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On turning drums with hard spots.
Years ago when I first got my G, I took the drums to a brake shop that had
a grinder attachment for grinding drums with hard spots. I believe this is
the only way to remove them. When you turn a drum with hard spots, the cutter
skips over them. You will then be able to feel them with your fingers. If the
drum has hard spots, but is still smooth, I would leave it alone.
Max diameter on drums has always been .060 over, no matter the drum. I’ve
seen ones that were out over .100 that still worked, but would be prone to
warping under hard braking. It’s more important that the drums on an axle be
close to the same size. Size difference will cause pulling.
Proper return springs that are in good condition are important too. If you
can see between the coils, they have been over-stretched, and should be
replaced.
I did have a working shoe grinding machine until the motor seized. I would
be interested in a machine for parts with a good motor if anyone has a
lead.
Don
Hi Henry ,
I get it — sort of betwixt and between .— given what happened
? leave drums alone ( out of round will cause a pulsating pedal you don’t have)
and removing material will make it weaker and more prone to that warping . Have
a machinist precision measure the drums , ID — get your new shoes ( both sides )
then have them precision ground to correct undersize compared to drums . ( I
forget gap but it is in the publication i mentioned , remember diameter and
radius aspect too ) Isn’t max oversize stated right in FSM? But does not matter
if you don’t turn anyway . Remember 12” shoes vary by year , two groupings ,
often mixed up on cars I have bought — a huge error. New shoes , but wrong
shoes — on “restored “ car . Also some aftermarket shoes seem to try to combine
both designs , really thoroughly confused me once. Be sure to read that
service pub end to end .
You will still need to adjust 3-4 times in first 1000 -2000 miles
maybe , give it time to bed in before judging it. We are used to auto adjusting
brakes , FSM says adjust every 2 K seems crazy now.
Someone wrote to listserver about a place that does that grinding ?
Shoes DO have to go - once wet... so I hear you ,,and both sides
must be the same . I am a big fan of silicone fluid but better maybe one thing
changed at a time . As a minimum put in all new of whatever is
the existing fluid. unless already silicone .
A New understanding , and more clarity for me anyway , in the past
few years on understanding brake fluids. Old style glycol fluid absorbs
moisture ( it is supposed to - to protect against rust! ) but then after many
years in a changing room temp or dead storage especially if car sits
( heat of use drives out moisture to some degree)and it becomes saturated
—cannot hold more.. soon excess water retained in glycol absorption (on a
cold day ) comes out of the glycol solution — at bottom of wheel cylinders ( of
course!) causes a pit of rust , then a seal failure — usually right after you
put in new shoes as that pushes piston back to a new place that places the
rubber lip often right over the rust pit. This latter syndrome is not imho
commonly understood . Common on our cars. Wheel cylinder leaks out of nowhere
thus have a cause .....
Mercedes clearly insists on changing it , I ignored it — after ten
-12 years it cost me $ 3000 in rusty brake cylinder / disc cylinder , ABS parts
/seal leaks on an old 300TD wagon I loved . Lesson for me in past, the
hard way .
I have seen many many 300’s with rust pits at bottom of the wheel
cylinder — some light ones can be honed out but better to go new ( for how long
? save old cores) or stainless or brass sleeve . Point is change brake fluid
every 5 years , pay attention to master cylinder fill gasket (?seals against
air/ moisture) and tightness . Dual master actually probably a smart idea
, given this — on a now very old car ... of unknown history .
silicone does not hold water but has its own issues . Difficult
bleeding if you accidentally aerate it at all while handling it , but
military uses it , due to typical long storage inactive . It
takes months for micro bubbles in a can on a shelf to come out . Never
shake . I buy that military thinking . Nothing to do with other pros and cons .
Well, John, thank you for your input. I am grateful. When I
am on the freeway, the car actually slows down fairly well under braking but
I’ve never had to make a panic stop. When I get off the freeway driving home
through the neighborhood i experience serious brake fade. That makes me wonder
about that one panic stop. Then I began to experience a serious pull to the
right during braking. I pulled off the left drum and the seal had let go,
soaking the drum and the shoes. So now I need new shoes. I read on the
listserver that one of us had bought street performance shoes from Porterfield
Brakes to good effect so I decided to replace with performance shoes.
