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  #1  
Old February 15th, 2021, 14:33
Black1990jeep Black1990jeep is offline
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Brake Up Grades for Rear Disc

Hi... I have a 1990 XJ, I have Ford Explorer rear disc brake conversion on my Currie nine inch Ford rear axle. My front brakes, master, propotioning valve, and single diaphragm booster are stock. I have 33x12.5 x15 tires. I want good braking!

Anyway the stock booster is leaking vacuum per my hand vacuum pump test, so time to replace it. That leads me to perhaps replacing the master while I am at it, and perhaps the proportioning valve too.

What upgrades are suggested if any?

Different bore master? Different booster? What about the proportioning valve?

I see Quadratech offers an upgraded booster and master kit for "rear disc brake conversions" , see link below...

https://www.quadratec.com/products/56210_1030_07.htm

What of this kit? I see they say it has a 1.125 inch master, what is stock diameter?

What proportioning valve should be ran? one from an explorer or?

I am still new too this and appreciate your insights.

Thank You!
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  #2  
Old February 15th, 2021, 17:20
RCP Phx RCP Phx is offline
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Re: Brake Up Grades for Rear Disc

I would definitely do a double booster conversion with a ZJ proportioning valve. There are lots of threads with this subject. Your MC should be 15/16", I have WJ/KJ brakes with a 1-1/8" MC to get my brakes the way I wanted them.
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  #3  
Old February 15th, 2021, 18:48
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techno1154 techno1154 is offline
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Re: Brake Up Grades for Rear Disc

I do not know about that thin from Quadratec,.. there are no reviews on it and
have not heard of it before.

Over the years I have been on site there have been plenty of discussions regarding brake caliper and master cylinder size that should go together.

My XJ still sports the OEM 1 inch master cylinder and booster. For brakes, the 2006 WK (first generation) rotors and twin piston are on the front with the 1996 grand Cherokee disks in the rear. I do not notice a difference in pedal height or firmness. My XJ now stops a lot faster with the 32 inch tires than it did with the OEM brakes and 27 inch tires.

A good combination valve will help to minimize rear wheel lockup in wet condition.
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1996 XJ; 4.0L; AW4; NP231; SYE; D30 and D44; ECTED; 4.10 gears; 30X9.5 -15 BFG/AT/KO; 3" lift; Rusty's LCA; JKS ADJ UCA; Kevins ADJ Track bar; Drawtite Front Receiver; Dual Electric Fans; Dual Battaries.
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Old February 15th, 2021, 20:01
Black1990jeep Black1990jeep is offline
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Re: Brake Up Grades for Rear Disc

Quote:
Originally Posted by techno1154 View Post
I do not know about that thin from Quadratec,.. there are no reviews on it and
have not heard of it before.

Over the years I have been on site there have been plenty of discussions regarding brake caliper and master cylinder size that should go together.

My XJ still sports the OEM 1 inch master cylinder and booster. For brakes, the 2006 WK (first generation) rotors and twin piston are on the front with the 1996 grand Cherokee disks in the rear. I do not notice a difference in pedal height or firmness. My XJ now stops a lot faster with the 32 inch tires than it did with the OEM brakes and 27 inch tires.

A good combination valve will help to minimize rear wheel lockup in wet condition.
thanks, Now the WK twin piston front calipers you speak of, are they a bolt on to the stock XJ (1990) steering knuckles, will they clear 15 inch rims?

I have 15 inch rims, and have Warn manual lock hubs, with different lug pattern than stock, i.e.... 5 x 5.5.
Also I have CJ7 front rotors which I assume are the same as XJ rotors except for the lug pattern, right?
prior owner had this work done, so I am reading this off his receipts. But I know the front calipers he had on there are stock XJ, cause I replaced them like for like and they are XJ fronts. So my CJ7 rotors are same diameter and thickness as stock XJ, correct?
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  #5  
Old February 16th, 2021, 02:04
SlowXj SlowXj is offline
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Brake Up Grades for Rear Disc

With 33s you should have good brakes in my experience.... I have stock everything except the 8.8 disks, and I also have 35s.... It stops better than my bone stock 99....

