Tubeless Tyre suddenly started loosing pressure

You sound like you've done more than I'd do! If a tubeless tyre is losing pressure and not that rapidly, i just add more sealant and carry on....i can't recall in years of running tubeless when that hasn't worked. Happened last week when i found my front tyre was getting soft when left...more sealant, all fine.

Sounds like tape failure. Road bike? See my TESA 4289 thread for opinions on number of layers of tape  required.

Tyre off is easy enough without too much spillage..

remove tyre just as you would for a tube puncture but have paper towels handy..

So…

1. Deflate
2. crack bead off on one side
3. With tyre upright and with/without tyre leavers depending on tyre, lift bead over rim at the top. Sealant will all be at the bottom at this point.
4. carefully work whole bead over the edge and then use paper towels to mop up as much sealant as possible from the bottom once it’s open.
5. I always use a hose at this point to start rinsing it out but you can get tyre off  now as most of the sploshy sealant will be gone.
6. Thoroughly clean tyre and then remove tape and clean rim using IPA finally before you apply new tape…

Are you sure that it's got sealant in the tyres ?

Are you sure that it’s got sealant in the tyres ?

it’s an mtb that was suppose to come from the shop tubeless, except they didn’t do it , so sent me a Peatys kit out to do it myself. (First time ever)

The rims were pre taped so just put 1 sachet of in the tyres as per  instructions . All been fine since until this random episode. Might try more sealant before faffing taking the wheel off.

The bike does need its first ‘free’ service so I might say to the shop it was bought from from them to sort

If you hadn't mentioned the air out the spokes, I'd have suggested adding more sealant (thanks for the reminder, I'd beat top mine up as being 6 months!)...
Sounds like the tape has moved a bit...could be done if the tape isn't properly tight on the rim and it has moved slightly. As the air is under pressure (and with the sealant moving around), it is possible the tape has been moved a bit more and now air is escaping as the sealant isn't reach the spikes to seal those.
You could try adding a lot more sealant and putting the wheel down on its side and slowly spinning it for a few minutes, then turn wheel over and repeat...this should help get sealant to where the air is escaping and it might reseal.
If you don't fancy that, it sounds like you'll need to remove tyre, clean it all up and replace and reseat.

I would be checking the lock ring on the valve stem is tight still, if this is lose then that could be letting air into the rim cavity. In the past I've also lost air through the rim where I've damaged the tape with a tyre lever when installing a difficult tyre.

Taking the tyre off without losing sealant is possible. Just keep the wheel on a 'vertical plane' and as you take the tyre off try not to make any sudden movements or spin the wheel too quickly as you work your way around. All the sealant will be pooled at the bottom. Lean it against something then proceed to knock it over 30 seconds later.

Lean it against something then proceed to knock it over 30 seconds later.

Most important step. Always remember to this part.

I would be checking the lock ring on the valve stem is tight still

Every single 'tubless losing air' issue I have had in the past four year has been down to the valve.

Side note, also worth making sure the valve is not too tight, as it can split the rim tape.

It sounds more like "pre taped" was just standard rim tape to stop the spoke holes rubbing/puncturing an inner tube, rather than actual tubeless tape (usually wider) to stop air escaping that way. I'd either add some electrical tape over (going around a couple of times) or just replace the tape. If it definitely is tubeless tape it sounds like it's either split or wasn't installed properly by the manufacturer.

If air is coming out the spoke holes (multiple) then it does sound like the tape may have lifted, and/or the valve has come slightly loose and allowed a leak path between the tape and rim.

Quite often once this happens you'll be fighting a losing battle until you clean it all out and re-tape the rim as the sealant will prevent the tape re-sealing. I'd either do as suggested above and remove the tyre to have a look, or (favourite option) ask the bike shop to have a look as then they'll be the ones dropping sealant on the floor instead of you 😀

You may however get lucky if it's just the valve come loose and losing air rather than sealant creeping past, so worth checking that first.

If you buy fresh tape, leave it on the radiator overnight to warm up a bit before applying it to your clean rim, rather than trying to do it at garage temperatures. It makes a big difference in getting it to stay put, in my experience.

Start using inserts then stop. That way, every time you have to remove a tyre, re tape and re seal, you bow down to the heavens thankfully and wonder at the simple joy of just changing a tyre and a bit of tape.

