Just put my Christmas tyres on some Mavic rims and doing it tubeless. All fine, leave them for a while and then go for a ride and on the downhills when I assume the wheel is being worked harder it starts leaking from the joint in the rim. I turn the wheel round to let the solution flood that area and it coughs and splutters and seems to seal but as soon as you start flexing the wheel again it starts leaking.
Is there a fix or do I need a new rim for tubeless?
Have had the wheel for a couple of years, dinged in places but pretty straight and until running it tubeless I would not know that there is a problem. Thanks.

Pinned; rather than welded – what rim? I’d have hoped that sealant would eventually plug any gap.

Slightly wider rimstrip may help, if the tyre’s sealing against it at the edge then the rim joint shouldn’t really be an issue.

araldite and duck tape.

Rim is a 321
Very awkward shape to try and get a decent seal with tape. Araldite I would have thought would crack when it flexes but will try some good old duck tape!