if you have aluminum stem should u use aluminum spacers or could you use carbon? it doesnt matter right?

99% sure doesnt matter

Doesn't matter. Just check from time to time that no corrosion is occuring. Don't let the interface get wet especially with salt like from sweat.

I don't know ... in another thread a guy who took Chemistry in college assured me that any time aluminum and CF come into contact they will exchange electrons, weld together, and ruin everything for miles around.

Seriously, I wish someone with real-world as well as scholastic experience could weigh in here. I know my CF seat posts have never welded to my Al frames ... but maybe I have been lucky.

I've got an aluminum stem adapter with carbon spacers, which have been in place for ~ 8 months with zero issues... FWIW.

I have a carbon steerer with aluminum spacers, stem, and cap with about 15k miles on them. No problems whatsoever so far. Another bike with carbon frame and aluminum seatpost and stem--again no problemo!

Doesn't matter - if there was any corrosion issue possible I'd think it would be with carbon spacers + aluminum fork STEERER tube and not the stem...in any case I had this combo on a bike for 10 years with no issues. Maybe if it was a tight fit and you sweat profusely on it for a LONG time something could happen.

7000 series aluminum is high strength But it contains a % of Zinc

as you should know common flashlight batteries are stacks of C & Zn.

6000 series has different constituent elements ,

in short not all aluminum is the same..




./.

Keep in mind that many of the successful examples here involve heavily anodized aluminum. My Al spacers, for example, are heavily anodized black. Al seat posts these days are usually anodized black. The aluminum oxide coating on an anodized Al part passivates the surface to further anodic reaction with the carbon. Whether we are talking Al frame and carbon post, Al post and carbon frame, Al steerer and carbon spacers or Al spacers and carbon steerer, even if the Al surfaces are bare, there is no reason to not go ahead. Just pay attention. Keep the surfaces dry and especially free of salt water. Inspect the parts every now and then.

I use carbon on my steel, aluminum, and carbon frame/headset.

All my stems are aluminum. I have carbon forks, with aluminum spacers, carbon forks with carbon spacers, and steel forks with a mixture of aluminum and carbon spacers. Never had an issue with any of them welding together.

You're living on borrowed time.

OP- Are these reputable, name-brand crabon spacers, or are they generic Ebay spacers? Don't take chances with parts that undergo heavy loading like a spacer. That's a mistake you'll only make once.

Relax. Your spacer is not going to act like a battery. Both of the components are rather inert and will not react with each other. If you compare them to a battery there is something missing and that is the alkaline paste that makes up the majority of the space in a battery. It is a zinc shell and a central carbon core. The reaction is between the alkaline paste and the zinc shell, not the carbon rod in the center.

I ride a Denali. According to some, I should be dead already.