Typing that question makes me feel dumb, but I've been wondering now for some time, so please put me out of my misery! I've searched the forums and can't find this topic, but apologies if it's been written about a million times already.

I've built a few wheels now, and am pretty comfortable with it, but have just bought some new Record hubs that I wanna build up with Ambrosia Excellight rims – so basically I don't wanna muck things up because they're expensive.

A mechanic friend of mine told me that you didn't really need two different spoke lengths for the rear wheel, as I had been told. In fact, he claims to often build the front and rear wheels with the same length spokes (he showed me a set of some retro Campy record hubs he'd just built up that he said had the same length front, rear [drive and non-drive]).

The reason this came up was because the LBS didn't have the lengths I need for the rear, or rather, that had the longer length but not the shorter. They seemed to think it would be no problem either, which got me thinking: does 1 or 2mm really make a difference?

I'd really appreciate some first-hand knowledge from an experienced wheel-builder.