Sent from my SM-G950U using Tapatalk
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Old February 16th, 2021, 11:01
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techno1154 techno1154 is offline
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Re: Brake Up Grades for Rear Disc

Quote:
Originally Posted by Black1990jeep View Post
thanks, Now the WK twin piston front calipers you speak of, are they a bolt on to the stock XJ (1990) steering knuckles, will they clear 15 inch rims?

I have 15 inch rims, and have Warn manual lock hubs, with different lug pattern than stock, i.e.... 5 x 5.5.
Also I have CJ7 front rotors which I assume are the same as XJ rotors except for the lug pattern, right?
prior owner had this work done, so I am reading this off his receipts. But I know the front calipers he had on there are stock XJ, cause I replaced them like for like and they are XJ fronts. So my CJ7 rotors are same diameter and thickness as stock XJ, correct?
No, the WK brakes are not bolt on to the XJ knuckles. They also require a minimum of 16 inch wheels. I am on 17 inch JK take offs with 5 X 5 lug pattern. I am not familiar with the Wrangler brakes except the TJ which are the same as the XJ as far as I know.

Having said all this, The master cylinder may or may not need to be replaced wit one of a larger bore. For many of us, the OEM 1 inch does the job perfectly.
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#594
1996 XJ; 4.0L; AW4; NP231; SYE; D30 and D44; ECTED; 4.10 gears; 30X9.5 -15 BFG/AT/KO; 3" lift; Rusty's LCA; JKS ADJ UCA; Kevins ADJ Track bar; Drawtite Front Receiver; Dual Electric Fans; Dual Battaries.
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  #7  
Old February 16th, 2021, 11:17
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techno1154 techno1154 is offline
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Re: Brake Up Grades for Rear Disc

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Originally Posted by SlowXj View Post
With 33s you should have good brakes in my experience.... I have stock everything except the 8.8 disks, and I also have 35s.... It stops better than my bone stock 99....

Sent from my SM-G950U using Tapatalk
When I change the tires on my XJ to 30 inch diameter, I did not like the brakes nor the ability to climb hills. Re- gearing my XJ and replacing the OEM brakes made me feel 100% more confident driving in fast moving traffic that are typical on city beltways. I am now running 31 inch for about 10 years. Everything is just great,... mostly. Climbing long hills like East Tennessee, West Virginia and others , 456 gears would be good to have.
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Patrick

#594
1996 XJ; 4.0L; AW4; NP231; SYE; D30 and D44; ECTED; 4.10 gears; 30X9.5 -15 BFG/AT/KO; 3" lift; Rusty's LCA; JKS ADJ UCA; Kevins ADJ Track bar; Drawtite Front Receiver; Dual Electric Fans; Dual Battaries.
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  #8  
Old February 16th, 2021, 12:15
SlowXj SlowXj is offline
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Brake Up Grades for Rear Disc

Yeah east end was much better with my old tired 4.0 having 4.10 to push 31s... It's a DOG on 35s lol

Sent from my SM-G950U using Tapatalk
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Old February 17th, 2021, 08:49
RCP Phx RCP Phx is offline
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Re: Brake Up Grades for Rear Disc

The main thing that you want to pay attention to is all the brake line thread size changes that Jeep used unless your prepared to fabricate new ones. This applies to both master cylinders and proportioning valves.
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Old February 17th, 2021, 11:55
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techno1154 techno1154 is offline
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Re: Brake Up Grades for Rear Disc

Quote:
Originally Posted by RCP Phx View Post
The main thing that you want to pay attention to is all the brake line thread size changes that Jeep used unless your prepared to fabricate new ones. This applies to both master cylinders and proportioning valves.
That is 100% true. I installed and after market Combo valve and had to get myself a bubble flair tool so I could fabricate some of the lines.
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Patrick

#594
1996 XJ; 4.0L; AW4; NP231; SYE; D30 and D44; ECTED; 4.10 gears; 30X9.5 -15 BFG/AT/KO; 3" lift; Rusty's LCA; JKS ADJ UCA; Kevins ADJ Track bar; Drawtite Front Receiver; Dual Electric Fans; Dual Battaries.
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