[JaredP91]

I’ve just made the switch to tubeless and encountered an issue when setting up the tyres.

When pumping one tyre up air is leaking from the valve stem and is audible on the inside of the rim. I’ve tried tightening the Presta valve nut more, and pushing the valve down to ensure it is seated as far down into the rim bed at possible, but still no luck.

The other wheel has the exact same set up and is holding air fine.

Any suggestions would be appreciated.

Topic

[Yearofthegoat]

Make the hole in the rim tape
Make the hole in the rim tape with a circular/conical thing, then heat up the end of the valve stem before pushing it through the hole. Be careful not to overheat it – hand hot is plenty.

It helps the rim tape to stretch rather than tear and you get a better fit around the valve stem once it cools.

[henrymorcs]

The O ring is the little

The O ring is the little rubber bit that fits with the valve tightening screw, it ensures that the interface between rim and valve is secure and you don’t scratch the rims. Although normally the issue is with the rim bed/tape/valve so I don’t think it would really solve the problem. 

Generally it’s an issue with the valve seal more than o-ring related. I also agree with others that overtightening is a no-no. With the tyres off I observed that the valve stem would actually start to be forced out of shape if tightened too firmly. This was the type you describe which needs to sit a certain way in the rim bed as opposed to the conical shaped stems you can also find which are probably less prone to this.

[Drinfinity]

Yes, add the sealant, and

Yes, add the sealant, and swish it around. 

[Secret_squirrel]

What is this o-ring of which

What is this o-ring of which you speak?  Not seen one on the 3 sets of hunt valves I own. 
Also this may be obvious but some of the bases of the valve stem are flat or ovalised and if that’s the case the long axis of the oval has to be paralell to the rim wall – it lets the valve sit lower in the rim centre channel. 

[hawkinspeter]

No worries. I seem to have

No worries. I seem to have made lots of mistakes with tubeless, so I have experience with the problems.

This morning I cycled to work for the first time in a month or so (I’ve been avoiding the rain, so haven’t cycled at all) and soon spotted bits of sealant flying off my front tyre. It was slowly leaking sealant for a good while, but the pressure didn’t seem to be dropping, so I just carried on cycling and it must have eventually sealed completely (or run out of sealant). Hooray for tubeless!

[Miller]

Good advice for the valve nut

Good advice for the valve nut to be finger tight only. Out on the road, worst case is you may need to remove the valve and you won’t be able to do that if the nut is jammed on.

[wycombewheeler]

I had this until i tightened

I had this until i tightened up the valve ring with pliers. Could be a problem if I need to fit a tube on a ride.

[henrymorcs]

I should have also added that

I should have also added that I came to this forum at the time of my issues and it was you that helped me out. Thanks a lot for that!

[Alfrado]

Might not be the valve seal.

Might not be the valve seal. Could be leaking through spoke holes into the wheel cavity then out of the valve hole.

[hawkinspeter]

I agree with henrymorcs –

I agree with henrymorcs – sealant should solve small issues, though re-taping the wheel is worthwhile if it’s a bigger leak.

[henrymorcs]

I had a very similar issue

I had a very similar issue back in May and adding sealant sorted the issue. I was quite confident the rim was taped properly – although I could hear the air leaking near the stem it was a relatively slow leak (25 mins or so to deflate) and so easy enough for the sealant to sort out. If it’s losing pressure really rapidly it may be best to double check the taping as it’s more hassle to sort after the sealant has gone in. I found putting a tube in and inflating it to force the rim tape fully down was quite helpful although I know some tubeless tyres are hard enough to get on the rim without tube so it may not be worth the thumb pain…

For context: the wheel arrived fully set up tubeless and – in theory – ready to go. However, after repeated loss of pressure (with sealant inside), I took the tyre off to find out that the rim tape was poorly set up and so the system was leaking air. I applied some new rim tape and set everything up to find the tyre slowly leaking (without sealant), and reluctantly decided to go ahead and add the sealant. Thankfully I’ve had no issues since – hopefully you’ll have the same experience. 

[JaredP91]

I have fitted the O ring with
I have fitted the O ring with the lock ring and tried both tightened and slightly looser.

This is before adding sealant, so that seems to be the next logical step

[pablo]

Have you fitted the O ring
Have you fitted the O ring with the lock ring? Don’t over tighten.
Have you filled with sealant or is this before filling? Filling may seal it.

[hawkinspeter]

Most likely the tubeless tape

Most likely the tubeless tape has got a bit damaged where the valve goes through – always use a pointy thing rather than a knife to make a small hole so that it doesn’t tear when you push the valve through it. I’ve also had issues with overtightening the valve nut and with a damaged o-ring – it’s better for it to be just finger tight and it may be worth swapping the o-ring if it’s not sealing well.

So, I’d be looking at re-taping the wheel and maybe replacing the valve nut o-ring if it’s damaged/cracked.

[Author]

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