J8 Master cylinder/booster measurements - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 31 Old 07-18-2017, 02:45 PM Thread Starter
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J8 Master cylinder/booster measurements

Looks like the J8 master cylinder and booster is one of the better routes to go for the brakes I'm running.
P5160050
however I run an AEV hemi. Anyone out there running the J8 setup with an hemi? does the booster fit?
or- anyone have the J8 booster that is willing to pull a few measurements off of it for me so I can see if it will fit? The AEV kit moves the steering shaft closer to the booster and thats the concern. Anyone pull a diameter and width off the J8 booster for me?
thanks
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post #2 of 31 Old 07-18-2017, 03:05 PM
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I have the jk8 master/booster and with an LS swap it all fits fine. I would ditch the hemi to solve the problem.
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post #3 of 31 Old 07-18-2017, 03:10 PM Thread Starter
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why didnt I think of that??????? lol
did you have to move the steering shaft at all with the LS swap?
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post #4 of 31 Old 07-18-2017, 03:25 PM Thread Starter
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or a pic of the stock next to J8 setup?
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post #5 of 31 Old 07-18-2017, 03:28 PM Thread Starter
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Quote:
Originally Posted by Dkjeep View Post
I have the jk8 master/booster and with an LS swap it all fits fine. I would ditch the hemi to solve the problem.
mind pulling a few measurements for me???
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post #6 of 31 Old 07-18-2017, 04:00 PM
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No steering shaft mods at all. Clears with room to spare. I don't have comparison pics, from what I remember the booster and master are both longer than stock but not sure about diameter.
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post #7 of 31 Old 07-18-2017, 04:02 PM
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That bolt on the steering shaft is the part that gets the closest to the booster and it comes within roughly 3/4" of the booster.
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post #8 of 31 Old 07-18-2017, 04:03 PM Thread Starter
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Originally Posted by Dkjeep View Post
No steering shaft mods at all. Clears with room to spare. I don't have comparison pics, from what I remember the booster and master are both longer than stock but not sure about diameter.
could I talk you into throwing a tape measure around it?
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post #9 of 31 Old 07-18-2017, 04:05 PM
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I can't get a tape around it. I've got too much shit between it and the driver fender.

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post #10 of 31 Old 07-18-2017, 04:09 PM Thread Starter
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Quote:
Originally Posted by Dkjeep View Post
That bolt on the steering shaft is the part that gets the closest to the booster and it comes within roughly 3/4" of the booster.

great pic, thanks!
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post #11 of 31 Old 07-18-2017, 08:49 PM Thread Starter
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Originally Posted by Dkjeep View Post
I can't get a tape around it. I've got too much shit between it and the driver fender.

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DK, I found out the AEV kit moves the entry into the firewall about 3/4" toward booster. That joint stays about the same. Any way to tell at the firewall how much room you have? the hose blocks it in the pic. Maybe top down?

thanks!

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post #12 of 31 Old 07-19-2017, 07:20 AM Thread Starter
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photo credit goes to a facebook group called 'JK-FourPLay'
Diameters look similar but definitely deeper.
DKjeep any way I can talk you into a pic at te firewall showing the distance between the steering and booster?vthe current one the hose is right in the way, maybe top down?
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post #13 of 31 Old 07-19-2017, 07:53 AM
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It will have to be Friday. I'm hopping on a plane right now.

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post #14 of 31 Old 07-19-2017, 10:49 AM
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Quote:
Originally Posted by Dkjeep View Post
I have the jk8 master/booster and with an LS swap it all fits fine. I would ditch the hemi to solve the problem.
That was damn funny! Quote of the week!!!


I too am running an LS and J8 master/booster without issues. if I get mine back tonight I can help with pics and measurements. The J8 is a HUGE increase in brake performance.


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post #15 of 31 Old 07-19-2017, 12:16 PM Thread Starter
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Originally Posted by Rubi-8 View Post
That was damn funny! Quote of the week!!!


