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1958 pressed steel brake drum

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Post Sun Mar 23, 2008 6:21 pm

Posts: 2687
Location: Los Angeles, CA
Does anybody know the difference betweem the 1937-1957 pressed steel brake drum and the early 1958 pressed steel brake drum? There is a different part number in the book

Post Sun Mar 23, 2008 8:19 pm

Posts: 122
Location: Mpls. area
Chris, was 58 when they went to the juice brake?

Post Sun Mar 23, 2008 8:35 pm

Posts: 122
Location: Mpls. area
It also looks like the 58 drum has a pair of square bosses, 180 degrees apart on the wheel side of the drum. I have no clue why. Mike

Post Mon Mar 24, 2008 6:50 am

Posts: 2687
Location: Los Angeles, CA
Chris, was 58 when they went to the juice brake?
Yes, 1958 was the first year.

It also looks like the 58 drum has a pair of square bosses, 180 degrees apart on the wheel side of the drum. I have no clue why.
Those "bosses" are not on the early 1958 pressed steel drum. Late 1958's used a cast iron drum with bosses.

Post Mon Mar 24, 2008 8:03 am

Posts: 1536
Location: S.Calif.

Rigid and hydraulic drums are 8" diameter. The rear brake arrangement changed in 1938 from a double spring to a single spring (at the bottom). The shoes widened in 1938 to 1-5/64". They stayed the same width until after 1962.
The cast drums and pressed steel drums were used different friction material. One was suitable for cast iron, one wasn't.
The lugs on the back of the cast iron drums were for (hammer) loosening the drum if it got stuck on the hub.
The only drums that are cast iron (aftermarket) now, are the '63-66 with the raised cast-in dust ring. And they changed to wider shoes. "Mercury" Morse told me cast iron drums can warp just sitting on a shelf. http://www.vintagebrake.com/
There is a difference in the pressed steel rigid ('37-57) and hydraulic ('58-62) pressed steel drums, but I don't know what it is, yet. I'll need to go out and make a side-by-side comparison. Yea, then they started using cast iron in late '58.
They used 1/8" rivets (and dowel pins) through 1959. They changed the rivet diameter in 1960 to 3/16".
All of the chain-to-transmission alignment was accomplished by recessing material from the drum side of the '58-62 sprocket for drum inset, or reducing the width of the backing plate spacer when they widened the shoes for '63-66.
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I measured both the rigid and hydraulic pressed steel drums. They are the same drum. The difference is, you see 5/16" more drum behind the sprocket on the rigid than on the hydraulic. The reason for that, is because the (hydraulic) sprocket has that recess cut-out so the hydraulic sprocket (on that same rigid frame drum stock) will (move to the left) and line up with the transmission.
V-Twin has two different part numbers. One for rigid and one for hydraulic. The drums are the same depth and diameter, the faces of the two sprockets are different.
If you tried to use a rigid frame drum and sprocket on a '58-62 hydraulic Big Twin, the rear sprocket wouldn't line up with the transmission sprocket and vise-versa.
Something's not right with my explanation though, if the '58-62 sprocket recess moves the sprocket to the left, then you'd see more drum on the hydraulic than on the rigid. There's an answer in there somewhere. If I have to place them side-by-side, I'd have to remove a rear wheel and I've got header-slotting this morning. Gi' day mate :!:

Post Mon Mar 24, 2008 7:20 pm

Posts: 2687
Location: Los Angeles, CA
If I have to place them side-by-side,

I think when you do you will find that the 1958 drum has a different grease cup. Or so I have been told.


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