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front to rear brake ballance and pulling

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RobSelina

RobSelina

Jedi Warrior
Offline
Having some fun fine tuning my brakes.

The system is basically stock except for steel braided soft lines. The MC was rebuilt a year ago. Front and rear brakes haven't been serviced in a while, but pads/shoes look fine front and rear.

Here's the issue - rear brakes lock up much quicker than the front ones. Depending on how well I have the rear brakes adjusted (left vs right) it will also pull pretty hard to the passenger side.

I've pulled the drums and I have an axle seal leak on the drivers side, it's dry on the passenger side.

I've been backing out the rear brake adjustment screws to try to ballance the front to rear brakes and also have her go straight under deceleration, but I'm not getting it very close and the e-brake is almost useless with the adjustments out that far. Regardless, I seem to lock up the passenger rear (the dry one) first, even with the adjustment way out...

I figure I need to fix that drivers side axle seal to even out the rear brakes, but as far as front to rear ballance goes I'm wondering what the best course of action is.

Were the brakes well ballanced from the factory? Since I don't kow how old the front calipers and pads are, would rebulding/replacing them be the first thing to try? what about a brake proportioning valve?

Any ideas or thoughts apreciated. I've been fighting this one for a little while and I'd like to get this little car to stop evenly.
 
Yes, before messing with a proportioning valve, I'd rebuild the calipers and install new pads, and probably new dics as well. You might also need to look at rebuilding your master cylinder (that's a fun job!).
 
oops, I just read that the MC was already rebuilt.
 
BTW, who rebuilt the MC?
 
hearing it was a fun job, I got the rebuild kit from Moss and let a local mechanic do it.

Think he could have done something incorrectly? It was leaking before the rebuild, pressure felt as good or better after getting it back.

One thing I should mention: There were two different rebuild kits shown for my year, one was in stock, the other backordered for months. I got the one that was in stock, hoping it was the right one, and he didn't have any issues so I assumed we were ok.....
 
Trevor, I'm mistaken. It was the clutch MC that was rebuilt, NOT the brake MC.

Think that should go on the list too then?
 
Definitely. My front brakes lock a LONG time before my rear unless I'm stopping really fast going down a steep hill. Then the weight transfer lets the rear lock up much sooner, but still not before the front.
 
Does your car have the 'proportioning' (brake failure) valve? If so it could have been un-centered during your MC rebuild and bleeding. If it is not centered it could be that your front brakes are not working.

Replace the rear axle seal and either clean off the oil from the linings or replace the shoes. Obviously the left rear shoes are contaminated hence the pulling to the right and only the right rear locking up.
 
[ QUOTE ]
Does your car have the 'proportioning' (brake failure) valve? If so it could have been un-centered during your MC rebuild and bleeding. If it is not centered it could be that your front brakes are not working.


[/ QUOTE ]

I thought it did have a proportioning valve, but I may be mistaken. How exactly woud one get out of center?
 
the Pressure Warning Differential Assembly (PWDA) is located below the master cylinder. it is either cast iron or brass. Hard to miss as all the brake lines start there. It has a shuttle inside the bore that keeps the front and rear systems separate as long as the pressure in each side is equal. should one side lose pressure the shuttle slides toward that side and trips the switch, turning on the brake warning light in the dash, if the light works. it can become uncentered and the switch plunger can get caught in the shuttle and prevent its recentering. Unscrew the switch, check the plunger and see if its bent. Also it should not leak brake fluid from the switch mount hole. If you need to rebuild it let me know i have a whole bag of the correct orings, and would be happy to share.


mark
 
"""""""I thought it did have a proportioning valve, but I may be mistaken. How exactly woud one get out of center? """""

Sounds like you have a shuttle valve and MIGHT not have a proportioning valve. Sometimes the two are combined ito one piece/part andits called a ...combination valve.

