[Chrysler300] Beating the drums-Whoa Nelly

["Rich Barber" <c300@xxxxxxx>]

Out of curiosity my ’64 300K advisory group started measuring the width of the machined surfaces in various 11” ‘64K brake drums and found the following:
			Nominal	Machined surface
Location	Type	Width		Width
Rear		HD	  3”		3 ½”
Front		HD/STD  3”		3 ¼”
Rear		STD	  2 ½”	3”-(est.-no data at this time)

We also found that the lengths of the replacement linings only approximated the lengths shown in the Chrysler spec sheets.

Whilst investigating, another "3" HD" rear drum was found to be equipped with the standard 2 1/2"wide shoes(as mine was).  Apparently works just fine while focusing all drum wear in a narrower band not in the center of the machined surface.

Points being: 
1:'64 Chrysler brake drums appear to have some extra iron in them and can be expected to have 1/4"-1/2" wider machined surface than the nominal width of the shoes.  This may be standard practice for all manufacturers and it does seem reasonable to have the machined width somewhat wider than the shoes to avoid unwanted contact.
2:  Measure your drum width to determine/confirm if you have HD brakes.  If so, insist on the proper width of rear shoes.  The HD brakes were standard on ram-engined '64K's and even had a different composition of the shoe lining, according to the spec sheets.  The HD brakes (and suspension) were available on other '64 Chrysler 300's for $35.95.
3:  If you want the same-dimensioned brake shoes as came on your car, research the lining length specs and pass them on to the reline shop before they bond on something from some other spec sheet.  This difference in lining length may not be all that important to brake function, but Chrysler did research and design some optimum lengths and contact area of the linings seems to be an important and oft-reported variable.  I can't imagine changing from asbestos-containing linings to current composition would have changed the lining length specs that much.  Friction theory holds that frictional force is due to the coefficient of friction between the two materials (lining and drum) and "force pressing surfaces together" (hydraulic pressure times area of wheel cylinder piston) and independent of the contact area.    Stability, contact dynamics and heat transfer no doubt drive the decisions on lining width, length and position.

Thanks to Messr's Jett and Pinder for their input.

Then, there is an issue of the groove cut into the center of the lining.  I recall that being to reduce squealing, but cannot confirm this.  Brake pros, please chime in.

C-300-K'ly,
Rich Barber (Back from the Chrysler Performance West Spring Fling XXVI in Van Nuys, CA--only three classic 300's there today)




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