Do tubeless tyres always pop when seating. Just done both wheels and they both look seated but neither popped. Fronts holding air fine but rear still losing air somewhere but I'm sure it'll sort itself out.

Not always Ray, sometimes they just seem to slowly slide / creep onto the bead.

Put some extra goop in the tyres then set the front to 10psi and the back to 13psi and went for a ride with no problems. Let some air out the back half way round so probably about 11psi now. Thinking I might drop the front pressure a tad too. Dropped the seat post a few mm, moved the saddle forward a few mm and tilted the loop bars back a touch. I reckon the fits pretty much dialled in now, .

I assume you've seated the tyres with more pressure than that Ray?

Oh most definitely, about 50 psi, .

As Stu says: sometimes they do, sometimes they don't, even the same tyre on the same rim.

I find that it's usually the tape that's the important thing to get right and is also the easiest to inadvertently mess up. If you catch the edge of the tape when putting the tyre on then you can cause a crease or similar meaning air gets in behind the tape and leaks out, usually at the valve.

I did Cath's front wheel yesterday morning: all went well. Got back in the afternoon and the tyre is flat. It's obvious that it hadn't seated properly so back out with the Airshot and gave it some real welly A few pops and again all seemed well but I thought I'd check. Submersion test and about once a minute a bubble pops out from the valve. Cath's back from work by now so we head out for a quick ride, all of 5km whoohoo!, to see if that will help. The tyre's still solid 24hrs later so it looks like the sealant has sorted things.

Unfortunately I'm now in a dilemma: it's her bike for the Highland Trail so do I risk leaving it as it is and really trust that the sealant has worked or do I take the tyre off and retape it?

After putting more gloop in and taking it up to 50 psi the second time I got a single pop from the rear before letting them down to lower pressures. I did a 20 mile ride on them and they're definitely seated.
I bought new valves and gorilla tape to set them up but found they already had tubeless tape fitted when I took the tubes out so I'm glad I didn't fork out for proper rim tape and gorilla tape is always handy to have.
Actually the easiest tubeless I've done to date but previous ones had been done with tyres not specified as being tubeless.

Bob... was the once per minute bubble coming from the edgof the valve (in which case I would personally take it out and sort out the rim tape... maybe ) or was the bubble coming from within the valve itself (in which case I bet a good cleanup of the valve core and dekunnking the little rubber washer inside the core should probs do the trick)...

It really is a dilemma is that one. Another thing you could try is letting out enough air to lose thw seal. Then try pumping it back up and if it holds, then, its a winner (winner chicken dinner). If it doesn't hold then maybe sort the culprit out... not sure if thats any help at all

Edit. Conversely it might just need an extra nip down of the tubeless valve against the rim with that little screwey washer thingy!?

Onw thing that I personally feel helps alot is a little grease/tf2 inside the valve core whilst its all still clean and free of gunk. Keeps it all nice and easy to unscrew the core by hand if needing to top up...

The bubbles were coming from behind the lockring.

Unfortunately I'm now in a dilemma: it's her bike for the Highland Trail so do I risk leaving it as it is and really trust that the sealant has worked or do I take the tyre off and retape it?

themost common place mine leak and i advise two things

1) tight valve stem but not overtight - I have unscrewed one from the rubber bung with excessive tightening
2) leave it and see if it seals - probably will if only a very slight leak
IME if they hold air - even at lower pressures it will eventually seal [ over say 3-5 days]by riding re inflating etc

EDIT: jut remembered i had a tubeless ready rim with pre installed tape that leaked at the valve and rim tape[ removed original, cleaned re installed with own proper tubeless tape] would not seal so had to get a tubeless rim strip set up to sort it

whitestone wrote: ↑Thu May 16, 2019 6:00 pm The bubbles were coming from behind the lockring.

In which case I would say its probably formed a good enough seal now with the sealant... maybe tighten the lockring a slight more and I wouldnt personally worry. You could always check by lettin air out and reinflating. Theory (in my head) d8ctates that there should be no firther bubble from there upon reinflation

Usually when I set up tyres tubeless I go for a quick ride on them just to check everything's bedded in. This time I left the tyre before heading off to work.

I decided to retape the rim and did it really neatly. Still leaks at the valve . I think it needs a ride to sort it out.

faff in the house is always better than faff on the trail

Seems like an interface between valve and inner rim/tape problem. You sure you didn't mistakenly do the hole a bit too big or possibly maybe the tubeless valve is just a bit rubbish...

Havw you got a spare valve that you could experiment with to see if that makes any difference. A pain is tubeless when it gives hassles like that but I'd get it sorted proper... one option could be to tighten the hole (some halfords yellow tube patches straight on and then a hot poker through it to keep the hole tight as poss)...

whitestone wrote: ↑Thu May 16, 2019 5:03 pm I did Cath's front wheel yesterday morning: all went well. Got back in the afternoon and the tyre is flat. It's obvious that it hadn't seated properly so back out with the Airshot and gave it some real welly A few pops and again all seemed well but I thought I'd check. Submersion test and about once a minute a bubble pops out from the valve.

I know this one well. I now just use some of that blue automotive gasket sealant round the valve when I put them in now, that and a variety of different shaped valves at my disposal (i.e round and rectangular ) which seems to have sorted the trick. Otherwise yes, if the valve seating wasn't quite 100%, you'd have to get the sealant round for the valve to seal.

Lazarus wrote: ↑Thu May 16, 2019 8:07 pm faff in the house is always better than faff on the trail

Yes but spaff on the trail is always better than spaff in the kitchen