er…helllp!

I've recently used Stan's kit to convert a pair of 4.2 rims to run tubeless, but after 2 or 3 weeks with no problems, the tyres now keep deflating overnight – can anyone offer a sensible explanation, and/or advice on how to fix 'em please? Anyone know if the 4.2's a bit of a bugger to convert using non-DT kit?

FWIW (apologies for any info overload), the rims are fairly new and still in good shape – no dings, gouges etc. The tyres are also relatively new Kenda Nevegal 2.1's (non-UST), that I'd used for about 100 miles with tubes. I used Stan's thin yellow tape, standard rimstrip and Stan's 'gloop'. I've converted 2 pair of wheels before, both which have old Nevegal 2.35 tyres – these are still running OK and loose very little air, even over 2 or 3 week period. Initial inflation of 4.2 & narrow Nevegal was far easier than my previous conversions – and there seemed to be less sidewall leaks, although lots of small leaks from beads. I eventually took 'em up to 50+ psi to seat the bead and this seemed to work (no bubbles on the washing up liquid test), and they held pressure for at least 2 weeks. Everything looked so promising, so can't understand why they're suddenly so leaky(?).

(I guess I should go out and do the inflate & soapy water test – but after 3 days consecutive riding & tyre pumping, followed by evenings of decorating – I'm too knackered to move from the keyboard.)

check the seal at the valve, if the valve lock ring jobbo thingy (little silver knurled bit that holds it to rim) comes loose it can bleed air. DO NOT overtighten it though as it'll tear the inner rim strim. That's the usual cause of random deflations with stans rim strips that i've found over the past couple of years.

sounds like your sealant has dried out, or run out. top up, re-inflate and give a shake maybe.

OK, ta for the feedback. I'll investigate the valves for leaks – hmm…also top up the fluid a bit (I know the rear has about 20% less fluid than front, 'cos my hand slipped 🙄 – and rear is the leakier of the two)