Experimental high performance semi-tubeless tire system for my Sherman and s18

[Phi1osopher]

I am on the leading edge of experimenting with a tubeless/semi-tubeless dual pressure tire system for my Sherman and s18.  I want a mini high pressure inner air chamber inside the stock tire, allowing me to safely run a lower psi while converting the tire to tubeless.  I've successfully done this with other non-EUC applications in the past with great success while significantly improving tire performance and safety.

The idea is to have a high pressure core inside the main tire to protect the rim, basically like many run-flat systems in cars.  This would allow the rider to have a lower main tire pressure for comfort and performance without fear of damaging the rim!   Depending on what I'm doing, my fully geared riding weight can be from 220lbs up to 260lbs; I dare not ride below 40psi, which still feels rock hard most of the time.... I would like to have my main air chamber somewhere around a nice and squishy 30psi, while retaining the ability to jump, go through rocks, and bounce up curbs without fearing damaging the rim.

I currently have a similar system already installed on my motorcycle made by "TUBLISS."  I guide off-road dual-sport motorcycle rides in Mexico, where everyone gets plenty of flat tires, but since converting to the TUBLISS system I have over 40,000 trouble free miles on my motorcycle.  I use the TUBLISS in conjunction with a dynamic balancing gel/ tire sealant called RideOn. (LINK)
Here is more info about the TUBLISS system I use in my KTM 690 Enduro motorcycle, where I run the inner TUBLISS at 110psi, and the main tire at 25psi:  
http://tubliss.com/tubliss/

Unfortunately even though I think they'd be perfect, TUBLISS doesn't make systems small enough for my EUC wheels -- the Sherman has a 'small' 14" rim...   So I am going to try to do something similar but different.  I bought a solid core kid's bicycle wheel (18 x 1.75) and intend to (1) install it inside my Sherman wheel, (2) convert the Sherman rim to a tubeless system, sealing it using RideOn, mounting my stock tire over the solid bicycle tire as a tubeless tire.  Here is the solid bicycle tire I bought: https://www.amazon.com/gp/product/B092HXLJ5T

The tire does not advertise the hardness as an equivalent psi, but it feels very hard when I try to squeeze it, maybe around 80psi....  It weights about 620g, while my spare s18/ Sherman tube weights 250g.  

Anyway, it seems like it could be a very good design for anyone who wants to run low psi in their tire, reduce getting puncture flats,  significantly reduce the risk of damaging their rim, plus maybe add the ability to carefully ride home on a flat tire.  Some potential drawbacks include the +370gram rotating weight increase. Another is if the solid bicycle tire isn't actually tall enough when mounted on the rim to significantly protect it.  A third is the possibility that the whole thing will make tire changes significantly more difficult, but as I have lots of experience with this sort of thing, I think this can be easily overcome...  

I'll post updates as I get further into the project.

[Freeforester]

Sounds like the answer to many a Sherman owner’s prayer! Will be watching for updates with interest, it certainly seems like you’ve already taken the idea beyond proof of concept, and it’s hard to see what’s not to like about the idea, assuming the reputedly ‘fragile’ rim gets protected. 

[RetroThruster]

Tubless is very popular here, be neat to see it on an euc.  Shane here likes to ride on flat tires