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Is There A Way to Tell What Brakes A Car Came With

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Scrappy View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scrappy Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2021 at 10:58am
Originally posted by tomj tomj wrote:

Wow.

Well it will be easy to tell -- new hubs will be smooth inside. OR SO I HEAR -- not having ever seen a new hub, but that's what the TSM says -- first installation cuts the splines in the hub, the axle being harder than the hub.

Yes, I'm aware of how a non-used hub looks and forms the splines upon installation.  The issue that I don't want it to be "easy to tell" only after it's in my hands, discovering that it's used and the wrong part when it was represented as non-used, then be told they don't take returns on used parts (even though it was misrepresented).  I've been burned by this exact same scenario before, thus my emphasis on ensuring it's the correct and non-used part.

Originally posted by tomj tomj wrote:

Brakes vs hub: I am skeptical. No AMC came with rear disc brakes, they were all drum brakes in the rear. There were a couple different size rear brakes, 9" or 10". As far as I know the hubs are the same. The hub depends on the axle and the axle depends on big (AMC20) or small (AMC15) axle assembly.
Perhaps my point is not coming through well.  I am not saying the car came with disc brakes -- I know it came with drum brakes.  It has disc brakes now and I have no way to tell what drums it had originally so I can find the proper hub.  The issue (if you follow the link to my other thread) is that I was attempting to remove the hub and it bent.  I need a new-to-me hub (whether actually new or not -- using old hubs has been extensively discussed with me elsewhere, it's not necessary to repeat here) and this supplier supposedly has NOS drum/hub assemblies.  My intent was to use only the hub part of the assembly.


Edited by Scrappy - Jun/22/2021 at 11:10am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2021 at 11:21am
Is there any way you can get pics of your hub showing the measurements? Stand it on the back side, measure from there to the face of the flange and from the face of the flange up to the end where the washer and nut go?

I have a couple of axles here with hubs on them - at least I thought I saw a couple when I was digging around on my high shelves. It may be very very difficult for you to find NOS hubs for the 20 as every owner of a Javelin or AMX would have snapped those up in a heartbeat just because. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2021 at 11:32am
Originally posted by billd billd wrote:


Imagine a brake drum that has to be 1/2" wider for car A than car B due to the larger brakes.
They use the same axle, the same axle tube, they have two choices - offset of the backing plate or offset the hub for the different brakes. 

I was looking for different parts for my SX4 and thought oh, this will be simple, it's the 15 and there's a hub for sale on eBay that's for a 15, I'll check the part number - then I looked in the parts book and crap, the hub for sale on eBay is for the smaller brakes, won't work. 
I've seen several size brakes for one axle but the axle wasn't different, just the drum, backing plate,etc. It seems to me the hub would be more expensive than a backing plate. Oh well, it is what it is and good to know. Wink

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scrappy Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2021 at 11:41am
Originally posted by billd billd wrote:

Is there any way you can get pics of your hub showing the measurements? Stand it on the back side, measure from there to the face of the flange and from the face of the flange up to the end where the washer and nut go?

Yes, I certainly can.  The hub is still on the axle, though, but I can easily do the measurements, as I have the proper tools for that (I'm a hobby machinist, but certainly not enough of one to make a hub!).  I understand this would only be the external measurements, without the bore sizes.

Originally posted by billd billd wrote:

I have a couple of axles here with hubs on them - at least I thought I saw a couple when I was digging around on my high shelves. It may be very very difficult for you to find NOS hubs for the 20 as every owner of a Javelin or AMX would have snapped those up in a heartbeat just because. 

Yes, getting NOS hubs is highly unlikely, it's just that the possibility seemed to exist with the supplier who supposedly has the NOS drum/hub assemblies.  As for snapping them up, that's what I was trying to do when I ordered two -- so I could have a spare.

I am not dead-set on getting NOS hubs.  If I have to, I will go the used route and have the keyway re-done, or buy a complete used shaft/hub assembly, which I know is available (but 3x as expensive and much more work than just doing a hub).

