Re: [Amc-list] 63 American front brakes (and suspension)

[Frank Swygert <farna@xxxxxxx>]

I agree with you about the lower trunnion design, especially the "non-locking" issue. It's easily fixed though, tack weld or stake in a spot or two when they are assembled. When new they are pretty tight, but with age and abuse the punched hole gets worn. Adding something like your shock mount (or mine) or a "girdle" (just two pieces of 1" angle iron, one on top, one on bottom of arms between shock and pivot, with bolts on the outside clamping the arms between the angle) fix the problems with little work. I drove and abused my 63 American for 14 years all over the country and only had that one cap work loose. That car literally went coast to coast! But I did have the parts strengthening the lower arms most of that time.

The stock brakes on the 58-63 American are 2"x9" w/1" wheel cylinders, 139.5 sq. inches of brake area. Stock 64 Classic six brakes are 2.5"x9" w/1-1/8" wheel cylinders, 153.76 sq. inches of brake area. I used those before I knew disc brakes would fit. Those were nearly as good as disc brakes on the little American! If you have the 10" brakes may as well use them, but if the drums do warp without the flange you won't like it! 


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Date: Sat, 15 Sep 2007 10:24:02 -0700
From: Tom Jennings <tomj@xxxxxxx>

Though more looking at it, and hearing Franks' loosening trunnion problem 
made me study it more closely, and the more I look the less I like.

That lower arm is a design problem, period. Right where the heaviest load 
is, force in all three planes!, is a non-positive fastener. Non-positive 
meaning no retaining locknut, just the threads of the trunnion nut engaging 
the sheet metal arm. It's weak by design.

Big brakes and modern fat tires would make this a ton worse! You could 
apply forces to that lower trunnion that would have been impossible in 
1963. 9x2 brakes and 6.00 tires, there's your force limiting!

AND 

Since I was at final assembly I decided to re-visit what it would take to 
put 10x2.5 drums on the front. It's possible!!

Fits the wheel and knuckle just fine. A non-compromising clearance notch 
cut into the backing plate would clear the steering arm. A 1/8" - 1/4" 
spacer, or disk brake spindles (tall) would reduce the side of the 
clearance notch.

HOWEVER -- the outer flange on the drum would have to be cut off. Drums 
generally ahve a flange that straddles the backing place rolled up edge as 
a dirt seal. The other lip would have to come off. This would hurt drum 
stiffness and probably heat-expansion issues, but since they're so absurdly 
oversized in the first place, it probably wouldn't matter.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)

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