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Senior Charter Member
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Discussion Starter · #1 ·
Guys,
I've been trying to upgrade my brakes and have gotten a lot of info from you and suppliers. In talking with one suppler he stated that the jeep MC would put more presure on the line and help stopping power. I thought that the jeep MC was used in conjuction with a booster. Will someone please give me the SKINNY on this? Is the jeep MC better than a stock mustang MC and should it be considered as a stand-alone-upgrade to my braking system? :confused:
Thanks,
Ron FFR1738
 

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Hey Ron
We need more info...what do you have now? Is there a problem or just upgrade time?
I have 84 Alum Jeep MC, SN95's all around...no booster.
 

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The Jeep master cylinder has a 15/16" bore, which is about ideal for our car weight and brake components. It is used WITHOUT power boost and WITH the pedal modification illustrated in the build manual. The Jeep unit has the best compromise between pedal travel and required pedal pressure.

The reason is that the stock master cylinder does not work well in an unboosted application because the bore is too large. Yes, there are Ford MCs that have a 15/16" bore and probably would work well, but the Jeep unit is cheap, easy to find, and has individual reservoirs so the distribution block can be eliminated.
 

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I recently saw a post where one of the experts said that adding better pads will also help a lot. I've got the Jeep MC with 4 wheel disc and stock pads. I'm not on the road yet, but if I want more stopping power, I'll get new pads.

I saw another post that stated that if you have the stock rubber brake line off the caliper, that after a while, they can start to flex. That will reduce your stopping power. If you still have donor stuff, that'd be something else to check.
 

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Discussion Starter · #5 ·
Thanks again guys,
With your help I've come up with a plan of attack. It does confuse me sometimes when there are so many inventive ways you guys solve the same problem...GN, JEEP, BOOSTED, NOT BOOSTED etc. I am wondering if I'll ever be happy with the disc/shoe brake setup (4 lug). I've read in the past that people race with them and are very happy with their performance.
I'll start with S.S. lines, better pads, shoes, and S.S. caliper bushings and of course flush-out the brake fluid and replace. Then I'll get a better idea of wether I need to do more.
Again thanks,
Ron FFR1738
 

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I have been searching and FAQing about this topic, and it seems there are some different opinions on the subject.

From what I have been able to gather, this is what I have come up with:

-You need a master for an 84 Jeep "Cherokee"
-You can use it with no proportioning valve
-You need to perform the pedal mod to the donor pedal as outlined in the FFR manual
-You install the master with only one of the two spacer plates

Is this correct, or am I wrong about something? And am I missing anything else needed to know? Does it matter if the Jeep master is for 2wd or 4wd? Thanks guys, this seems to be a hot topic, but the info is a little vauge.

Sal
 

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Heat & Beat Specialist
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529 Posts
We used the 84 Jeep MC. Napa part# 101896. We used a adjustable prop valve for the rears. Fronts are fox Mustang stock, rears are SN95 non-cobra on Richard Oben's brackets. We are using Hawk HPS on front and rear. We know 2 guys with this caliper/pad setup, and they love it. These guys started with stock disc/drums and moved to rear disc , then added Hawks. They said the Hawks made the largest measured improvement. So, I guess if you were gonna do just 1 thing you should get some good pads.
 

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AutoZone 10-1896. Got the aluminium one on the third try (sucker weighs less than the box it came in), pedal mod AND GET Whitby's adjustable rod. Makes life EZ.
 

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Discussion Starter · #9 ·
Guys,
More good input. I've already changed my mind...talked to Richard and ordered his conversion. Now I guess I'll talk to Jeff and get adjustable rod.
Thanks,
Ron FFR1738
 

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Originally posted by Ron FFR1738:
Guys,
More good input. I've already changed my mind...talked to Richard and ordered his conversion. Now I guess I'll talk to Jeff and get adjustable rod.
Thanks,
Ron FFR1738
Ron, got any info on this "conversion"?

Sal
 

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Ahh ok. I'll be using the IRS so I'll have the stock T-bird discs on the rear, and the 5 lug LSC rotors on the front. Can I still use the Jeep master with that setup?


Sal
 

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Power Surge,
That's fine, but using the 73mm LSC calipers on the front instead of the Mustangs gives a better balanced sytem without need for a proportioning valve.
Frank
 

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I would be cautious on the front 73 mm calipers. People say they do NOT add any braking ability.

No prop valve with Mustanh fronts and T-Bird rears is ok. The prop valve on 3850 is backed all the way out, and still not too much rear brake.

Sal, regarding your first question on spacers, with a Jeep pushrod shortened to 5.5" center of pivot hole to end, zero spacers are needed. Here is a pic:

Shorten by cutting a section out near the pedal end, thread with a 3/8" dye, and install a 3/8" NC coupler.
 

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In a previous post, Richard Oben suggested just cutting the Jeep push rod and using a short length of 1/2" tube with JB weld. Because it's in pure compression, there shouldn't be any issues with doing that, and it's a lot easier than threading. Took me about 5 minutes to complete. He also suggested making the rod EXACTLY 6" long, with two spacers on the MC. So that's what I did. Not plumbed yet, so I'm trusting his judgement. In fact, plumbing this weekend...

He's answered this question numerous times. Do a search on the Ask North Racecars board and you'll see a bunch of good info.

All the best,
Tag
 

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Orbiting FFCobra.com
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I cut my pushrod down, threaded both ends and put a coupler in the middle. It took me about 45 minutes and I've got my own adjustable pushrod for about $3.00 in parts.
 

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I have been hanging around the GT40 forum a lot lately, asking all sorts of questions for my upcoming build. One bit of very pertinent information regarded bore size of brake master cylinders.

What I learned was, the smaller the bore, the greater the line pressure is with the same amount of pedal pressure applied. Or, less pedal pressure to achieve the same stopping power.

The reason everyone uses the Jeep MC is as Oldguy stated. The smaller bore on the Jeep MC results in more line pressure; hence, no need for a power booster.

But there is a limit to how small the size bore you can use. Going too small and you can actually have too much line pressure.

For these cars I wouldn't go with anything smaller than 7/8" bore, and 1" bore being the largest.

2FAST
 

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He also suggested making the rod EXACTLY 6" long, with two spacers on the MC.
The spacers are about 1/4" thick so two are about 1/2"; hence a 6" pushrod. To eliminate the spacers, use 5.5" pushrod length. Everything clears and the brake pedal extends just right. Either way works perfect; the difference is spacers or not.
 

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I've already installed the stock donor MC and Dist block since that's what all the pictures showed. Didn't read the top of p22 till I saw another post. How bad will the brakes be?

If I do change, what is the plumbing like?
 

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I have the jeep MC and did the pedal modification. I haven't heard anything about the angle of the push rod. Does it make a difference? The mustang push rod has an offset which (to me) looks like it puts it at the same angle as the MC. I like the idea of the adjustable lenght, so it looks like tomorrow I will be cutting and threading the Mustang push rod. Or has everybody been leveling out their MC(mine looks angled and FFR says that is normal).
 
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