How exactly can you tell (just by looking) that the nipple used to tighten a spoke is brass and not aluminum? I know some are silver - not sure if they are painted silver or what. But without scraping or causing any damage to the nipple, how would one know for sure if they have no experience between the two.p.s. I don't know how heavy or light either is, so if that is one way to tel, it's not a good way for me.
Commercially pure aluminum has a tensile strength of approximately 90MPa and can be improved to around 180MPa by cold working. Typical Brass alloys have tensile strengths in the range 250 - 500MPa. There maybe different brass materials which exceed this limit. There may be those which are lower in tensile strength than the minimum of this range. Check in the web. But, according to these data, you can see that Brass is stronger than Aluminum. So, the brass plate is stronger than the Al plate. However, Aluminum is a pure metal. Brass is an alloy. So, there maybe different brasses depending on their composition.
Well, in reality you can't tell just by looking. Aluminum nipples are generally only found on superlight race wheels rather than run-of-the-mill stuff. Brass nipples are hardly ever gold colored- they are usually chrome plated or black while aluminum and plain steel nipples can be just about any color. Aluminum nipples are VERY soft compared to brass and will strip and fail in the hands of the amateur builder or repair person. UNfortunately, this is the best way to determine whether a nipple is aluminum or brass while on the wheel- when it fails due to poor skills or overstressing the wheel.
