. Thats tiny! I know people have been using narrow tape, or multiple layers, but that creates an ENORMOUS potential failure area.

    Tape that isnt mechanically locked by the tire has to rely on adhesive to bond, and you have 2 edges of potential leak. On a 29er rim, this is 3904mm of potential leak area. Thats more than 100 times the length of full width tape.

    Not to go too far off on a tangent, but I don't think the valve stem actually leaks as much as people think. Its almost always the tape. A soft rubber cone shaped stem is going to seal damn near no matter what.

  18. #18
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    I just cut an X with a sharp knife as per Stan's instructions and have never had an issue.
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  19. #19
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    Quote Originally Posted by One Pivot View Post
    I use an exacto knife to cut the tape out in a circle. The rim guides the knife and cuts a perfect, smooth circle.
    Quote Originally Posted by J.B. Weld View Post
    I just cut an X with a sharp knife as per Stan's instructions and have never had an issue.
    I've done both of these with no issues. I have never bothered to put sealant around the stem because it does that itself when I shake the tire (or go for a ride) after inflation.

  20. #20
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    Soldering iron to make perfect hole, push stem in while plastic is soft to make a seal.

  21. #21
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    I believe I just crammed the presta tip through the hole then subsequently secured it with the lock not and never looked back. I am using Stans valves which have the tapered rubber plug which in turns is pulled against the hole.

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