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 insist your 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 bonded to the well of the wheel which needs to sent off to 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 in 2000 miles, 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. An an MoT weeks later they noticed the pressures were well down, but the stiff TL tyres disguised it, 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. I think they probably offer safety rims now; certainly on the AT 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.
Airtight: Vulcanised band
Central Wheel Components in the UK do a version of the BARTubeless spoke sealing. They call it Airtight. It’s now £119 a wheel but takes less long as it’s possibly done by ATS (a big UK tyre outlet owned by Michelin), so doesn’t require sending abroad.
All I know is what I can read on the right: a thick rubber band is vulcanised into the rim’s well, sealing off the spoke holes. Because it’s vulcanised – a form of rubber ‘heat welding’ – rather than just glued like tapes, you’d hope the seal will be more secure and permanent.
The only restriction is that the band can only be applied to a 3.00-inch (WM5) rim or bigger. I have this system on a rear wheel of my Himalayan project bike on an Excel rim with the safety lip and 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 until later.
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.