Brake upgrades?

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Artif
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Brake upgrades?

Post by Artif » Tue Jul 21, 2020 1:05 pm

Looking to upgrade the front brakes on the 79 J20. Bigger tyres (33's) and modern driving combined with 70's brakes makes for some interesting moments.
The current discs are in very good condition and I have new "ceramic" pads ready to fit.
The main problem, however, looks like the single piston calipers up front.
I've seen wilwood do a twin piston caliper, but is there any other bolt on twin/four piston calipers?
P.s tried a search and seen a mention of gm calipers that might fit, but I want to be sure before ordering, as the shipping gets expensive to the UK
Cheers

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Stuka
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Re: Brake upgrades?

Post by Stuka » Tue Jul 21, 2020 1:44 pm

I have to say in my J10, I have never had an issue with stopping power. And I have certainly had to do some emergency stops before. Before going and doing upgrades, have you verified both the brake fluid is in good condition, and that the lines have no air bubbles?

Upgrading the rears to disc can certainly help. For the front, if cooling is the issue you can go with slotted rotors. The J20 already has larger rotors and calipers than a J10/Wagoneer. I am sure you can find some lager diameter brakes with calipers that will work. It will require going with larger wheels most likely.

Are you doing a lot of towing or hauling?
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


rocklaurence
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Re: Brake upgrades?

Post by rocklaurence » Wed Jul 22, 2020 6:54 am

A popular upgrade is using the Chevy JB7 caliper and pads. The piston is approx' 30% larger ad the pads are much bigger. Search JB7 here on the site and many people have done it.


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Artif
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Re: Brake upgrades?

Post by Artif » Wed Jul 22, 2020 10:59 am

Brakes are in good condition, po fitted new hoses with the lift kit.
They just don't work that great. I've done the drilled and grooved rotors on other vehicles but better calipers make the biggest difference for the price.
I recommend watching this video regarding braking distances and larger tires, certainly opened my eyes.
https://youtu.be/jO6QYM59ANw

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Stuka
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Re: Brake upgrades?

Post by Stuka » Wed Jul 22, 2020 12:40 pm

You should really check the system for air. 33's aren't a large tire, and with the J20 already having bigger brakes, it really should stop well when empty. Hauling/towing changes things.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


SJTD
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Re: Brake upgrades?

Post by SJTD » Wed Jul 22, 2020 3:39 pm

What are the diameters of the two pistons on the calipers you're looking at?
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.


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Artif
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Re: Brake upgrades?

Post by Artif » Fri Jul 24, 2020 11:13 pm

Willwood state the piston area is 6" on their calipers, but they only do up to '78.
I think the 79 has metric fittings but I'll be checking that out later as the clutch is first priority.


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Re: Brake upgrades?

Post by SJTD » Sat Jul 25, 2020 7:10 am

I find that your calipers have a 2.9 dia piston which has 6.6 sq in area. Obviously Willwood's would be worse whether you can make it work or not.

Two pistons isn't necessarily better. Trying to fit two with a total area greater than a single in the same space probably won't work. Now if it comes with a custom mount too...
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.


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Artif
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Re: Brake upgrades?

Post by Artif » Mon Jul 27, 2020 11:10 pm



rocklaurence
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Re: Brake upgrades?

Post by rocklaurence » Tue Jul 28, 2020 6:18 am

Ive never understood how they list the piston area of Two 2" pistons as 6.24 when 6.24 is the area of one piston. Shouldnt it be 12.48 for the two 2" pistons? Im certain that each piston isnt 1".

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Stuka
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Re: Brake upgrades?

Post by Stuka » Tue Jul 28, 2020 7:07 am

rocklaurence wrote:
Tue Jul 28, 2020 6:18 am
Ive never understood how they list the piston area of Two 2" pistons as 6.24 when 6.24 is the area of one piston. Shouldnt it be 12.48 for the two 2" pistons? Im certain that each piston isnt 1".
The area of each piston is 3.142 sq in. So when they are both added together you end up with 6.284 sq in.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


SJTD
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Re: Brake upgrades?

