Brake performance

I'm rollin some heavy 33"s. I've got the dual diaphragm booster and a ford 8.8 rear with discs and a proportioning valve.

My braking SUCKS. I have seen it written that I should be able to lock up the tires with this setup. NOT EVEN CLOSE. I'm a big strong guy and I can TROMP on that brake pedal and they will not even SCUFF let alone lock. I am engine braking all the time because my brakes suck so bad. And now I want to tow a boat. I've got 4.88 gears so I can engine brake like nobody's business but it's hell on my poor AW-4.

The discs and pads are pretty new. The calipers were replaced not that many years ago. I bled the piss out of them a while ago and it didn't really help.

They hold when you step on them so I'm assuming MC is OK. They don't pull so I'm guessing calipers are OK.

I'm pressing the pedal down to full travel AFAICT. I mean I have tried STOMPING on it (I can deadlift 300 so I'm not ****ing around).

I'm thinking WJ caliper upgrade but before I go through that I want to make sure there isn't something else wrong.

Should my braking really be this bad or is something wrong?

How else could I troubleshoot this?

Would different pads/rotors/calipers help? Any other low buck brake upgrades besides WJ? Don't want to go 16" wheels...

This looks like what I really want, but I have to save my pennies. Unless somebody is upgrading axles and wants to sell their used kit cheap hint hint http://www.shop.blackmagicbrakes.com/VANCO-15-Big-Brake-Kit-with-BMB-Pads-for-15-Rims-BBK-NDM15.htm

How are your soft lines? if you have old/bad lines they can expand/close up and drastically decrease your braking. Also if your hard lines have corroded they might have debris in them blocking them.

If you have everything setup correctly:

1.) You still have air in your lines somewhere. Think you got it all out? You bled it 2452354 times? Try another few hundred times. This is where a vacuum or pressure bleeder are well worth it.

2.) Check all of your lines. Have you had any brake fade, or were they this way since you did the install?

3.) After going through all your lines, and rebleeding several times, one could verify via a pressure gauge attached to the caliper (though this can be a real PITA).

Something isn't right in your system. I was able to pretty well lock up 35's with a D30/9" combo, the 9" having drum brakes.

I'm rolling 35s stock front brakes and rear drums and my brakes are great and only upgrade is extended stainless lines you definitely have something wrong


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Cheapo pads?

Do the stainless lines for sure.

Could be... I usually buy premium semi-metallic pads but I don't remember what these are specifically, and lord knows "premium" might not mean much. Maybe after I bleed the piss out of it some more I'll try a known good pad rotor combo like black magic or something.

Desertjeeper did the original buildup

http://www.naxja.org/forum/showthread.php?t=914220

The rear disk proportioning valve is an XJ proportioning valve, should I replace it with something else?

he didn't say anything about the extended brake lines; they appear to be stainless braided. the clear plastic covering the stainless braid is degrading a bit but the stainless braid itself looks great.

part of it is that my wheels are friggin heavy I think. I noticed it got worse when I replaced my worn out BFG MTs on alloys with cheapo ATs on steelies

So your proportioning valve is the stock XJ one?

I'd swap in one from a ZJ and see from there.

I have never tested the braking of heavy steel wheels vs light alloy wheels. But I have wondered whether the weight of the wheels is really a huge factor in braking capacity. Most of the angular momentum is on the outside where the tire is, and the tire weighs much more than a wheel.

Maybe someone will come along and educate me why I am wrong.

It's not the wheels, it's something internal to the brake system.

I ran 35's on black steelies, and could get mine to lock up at 50mph or so.

And I didn't have discs on the rear.

n1ywb said:

Desertjeeper did the original buildup

http://www.naxja.org/forum/showthread.php?t=914220

The rear disk proportioning valve is an XJ proportioning valve, should I replace it with something else?

he didn't say anything about the extended brake lines; they appear to be stainless braided. the clear plastic covering the stainless braid is degrading a bit but the stainless braid itself looks great.

Click to expand...

The guts from a 94 to 98 ZJ prop valve.