Sports-1
The Silkroad frames are some of the first to pass the highest safety testing a bike can undergo, which is for a combined rider, bike and luggage weight of 180kg/400lb.
It helps that the Silkroad uses oversized, thick-wall tubing to build a strong structure that can resist the twisting forces between the front and rear luggage. I can only think of a handful of brands with the equivalent tubing spec. While steel normally has a different ride feel to say aluminium, when it comes to super-stiff touring bikes with a bunch of luggage attached, it’s actually hard to discern between materials.