I have a mavic wheelset that has Schrader sized holes and uses a grommet to step down the hole to presta sized.
Has anyone had any joy getting this to work tubeless?
If yes, I assume running the grommet under the rim tape and just pushing valve through?
Cheers

The valves WTB and Superstar sell work well- they have a huge conical base that’ll often (probably not always- depends on shape) seal a schrader hole just as well as a presta. I wouldn’t use the grommet at all but you might want to find one of the lockrings with the adaptor step

Another approach I used, before I found those, was possibly mental but it worked- I filled the hole with chemical metal then redrilled it for presta. That was for a rim that’d been horribly drilled out by some idiot, but it’d work for factory too.

Could you not just cut up a Schrader rude and use the valve from that? You’ve probably got lots lying around. I find the spout of the Stan’s bottle fits perfectly in a Schrader valve with the core removed. And they get gunned up less than Presta valves.

Tom KP

Thanks both. Good to know.
I’d just assumed only presta had removable cores – been years since I looked at a Schrader, but if they’re removable too that would eliminate any possible gap.
No issues having no lock nut then?

I’ve bodged a tubeless set up with a schrader rim/presta valve using a grommet before and it worked, as you say cover with rim tape and make a presta size hole, the sealant will fill any gaps. Even easier if your valve has a rubber o ring seal

You can buy Schraeder tubeless valves

You can buy Schraeder tubeless valves

I was going to say that but didn’t want to spoil their fun trying to bodge it.

Doh! Thanks for pointing that out, had no idea they existed… problem solved!

I dont really understand.

The downsizer thing i use fills the outer hole ie you can see it betwixt spokes.

The hole on the inside is just riund and the valve sits in it quite happily?

Yeah I’ve done this fine. Cut a cross in the tape, poke valve through and use the grommet and collar outside the rim.