BUT.....before you do anything you have to fix the oil leak at the rear hub and if the rear shoes have oil on them you must replace the shoes w/ new. Do both sides and do both rear wheel seals. Check the sealing area on the r.e. housing and polish with 400 or 500 grit paper if necessary for a good surface for the seal to ride on. When you fill the diff w/ oil do NOT use synthetic and keep the oil lvel down 1/2" below the fill plug hole.

make sure the drums are round and concentric..adjust snug rotating drums...8 clicks out is about right. Redo when the shoes are bedded after 8-9 slow stops again at 8 clickz

now you can proceed to the rest of the brake system ...with decent pads in the front and a well working system the fronts should lok up slightly b4 the rears when the brakes r hammered.
 
gotcha.

I 'think' I'm okay in that department then. The little red light above the steering wheel does work when I test it, so is it fair to assume that my MC is ok?
 
i would pull the switch and check to see if the light is on . It is a normally closed switch, by unscrewing it and then plugging it back in the light should come on, and should go off if you press the plunger in. If this works then most likely your pwda is centered.

you could alway back off your rear adjusters and then see if the fronts are locking up. if they do then you most likely could assume that your MC is ok.

as mentioned you do need to fix the seal and replace the rear shoes that are oil soaked.



mark
 
anyone have a little writeup on replacing that seal?

At the risk of sounding like an idiot, I'm not exactly sure how the axle is retained in the housing. The two other semi-float axles I've worked on don't have 3rd members and the axles are retained with c-clips...
 
If memory serves, you'll have to pull the axle. Then you can remove the axle hub from the axle tube. Knock the bearing out of the hub and then the seal. In the infamous words of chilton...reassemble in reverse order...lol. Seriously, it isn't that bad once you tear into it. It is pretty obvious when you get there as to what needs to be done. When you put the axle back together, use a new o-ring and paper gasket. I used hylomar sealant on the paper. I also replaced the bearings while I was in there but you don't necessarily have to do that.
JC
 
okay, so if I understand correctly, I'm removing the axle hub & axle as a single pice from the housing, then separating them?

Think I'll stop by NAPA on the way home and order new gaskets and bearings.
 
I don't think so, it's been a while but if I remember right. You'll pull the axle by removing 3 countersunk screws and sliding the axle out of the housing. Seems like I had to rig up a puller (creatively) to pop mine apart the first time cause the gasket was stuck with permatex. Anyway, after you slide the axle out of the tube you should see a large nut that holds the axle hub onto the axle housing. Remove the nut and you can take the axle hub off. At least that's the way I remember it. Remember, on the hub there is an oil seal at the back and a paper gasket and o-ring on the front. If I'm leading Rob stray someone feel free to chime in and set me straight. It's been a while since I worked on that end of the car.
JC
 
JC is basically correct.
I think the axle can be pried away from a the hub with a screwdriver (after the three screws are removed). The big nut is around 46 mm (or whatever that is in inches?...did this a lot recently but I didn't look at the socket size)). I use a new O-ring but just sealant instead of the paper gasket. The seal is in the back of the hub so you have to slide that off after the big nut has ben remeoved.
Basically, that big nut holds the whole thing together...if it comes loose, your wheel will come off. There's a metal bent-tab washer that keeps it on and some of us use Lock-tite as well.

Don't bother with new brake shoes until you get the leak stopped.
My fronts always lock up first...I'm planning on plumbing in a mechanical proportioning valve (and ditching that other "balance" thing ot whhatever it is) after I get mine all worked out. I'm hoping the extra inner seals on the axle (whenb I has the diff out) will reduce/elimate the leak).
The picture below (form Moss) may help.

SPM-027.gif
 
Thanks for the info guys.

Priced out the parts at NAPA and Moss (Moss was cheaper) but I've also contacted a BCF member, see if I can get pads & shoes that may be better for racing.

I'll clean all the existing brake parts off when I replace the seal, make sure it holds before I put the new brake pads in.

Thanks again!
 
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