Warped rear juice brake backing plate

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2dogs
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Bikes: 1963 FL motor in 1965 frame with an assembly of other old and replica parts.
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Warped rear juice brake backing plate

#1

Post by 2dogs » Mon Aug 30, 2004 11:59 pm

I'm getting aggravated with this 1958 - 72 style hydraulic rear brake setup. I have the 2 1/8" deep '63-72 style drum designed for the wider shoes. The original Bendix '63-72 backing plate with the rolled edge dust ring appears to be warped forward of the anchor bolt near the front shoe adjuster. The backing plate with or without the shoes drags at this apparent low spot all around the drum and when tightened down with all the axle hardware in place on the swing arm, it is pinched so tight the wheel won't turn.
Anyone else seen this type of situation? Is a warped backing plate (two of them now as I just received a second one off an ebay purchase) a common problem?
I have what I believe is the correct axle sleeve and spacers based on measurements from Bruce Palmers book.

Would appreciate any suggestions if someone else has run into this.



Cotten
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Re: Warped rear juice brake backing plate

#2

Post by Cotten » Thu Sep 02, 2004 12:13 pm

Yes, it is much too common of a problem.
I have straightened my own in a press, but it takes much patience and attention, and occasionally I give up.

VintageTwin
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Re: Warped rear juice brake backing plate

#3

Post by VintageTwin » Thu Sep 02, 2004 3:28 pm

There is a 58-62 rear backing plate. There is a 63-66 plate. You can tell the difference by the hole for the slave cylinder. 58-62 is unique. Has a keyhole shape. You need to keep the parts separate. I'm pretty sure you can't mix the years. 58-62 have their own shoes and drum and plate. Your's sounds like 63-66. Some of the aftermarket drums are too deep. Fuzzy's knuckle shoes on his rear drum bound when the axle was tightened. That was the reason. Could have been a number of problems, gussets off, spacer, plate etc. It was his drum. Cast or stamped to deep.
Can you believe that V-Twin makes a '36 only backing plate, and a repop '36 frame? Doesn't even have the trans. kicker support plate!

2dogs
Posts: 34
Joined: Thu Jul 12, 2007 4:13 pm
Bikes: 1963 FL motor in 1965 frame with an assembly of other old and replica parts.
Location: Western Colorado

Re: Warped rear juice brake backing plate

#4

Post by 2dogs » Sat Sep 04, 2004 8:32 pm

Cotten: I have only a small bench vise and a hammer, not the best tools for straightening a backing plate. The original Bendix plate I have is warped beyond my ability to fix. The repop chromed backing plate I purchased recently on eBay is not warped as badly and I had less scruples about using brutality on it. Thanks for the info on the commonality of the problem.

Plumber: My backing plates are both the '63-72 type with the different shaped reinforcement plate and larger mounting hole to accommodate the larger brake cylinder. The drum is the deeper '63-66 cast iron type with the raised edge and accomodates the wider brake shoes.

A machine bushing between the axle sleeve and the backing plate, some whacking and bending , and a bit of filing in the front shoe where it dragged on the inside of drum has the wheel turning easily now.
I guess this is the untrained, ill-equipped Joe-Shit-The-Ragman-Wrench approach to fitting together an old, modified FL: Beat, file and bend the parts into submission when correct fitment eludes him.

VintageTwin
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Re: Warped rear juice brake backing plate

#5

Post by VintageTwin » Sat Sep 04, 2004 8:44 pm

About the same fitment procedure as Replica.

gordon

Re: Warped rear juice brake backing plate

#6

Post by gordon » Sat Nov 06, 2004 9:09 am

I'm building a ground up pan in a 58-64 swing arm frame and just had the same problem last night while assembling the rear wheel brake etc. tightened the axle a little and the wheel would lock up.
the problem was the swingarm was a 58-62 which will not work with the wider 63 and up wider brakes! The outside half round dust lip on the brake backing plate 63 and up hits the casting rib on the 58-62 swingarms a few inches foward of where the lower brake plate anchor stud goes through swingarm and binds the brakeplate to the brake drum. I found a 63 and up swingarm in my stash which HD designed to have enough clearence for the new brake in 63 put it on and solved the problem! You might want to check the year of your swingarm

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