Post by SJTD » Tue Jul 28, 2020 7:23 am

Still less than the stock 6.6 but again I was looking at '79 diameter and those are for '78.

But my point is that two pistons don't guarantee more braking "power" than one. Fix what you have first. Is the booster operating properly? Is the master the correct part? A bigger bore there will give you less power.
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.


rocklaurence
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Re: Brake upgrades?

Post by rocklaurence » Tue Jul 28, 2020 7:25 am

Stuka wrote:
Tue Jul 28, 2020 7:07 am
rocklaurence wrote:
Tue Jul 28, 2020 6:18 am
Ive never understood how they list the piston area of Two 2" pistons as 6.24 when 6.24 is the area of one piston. Shouldnt it be 12.48 for the two 2" pistons? Im certain that each piston isnt 1".
The area of each piston is 3.142 sq in. So when they are both added together you end up with 6.284 sq in.
So, your saying that each piston diameter is 1"=3.142 PI? Arent they 2" in diameter?

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Stuka
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Re: Brake upgrades?

Post by Stuka » Tue Jul 28, 2020 1:27 pm

rocklaurence wrote:
Tue Jul 28, 2020 7:25 am
Stuka wrote:
Tue Jul 28, 2020 7:07 am
rocklaurence wrote:
Tue Jul 28, 2020 6:18 am
Ive never understood how they list the piston area of Two 2" pistons as 6.24 when 6.24 is the area of one piston. Shouldnt it be 12.48 for the two 2" pistons? Im certain that each piston isnt 1".
The area of each piston is 3.142 sq in. So when they are both added together you end up with 6.284 sq in.
So, your saying that each piston diameter is 1"=3.142 PI? Arent they 2" in diameter?
To find the area of a circle you use A=πr2. If the diameter is 2", the radius would be 1".
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ


jeepman6
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Re: Brake upgrades?

Post by jeepman6 » Tue Jul 28, 2020 5:26 pm

Please excuse the hijack, to put JB7 calipers and pads on a J10 is there a problem with the flex line connection? If so can I use the Chevy flex line?


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Re: Brake upgrades?

Post by rocklaurence » Wed Jul 29, 2020 7:12 am

jeepman6 wrote:
Tue Jul 28, 2020 5:26 pm
Please excuse the hijack, to put JB7 calipers and pads on a J10 is there a problem with the flex line connection? If so can I use the Chevy flex line?
Yes you can or you can grind off the key on the caliper and use the Jeep line. I install the bango bolt when grinding off the key because if you nick the seat it will leak.


jeepman6
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Re: Brake upgrades?

Post by jeepman6 » Fri Jul 31, 2020 10:22 am

My flex hoses are old, does the chevy hose fit the jeep end as well as the jb7? If so what part do I ask FLAPS for '85 chevy 3/4 ton?

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fsj454
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Re: Brake upgrades?

Post by fsj454 » Fri Jul 31, 2020 5:02 pm

Lower GVRW J20 WILL HAVE jb6 . Higher GVRW J20 WITH 13 INCH REAR Drums will have jb7 . All j20s are not the same
:fsj:454.nv4500.205.twin stick.hydo boost. hydrolic clutch.dana 60s.soa.37s 17inch.tration bar.warn 1200. 4 wheel disc.aero29 gallon .conferr roof rack.spal pulse width modulation.spal duel fans.painless battery isolator.duel batterys.factory cb. headers 2 1/2 duels.4.56 Detroit locker.alloy 35 spline axles.stainless brake lines .holley 770.edelbrock.fuel.water.intake.H4s.head light relays.racho 9000 shocks.rock ram.steering box brace.j20 steering box.msd8265 probillet distributor.msd super conductor wires.

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