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Rear braking more than front... how/why?

xj-boonie

xj-boonie

NAXJA Forum User
Location
Hastings, MN
When I brake, it seems like the rear axle is providing more brake force, and the the rear will lock up first.

I just got done swapping axles on my 96 XJ (4.0L, 5spd, 210,000 miles, 4wd, no abs, 31" Mickey Thompson MTZs). I put in a 85ish XJ D44 in the rear with an Aussie Locker, and a 97 XJ HP D30 in the front. The D44 has all new drum brakes - everything from the soft line from the body to the drums (I know - for the expense I should have went to discs....). The D30 has rebuilt calipers, new pad and hardware, new lines, and turned rotors that are very near new thickness. My old axle had some large divots where the brake pads were riding, but the 97 D30 had very slight ones, so I ramped the ends of them with a file. Plus, when I put the new pads on, they were resting on spots no where near the slight divots.

I haven't tried a true panic stop yet, or tried it on the grave.

Any thoughts?

Thanks,
Mike
 
Probably need to better bleed the system. Sounds like air in the front circuit.
 
the rears lock up first because of weight transfer. when you brake hard a lot of the weight comes off of the back end of the vehicle and due to the fact that it's getting the same amount of braking force with essentially less force to keep it moving forward it'll lock up. if you can lock up anything on dry pavement i'd say your brakes are working just fine.
 
Some shoes tend to lockup easer when cold damp then others. Your new ones may be this way. Are the 44 drums the same size as the OEM ones?
You may have the shoes a little tighter then the old well worn ones. Showing up as early lockup. This is VERY common after a brake job. If so, it will correct itself.
 
No, the old axle (chrysler 8.25) had 9" drums, the D44 has 10". I replaced everything - all the hardware, wheel cylinders, shoes, drums, hard line, and soft line.
 
XJ's have a proportioning valve in the rear brake system to insure the front discs will lock before the rear brakes (drum or disk)--weight transfer is accounted for.
Another question for XJ-boonie--if you stand on the brakes, will the fronts also lock up? My guess is they won't, which would indicate more bleeding in the front circuit.
 
Haven't tried standing on them yet. Does it matter if it's dry or wet, cause it's raining to beat all heck right now.
 
Ainsure the front discs will lock before the rear brakes
===================================
To be picky they should lockup at the same time. If everything is just right. Seldom is.
Plus IDEALY it should be set for this to happen when your at 50% of max load.
Once again this seldom happens.
MJs have a P value that was height sentive. As you loaded her down and the rear sinks a rod conected to the P value from the rear axle. Would incress the percentage of rear braking effort. IDEALY

Bleed the hell out of her. Bigger brake in rear maybe the problem.
bigger tires will fix that.

A good bud is hard to find!
Even harder to lose.
Work safe.
 
Last edited:
Rears will lock before fronts... 9 times out of 10......

Weight transfer....

With enough pedal force ALL will lock....

Also, make sure that they are adjusted properly.....
 
The rear brakes will apply just a split second before the front just like it was said before in this post but if you have the parking brake adjusted to tight it will drag causing the felling of more braking in the rear. I have the same felling
 
in all practical situations you shouldn't be locking them anyway... but i guess it's a decent measure for which ones are doing "more" stopping.
 
Mine rear shoes like to "hang" after I hose it off (if I set the E brake, if it's not set they grab, HARD). I figure it is surface rust and water inside the drum, so check for foreign liquids as mentioned earlier in the thread....

Also, my other issue with the brake grab is the amount of sand intrusion (Yeah, I know, thats what I get for living on the beach....), so check for foreign matter too.....
 
You went from a 9" rear drum to a 10" rear drum, so you now have more stopping power for the rear end. The proportioning was set up for 9" inch drums on your Jeep you may need to adjust this.
 
in2fords: I didn't modify the calipers, just smoothed the typical divots on the hub ears that the pads slide on. They are the right pads.

It seems like the right rear locks up first, at least when I tried it in the rain, and on the dry.

I'll take the wheel and drum off tomorrow and see what's in there.

It just really feels like the fronts are appling as much pressure as they should... Not so much front dive, but rear end rise due to the rear brakes. I want to take it to a gravel road and see if I can lock up the fronts.
 
Asher.mich said:
You went from a 9" rear drum to a 10" rear drum, so you now have more stopping power for the rear end. The proportioning was set up for 9" inch drums on your Jeep you may need to adjust this.
Click to expand...


Its the same prop valve for the d44 vs the d35 xj's.
 
Before i converted to disc rear brakes, I would usually lock up 1 rear wheel, then both front, and then the other rear if I *REALLY* stood on it.

I did a WJ conversion up front, and that pattern stayed the same.

Did a disc brake conversion on the rear using a hybrid of explorer and expedition parts, and installed an adjustable prop valve at the same time. I havent actually locked up any wheel since I did it, but it will put the steering wheel through your teeth.
 
cal said:
Its the same prop valve for the d44 vs the d35 xj's.
Click to expand...

So does this mean I should be OK running an '87 D44 with drums under my '99 XJ without making adjustments and/or modifications to my braking system?

I'm setting up my D44 to work with my ABS but I don't see that causing any additional problems. In fact I'd imagine it would actually help as it would sense rear wheel lock up and reduce pressure if necessary.
 
fyrfytr1717 said:
So does this mean I should be OK running an '87 D44 with drums under my '99 XJ without making adjustments and/or modifications to my braking system?

I'm setting up my D44 to work with my ABS but I don't see that causing any additional problems. In fact I'd imagine it would actually help as it would sense rear wheel lock up and reduce pressure if necessary.
Click to expand...

Shouldnt be a problem.
 
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