21st century brake lining technology. That is one method to
improve braking performance without outwardly changing the car. Most of the
listservers have gone to 2-wheel and 4-wheel disc brakes and modern master
cylinders but I didn’t consider those changes because I am making a serious
effort to keep my car box stock. If I made the effort to put 4-wheel disc
brakes, a two-sided master cylinder and all that stuff, I would yank the 1957
392 and put in a 2021 392 crate motor and get rid of the annoyingly cranky WCFB
carburetors. I could still say I had a 392, but I would have 650 hp. Anyway, I
am the type of person that, once I have everything apart I like to fix
everything I can. That’s why I wanted to turn the drums. The Chrysler manual
says that if the drums are more than .004 out of round, they have to be turned.
The drum surfaces are actually quite smooth, virtually no grooves but both drums
have little “hot spots”, little shirtbutton-sized marks at regular intervals
around both drums. They are visible but I cant feel them. I went to two brake
shops. They were not capable of turning the drums because of the hot spots. I
went to a third shop-same story but the guy was kind enough to measure the
diameter of the drum but none of the shops I visited were able to tell me the
maximum diameter of the drum. Porterfield said they would arc the shoes to fit
the drums. I found a machinist who would turn the drums but he needed to know
the maximum diameter and rightly so: I don’t want to turn the drums beyond the
max. If I discover the drums are maxed right now, then I will just put the drums
back in the car, hot spots and all, and hope they aren’t more than .004 out of
round. Henry BTW when I pulled the right drum, not the problem side, it
was fairly obvious visually that only about 75% of each shoe was contacting the
drum. It taught me what you said all along that matching the shoe to the drum is
important but apparently there aren’t any shops that have the capability of
arcing the shoes to the drums so I’m going with Porterfield. From: chrysler-300-club-international@xxxxxxxxxxxxxxxx
<chrysler-300-club-international@xxxxxxxxxxxxxxxx>
On Behalf Of John Grady you really should not turn them , even if scratched or
grooved. . new or turned ones will scratch or groove anyway in a thousand miles
. your existing shoes match that grooving now . ——unless you have a guy with rare correct machine to
turn new shoes to match , you will suffer with many new frustrating brake
problems . just mho. why do you want to turn them ? unless shoes are toast , leave
it alone ? Those brakes went 50 k + in the day , rebuilding them for
nothing brings in lots of problems , and as a classic car you are not generally
going to go tens of thousands of miles. All brand new parts this problem happens
..... There is an excellent chrysler publication , about the “ new
three platform brakes” may be on our web site. lots of info , maybe 50
pages . on internet . looking back 50 years now , the reputation for “ being
difficult brakes” starts with drum turning , and then shoes do not fit
right. They will Touch in one small spot for a very long time , as incorrect
radius- and thus feel ineffective . fyi , John Sent from my iPhone not by choice
I am having the front brake drums turned from my 300C. For
some reason nobodys brake drum-turning book goes back to 1957. Does anybody happen to know the maximum diameter of the front
brake drum? Is the rear drum the same maximum diameter? Henry -- -- For archives go to http://www.forwardlook.net/300-archive/search.htm#querylang --- You received this message because you are subscribed to the Google Groups "Chrysler 300 Club International" group. To unsubscribe from this group and stop receiving emails from it, send an email to chrysler-300-club-international+unsubscribe@xxxxxxxxxxxxxxxx. To view this discussion on the web visit https://groups.google.com/d/msgid/chrysler-300-club-international/3489DC4D-235C-46EF-B0AB-F48C136F9FB8%40gradyresearch.com. For archives go to http://www.forwardlook.net/300-archive/search.htm#querylang --- You received this message because you are subscribed to the Google Groups "Chrysler 300 Club International" group. To unsubscribe from this group and stop receiving emails from it, send an email to chrysler-300-club-international+unsubscribe@xxxxxxxxxxxxxxxx. To view this discussion on the web visit https://groups.google.com/d/msgid/chrysler-300-club-international/14A4B0AF30524E44B9D6E49CE6074699%40OwnerPC. |
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