The thing I thought was a bit odd was that I emailed and said “can I have light ones please”, they came back and said “the lightest we can do is 355g, is that ok?”, I said yes, 2 weeks passed, they said “actually one’s come to 356g, is that ok?”. So:

a) I lied, one of mine is actually 356g
b) they appeared to offer light ones before they made them, which suggests the raw constituent parts are not the same.

Didn’t Stans used to charge extra for the lighter versions of the same model?

Yeah for a while they did two weights of Olympic, <330g ones were more.

b) they appeared to offer light ones before they made them, which suggests the raw constituent parts are not the same.

Assuming that they have some QC (and they do have a decent rep so I reckon that’s a fair assumption), from a manufacturing POV, they’ll know the statistical range of weights they’ll get when they make a batch of say 100 rims. But that’s just a probability thing so it turns out that in your batch they didn’t get any at 355g. Doesn’t mean they’re made any differently.

EDIT – though it is possible that they do – maybe one layer less carbon for example.

Went and googled Christophe Sauser’s bike. Not my type of bike at all. So why do I want it?

http://velonews.competitor.com/2013/08/mtb/pro-bike-gallery-christoph-sausers-specialized-s-works-stumpjumper_298554

They may have more than one production line making that bit, so each line will have it’s own mould, dies etc, hence the variation. If you buy lots you may find two from the same line, which may be closer in weight.

Went and googled Christophe Sauser’s bike. Not my type of bike at all. So why do I want it?

That’s not the best example granted- seems he is on more sponsored parts nowadays. Doesn’t need to be your type of bike but in a discussion of caring about weight, Sauser always used to be one of the better known examples of a Pro caring about the finest details (and being allowed to indulge in this by his sponsors).

His full sus Epics were always nice and one of the lightest bikes on the WC circuit. AX everything, custom tuned Eggbeaters, nude frames hand picked for weight from the factory, alu cassette, Extralite bar ends, etc. One of the few guys to spec genuinely WW parts from a range of manufacturers. Nevertheless I think he still has quite a few subtle, quirky component choices on an apparently stock looking factory bike in the hardtail in the link like Kappius hubs but it isn’t clear from the picture.

They may have more than one production line making that bit, so each line will have it’s own mould, dies etc, hence the variation. If you buy lots you may find two from the same line, which may be closer in weight.

I think this is probably the case plus the real skill in making consistently light CF parts is controlling the amount of resin in the process. Too little is really not good but too much (within reason) just makes for a slightly heavier but safer part hence a tendency for adding slightly too much rather than too little.

They weigh less when filled with air – FACT.

I think they are heavier when filled with air.

Didn’t Stans used to charge extra for the lighter versions of the same model?

Intel used to (and probably still do) sell versions of the same CPU with different clock speeds. What they actually did was manufacture them using an identical process and then test them at various speeds. The ones that proved stable at the higher speeds got labelled and configured with that speed.

That’s how Scott (used to at least) assign their frames too – weigh them as they come off the production line, lightest ones are Ltd, then RC, then 10, then 20 etc etc.