I too am running an LS and J8 master/booster without issues. if I get mine back tonight I can help with pics and measurements. The J8 is a HUGE increase in brake performance.
thanks, I think I've got it figured out. AEV confirmed that the bolt that DK mentions (in his pic) is going to be the tightest spot. Based off all the info I've found, I think it will fit, might have to clearance that bolt head or use a low profile bolt but should fit.

Anyone know enough about booster to know if we clearance the booster at that spot will it affect anything? by clearance I mean beat it with hammer till it clears the bolt
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post #16 of 31 Old 07-19-2017, 01:44 PM
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Quote:
Originally Posted by pkrfctr View Post
thanks, I think I've got it figured out. AEV confirmed that the bolt that DK mentions (in his pic) is going to be the tightest spot. Based off all the info I've found, I think it will fit, might have to clearance that bolt head or use a low profile bolt but should fit.

Anyone know enough about booster to know if we clearance the booster at that spot will it affect anything? by clearance I mean beat it with hammer till it clears the bolt

The bolt can be replaced with a lower profile head bolt or just ground down.

I can NOT under any circumstances suggest beating, grinding, or clearancing the booster in any fashion. It's relitively thin and you need it to hold vacuum.....

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post #17 of 31 Old 07-19-2017, 08:12 PM Thread Starter
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The bolt can be replaced with a lower profile head bolt or just ground down.

I can NOT under any circumstances suggest beating, grinding, or clearancing the booster in any fashion. It's relitively thin and you need it to hold vacuum.....

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yeah I was kidding about the beating part. low profile bolt should be fine. Actually recieved a few pics today that look like the regular bolt will be fine. thanks a ton for your input!!!
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post #18 of 31 Old 07-20-2017, 03:16 AM
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I am running a 6.4 Hemi in my jeep and had to move the steering shaft over. Everything fits with the J8 booster.

Ton's, 40's, 6.4 Hemi
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post #19 of 31 Old 07-20-2017, 07:41 AM Thread Starter
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I am running a 6.4 Hemi in my jeep and had to move the steering shaft over. Everything fits with the J8 booster.
perfect thank you!
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post #20 of 31 Old 07-26-2017, 03:05 PM Thread Starter
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parts came in, any suggestions on bleeding the whole thing? Bench then car?
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post #21 of 31 Old 07-26-2017, 03:17 PM
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Quick bleed on the bench the bleed the entire system. It goes really quick.
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post #22 of 31 Old 08-10-2017, 03:39 PM
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Is this the cylinder/booster that works w tons? Or are there better options for that?
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post #23 of 31 Old 08-13-2017, 09:01 AM
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Not wanting to high jack but looks like a good place to keep info flowing. I am going to be lazy here and ask you guys the part numbers you used for the master cylinder and booster. I just got back from Colorado doing the trails around Ouray and I absolutely need to increase my brakes. In low range reverse on the side of a mountain it will push thru the brakes (pedal to the floor and park brake pulled). I already have the J8 front rotors and calipers but need to increase the rear diameter and the master cylinder.

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post #24 of 31 Old 08-13-2017, 08:15 PM
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Quote:
Originally Posted by Jeremi View Post
Is this the cylinder/booster that works w tons? Or are there better options for that?
Yes
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post #25 of 31 Old 08-13-2017, 08:16 PM
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Quote:
Originally Posted by 4wheels4life View Post
Not wanting to high jack but looks like a good place to keep info flowing. I am going to be lazy here and ask you guys the part numbers you used for the master cylinder and booster. I just got back from Colorado doing the trails around Ouray and I absolutely need to increase my brakes. In low range reverse on the side of a mountain it will push thru the brakes (pedal to the floor and park brake pulled). I already have the J8 front rotors and calipers but need to increase the rear diameter and the master cylinder.
There is one part # for all of it. I can get it in the morning.
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