These two methods are the only professional spoked wheel options I know of available in the UK. In the US Woody’s Wheel Works have been sealing rims for years, but even they admit it’s a tricky business. All will probably insist your supplied rim has a safety bead.
BARTubeless polymer band
A new idea I tried in late 2015 on my CB500X was permanent rim sealing by BARTubeless in Italy (left), as suggested by Rally Raid. I was one of the first in the UK to try this. They come with a 4-year guarantee. A polymer is applied and sets hard in the well of the wheel, which has been heated by steam. It gets done in Italy.
The tyre was a Golden Tyre GT 201 tubeless on the back and a similar K60 on the front. More here and here. One thing with Bart and similar thick linings is that they take up a bit of well depth in the rim which reduces the slack needed for easy tyre fitting or removing. I recall RR said the rear GT tyre was hard to fit.
I thought I had no air loss but tbh I don’t think I checked much, and over a couple of months there was quite a lot of leakage. Could have been the tyre bead, the valve, even the alloy rim might be porous. At an MoT weeks later they noticed the pressures were well down, but the stiff TL tyres disguised this, as they so often do.
Note in the picture top left the label says not to drop below 1.6bar (21psi) because the rims used by RR then did not have safety lips. They probably offer safety-bead rims now; certainly on the Africa Twin Bart rims they now sell. In the UK, wheel specialists Central Wheel Services near Birmingham will BARTubeless two wheels for you for £300.
Balance the cost of either of these proprietary rim sealings with the many hours but modest cost and possible satisfaction of doing it yourself.
CWC Airtight System: Vulcanised band
Central Wheel Components in the UK do a version of the BARTubeless spoke sealing. They call it Airtight. and again, as far as I know, I was among the first to try it on my Himalayan ride to Western Sahara. It costs £120 a wheel but it’s done in the UK (by ATS, a UK tyre outlet owned by Michelin).
A hooped band whose size matches the wheel rim is fitted to the rim and heated to vulcanise in two stages over two days. Alternatively, on narrow front wheels liquid rubber is applied in three stages and cures in air but takes four days. The reason I use this is because the rim section is narrow. If I was to convert your rear wheel.
There’s not much more detail on this brief page. Because the band version is vulcanised – a form of chemically (sulphur) assisted rubber ‘heat welding’ – rather than just glued like tapes or sealants, you’d hope the seal will be more secure and permanent, certainly more than tape which can come away when it gets hot.
I had this system on the rear wheel of my Himalayan on an Excel rim with the safety lip and fitted with a Michelin Anakee Wild 130/80-17 M/C 65R TL plus a splash of Slime.
In Morocco I’d guess it lost a pound or two psi a week judging by the readings off my TPMS – though with elevation and temperature changes it was hard to evaluate accurately. This was with Slime plus a small nail in the back which I chose not to remove.
I think I prefer Airtight over the BARTubeless as the rubber may be lighter, would flex with the wheel and it takes less long.
Alpina sealed spoke nipples
The Italian Alpina system individually seals each spoke nipple with a rubber o-ring, and is sold for many road bikes and so must be considered road legal.
The benefits of this system is that spoke tension can be adjusted while maintaining the tubeless seal. But how often do you do that on a decent rim? The permanently sealed bonding systems above may not work so well doing this, but as we know we’re usually talking very small turns of the nipple to adjust tension, and should a leak develop it can be re-sealed. Also, there are 36 potential leak points. It seems a way over-complicated way of doing it compared to a single band like Airtight or BARTubeless inside the well.
Beautifully forged after-market Italian Kineo tubeless rims, popular with custom builders. They’re the only ones I know of and for a Transalp will be at least €1000 each. You’re welcome.