Alluminium bb and headset

Are alluminium BB and headset preferable on an aluminium frame?

They are lighter but are they better also in terms of termhal expansion and to avoid loosing the Frame's BB thread?

Interesting question. A quick look on Wikipedia shows that the thermal expansion coefficient of aluminium is about twice that of steel. So in theory, a steel component inside an aluminium tube will expand less for a given temperature change and thus loosen. But in practice, I've never heard this being a problem.

Tnx, I have to decide between aluminium or steel bb and headset for my aluminium fixed gear and don't know if it's worth spending twice as much for the formers

Tnx, I have to decide between aluminium or steel bb and headset for my aluminium fixed gear and don't know if it's worth spending twice as much for the formers

You are better off picking between cage bearings and cartridge bearings and then sizes. You should be able to pick up most of the common types for £10ish if you aren't fussy about colour/logos too much.

I just got one of these myself, oversized lower bearings to make it a bit more heavy duty(the lower ones always go first, weight and they get more dirt in them).

http://www.planetx.co.uk/i/q/HSFSPIG/fsa-the-pig-headset

This was one of the cheap china offerings I was looking at as it has cartridge bearings.

Gineyea Threadless External Headsets Sealed Cartridge Bearings CNC 1 1/8" (Black): Amazon.co.uk: Sports & Outdoors

I have the sizes and types. Semi integrated hs and cartridge bb, both vp components. Just that both have two versions, a cheaper steel and more expensive alluminium. My frame is alluminium with fork steel. Weight difference might be not that big, but in terms of durability and compatibility I was wondering if there was any advise. Cheers.

I have the sizes and types. Semi integrated hs and cartridge bb, both vp components. Just that both have two versions, a cheaper steel and more expensive alluminium. My frame is alluminium with fork steel. Weight difference might be not that big, but in terms of durability and compatibility I was wondering if there was any advise. Cheers.

The only thing I can think of is that far far far in the future if you leave it outside for an entire winter or something the steel will rust a bit.

Hope you aren't paying too much for them.

http://www.chainreactioncycles.com/vp-zero-stack-threadless-headset/rp-prod108121

Not too much I hope. Fact is that I was all for alluminium, but since my bar ends shattered under the weight and I had to replace my alluminium seat clamp bolt after one week, I prefer being careful. I used to hate that my fork is steel but that might be not too bad afterall and my alluminium crankring just doesn't seem as sturdy as a steel one. So was wondering about those two components too. Having the choice, didn't want to make mistakes but I'll probably go alluminium for both. They basically become part of the frame once installed and I guess should be the same material.

Actually, you are better off with steel forks, resilience not withstanding. Steel fork tubes can be made thinner then aluminium ones and so give a better ride. If you make aluminium forks as thin as steel then they're not strong enough and you can't increase the tube diameter because there isn't the room.

Parts of me still want a completely aluminium bike

You still can. Very, very cheap BSOs use aluminium frames with aluminium forks. The ride quality is awful but at that price (and for the intended market), it doesn't matter. Slightly more expensive alu bikes use steel forks for the reasons above. Decent alu bikes have carbon forks.

Btw, I'd like to apologise for my spelling of aluminium. I'm italian ;)