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New tubeless - slow leak

Old 02-02-23, 11:09 AM
  #1  
Telkwa
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New tubeless - slow leak

Good morning!
I went to tubeless a while back. Using the full Bontrager kit on some Duster Elites. Bontrager sells a hard plastic rim liner and a valve stem that fits into a recess in the liner. I don't know if it's a poor design or operator error, but the valve stem was never secure in the recess. I could poke the stem with a finger and hear air hissing out. The stem would twist out of the recess with very little torque applied, such as removing the core.

Gave up and went back to tubed.

Recently I went back to t/l with one wheel, but using DT Swiss 25mm tape (rims are 22mm), Muc-off valve stems, and FSA offset rim washers. The Muc-offs seem like a nice product. I used the rectangular "foot" because it settled right into the rim's center channel and seemed to provide the most sealing surface around the hole.

I have a slow leak or leaks. Losing half the air after a day or two. Yesterday I started rotating the rim several times a day, hoping sealant finds leak(s). Haven't taken a ride yet.

Does anyone have any suggestions? Seems to me that dipping the wheel into a water tank won't tell me much unless it's leaking right at the valve stem, or along the bead. Bubbling at the spokes would be meaningless because the air could be coming from any spot on the rim tape, correct?

I also thought about adding a double dose of sealant. I put about 35cc in the first time.
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Old 02-02-23, 11:26 AM
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Originally Posted by Telkwa
Bubbling at the spokes would be meaningless because the air could be coming from any spot on the rim tape, correct?
.
Correct. The air leak could have started anywhere along the tape. You'll just have to redo the taping. Why didn't you stick with Bontrager's plastic liner? Seems like that one is more foolproof, right?
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Old 02-02-23, 11:38 AM
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tighten the valve stem till it does not leak this has been an issue with me. once its tight enough I don't get leaks. I have had the nut come lose too.
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Old 02-02-23, 11:47 AM
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Bontrager's rim liner is thick, reducing the room in the center channel for getting the tire on & off, and it seems to make tire removal much harder. Plus that dumb recess that doesn't seem to hold the valve stem.
Of course, all the problems could be my own incompetence.
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Old 02-02-23, 12:01 PM
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What is the tire ?
What type of Sealant ?


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Old 02-02-23, 12:12 PM
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Originally Posted by Telkwa
Bontrager's rim liner is thick, reducing the room in the center channel for getting the tire on & off, and it seems to make tire removal much harder. Plus that dumb recess that doesn't seem to hold the valve stem.
Does the square valve stem base work better in this recess? It helps to really tighten down on the locknut too.
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Old 02-02-23, 01:33 PM
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rotating the tire won't seal it if the leak is at the valve or even the bead.
First off I'd take the wheel off and use soapy water to find the leak. If it is the valve put the valve at 6 o'clock and bounce it against the ground. That splashes the sealant up against the valve seat.
If it is the bead you have to do the old shaky dance. Most people skip that these days when doing tubeless since most of the time riding will splash the sealant around on the bead good enough. You can also lay the wheel on it's side using a bucket to help with sidewall leaks and to a leaser extent bead leaks.
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Old 02-02-23, 01:48 PM
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Tire is Conti Protect Cross King 29" Rim is Bontrager Duster Elite 22mm wide.
I'm using the Bontrager TLR tire sealant because that's what I have.

Bought a 32 oz. container so I still have enough for a couple more tries although it's about time to buy some more sealant. Thinking about trying the Stan's because sometimes we go riding in cold weather. Any suggestions for sealant would be appreciated.

My rear tire is still tubed so I'm thinking about putting one of the Bontrager t/l rim strips back on. I would use another Muc-off valve stem instead of the Bontrager stem which I was never happy with. Those Bontrager hard plastic rim strips are difficult to remove. Hopefully I didn't damage either one of them peeling them off.

So, just to clarify, it's my front wheel that I converted back to t/l a few days ago. DT Swiss 25mm rim tape, Muc-off stem, FSA offset washer, and Bontrager TLR goop.
If I go back to t/l on the rear tire it'd be Bontrager hard plastic rim strip, Muc-off valve stem, FSA washer, and what remains of the Bontrager goop.

Canker, thanks for the tips. I'm gonna go outside and spray the slow leaker down with soap/water. See if anything presents itself.
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Old 02-03-23, 10:37 AM
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Sprayed the wheel with soap/water. Big bubbles forming at the base of the valve stem.
I don't know what's the best thing to do in this case. Pulled the valve stem core and added another 35 to 40cc of the Bontrager TLR sealant, roughly doubling the original amount. Installed core and gassed it up. Shook the wheel. Now I could hear sealant sloshing. Shook the wheel, bounced it, etc. for a minute, trying to get sealant to splash against the base of the valve stem. Sprayed soap/water, bubbling stopped. Shook it some more, bubbling returned. So I brought the wheel inside the warm house and began sloshing it around every time I walked past it.
I'll keep doing that today and see what happens.

Thanks to everyone for their help!
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Old 02-03-23, 10:43 AM
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Originally Posted by Telkwa
Sprayed the wheel with soap/water. Big bubbles forming at the base of the valve stem.
I don't know what's the best thing to do in this case. Pulled the valve stem core and added another 35 to 40cc of the Bontrager TLR sealant, roughly doubling the original amount. Installed core and gassed it up. Shook the wheel. Now I could hear sealant sloshing. Shook the wheel, bounced it, etc. for a minute, trying to get sealant to splash against the base of the valve stem. Sprayed soap/water, bubbling stopped. Shook it some more, bubbling returned. So I brought the wheel inside the warm house and began sloshing it around every time I walked past it.
I'll keep doing that today and see what happens.

