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New big rotor scarebird kit

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scarebird Quote  Post ReplyReply Direct Link To This Post Posted: Mar/16/2018 at 10:31pm
We have noted the concern on the two kits regarding pedal pressure.  Both kits use calipers that have 2-1/2"Ø pistons, these usually work fine for manual brakes.  Both calipers are noted for being relatively powerful for their size and weight.  The caliper architecture runs from 2" to 3-1/4" piston size.  As we are about halfway thru the current batch of brackets for the heavy duty we will look to see if we can run a bigger piston caliper - but the issue here is plate offset - it will hit with the shallowest AMC spindle base..

In the mean time, my personal car (Trans Am with manual 4 wheel disc) runs a Mopar minivan master which has a bore of 15/16"; a normal size person can drive it, though a 90 pound teenage girl not so much...

...and I did not know about the coefficient ratings on the side of the pad - more research is in order here, thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote IowaTom Quote  Post ReplyReply Direct Link To This Post Posted: Mar/27/2018 at 3:00pm
Ramblage - Were you able to fit the Scarebird discs on your '59 without having to modify the steering arms?  I see they have only 4 options on their website for AMC and nothing seems to be for the '59 vintage.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Mar/29/2018 at 6:47am
The regular size Scarebird kit will fit ALL AMC Rambler vehicles. You might have to swap them side to side to mount the caliper in the rear instead of the front (or vice versa), but that's it. I can't say about the large diameter, never tried one of those. You might need a 1/4" wheel spacer, but other than that you should have no issues... and the regular size is plenty braking -- same size as Hornet/Concord factory brakes. I'd space the spindle out with longer grade 8 bolts and washers (or 1/2" nuts make good spacers). Use grade 5 or 8 washers and nuts for spacers as they are hardened and won't give any. I'm using a nut and a couple washers to space mine out, but for the deep wheels I need for the Jag IRS. Spaced front out so can use the same depth all around.


Edited by farna - Mar/29/2018 at 6:50am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lyle Quote  Post ReplyReply Direct Link To This Post Posted: Mar/29/2018 at 12:49pm
Cannot disagree more on using nuts as spacers for any machine component let alone a vehicle on the road.
Fasteners are used to clamp machine components together and the strength is in the clamping force between the machine faces.
A wheel spacer is made of good quality T6 aluminum or steel and never use that off shore pot metal that's pedaled on-line.
Using a nut as a spacer puts all the shear load on the fastener. Build did it right when he needed to adjust a spindle by machining the machine faces. If you need to extend the wheel out use a high quality wheel spacer or adapter.
If you need to push the spindle out, get new spindle for the job or have a machined steel plate as a spacer. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Mar/29/2018 at 1:31pm
Like my neighbor did - a well-respected machine shop made him plates.

I would have only gone with grade 8 washers as spacers - and at the most one thickness-  I'm glad I didn't.
I don't agree that those kits "fit all". They fit models only where you have the correct spindle mounting thickness or can have one machined, or make a plate. 
Washers - maybe, one thickness, but not nuts as those are then individual parts and don't have a large FACE to press against. At least a washer has some surface area - more than a nut has. 

I have to agree with Lyle - you smack those brakes and are on sand a bit or wet pavement and the wheel slides a bit and then suddenly GRABS hard, you have three thousand pounds hitting those spindles. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scarebird Quote  Post ReplyReply Direct Link To This Post Posted: Mar/29/2018 at 5:04pm
Originally posted by billd billd wrote:

Like my neighbor did - a well-respected machine shop made him plates.

I would have only gone with grade 8 washers as spacers - and at the most one thickness-  I'm glad I didn't.
I don't agree that those kits "fit all". They fit models only where you have the correct spindle mounting thickness or can have one machined, or make a plate. 
Washers - maybe, one thickness, but not nuts as those are then individual parts and don't have a large FACE to press against. At least a washer has some surface area - more than a nut has. 

I have to agree with Lyle - you smack those brakes and are on sand a bit or wet pavement and the wheel slides a bit and then suddenly GRABS hard, you have three thousand pounds hitting those spindles. 

AMC made the outer stub of their spindles the same dimensions, we noted this and mount the bracket on the outside, so unless the bracket/caliper interfere with other suspension components it will work regardless of spindle base thickness.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Mar/30/2018 at 7:23am
I had this discussion with a mechanical engineer when I was in the USAF and knew a couple in Civil Engineering. As far as the AMC spindle is concerned, there is no issue. The spindle clamps at a small flat surface around the bolt, no bigger than an average washer. The nut in question (a normal 1/2" nut, IIRC), is nearly the same diameter as the clamping surface. In effect all you're doing is extending the clamping surface. As long as the bolt is tight you're not increasing shear loads. This is according to the engineer who I took an actual spindle and nut. I wouldn't go crazy with spacing, I'm about 5/8" out IIRC. I don't think I'd have gone much (if any) further... maybe another washer, but that's about it.

I've had the spindles off since this was done in 2003... no signs of undue stress on the bolts or anything. Now if the bolts lost torque or weren't tight for some reason, it could add stress. Haven't checked anything under the car in a while, but when I have to work on anything on the front end I check to make sure everything is tight, as I have other mods to the steering and suspension. Always a good idea to check welds and bolt tightness when under there anyway.

That said, a plate or exact diameter spacer would be a better idea. Maybe I should have said the Scarebird kits will "fit all AMCs with minor mods". The Scarebird kits mount on TOP of the spindle, not behind it -- at least they did... this may have changed with the most recent design. The reason for doing it that way was to eliminate the different thickness spindles from the equation. The original AMC setup with Ford Ranger rotors mounted behind, and was sized for most drum brake spindles. Some of the big cars used a wider drum and slightly taller spindle, and all but the Bendix four piston disc brakes use a taller spindle.


Edited by farna - Mar/30/2018 at 7:26am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Mar/30/2018 at 8:24am
One must be careful in where and how the calipers are mounted. Keep in mind AMC put the calipers in front of the steering axis because the steering arm itself bolts diagonally - the front bolt is low, the rear bolt is the upper one. 
 There's not a lot of space to flip the caliper to the rear of the steering axis. 

Take a look at this left side shot of the rear part of the parts - I question the clearance.
AMC put the calipers on the fronts of these cars, Concord, etc. - and to the rear on Eagle but then the steering arm and other parts are down low to clear the axle.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Mar/31/2018 at 8:38am
I always mount the calipers the way they came off the donor when possible. On the early AMCs with trunnions and that weren't made with disc brakes in mind I've had to swap them. The first calipers I swapped onto a 63 American. Calipers were originally mounted to front (79+ brakes), but I had to mount to the rear for clearance issues.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Apr/01/2018 at 12:04am
Originally posted by Scarebird Scarebird wrote:

AMC made the outer stub of their spindles the same dimensions, we noted this and mount the bracket on the outside, so unless the bracket/caliper interfere with other suspension components it will work regardless of spindle base thickness.


this.

thanks scarebird for the continuing tweaking of your systems. i've had two maybe generations of them. the previous one i had to grind a bit to fit the '63 American (after which it worked perfectly) but then the next set solved it all issues out of the box. it sits outboard so it not longer cares about spindle height. nice.

1961 roadster american
195.6 OHV, modded
T5z, 3.42:1 mustang axle
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