Some questions from a tubeless virgin

Xc rims and 30 psi? I run mine at 18.

Maybe try a longer loop to get the sealant into all the gaps

Start with the easy fix and make sure you're valve is tight and has the correct profile rubber seal

If it's holding pressure for the duration of a ride then I'd just pump it up before the ride and it might hold pressure better after a few rides. Check if you can still hear liquid sealant in a few weeks (take the wheel out and shake it, you should be able to hear a puddle of sealant splashing a bit), if you can't hear anything then it's probably dried in the process of sealing leaks and will need a little too up. You shouldn't need to add much as the initial amount will seal the big holes so the additional amount should in theory remain liquid and fix future punctures.

I must admit, I wasn't that impressed with Peaty's tape. I've been using Stan's for many years but decided to re tape an old wheel with Peaty's earlier in the year. I found it difficult to get it to stick down "properly" when installing and made a faff of it to be honest. I then had a slow leak for months with that wheel. Finally got fed up last week and re taped with Stan's plus a new rear tyre. No leak. Could be my shoddy attempt at Peaty's tape, could be the old tyre I used.

I find Stan's easier to use. I use a hair dryer to heat the rim and tape as I apply it, stick the tape down firmly on one side of the rim and then gently mould the tape to the rim bed from the stuck down side to the other side while using the hair dryer to keep it warm. Ends up with the tape being nice and even with no air bubbles. That method really didn't work with Peaty's. Maybe due to the tape being less sticky than Stan's.

Add more sealant and put wheels on their side and spin them round...sealant coats the sides, then after a few hours flip wheel over and spin and then leave for a few hours.

Won't completely fix but should reduce the number of leaks.

How hard your tyres to lose 30psi? Each to their own, but that sounds like a lot of air... probably does depends on tyres and ride weight though.

1) What pressure are you running to be able to lose 30 psi? I run betwee 18-25 psi depending on what I’m riding and what tyres are on there. Generally I runnaround23 psi for most riding. Up the rear to 25 if it’s particularly rocky / fast. 18 is on the front is   with a Hillbilly if it’s relatively slow speed biblical slop.

2) I’ve always lot some psi between rides with tubeless. Not much but I do tend to tip up each ride. Only a couple of psi really - nothing major.

3) The best tape I’ve found is DT Swiss. I tend to tape in the garage but I warm the rim with a hairdryer before starting and then pull the tape really tight as it goes into the rim. I run tend to go round with the hair drier and a wide plastic tyre lever and make sure the tape is fully stuck down into the rim.

4) Sometimes the tubeless seal is better after a couple of rides once all the sealant has got into all the bits of the wheel / tyre.

losing maybe 30psi over the course of 2-3 days in one tyre

Is this a typo? 

Putting excess pressure into a tubeless setup is not a great plan. And if this is an MTB setup and 'a bit' is 30psi, that's excess pressure. 

But I'm getting slow leaks - losing maybe 30psi over the course of 2-3 days in one [XC] tyre

https://share.google/7CUr2onIG4vrmHY6W

Righr, thanks all.

To clarify, an overall 30psi+ was what I went for initially to get beads seated, check for leaks etc. Its certainly achieved the latter. I was planning to drop a bit for actual riding. Pretty much all of that is leaking out though, so even if I'd set them up to (say) just 18, they'd still be flat a day or so later. Clearly something's not right.

I chose Peatys tape because, well, most others are American, and they can narnies. Maybe I've handicapped myself a bit there.

Slightly reluctant to fiddle with the valves initially, so I'll start with boshing a little more sealant in and sloshing it around, probably at lower pressures too. Then see how that goes, including a ride. If no better, I guess it's re-apply tape (with a little heat) and start again. Never easy, is it?

You said..

