Another tubeless struggle - advice welcome

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GideonReade
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Another tubeless struggle - advice welcome

Post by GideonReade »

My old '98 Trek Y5 MTB has always been a bit prone to flats, I think partly because it's always had pretty lightweight tyres, and quite likely light tubes. Logical as it's a Californian x-country racer (I'm neither, but always appreciated it's lightness).

Other halve's new Whyte has been good on tubeless, and Son-in-law offered a rejected, barely use, Specialized The Captain 2Bliss, only ever used with tubes. And Stan's sealant. So here goes.

Read lots, bought tape & valve. Borrowed compressor, readied bead squashing tape. Helluva a job getting it to initially seat, but I don't know how long stored and I didn't know to leave it tubed for a while. Anyway, past that stage now. And past the stage of finding an unsealable gash and opening up to patch that. It now pumps up fine, but after several hours flops back to I think about 15-20psi: too soft for this size & me.

Tried lots of rotating, tilting & bouncing. Eventually got to a water test.

Many, many ultrafine streams of tiny bubbles from the sidewalls!

Suggestions appreciated!
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SimonCelsa
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Re: Another tubeless struggle - advice welcome

Post by SimonCelsa »

Just to clarify; do you mean bubbles from the sidewall - i.e tiny holes, or bubbles from the sidewall / rim seal interface. I imagine you mean the latter, if the former then the tyres are scrap!
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Paulatic
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Re: Another tubeless struggle - advice welcome

Post by Paulatic »

[
GideonReade wrote: 9 May 2021, 12:33pm Tried lots of rotating, tilting & bouncing.
At what pressure do you do this?
The mistake I made in my learning curve was having too much pressure at that point. I’ve discovered <20psi does a better job.
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GideonReade
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Re: Another tubeless struggle - advice welcome

Post by GideonReade »

Hi Simon, it's the sidewall, not at the rim. However, my understanding is that sidewall porosity is normal, though not universal maybe. We rely on the gunk to seal it up. I think I read so, anyway...

Hi Paulatic, ah, that might be my issue. I have indeed pumped it fairly firm. Perhaps I will let it go down then see if a bounce or a ride helps. I do recall reading something like "not over 45psi". Although how that'd work with a 28mm tyre I'm not sure.

Cheers both!
pq
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Re: Another tubeless struggle - advice welcome

Post by pq »

I've had this happen a few times. Persisting with it for a few rides has always done the trick for me, after a bit the sealant plugs up all the tiny holes making the tyre porous.
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MikeDee
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Another tubeless struggle - advice welcome

Post by MikeDee »

You have to distribute the sealant all over the sidewalls to get them to seal. Turn the wheel in all sorts of orientations and shake to get the sealant all over the inside.
Last edited by MikeDee on 9 May 2021, 4:43pm, edited 1 time in total.
geocycle
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Re: Another tubeless struggle - advice welcome

Post by geocycle »

Yes, I’ve been struggling to understand a bead of sealant appearing on the side walls of my Schwalbe pro ones. It appears along the seam between the tread and sidewall. My approach has been more sealant and it seems to be not losing much pressure. Bit irritating though.
GideonReade
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Re: Another tubeless struggle - advice welcome

Post by GideonReade »

Well, a few months on, and I really could do with more advice on this. How's it been?

Pros: I runs fine, and has never appeared to drop pressure during my typical 3 hours rides. I have been using it at 30-45psi, more usually 35-40.

Cons: But left in the garage, after typically a week, it's dropped to an unusable pressure. But is still in place. Once, left 3 weeks, it went right down, but pumped up & reseated fine.

I've replenished sealant once, but I don't think it had run out. It's used almost exclusively off-road - South Downs - the wheels get plenty of joggling about once it's out.

From current performance, it's sort of usable on a play bike, but not an encouragement to convert more wheels to tubeless. Meanwhile, better half's MTB, new & tubeless in 2020, rarely needs even a top up. Just like a tubed bike with good tyres & butyl tubes (our tourers).

How can I close the performance gap, and get my tubeless conversion to keep pressure over 2 weeks or more?
pq
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Re: Another tubeless struggle - advice welcome

Post by pq »

Usually you can't. One of the issues with tubeless is that you have to top up the pressure regularly. Having said that I do have a pair of wheels which lose no pressure at all, but that's the only time it's happened and I'm not sure why.
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GideonReade
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Re: Another tubeless struggle - advice welcome

Post by GideonReade »

But that doesn't make sense to me? My van's tubeless, my motorcycle's tubeless, the two bought-tubeless MTBs in the family... All seem to go on and on without weekly top-ups, never mind weekly 50% replenishment.

Somethings is different!

I appreciate the powered vehicles have *much* thicker rubber. Maybe the old tubeless-ready tyres have slightly porous rubber, but not enough to drive sealant in.

Maybe there's an unsealed path at the edge of the tape, to the rim void, and out of a nipple? I guess little if any sealant gets into the rim void (I can't see any at the nipples), but the rim tape should seal... How does a "for tubeless" rim differ?
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Paulatic
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Re: Another tubeless struggle - advice welcome

Post by Paulatic »

It’s a mystery to me.
I’ve. One bike running tubeless with same Giant tubeless ready rims. Presently both fitted with Gravel Kings. Rear seated easily and keeps its pressure for a couple of months easily. Front was a pig to seat and needs blowing back up to working pressure every few days.
Got a big hole in rear in May. Too big for sealant so it has a patch inside tyre and yet still holds air well.
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AndyA
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Re: Another tubeless struggle - advice welcome

Post by AndyA »

I think, everything else being equal, your experience can be explained by your tyres having thin, leaky, possibly cracked/degraded sidewalls to start with. It definitely echoes my experience with GP5000 32mm on my tourer and Nobby Nic 3" on my MTB. The GP5000 go down to 30 from 60 psi within a month, the Noby Nics still had useable pressure after a lockdown enforced year of disuse. GP5000 had fizzy sidewalls initially, but not the Nobby Nic
hamish
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Re: Another tubeless struggle - advice welcome

Post by hamish »

I think your problem may be old tyres that have been used tubed before converting?

I never have sealant leaks on new tyres. But I also run them at lower pressures than you. They hardly go down between rides.

Assuming the rims are taped and leak proof, I am guessing that new tyres would solve your problem.
geocycle
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Re: Another tubeless struggle - advice welcome

Post by geocycle »

I have the same issue with Schwalbe pro ones. Run them at 60-70 psi then they will lose 10 psi in a week sometimes more. The sidewalls are permeable to air as is shown by the sealant beads that develop but have suspicions about the valves as well. Not too much of a problem for day rides but makes me question using them for a multi day tour.
GideonReade
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Re: Another tubeless struggle - advice welcome

Post by GideonReade »

That (leaky sidewalls on old tyre) sounds feasible, although it lacks a zero-cost means of verification?

Is there a way to check that the rim (taped, with 2 layers as recommended somewhere) really is leakproof?

(Note "rim", not "rims", I only did one wheel).

Sounds like to go forward I have to shell out for a "known good" tyre. :cry:

The theory doesn't work for Paulatic's variation though - twinned rims & tyres yet completely different results. Valve? Dented rim? Manufacturing variation?
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