Hello,

I recently bought an all original 24,000 mi survivor 78
Dodge aspen.


It had sat for a long while before I obtained it.

I rebuilt the master cyl and flushed the entire system.

I now am having the rr. Lockup on moderate to severe
Braking. The car needs front shocks, it dives quite abit forward
When braking. Can I solve this by unadjusting the r rear brakes and then
Not installing the self adjustment cable, or is my issue
Shocks or prop. Valve?

I did not open or remove that valve yet.


Thanks
Greg

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http://www.youtube.com/hyperpack

What's the current size of the rear wheel cylinders?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

not quite sure on that Ed.

probably 15/16 I would guess or whatever would be stock on a 78 aspen with 10" rear brakes.


I have to look into that.

it's just the right rear that locks up not the left rear.


Greg

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http://www.youtube.com/hyperpack

Oil or fluid on shoes.

Richard

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Part of Tyrde-Browne Racing

Make sure the primary and secondary shoes are in the right spot too.

I am pretty sure that was correct but I will double check .

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http://www.youtube.com/hyperpack

I will look into that as well.

ca I use brake cleaner to "solve" that one.

pun intended as brake cleaner would be a "solvent"


Greg

_________________
http://www.youtube.com/hyperpack

One side only could be the automatic adjusters on that side aren't working

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Make sure you have the same size wheel cylinders on both rears they made at least 3 different bore wheel cylinders for 10 inch brakes could be mix/matched also if they are the same you can go to a smaller bore wheel cylinder to stop the lock up on the rears Chrysler did this to stop this problem. I believe Mopar Action Magazine did an article on this topic.

Brian

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63 Plymouth Valiant Wagon

Others have given good advice on things to check. Here's a couple more possibilities. Weak shoes return springs. A sticking or seized wheel cylinder piston. Or, insufficient toe-heel clearance between the shoes & the drum.

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63 Valiant Wagon
225 - 4 bbl

Seized wheel cylinder on opposite wheel or contaminated shoes on locking wheel would be high on my list. Next would be poorly adjusted shoes.

Cleaning a contaminated shoe is a fools errand, oil soaks deep into lining, and heat brings it to surface. If shoes are contaminated, toss'em, and install new ones making sure they have the same radius as the drum that they will be used in so full contact between both parts is accomplished. Also be sure both drums are not turned past speck, and that both drums are same dimension; in other words don't have a new drum paired with an old turned drum on same axel.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

That's exactly what you don't want. On a "self energizing" Bendix brake design, the shoes have to be slightly smaller radius than the drum- hence the term, "toe-heel clearance". If the shoes are "full-contact", then the brakes become almost impossible to modulate, they're effectively either on (locked-up) or off. Many problem cars I had 20+ years ago that had lock-up complaints were fixed only by radius grinding the shoes to create clearance at the ends- ie, partial-fit.

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63 Valiant Wagon
225 - 4 bbl

Perhaps I should amend my comments above. What I was referring to was a stock radius brake shoe being installed to an oversized drum (turned to max dimension or beyond) needing to be re-radiused to properly fit old drum. In the old days there was a machine that brake shops used to properly accomplish this task of fitting shoes. You are correct shoe has to have a bit of run-out at their ends, or they will fetch up.

If you have just the center of the shoe contacting drum, braking ability will be greatly diminished at that wheel, and if the opposite drum is standard dimension on that axil its normal braking action will appear to be excessive in contrast causing one wheel lock-up.

One other condition that I experienced in the old days with my first Dart’s easily locking rear wheels was due to excessive moisture or humidity collecting over night or during wet days between drum and shoe. This problem was the result of a lackadaisical mechanic not installing rubber plugs back into adjuster holes. The rear wheel wheels would lock on painted crosswalk surfaces, wet pavement, dusty pavement, etc. until rear shoes were heated enough to dry them out. I also suspected the fool didn’t properly clean braking surfaces during reassembly.

One more thought, check rear tire pressure, over or under inflation will reduce contact patch area causing reduced traction and easy lock-up under moderate braking, and conversely more robust burn-outs (but that’s another subject). LOL

This was one reason I began making my own repairs, that and being a broke college student with more pressing needs on my cash reserves from girlfriends, skiing, and tuition being higher priorities over hiring mechanics. After all gas was 29-32 cents a gallon, a burger at McDonalds was around 25 cents, and books and tuition about a grand… Ahhhh; the good old days when minimum wage was pegged at around a $1.60 an hour, and draft lottery drew into low 300’s.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Awww- shucks! Here i was all ready to start quoting chapter & verse from the FSM!

Certainly incorrect or sloppy assembly will cause problems- other times I've seen some friction material compositions that just "soak up" ambient moisture if they sit more than a day or so- then they're grabby until they heat up. The only cure sometimes is to go to a different brand of brake shoe.

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63 Valiant Wagon
225 - 4 bbl

got this one solved..


the lr wheel cylinder was not operating..

the cast iron housing did agree with the aluminum piston. cleaned and freed and reassembled everything checked all other suggestions..


matching 15/16 wheel cyls..
shoes installed correctly
both sides adjusted correctly
all springs present and operational

no contaminated linings or drums.


re bled the rear brakes and did a few panic stops...

nice and controlled now! thanks



Greg

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http://www.youtube.com/hyperpack