The Ford Barn - View Single Post - Brake drums ; cast iron vs ductil cast iron .

MikeK · 04-08-2013, 08:43 PM

I believe both the Brattons and Snyders US made drums are the same ductile (nodular graphite) cast iron. The imported drums are standard gray (flake graphite) cast iron. Strength is not the real issue. Resistance to cracking is.

In the US the DOT does not permit gray iron drums on trucks, only ductile. An extremely hot gray (flake graphite) cast iron drum splashed by driving through a puddle can fracture causing a catastrophic wheel lock up. With ductile iron, the drum only warps severely, ruining it, not you.

A secondary issue is specific to model A's with swaged wheel studs. I personally know of several of the cheaper import non-ductile iron drums that developed hairline cracks radiating from the studs where the swage imparted tensile stress.

04-08-2013, 08:43 PM	#2
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: Brake drums ; cast iron vs ductil cast iron . I believe both the Brattons and Snyders US made drums are the same ductile (nodular graphite) cast iron. The imported drums are standard gray (flake graphite) cast iron. Strength is not the real issue. Resistance to cracking is. In the US the DOT does not permit gray iron drums on trucks, only ductile. An extremely hot gray (flake graphite) cast iron drum splashed by driving through a puddle can fracture causing a catastrophic wheel lock up. With ductile iron, the drum only warps severely, ruining it, not you. A secondary issue is specific to model A's with swaged wheel studs. I personally know of several of the cheaper import non-ductile iron drums that developed hairline cracks radiating from the studs where the swage imparted tensile stress.