Bike size

[KDean]

I've seen a Thorn Stirling mtb for sale I'm interested in , According to the seller it weighs 12kg ( unlike the one on SJS ) ,the only thing is it's suitable for someone up to 6ft 2" & I'm 6ft 3" .would you let that put you off ?

[PH]

Bike size guides are just that, guides. Something that might be perfect for someone of your height, might not for another of the same. 
I fit across three sizes of bike measured in the trad way 58, 60, 62.  On a compact frame it gets even easier, you only need enough standover height and enough reach not to need a unreasonably long stem. I'd say you'll certainly fit on a bike a fraction small for you, but there's no way of knowing if you'll be happy with that.  Are you happy with the fit on your current bike/s?  Measure that accurately if you don't know it and see how it transfers.

According to the seller it weighs 12kg ( unlike the one on SJS )

Just looked and the one on SKS is 16.38kg with a lighter fork.  To me that 4kg+ difference sounds too good to be true.

[KDean]

That's what I thought ,but then they have had different models ,Maybe different grade Reynolds tubing is used ,My Ribble is Reynold 725 compared to the Nomad 969 & The Ribble weighs 12kg .

[PH]

That's what I thought ,but then they have had different models ,Maybe different grade Reynolds tubing is used ,My Ribble is Reynold 725 compared to the Nomad 969 & The Ribble weighs 12kg .

No sorry, it isn't possible that different grades of steel will make a noticeable weight difference, all steel weighs the same, a better grade of steel means a bit less can be used, but on a similar style of bike we're talking a few grams.  Even on considerably different styles of bikes we're rarely talking more than half a kg. 
The problem with weight comparisons is that not everyone includes the same things.  I think that's the only honest explanation for the difference we see here.

Out of interest, how much does your Nomad weigh?

EDIT - Just to add in case it isn't entirely clear, I'm only talking about weight.  Frames that weigh half a kg different can have a very different feel.

[KDean]

My Nomad is a 620l & is over 17kg ,with thorn racks .

[PH]

My Nomad is a 620l & is over 17kg ,with thorn racks .

Mk 3?
If so the weight of your frameset is is about 4.8kg depending on forks. By any standards, that's a heavy frame.
It's still all you have to play with if you keep the same kit. 4.8kg.
Sticking with touring frames, though none of these will have the same luggage capacity as a Nomad - A titanium frame and carbon fork will save a whooping 2kg, about 40%.  A lighter steel frame and carbon fork saves about 1.4kg.  A lighter steel frame and lighter steel fork saves around 1kg. 
Anything else is about leaving stuff off, or buying lighter components, though that can involve other compromises.

I hope you don't think I'm unduly negative, even if you do, I'd rather be the spoilsport on a forum than see someone go waste thousands of pounds chasing something that isn't realistic.

[KDean]

No ,you have been very helpful, I'll do more research , I'm not going to need to carry as much as this bike is capable of , I've been put onto Stan's no tube rims ,they are half the weight of the Ryde Andra ,It's a MK2 by the way