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More disc brake discussion

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2javman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 2javman Quote  Post ReplyReply Direct Link To This Post Topic: More disc brake discussion
    Posted: Jan/10/2018 at 9:09am
I know there have been lot of discussion on disc brake swaps on the forum but I wanted to just ask for some input on the brake system as a whole. I have already converted my drums to disc with the 80 concord set up some 20 years go. Thinking about going bigger and lighter though. I've seen the scarebird kits and the wilwood kits. What I wondering was as long as you make sure your mc can provide the pressure and volume the calipers require can you use what ever combo you want providing it has the same bolt pattern? I also know there are different master cylinders for disc/drum disc/disc and I already have an adjustable proportioning valve. The wilwood front kits are $725. Why couldn't you get a scarebird kit, and instead of the gm truck caliper use the wilwood dynalite calipers with the sport track rotor (or other ford, mustang,e.i.) rotor? You would still be under $500 and have the lighter aluminum caliper. For the rear couldn't you just use mustang or thunderbird rear calipers and rotors? I realize I'd have to make my own brackets which won't be an issue. Btw this is on a 70 javelin. Also, does anyone know the maximum rotor size I could use with a 15 inch wheel? Thanks in advance for your input, I'm just trying to feel this out before I go out and buy a bunch of unusable parts.
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nickleone View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nickleone Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2018 at 9:57am
Just a thought. Have you checked the possibility of using a complete Mustang rear.
My local Pull and Pay only gets $125 for a complete rear.

Nick 
nick
401 71 Gremlin pro rally car sold
390 V8 SX/4 pro rally car sold
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Red Devil View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Devil Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2018 at 11:21am
Braking is about converting a car's kinetic energy into thermal energy and dissipating that thermal energy quickly before the next braking cycle. A larger pad does a better job. A higher pad coefficient of friction does a better job. A rotor with more thermal mass (heavier) to absorb more energy with more surface area and efficient venting to improve radiant and convective heat transfer will do a better job. Efficient ducting for more airflow will do a better job. A caliper with more piston area (and matched master cylinder) does a better job.

Tires and road surface are typically the limit for passenger cars - less so the brakes ... unless your pad compound has poor CoF or poor temperature limits.

Not enough rotor mass and/or cooling or not enough pad with a low temperature limit will overheat and fade. Not a good plan. Too much rotor mass or caliper hurts dynamic response, but at least will stop safely. Caliper and master should be sized so braking torque is close to stock with stock-type tires or can increase if tires have more grip.

Wilwood AMC kits are designed for a street cruiser, save weight over stock and are fine for their intended use. They use light weight, narrow, dirt-track style rotors with small-pad, light weight fixed-mount calipers. Main advantage over stock discs is a 2-piece rotor, lower weight and they look nice. IMO, they are not more capable than most stock discs with upgraded pads.

Stock KH caliper (single 2.75" piston) w/ 11" x 1" thick rotor has more pad area, more pad volume, more rotor thermal mass and more braking torque (with same CoF pad) than a Willwood Dynalite 4x1.75" piston caliper kit with 12.19" x 0.81" thick rotors. The KH caliper has 5.94 sq.in. effective piston area and the Dynalite has 4.81 sq.in. KH pads are 6" wide x 0.595" thick vs. 4" wide x 0.49" thick for the Dynalite.

For the 2.6" piston Bendix ... Wilwood may have slight edge, but less pad volume ... but I personally don't like the Bendix floating design.

If planning to make your own brackets and wanting an aluminum Wilwood caliper, I'd suggest the D52 caliper with 2x2" pistons in front and 2x1.25" pistons in rear for good balance. D52 pad options are almost unlimited, readily available at local parts stores, calipers are floating so accommodate a bit of flex in stock components or less-than-perfect mounting without excessive piston knockback, available for a 1.25" thick rotor and you could start with $30 parts store rebuilt cast iron D52s and change later if wanted.

You may be able to adapt a common stock car D52 rear caliper bracket to the front using the existing front bracket and to the rear axle housing flange with suitable spacers. Take your used AMC rotor and have the rotor machined off to make it a hub for the front and use a suitable hat and rotor and done. Jeep Cherokee floating rotor would be the economical 11" x 1" option and Ford Ranger for a 12" x 1" option ... or use 2-piece rotor and hat for lower weight and better rotor options.

If you have the KH calipers, Porterfield offers pads from street (Hawk HPS, Porterfield R4S) up to racing (Porterfield R4, R4-1, R4-E; Raybestos ST-41, ST-43, ST-45, ST-47). Search for '73 Challenger on their site (same pad). EBC also offers their Yellowstuff pads for street/autocross (EBC DP41176R).

Expect Porterfield have similar pad options for the Bendix caliper ... best to give them a call. Their R4-S compound would be a good street choice and your lowest cost brake upgrade option.

