At least post all the page Trev it says not recommend, not illegal.
It is NOT recommended to install tubes in tubeless tyres, because of the potential danger of experiencing a sudden loss of pressure due to the tube not being seated properly or the tyre being
www.bigtyres.co.uk
FITTING TUBES IN TUBELESS TYRES
It is NOT recommended to install tubes in tubeless tyres, because of the potential danger of experiencing a sudden loss of pressure due to the tube not being seated properly or the tyre being punctured. This could lead to a fatal accident.
Tyres designed for tubes have a smoother inner surface, while tubeless tyres do not. As a result, tubes can chafe and puncture in a tubeless tyre due to the roughness of the tyre and wheel.
When a tubeless tyre is punctured, the penetrating object is gripped by the inner liner (the built-in tube) and thus air loss through the penetration will be gradual. By contrast, when a tube type or a tubeless tyre fitted with a tube is punctured, once the tube is penetrated, air loss will normally be sudden. In this case, air will rapidly escape through the valve hole in the wheel and between the tyre beads and the wheel which, with a tube fitted, no longer provides a hermetic seal. Sudden pressure loss in a tyre can result in the bead dislodging and a loss of vehicle control.
When a tube is fitted to any tyre, it is important that the inside of the tyre is carefully examined to ensure that there is no feature which could cause premature tube failure due to cuts or chafing. Such examples are:
Any tyre manufacturer’s paper or plastic identification labels must be removed and label indentations buffed smooth.
Damage to the inside of the tyre, possibly due to a previous penetration or repair.
Also, the increased thickness of the tyre / tube assembly can cause running temperatures to increase and could under prolonged conditions cause premature tyre failure.
Inner tubes should not be used as a means of repairing a puncture to a tubeless tyre, as a proper repair should be carried out to retain the tubeless properties of the tyre.
Inner tubes must be fitted to all tyres that are NOT marked as "Tubeless" and to all tyres marked as "Tube Type".
Wire wheels, multi-piece wheels and some single piece wheels designed for tube type applications CANNOT be used as tubeless fitments and the use of a tube (regardless of whether the tyre is "tube type" or "tubeless") is ESSENTIAL FOR SAFETY. Always use tubes in such fitments.
We do not accept any liability for any consequences that may occur as a result of using an inner tube in a tubeless tyre.