But I'm getting slow leaks - losing maybe 30psi over the course of 2-3 days in one tyre, and a bit slower in the other.

but now you are saying

To clarify, an overall 30psi+ was what I went for initially to get beads seated, check for leaks etc. Its certainly achieved the latter. I was planning to drop a bit for actual riding. Pretty much all of that is leaking out though, so even if I'd set them up to (say) just 18, they'd still be flat a day or so later. Clearly something's not right.

So what you are actually saying is it went totally flat over 2-3days, not (what I had assumed) it had got a bit softer over 2-3 days. The latter is pretty normal but not ideal (I've got some wheels that have been not used for more than a year that are still just fine). The former is clearly a problem.

I'd go old school and inflate and dip in a bath or big vat of water and slowly rotate to see where bubbles are coming out of. At that rate, I'd expect some. My bet would be the valve seating. Other would be the tape - when you first do tubeless you don't appreciate how clean the rim needs to be to get an airtight seal.

I'd go old school and inflate and dip in a bath or big vat of water and slowly rotate to see where bubbles are coming out of. At that rate, I'd expect some. 

This. I had a CX tyre losing 20psi over a couple of days. I dunked it and it was a problem with the sidewall and nothing to do with the setup

Going completely flat is almost certainly valve or tape issues. Some tyres have very porous sidewalls which can take a week or so to “seal” properly and in some cases, Rene Herse and Challenge tyres for example, you need a sealant like Orange or Challenge to deal with the sidewalls. Even then they will only lose 5 or so PSI at road type pressures (50-60psi) so I doubt that’s your issue. 

+1 DT Swiss being a good tape to use. Sticky enough and pliable enough to be applied at room temperature without the need for a hairdryer or putting a tube in overnight to seat it. Loads of people recommend TESA 4289 but I tried it and thought it was garbage. Too stiff to mould into the rim bed and not sticky enough even with a hairdryer and about 4 pairs of hands to hold everything. Schwalbe tape is good initially and easy to apply but I’ve had 2 lots fail at the spoke holes after about 12 months. 

I dunked it and it was a problem with the sidewall and nothing to do with the setup

Yeah, could be that too. I had a tyre that turned out had an issue at one of the little sprue points (where the little bit of rubber sticks out) on the sidewall and no amount of sealant ever sorted. 

Odds are still on the valve or tape though especially as a newbie first time setup. 

Bucket of very soapy water and investigation first.

Personally I don't like peaty fluid. Tried one bottle but reverted to tried and tested normal stans. 

@timba I think you have it, sir. At 40psi, dunking produces several areas of little bubbles from the sidewalls, so I'm going to pop the beads, bosh a bit more sealant in each tyre, reinflate and go for a ride. Then do the 'lying on their sides for a day' thing as well.🤞 

There's no obvious leakage from the rim or valves.

I'm going to pop the beads

Long term, you want to move on from that. Once you've got the bead seated well you don't want to be breaking that if you don't need to.

You need to buy yourself a valve core remover (some valve caps have them built in so you might already have one) and a sealant syringe. Not a lot of cash. Then you can top up the sealant through the valve with a known dose volume as and when without the mess and faff of unseating the tyre.

Also - and you probably know this already - tyres inflate and seat for the first time so much easier if the valve core is removed. Just hit it with a load of wind fast to get it seated, remove the pump/compressor line and the once the tyre has deflated pop the valve core back in and reinflate.

BTW - what were the tyres? Leaking from the sidewalls is common (and sometimes fatal and can't be resolved) in non tubeless ready tyres. But if they were tubeless ready it's a manufacturing flaw and very unlucky to have on your first attempt. 

Thanks convert.

Yes, there's a core remover in one of the caps. Just used it to allow a good dose of air via the Airshot. That's the tyres reseated now, and resting on their sides while late breakfast.

Don't laugh, they're 26" Panaracer Fire XCs... 'TLC' on the walls. I know, I'm somewhat slow to get with the modern ways. But I still like the bike, it does everything I'm likely to need for the moment. We tried to set up a pair of Conti XKings last week, but it quickly became very clear they weren't going to be compatible.