My tubeless tyres keep going flat after a day or two. I have tried all the usual tricks that have worked before, topping up with wheel milk, new valve cores, looking for thorsn etc, but nothing works. Does there come a point when tyres become too old and porous? The back is nearly worn but the front is fairly new. Suggestions appreciated.

UST or standard tyres?

Take the tyres off, check the rim tape, if it looks ok, put them back on. Top up the latex, put some air in, go for a quick spin around the block. Make sure valve collar is tight (finger tight).

Not much else you can do.

Bit of grit/dirt / old dry latex twixt rim & bead ?

Pump up to 60psi, take out for a short road ride, then leave overnight.

Tubeless tyres often don’t seal well unless they’ve been over inflated first IMO, but pump en up to 60, slosh the sealant about a bit, and they’re usually fine.

don’t pump them up to 60 if they are stans rims though, follow the max psi on the rims depending on tyre width or you might blow them up.

i think you’ll need to provide more info for further help – eg what rim.

my cx tyres did this until I took them off, cleaned with meths and then reassembled.

otherwise, big bucket of water to find where.they’re leaking from.

Clean the wheels off and pop them in the bath, you’ll soon see where the leak is coming from – mine came from the bead as I’d used specialized sealant rather than stans (as i couldn’t get any) and it’s less runny so didn’t slosh into the bead.

I say clean them first cos mine looked like a cloud of dirt coming from the bead but was actually really fine bubbles.

Get a water bottle full of concetrated washing up liquid/water solution and pour it over the valve and rim/tyre seal. If it is leaking you will see bubbles.

They are Arch rims with Maxxis Advantage tyres not specific UST but they are about the third set with no particular trouble previously. I always have used JRA wheel milk.

I’ve just got arches after using crests and have found them a nightmare compared to crests which were dead easy. There are these little drilled holes in the arches to allow the anodizing fluid to drain out of the arch chambers, you can see them on the raised areas either side of the tyre channel. the standard 21mm tape that comes with teh tubeless kit isn’t quite wide enough to block these off and I’m pretty sure this is why mine didn’t hold air. It seems that the sealant has leaked through these and back through the spoke holes and allowed the tape to raise and become unstuck.

I’ve just got 25mm tape as recommended on the stans forum to cover the holes but I think I’ll also seal up these holes first as I’ve also found out they can fill up with water, hopefully it’ll work… might be a similair situation for you?

cheers Jim I will have a look but what puzzles me is the way they have suddenly started this after being fine for ages.

Has this problem suddenly started happening, or has it been happened since you put the tyres on? (You say the back tyre is worn, has it worn through use as a tubeless tyre?)

I found that folding beads tend not to seal very well, and maxxis in particular seemed to have little raised blocks at regular intervals on the bead, I assume from manufacture, that caused air leaks. I found the best way to deal with them was to file them flat.

If the tape has raised anywhere air wil be escaping from the valve hole, pump it up and stick it in the bath and see if air is coming out of there.