Brake Upgrade Q

[ZJ TINS]

Ok so I read all the threads on brake upgrades (search does work). I guess to most interesting one for me is the kung fu upgrade. Some issues it raises I didnt not see a write up for however.

So in no particular order here are some questions. Maybe when answered we can sticky them somewhere as a guide.

So a MC from a E250 86 Ford coupled with an 90(?) XJ booster fit each other. Is there a XJ booster which fits and is a double diaphragm?

Is the double diphragm booster a drop in for the ZJ booster or is there work to be done(XJ booster to ZJ frame)? Have seen conflicting reports of what needs to be done. By this I mean the rod with circular opening to link the brake pedal.

It looks like the Ford brake line openings are on the opposte side of the MC and the lines need to be rerouted and adapters added. Is it easier/cheaper to just get new lines bent?

Any problems with keeping in the ABS and front/rear pressure dritribution block, or is it necessary to get a F/R adjustable block?


Even though its -8oF with a 25 knot wind right now I figure I can heat the garage enought to work in there for this project over vacation. Its either that or build a bathroom downstairs.

Merry Christmas (frack happy holidays I am not PC and dont care)!

[ATL ZJ]

Master cylinder selection should be based on the volume of your calipers and/or drums. What axles do you have? If you have stock axles and jumped to the E350 master, your pedal would feel like a rock. Tons of pressure but no mechanical advantage over your calipers. Let me explain. Larger bore master cylinders allow for greater braking pressure.. but if the ratio of your master cylinder volume to caliper volume is too high, the input force required (on the pedal) will also be very high. Very minor increases in MC bore cause dramatic changes.

The stock ZJ master cylinder bore is 1". While running a d44 front with Waggy calipers and an 8.8 with Ford calipers, I decided to swap in a MC from an '86 E350 along with a brake booster from an 88 XJ. The ratio was way off and I had a gorilla pedal, regardless of my pushrod adjustment. (too far out and they would drag, too far in and the brakes would barely do anything.) I just didn't have big enough calipers to support that huge master cylinder. The 86 e350 master I grabbed has a 1 1/8" bore. However, drum brakes generally have more volume than calipers so some medium-size axles with drums may be able to support the e350 MC.

Anyways, I decided to try the 88 XJ master cylinder, which has a 15/16" bore, and it worked great. It would lock up 37" Iroks. One thing I liked about this setup was that I had excellent pedal feel even with the motor off. You can "cheat" your way back to having a good pedal response by using hydroboost or a massive brake booster, but I like to avoid doing it, mainly for SHTF scenarios (pointed down a steep incline and the motor stalls.) I try to design my brake systems to function well with manual brakes only, in case the booster is lost, or I just don't feel like cranking the rig to move it 10 feet down a hill.

Now I'm running the 86 e350 MC with the 88 XJ booster to push fluid to my Ford Dana 60 calipers (front) and Chevy 3/4 ton calipers (rear) and I finally have enough caliper volume for the e350. My brakes work great.

I had already ditched ABS before all of these setups, so line routing was easy. It's really not hard regardless, just gives your flare tool a workout. If you want more info, search on pirate for posts by the user "VancoPBS". Van chimes in on a lot of good discussions that can help you make more informed decisions.

[rstrucks]

Cam, I just wish you sounded like you knew what the F you are talking about.

Good info.

[ATL ZJ]

Ha I wish I did too..

To answer your other question, the XJ booster and its pedal linkage assembly both bolt up to the ZJ firewall, IIRC. The e350 master bolts to the XJ booster with a little bit of grinding and enlarging the mounting holes slightly.

[paulkeith]

billavista's brake bible on pbb has tons of good info, and all the physics behind what cam described. better to learn a system and understand how it functions before just throwing parts at it.

linky: http://www.pirate4x4.com/tech/billavista/Brakes/

[ZJ TINS]

Pardon my denisty, you liked the XJ 15/16 MC but ended up with a 86 e350 MC with the 88 XJ booster? I thought he 250 was smaller than the 350. I know I am going to have to press harder and am willing to give up some for better breaking.
Is thw 88 XJ booster double diaphram? I am at 31"s now and max will be 34"s.


Also I am disk front and rear.

[northgazj]

I think you missed the part where Cam stated he is running a 60 and 14 bolt now which have larger calipers and can handle the extra fluid from the E350 MC.

[ZJ TINS]

ahh. I read the article (cool stuff). My issue seeems to be even when properly adjusted i cannot get enough brake clamping force when at the max pedal travel range. I know i could get a hydrualic brake bosster but waay too much money. I dont feeel i need that much improvement just some for a cheap/reasonable price. I have good aftermarket pads and rotors (which helpded) just want a little more. For instance I cannot stop when going max down hill grade even without the trannny in gear.

[IMin4Low]

You want to know anything about brakes, call these guys.

http://www.vancopbs.com/

They've anwsered EVERY brake question I've ever had & been on the money.

[OverlandXJ]

Pardon my denisty, you liked the XJ 15/16 MC but ended up with a 86 e350 MC with the 88 XJ booster? I thought he 250 was smaller than the 350. I know I am going to have to press harder and am willing to give up some for better breaking.
Is thw 88 XJ booster double diaphram? I am at 31"s now and max will be 34"s.


Also I am disk front and rear.

No, XJ dual diaphram started in 95. This is the booster alot of the pre 95 XJ guys are swapping to with F/R disc. The ZJ 4 wheel disc prop valve is another hot item for XJ's.