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Rolling my own rear disc brakes - 61 American

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farna View Drop Down
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    Posted: Jan/28/2023 at 2:49pm
I've been planning what I want to do about brakes on my 61 American convertible. The previous owner (I just got it in mid December) had taken at least the front brakes off (haven't checked rear) before deciding he was in over his head and should sell the car (he hadn't had it but about a year). I've decided I'm not doing a full restoration, but will be modifying it some -- mainly for safety. I'm considering a newer drivetrain, but not for now. The 196 OHV runs, though I can't say how well (just heard it crank and idle), and the auto trans (which should be an M-8 for 61) supposedly works well. If they do I'll keep them -- at least for a while. If not I'll probably transplant a four cylinder -- maybe an AMC/Jeep 2.5L like member WARBED did with his 59 (https://theamcforum.com/forum/59-rambler-american-sw-rebuild_topic49472_page4.html), but I'm not sure yet. I've been researching a little, and so far I've found that if I want something relatively new (say the last 10 years) it is probably going to be expensive since I want to keep an auto trans so my wife can drive it. Would be much simpler to put a manual in! All the newer autos are computer shifted. Good stand-alone controllers are $800-1000 and only for a limited number of trannys. Keeping the stock controller and ECU would be difficult also, especially for a Ford engine/trans, as they started using a system where the ECU "talks" to the instrument panel and trans about 20 years ago. If any of the components have been changed the engine won't start. Don't know if foreign cars are the same, but suspect so. Was thinking about the GM 2.9L four, but now not sure. I think the GM five cylinder is still too long, I know for sure the I-6 is.

Anyway, my original thought for the rear discs was to use 90s Subaru Loyale front calipers since they have a park brake built in that uses a simple cable. Not as complex as the GM calipers, and I don't need a big caliper either. The issue with those is I'd have to use a different rotor. As I was researching I came across 98-07 Honda Accord rear calipers. They have a simple cable connection and use 5 x 4.5" rotors. Using different rotors with the Subaru calipers would work as long as they were of similar thickness,  but the local Pull-A-Part has 10-12 Honda Accords in the yard -- no Loyales. The larger Legacy uses a small drum inside the rotor as many cars do, and that would be difficult to retrofit.

I'll have to make sure the offset works as well as the center hole of the rotor. Since the bolt pattern is the same as my Rambler that's not an issue. The rear rotors are solid instead of vented, but that shouldn't be an issue. The rear rotors on my 63 Classic are solid also (87 Jaguar IRS). I'll just make a bracket and weld it to the AMC 15 axle.

2000 Accord Rear caliper. Note threaded mounting holes.


2000 Accord rotor center hole. 64.2mm = 2.53". I can always have the hole turned larger if needed, that will be simple enough. Bolt pattern is 5 x 114.3mm (5 x 4.5"), which is a plus.


Rotor total height and thickness. 48.3mm = 1.90". Will have to make sure that works. Might need a spacer between rotor and wheel for caliper clearance, but doubtful.


Of course I'll have to check these diameters and make sure the rotors fit over the ends of the AMC 15 also. Of course I can use any rotor of a similar diameter as long as there is enough area for the brake pads. 259.7mm = 10.22", 168.1mm = 6.62". The inside diameter of the center will be smaller, but I'm pretty sure six inches is plenty to go over the end of the AMC 15 axle.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nickleone Quote  Post ReplyReply Direct Link To This Post Posted: Jan/28/2023 at 4:38pm
Frank,
 Loyal disc dims for front

ABS Sensor Ring IncludedNo
Bolt Circle Diameter (IN)3.543
Bolt Circle Diameter (MM)90.000
Bolt Thread Pitch (MM)1.250
Disc MountingBehind the Hub
Discard Thickness (IN)0.630
Discard Thickness (MM)16.000
Misc Holes0
Mounting Bolt Hole Quantity4
Nominal Thickness (IN)0.709
Nominal Thickness (MM)18.000
Outside Diameter (IN)9.528
Outside Diameter (MM)242.000
Overall Height (IN)1.732
Overall Height (MM)44.000
Solid Or Vented Type RotorVented
Surface TypeSmooth
Vane StyleStraight

A shim would close the gap on the Honda rotor.

Nick
nick
401 71 Gremlin pro rally car sold
390 V8 SX/4 pro rally car sold
1962 Classic SW T5 4 wheel disc brakes
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jan/29/2023 at 7:26pm
Thanks Nick! The only issue with the Loyale rotors is I'd have to drill them for five lug. Doable, I know. The vented rotor would be nice, but almost all standard production car rear disc rotors are solid.

