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Dry Tubeless: The Lightest Possible Pneumatic System for Cycling



 
 
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  #1  
Old September 16th 20, 10:56 PM posted to uk.rec.cycling
Bret Cahill
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Posts: 833
Default Dry Tubeless: The Lightest Possible Pneumatic System for Cycling

I apply a thin [~1 - 2mm] bead of really thick non curing sealant on the bead of a tubeless ready tire. The rim, of course, needs to be tubeless ready as well.

You can then use a compressor to blast the tire bead onto the rim as with conventional sloshing liquid sealants.

Dry tubeless is the lightest possible pneumatic wheel and should be used in competitive road races / time trials, at least where roads are free of debris and punctures are rare.

The 2nd lightest possible wheel, also dry if not entirely tubeless, doesn't require a compressor to set the bead. Just make up a baggy inner tube from a plastic film that weighs only little more than the valve. You can do this with heat sealable Mylar much easier than you think. It doesn't need to be a circular inner tube. A long fat noodle will work. The diameter needs to be at least as large as the width of the tire as it will not stretch much. 15% larger should be generous enough. Set the iron for polyester and use thick sealant between the valve and the plastic. Then tie it up so it doesn't leak.

A few kPa will set the bead so even Mylar balloon film can be made to work. Prepper food packaging film is somewhat thicker and stronger and the weight is still negligible.

They should have done this decades ago, not just in cycling but in heavy vehicle tires where even service air isn't enough to set the bead.

https://www.youtube.com/watch?v=Q-3U-TRkJx8

After the bead is set with the temp tube pump up to pressure by one of the following 2 approaches:

1. Two valve system: The rim is drilled for a second valve hole for a tubeless valve to pump up to pressure. The tube collapses under the external tire pressure and goes for the ride doing absolutely nothing.

2. If you cannot stomach drilling another hole into your carbon rim a slow leak can be designed into the temporary plastic inner tube. Pump up to full pressure using the tube valve. If possible allow a little time to let the temp tube leak out before riding. If the tube remains plastered to the inside of the tire under full pressure, the flexing part of the tire will destroy any plastic tube in 30 km. This may not be a great issue depending on your situation.

As above, the tube collapses under the external tire pressure and goes for the ride doing absolutely nothing.


Bret Cahill







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  #2  
Old September 16th 20, 11:48 PM posted to uk.rec.cycling
Bret Cahill
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Posts: 833
Default Dry Tubeless: The Lightest Possible Pneumatic System for Cycling


I apply a thin [~1 - 2mm] bead of really thick non curing sealant on the bead of a tubeless ready tire. The rim, of course, needs to be tubeless ready as well.

You can then use a compressor to blast the tire bead onto the rim as with conventional sloshing liquid sealants.

Dry tubeless is the lightest possible pneumatic wheel and should be used in competitive road races / time trials, at least where roads are free of debris and punctures are rare.

The 2nd lightest possible wheel, also dry if not entirely tubeless, doesn't require a compressor to set the bead. Just make up a baggy inner tube from a plastic film that weighs only little more than the valve. You can do this with heat sealable Mylar much easier than you think. It doesn't need to be a circular inner tube. A long fat noodle will work. The diameter needs to be at least as large as the width of the tire as it will not stretch much. 15% larger should be generous enough. Set the iron for polyester and use thick sealant between the valve and the plastic. Then tie it up so it doesn't leak.

A few kPa will set the bead so even Mylar balloon film can be made to work. Prepper food packaging film is somewhat thicker and stronger and the weight is still negligible.

They should have done this decades ago, not just in cycling but in heavy vehicle tires where even service air isn't enough to set the bead.

https://www.youtube.com/watch?v=Q-3U-TRkJx8

After the bead is set with the temp tube pump up to pressure by one of the following 2 approaches:

1. Two valve system: The rim is drilled for a second valve hole for a tubeless valve to pump up to pressure. The tube collapses under the external tire pressure and goes for the ride doing absolutely nothing.

2. If you cannot stomach drilling another hole into your carbon rim a slow leak can be designed into the temporary plastic inner tube.


Use one or more 32 gauge 250 micron outside diameter needles like for insulin or flu vaccine shots to set the leakage rate. Make sure the needles can't puncture and rip other places on the inner tube.

Pump up to full pressure using the tube valve. If possible allow a little time to let the temp tube leak out before riding. If the tube remains plastered to the inside of the tire under full pressure, the flexing part of the tire will destroy any plastic tube in 30 km. This may not be a great issue depending on your situation.

As above, the tube collapses under the external tire pressure and goes for the ride doing absolutely nothing.


There are two reasons for a metered leak:

1. Before you ride you want to check for leaks in the tire that might appear after the plastic tube is destroyed from flexing.

If it leaks too slow or not at all and you might not discover these leaks.

2. You may need to use the temp tube in an emergency.

If it leaks too fast and you won't get the full range, may just 5 km instead of 15.

Guessing wildly one 32 gauge needle might take several hours to deflate an inner tube inside of a "dry tubeless" road tire.

For an exact number:

https://www.efunda.com/formulae/flui...e_friction.cfm.


Bret Cahill



 




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