Thanks to everyone for their help!
Are you seeing sealant bubbling out?
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Old 02-03-23, 11:07 AM
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No, I never saw any sealant leaking or bubbling anywhere. Along the beads or valve stem or the outer circumference of tire. I know there were some small leaks between knobbies because I saw some sealant leak out months ago but not seeing anything now.

Took the wheel outside just now and sprayed soap/water at the valve stem. No air bubbles. Haven't checked air pressure. Will do that today. Crossing my fingers.

Last edited by Telkwa; 02-03-23 at 11:20 AM.
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Old 02-03-23, 12:00 PM
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To correctly tighten valve in rim, use a hard object to push the valve in from the tire side, compressing the rubber seal. While applying pressure, handtighten the lockring.
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Old 02-03-23, 07:45 PM
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Originally Posted by Kontact
To correctly tighten valve in rim, use a hard object to push the valve in from the tire side, compressing the rubber seal. While applying pressure, handtighten the lockring.
I agree with this completely, and have done so many of these tubeless valve stem installations at my shop it's a muscle memory thing for me. The only possible variation I'll add is that I use my thumb as the "hard object."

When it comes to creating an air tight seal, just remember, it's not the presta nut on the outside of the rim that's creating the seal, it's the rubber base of the valve stem on the other side of the rim that's creating the seal. The key is pushing that rubber grommet/seal FIRMLY "into" the valve hole by whatever means; the presta nut is tightened to hold that seal in place, and it will, if you do it correctly.
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Old 02-04-23, 12:25 AM
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I agree with others, seems the problem is not getting the valve stem tight enough. Given the stems have a rubber seat, with enough pressure they should seal without relying on sealant. Of course, some sort of very small leak is possible. You should definitely not be able to push on the valve stem and make it move and cause a leak when doing that.

When using tape, be sure you create the stem whole through the tape using something like an awl. You want a nice round hole made by puncturing the tape, not by cutting the tape. You especially do not want something like an + made with two cuts.

A hole created by an awl will be smaller in diameter than the valve stem. As you force the stem through the hole the tape will stretch out and you'll get a nice tight fit there. This won't be the seal you need, but it ensures you have as much contact area between the tape and the rubber seal of the stem.
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Old 02-04-23, 01:15 AM
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Originally Posted by Telkwa
Gave up and went back to tubed.
Hmmmm ...
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Old 02-05-23, 10:31 AM
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Jeepers, guys -

There sure are a lot of potential mistakes involving a t/l installation. I think I made all of them.

I had mentioned previously that the Bontrager rim strips have a small recess at the valve stem hole that accepts the oval-shaped "foot" of the Bontrager t/l valve stem. I went back and looked at the white Bontrager rim strips that I pulled out of my tires. There is no recess. Can't explain why I thought there was. There's a small square shaped area that's a little bit thicker than the rest of the strip, and a round hole going thru the center of that square.

I was asking for help months ago on this website, and a guy suggested replacing the Bontrager valve stem with a Muc-off or some other good stem. That's what I shoulda done. The Bontrager valve stem relies on a tiny O-ring to seal. Seems to me a conical rubber foot would work better.

It's been a coupla days now since I started this thread. I've shaken the wheel numerous times, trying to splash sealant up against the valve stem area. It seems to be holding now. Mtracer made some good points about creating the right hole thru the tape. I didn't create the perfect hole thru the tape but I didn't totally screw it up either. Next time I'll take the time to do it right.
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Old 02-05-23, 10:56 AM
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also don't apply the tape unless the wheel is warm. my shop was maybe e 60 degrees but 45 minutes ago I rode into work and it was maybe 40 outside. I had a hard time getting the tape to stick to the rim and its self. but it's holding I thought I would have to redo it.
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Old 02-05-23, 11:30 AM
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Yeah, foofer, I shoulda done the taping inside the warm house. The shop was about 40 degrees. One more thing on the long list of steps to a successful (or not) t/l installation.
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Old 02-06-23, 11:02 AM
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Originally Posted by Telkwa
Jeepers, guys -

There sure are a lot of potential mistakes involving a t/l installation. I think I made all of them.
You're certainly not alone there. On one rim I taped- everything went fine the first time around. On the second rim I had to re-tape 3 times. After the third time, even though it seemed OK, I pretty much lost faith in tape. Even if it holds air for a few days, I have no guarantee that it won't spring a leak some time down the road. Like 15 mile down the road. I switched to Mavic UST tubeless rims with no spoke holes and no need for taping. That worked 100% all the time. Now both my kids' MTB's are using this type of wheels. I totally recommend using this type of closed rim for going tubeless. I will never recommend taping up rims to anybody.
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Old 02-06-23, 11:14 AM
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I do not understand how they make rims with no spoke holes

OK I just watched a YouTube of a guy lacing a UST rim with no spoke holes. Wow.

Last edited by Telkwa; 02-06-23 at 01:37 PM.
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Old 02-06-23, 11:38 AM
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Originally Posted by Telkwa
...Gave up and went back to tubed.
I get ya... But slow leaks can be a real bugger in tubless or tubed. So many people are totally satisfied with tubless its hard to judge which is better. On tubes there have been a few times I just ditched the tube because I could not get a handle on its slow leak...
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