Jersey Tom wrote:Hubs too I'd imagine.
Steel is good stuff. Don't fall into the trap of thinking it's heavy.. and that heavy is bad. I'll admit my knowledge of steel specs outside the US is a bit rusty (pun!)... but stuff like 4340 and 300M (or EN24, EN26, EN36A ??) can have very, very high yield strength. When you have a high yield strength you can typically use less material and lightweight steel parts.
Really it's a question of efficiency, how much strength can you get per some size and mass of part - and that varies with alloying and temper. For that matter you could have aluminum parts made from some crap alloy which then wind up being quite heavy.
I thought hubs/rims were magnesium?