(01-22-2010, 09:38 PM)j beede Wrote: Technically you are incorrect as anodized aluminum (Rc~80) is quite a bit harder than steel (Rc50~60). Of course the hardness of the aluminum is really due to the nanolayer layer of Al2O3 formed at the anodized aluminum surface (which admittedly is pierced rather quickly). Actually, my braking surface project is not so sacrificial as I view the rims as scrap the way they are--even though the wear indicator is still visible. I have looked at some used rims over the past few days and see that I am not the only one with nasty braking surfaces. It surprises me that cyclists put up with this. Stickiness I am not interested in... quiet braking during early morning rides is my goal!
...j
I'm not going to have a metallurgical discussion over this, but steel is hard all the way through, while aluminum, as you point out, only has a very thin layer on top of the material that is harder than steel. The rest is soft.
And since they are already viewed as scrap, try slate. It might work. I called a friend, and he suggested using slate to resurface the rim, giving it a really good surface to grip to.
And when I said "sticky", I was referring to a nice surface that the brakes would want to hold on to. Sorry for the confusion.
I really do hope this helps. Good luck! Let us know how it turns out.
Well, I'll be damned! I looked this up right after I posted, and this popped right up!
http://www.instructables.com/id/bike-rim-resurfacing/
Looks like my friend might be on to something.
Note: I have NEVER tried to resurface a rim with slate, but it does make sense.