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Brake Drums again - Update

To: Healey List <healeys@autox.team.net>
Subject: Brake Drums again - Update
From: Dave & Marlene <rusd@velocitus.net>
Date: Wed, 05 May 2004 01:43:32 -0600
I just checked out the front brake drums on my BN2. Set a drum up in my 
lathe & measured with a dial indicator. After chucking on the center 
hole, & zeroing there, measured the total indicated runout (tir) at the 
flange inner surface & the inside shoe surface at .008".  The outside 
drum surface measured the same runout. Drum wall thickness varied from 
.300" to .296". I think .004" off center in the casting is pretty good 
for 48 year old drums. Don't know why the runout was between the center 
hole & the rest of the drum. But then I don't know the machining 
sequence that was used. The other front drum was nearly as good with 
.009" tir. No taper (bellmouth) & no egg shape as measured with an 
inside micrometer. Didn't bother to check the rear drums. Drum id's were 
11.005". Don't know if this is standard. Have never had any vibration 
problems, & have never checked balance. Was just curious. I think this 
proves that the factory could get it pretty close, at least in 1956. 
Maybe they got sloppy later on. Or maybe just lucky sometimes.

I would be interested in what others find if they try the same measurements.

Dave Russell
BN2





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