If that doesn’t float your boat, just take it off and add fresh tape. Once you’ve done it a few times it’s a very quick job so this could be seen as good practice 🙂

Yep, re-tape with care, remove all old tape and clean off all old residue, use the blunt end of a plastic tyre lever or similar to push the tape into all bits of the rim bed profile. A cheap tubeless syringe is your friend here. https://www.merlincycles.com/joes-no-flats-sealant-injector-307031.html?utm_source=PHG&clickref=1011lA96ygzB&app_clickref=1011lA96ygzB&source=PHG&utm_medium=Affiliates&utm_campaign=genieshopping

Once you unseat one bead you can suck up remaining sealant and put it into a container to reuse. Tyre only needs a bit of a wipe to prevent mess, but does not need to be sanitised with a hose.

When you reseat the tyre, using soapy water can work wonders and save time seating stubborn bead. If you have a syringe you can inject the correct amount through the valve (core removed), which is less messy. You can do the sealant after the tyre has seated to save potential mess if it is problematic seating.

Other tips; only poke a hole with an awl in the rim tape for the valve, not an 'x' cut, seals the valve better. Also check the valve core isn't clogged if reusing the core, as this can prevent them shutting properly and leaking a little and clogging more.

As others said check the valve first, cos it's easier. Air coming out the spokes is either tape or valve, people tend to assume it's tape but air that gets into the rim from anywhere comes out the spokes.

Wow , you leave your central heating on overnight

I would absolutely not add more sealent if air is coming out of the spoke holes. You'll just fill your rim cavity with sealant.

Worse case, you could weaken the rim long-term, and/or the spoke nipples, depending on the sealent type and wheel materials -- but that's just something I've read on forums, may not be true.

It very likely needs retaping, which may make you hate tubeless. But once done properly, it should last ages and pay itself off in terms of effort.

What rims are they? Some manufacturers (eg DT) do a great job, others tend to be a bit crap.

Worse case, you could weaken the rim long-term, and/or the spoke nipples, depending on the sealent type and wheel materials — but that’s just something I’ve read on forums, may not be true.

I would absolutely be filing that under 'things that have only ever happened on the internet'.

What rims are they? Some manufacturers (eg DT) do a great job, others tend to be a bit crap.

They are Orbea own brand jobs.

Anyhow booked in with the shop I bought it from, just reminded them they ‘forgot’ to do the tubeless conversion when the bike was new and I had to do the conversion myself .

They have agreed they will resolve

 Lean it against something then proceed to knock it over 30 seconds later.

No need to knock it over, it will flop down under it's own weight and the sealant will spill out - because the tyre carcass wasn't quite as rigid as you thought.

I would absolutely be filing that under ‘things that have only ever happened on the internet’.

Probably

https://velo.outsideonline.com/road/road-racing/technical-faq-corroded-rims-and-hot-heads/

This guy has an indirect explination for how sealent corrodes alloy nipples, though I've no idea if it's true

https://bikerumor.com/found-good-guy-tire-sealant-wins-hearts-plugs-holes/

Well took it to Leisure Lakes Frodsham, probably not a month ago for them to solve. All they did was tighten the valve. (2hr drive later)

Fast forward to this weekend and tyre flat again.

Last night took the tyre off and not a huge amount of sealant left in there. Original tape raised at the join and sealant under prob half of all the spokes ☹️

Not rating LL Frodsham at the minute as they appear to no naff all about bikes (other issues too)

Waiting for it all to dry out as I had to hose it all down, then we clean and start again….

I don't think peaty's sealant has a very good reputation . I would try stans

Well took it to Leisure Lakes Frodsham, probably not a month ago for them to solve. All they did was tighten the valve. (2hr drive later)

I'd be slightly miffed having to set up the tyres tubeless myself , although TBH with modern rims and tyres it's rarely the faff it once was. But why would you drive 2 hours to sort out a puncture?  Even if you'd had to order new tape and sealant it would probably have been cheaper than the petrol.

And nipping up the valve does solve it in 95% of cases IME.  

As someone else suggested, Electrical tape (particularly the 50mm wide rolls so you don't need to overlap layers) makes a good top layer over the tubeless tape.  It's stickier, thinner, and conforms better so you can get it right up the side of the rim then trim off the excess with a scalpel/razor blade once the tyre is in place. It's not (generally) tough enough to do the job on it's own through. 

These 60ml dosing bottles are great for putting more sealant through the valve stem, and also extracting pooled sealant from the tire carcass when changing or reinstalling the tyre the right way round…

Metal thingie is the valve core remover, also super useful.

https://www.halfords.com/cycling/bike-parts/inner-tubes/schwalbe-doc-blue-tubeless-tyre-sealent-585684.html