Tempted to have a go with an old set of wheels, drill the rim, tubeless valve and then a small inner tube (maybe a bmx?) via normal hole.
It sounds straight forward....and if it doesn't work I'll just plug the hole and go back to using tubes on them.
Anyone had a go?
Or an idea if you can get away without drilling?
wouldn't work, with an inner tube the pressures in the two chambers would equalise, you need a more rigid inner chamber to run a higher pressure than the outer.
I'm thinking the inner/small tube needs to be fairly rigid, otherwise it'd just expand and fill they tyre volume at a single pressure.
A 1" tyre inside might work.
I am far from convinced of the advantages of procore anyway, I would rather have the extra weight as beefier sidewalls. It didn't seem to have any great advantage on the world cup downhill tires of rims so far this year.
I think it will slip into the parts bin of history pretty quickly.
I think if done well (ie allows tyre to be fitted easily) it might do a good job of holding the bead down & stop burping, which seems to be a bigger issue on DH tubeless
The new wider rims with a bead seat are much better advancement for that IMO. With my LB 38mm rims it is a fight to break the seal and push the bead into the centre channel.
I still think a nice deepish central channel to allow easy fitting, but that channel somehow contains an inflatable bit, would be a help - not sure I buy the need for an actual tube in there as support for the bigger carcass (though the precedent for spacers in forks & shocks might suggest that the same principle is valued elsewhere)
You don't need a tube, you need a very, very light tub tyre, that could work.
Can't find it now, but it has been done using a road tubular tyre.
There is a video on YouTube.
I Set it up on an old mavic d521. I used a lightweight 26" slick as the inner tyre. The main advantage is that once the inner tyre is up to pressure, the outer tyre cannot move off the non tubeless rim and you can ride it flat. It worked out slightly heavier than a DH tube.
I was going to set it up on my new 650b bike for the Mega but didn't have time as I only had the bike built the day I left, plus I had proper tubeless rims so thought it'd be ok.
If I had set it up then maybe I wouldn't have had such a stupid number of flats in practice.
There are two approaches to it:
Road tube+trainer tyre. What Schwalbe have made is similar to this, but with a special valve that means you don't need to drill the rim, and an airguide that lets air into the MTB tyre.
Modified tubular tyre: This is what Deaneasy did, and the video cchris2lou mentioned is theirs. It had a bulky valve and seemed to require a modified rim, but with a better valve design it could be workable with an unmodified rim. Going by a photo that was going round a few weeks back, it appears they might be going into production with Tufo.
I've tried with a 29er and a 700c tubular, but can't get the second tyre bead in when the tub is in place. Might work with 650b and a 700c tub. When you inflate the tub shrinks onto the rim
When you inflate the tub shrinks onto the rim
Despite internet theorists disputing this last time I said the same, as someone who's tried it I too can confirm this. 700c tubs seem about right for making it all mountable and dismountable for a 26 rim. 650b tub on 26 made it a total pain in the arse to get a tyre back off.
For the OP apart from the obvious reasons
Bored
Bet with a mate
Just because
Why do you think you need pro core? Pressure issues? Burping issues?