Before anyone suggests it, yes, I am aware of the single-piece axles offered by Dr. Diff and Moser.  Let's not go off on that tangent, please, as those will not meet my needs for side-loading (I autocross) unless I get custom assemblies and housing ends, which will add $$$ not only due to the axles and housing mods, but will add more $$$ for different brakes and will take significantly more effort.  Again, I am aware of this and don't want to get into this discussion for now -- it's a last resort.


Edited by Scrappy - Jun/22/2021 at 11:49am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2021 at 11:54am
Originally posted by Mopar_guy Mopar_guy wrote:

Originally posted by billd billd wrote:


Imagine a brake drum that has to be 1/2" wider for car A than car B due to the larger brakes.
They use the same axle, the same axle tube, they have two choices - offset of the backing plate or offset the hub for the different brakes. 

I was looking for different parts for my SX4 and thought oh, this will be simple, it's the 15 and there's a hub for sale on eBay that's for a 15, I'll check the part number - then I looked in the parts book and crap, the hub for sale on eBay is for the smaller brakes, won't work. 
I've seen several size brakes for one axle but the axle wasn't different, just the drum, backing plate,etc. It seems to me the hub would be more expensive than a backing plate. Oh well, it is what it is and good to know. Wink

I suppose it depends on where they bought the brake assemblies, or HOW they bought them. 
The parts book says the hub is part of the "brakes and wheels" - NOT part of the "axle" or drivetrain. 
So the AMC parts counter guy looked in group 8 - brakes - to find the hubs, then they had to know the vehicle and brake size. 

It took me a while to realize why I had this so engrained into my head - I experienced it myself years ago - I noticed that when I snapped the end off  the axle of my SX4 (INTERNALLY, not the hub end!) and I grabbed the axle from parts car I had at the time, I had trouble with the drum scraping and grabbing the backing plate. That's when I started asking around, the Eagle people, first - and found differences. 








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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Jun/22/2021 at 11:42pm
I was wrong in my assumption about hubs being the same, corrected by billd. 

The 77 Hornet/Sportabout axles I pulled, I did so to retrieve the 10 x 1.75 brake assemblies, hence the hub press-off. But of course the backing plates from a '20 won't bolt onto a '15 and this was long enough ago I had forgotten the distance and things like "forums" didn't exist! So it was bang about in the dark...

Anyway, I have the hubs clean and handy, so fwiw, post the measurements of what you got and how you derive 'em and I'll do the same. 



For proof, you could ask for a phone photo of the inside of the hub, with a bright light. But if they knew what unused hubs were they'd know what they are worth, and would probably be charging accordingly. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2021 at 6:55am
I don't have my 79 TSM in an accessible place right now. The only reference I have (Chilton's AMC, 75-86, #7199) says that all 79-80 Hornet/Spirit/Concord used the same rear brakes EXCEPT the four cylinder model. Has diameter of drums (10" for 79), but not width. I would suspect that the Spirit used the narrower brakes. I do recall the specs are the same as the TSMs... I've cross referenced the book before.

For Hornet/Concord/Spirit/Gremlin:
75-76, sixes used 9", V-8s 10"
1977 all used 10"
78-80  four cylinder used 9", all others 10"
81-83  all used 9" except wagons, which used 10"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scrappy Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2021 at 11:07am
OK, here are the dimensions of the existing hub on the car:


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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73Gremlin401 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2021 at 11:21am
I remember when George did the conversion, but I wasn't around to witness it, so some of my info will need some verification.

The rear axle in that car should have had the 2" wide shoes - generally, 2.5" was reserved for Matador/Ambassador wagons only, although I'm sure there's some other applications I don't know about.  But on a lightweight Spirit, 2.5s would have been overkill.

You may want to reach out to Jeff P - he probably knows this stuff off the top of his head.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scrappy Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2021 at 11:25am
Originally posted by 73Gremlin401 73Gremlin401 wrote:

You may want to reach out to Jeff P - he probably knows this stuff off the top of his head.

Jeff and I are friends and we've been discussing the issue.  I'm sure if he had info to add he would have told me by now, but I don't know what I don't know, so is there something particular that you think hasn't been brought up yet?
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