D52 kits:http://www.wilwood.com/BrakeKits/BrakeKitListFront.aspx?mincatdesc=D52 Front Caliper Kit
... can order through Summit, Jegs, etc. for significant savings.

https://www.porterfield-brakes.com/

... Nascar runs up to 13" diameter rotors in a 15" wheel, so depends on your wheel and caliper combo.

Hope this helps,RD
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LakesideRamblin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LakesideRamblin Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2018 at 4:54pm
Put this Wilwood kit on my 15" front wheels.



LakesideRamblin
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"If you could kick the person in the pants responsible for most of your trouble, you wouldn't sit for a month." T. Roosevelt
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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2018 at 5:52pm
My thoughts for a brake upgrade if you are making your own brackets would be to use Chrysler/Dodge SRT8 Brembo callipers and rotors, re-man callipers from Rockauto and new rotors are cheap enough or just pick up a set at a junk yard. The only problem with this is the 360mm rotor will not fit inside a 15" wheel and maybe not even 17", but they are damn fine brakes.
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2javman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 2javman Quote  Post ReplyReply Direct Link To This Post Posted: Jan/10/2018 at 11:41pm
Thank you again for the input this helps me a lot everyone. A lot of good info Red Devil got me really thinking now!


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343sharpstick View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2018 at 12:11pm
Some very good information here, Thank you!
I have the Aerospace kit, and it's been great for nearly 10 years now.
I've been looking at an upgrade, as I have 17 inch wheels, and would like to put together a package that has a 13 or 14 inch disc for the front of the car.
It seems everyone wants the biggest brake that can fit in a 15. How many AMCr's want to run a 17 or larger? Seems like only a few.
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343sharpstick View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2018 at 3:16pm
I just did a bit of research on available willwood components. I've contacted Wilwood to verify that my research is correct.

Using the hubs from the current AMC kit, it looks like you can mount the larger 12.72 Dia. “GT 48 Curved Vane Rotor” (PN 160-2540 & 160-2541) in place of the 12.19 inch rotor that’s packaged with the AMC kit (160-7104 and 160-7103).
Both have the 8 x 7.00 Rotor Bolt Circle dimensions, The only issue is that the Rotor Mount Hole Size is slightly different (0.316 compared to 0.326).

Then in looking at available calipers, a good, affordable 4-piston caliper would be the “Forged Superlite Internal 4” (PN: 120-11330 & 120-11329).

I would need to fabricate a bracket to mount the caliper, but this may be a good option if running a 17 inch wheel, and wanting to do more performance oriented driving.
I'll let you all know if I hear back.

Edited by 343sharpstick - Jan/11/2018 at 3:20pm
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343sharpstick View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Jan/15/2018 at 10:22am
Just got confirmation from Wilwood that you can bolt the 12.72 inch “GT 48 Curved Vane Rotor" to the available wildwood hub assembly.
Down-side is it's a bit spendy at $224.93.

Also the “Forged Superlite Internal 4” would be the appropriate caliper for that rotor and application. The price on those Calipers is very reasonable, starting at $199.44.
This would of course move the rotor inboard .44 inch.

An upgrade beyond that would be the 13.06 x 1.38 rotor, same price at $224.93, but would require the use of the Grand National Caliper (120-3031-RS & 120-3030-RS) at $385.50.


Edited by 343sharpstick - Jan/15/2018 at 10:47am
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Red Devil View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red Devil Quote  Post ReplyReply Direct Link To This Post Posted: Jan/15/2018 at 11:42am
Good info! Thanks.

An economical 12.88" x 1.1" Wilwood rotor option would be their Challenge-series rotor combined with a hub, caliper & bracket to suit.
http://www.wilwood.com/Rotors/RotorProd.aspx?itemno=160-12191
$139 at Summit.
https://www.summitracing.com/int/parts/wil-160-12191/overview/
Rotors have a 3.06" pilot and use a register ring to fit to various hub pilot diameters (as do many of their hats).

Cheap hub would be a stock disc with rotor turned off (drum hub flange is a bit thin so may flex too much for a fixed caliper)... or save some weight with a Wilwood aluminum hub (about $130 ea.). Since you don't need a hat or adapter plate, cost may be in the range of their standard AMC kits ... depending on caliper choice, hub and cost to make a bracket. May need a thin wheel spacer to clear the caliper if using a FSLI, depending on your wheel.

Not as capable a rotor as the 12.72" x 1.25" ... but depends on application, pad choice and cooling as to how much rotor you need?

Once you get beyond the 12.19" diameter used in lower levels of stock car racing, rotors tend to get pricey ... unless you can find a suitable stock rotor that works.

Hope this helps,RD.
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