I measured the rear hub on the AMC 15 today, it's only 2". So the 2.53" center hole in the Honda rotor will work great! Should be able to put the rotor on the rear with no problems. I didn't pull the rear drums and measure the axle end though. That's the only possible issue now.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nickleone Quote  Post ReplyReply Direct Link To This Post Posted: Feb/03/2023 at 7:00pm
Frank,
I listed the Loyale rotor for the DIMS etc not to use.  Loyale rotor thickness is different than Honda rotor you can use shims attached to the pads.

nick
401 71 Gremlin pro rally car sold
390 V8 SX/4 pro rally car sold
1962 Classic SW T5 4 wheel disc brakes
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Feb/13/2024 at 3:31pm
I finally got around to measuring and mocking up a rear disc brake bracket for the AMC 15 axle. I need a couple people to double check my measurements, and to check a later model AMC 15 to see if it's the same as an early model (the ends that the drum brake backing plate bolts to). I mocked the bracket up on my 61 American, want to make sure something like a 70s Hornet/Gremlin is the same. 

If someone has a 70s (or early 80s) car with an AMC 15 and can measure the bolt pattern, it's 3-1/4" between the top two bolts (front to back), 2-3/4" between the bottom two bolts (front to back), and 1-3/4" between the top bolt and bottom bolt (on each side). All measurements are center to center. 

If the distance between the bolts are the same as the 61 I'm certain the placement and pattern (in relation to the axle shaft) are as well.

I want to make a CAD file from the drawings I have and have a batch laser/waterjet/plasma cut. Once that happens I'll have them for sale! I'll be making a park brake cable bracket also. That's the easy part! Will sell the park brake and caliper brackets as a set.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: Feb/13/2024 at 3:43pm
Just something to add since you're using the AMC rear, make sure there's very little end play on the axles or you'll have problems with the rotors pushing the pistons back in. When I did the disc conversion on my AMC 20, it had way to much end play so I had to change the shims to reduce it.

"Hemilina" My 1973, 5.7 Hemi swapped Javelin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Feb/15/2024 at 8:44am
Great tip! I'll make sure to check that. I just made a CAD file for the AMC 15 rear disc plates and put an order in to Send-Cut-Send for a few to test. So if anyone with a Hornet/Gremlin/Concord/Spirit... and American/Javelin with six cylinder rear axle wants to test fit I may be willing to send some brackets. Using discs does require cutting the backing plates, at least the portion where the caliper sits. The rest can be left for a dust shield -- wish I'd thought about that before cutting mine all the way off! 

To go back to drums would require new backing plates. I considered making the bracket so it attached to the very end of the axle (it attaches to the rear of the flange now) and machining to hold the seal, but that would require removing the hub to put it on and take the backing plate off. As long as the discs work well there's really no reason to go back to drums.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Feb/24/2024 at 6:52pm
I got the first set of caliper brackets. I goofed and mis-read the plate thickness -- got 0.030" instead of 0.300"! Well, they are good enough to check for fit. TomJ measured some seals he had and it looks like I might be a little off on a couple of  the holes. I made a thin plywood mock-up and made a CAD drawing from that, sent him the CAD drawing to check. The thin plates will be good to check for fitment, so no real loss.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Feb/25/2024 at 5:00pm
Originally posted by farna farna wrote:

I got the first set of caliper brackets. I goofed and mis-read the plate thickness -- got 0.030" instead of 0.300"!


Bummer! But actually advantageous fir a fitment first pass, obviously you can't drive on them but nicely easy to mod  for fitting and sending back out. Actually thats a good idea you stumbled on; make 'em 1/8" or whatever, easy to hack up, check fit, and get a sense of how thick they need to be (I assume 300 thousandths is generous).

1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5
http://www.ramblerLore.com

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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Feb/29/2024 at 7:38am
Test fit the thin test bracket. Only have to move one hole, and not by much! Will fix the CAD file and be good to go. The 0.030" thick bracket is stiff enough to mount the caliper so I could check placement. A 9/16" thick spacer is needed to center the caliper over the rotor perfectly. I can't find a ready made 9/16" thick spacer with a 13/32-7/16" hole (for a 10mm bolt) and thick walls. Well, can't find a 9/16" thick spacer except for some very small ones for 10-32 screws. Not sure if I'll send out with no spacer or get 1/2" spacers and a washer... or send out with the 1/2" spacer and note that a washer or two may be needed to properly space the caliper. The is probably some variation in distance between the back of the axle end (inside side) and the bub anyway. longer 10mm bolts will be needed for the calipers also. The original will work, but only about 3/16"-1/4" of threads in the caliper body instead of 1/2"- 3/4" (the original cast iron mount on the Honda is just over 1/2" thick).
Frank Swygert
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