Although neither the Brompton rims nor the Schwalbe Marathon Plus tyre are designed for tubeless running I was able, with careful use of Stan’s Tape, valve and sealant, to use this very successfully with no real issues until last week.
I’ve been running tubeless on the Brompton for about a year. So successful is this that; 1- So far I haven’t had a flat, and 2- the tyres have virtually never needed pumping they are so airtight.
However, on the last regular Tour de New York City run, the rear tyre slowly deflated and I had to install a regular tube to fix things.
Well, this did confirm that in the rare event of having a flat in a tubeless tyre using a regular tube as a repair is perfectly feasible and satisfactory.
However, I did note that when I first removed the tyre there was no liquid Stan’s sealant in the casing, hence, I suppose, the reason the tyre deflated. But there was no evidence that the fluid had done its job and sealed any holes or punctures. It just seemed to have disappeared.
Having spoken to Cody, one of the great team of mechanics at Halter’s Cycles, it appears he had a similar issue with a Schwalbe tubeless conversion.
Bear in mind the Marathons are not specced for tubeless use although they work perfectly well. But, most tyres designed for tubeless use are lined with a material impervious to sealants, whereas regular tyres often have a layer which just soaks up any fluid until it’s saturated and there’s no fluid left in the casing to do its job of sealing any holes which may occur as was the case here. In fact there was no actual puncture, but air was escaping via the rim and bead.
So assuming that the tyre has soaked up all the sealant it’s capable of in the past year I’ve reinstalled tyre as tubeless with a new dose of sealant and all seems to be good again. I’ve dosed up the other wheel as well just in case.