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#220050 - 02/10/09 09:42 AM tricks to reduce drag on stock a-body discs?
dirtybee Offline
super stock

Registered: 04/14/07
Posts: 807
Loc: Toronto, Canada
i posted on Q&A also, just wondering if there are any tips or tricks people may want to share on how to get my front discs to spin more freely? they have quite a bit of resistance. manual a-body discs on a '70 b-body street/strip car. i'm lookin' to scrub off some ET for free 'cause i'm broke and bored
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#220051 - 02/10/09 10:10 AM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
lewtot184 Offline
master

Registered: 06/09/08
Posts: 2736
Loc: usa
i'm going thru some a-body front discs on a b-body issues. i don't have an answer to your problem but i do have some observations. when i switched from a 1.03 bore master cylinder to a 15/16 bore master cylinder the calipers would lock up. switched back to the 1.03 and the calipers are free. neither master cylinder has residual valves. the pistons in the calipers are very tight; i think too tight. i think the 15/16 bore master cylinder is applying more pressure moving the piston out of the caliper further. because the pistons are so tight they just can't release. i'm trying to find some rebuild kits (o-rings-dust shield) to see if i have the wrong o-rings. i hope yours stops better than mine, 'cause mine ain't worth two dead flies!

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#220052 - 02/10/09 10:34 AM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 31716
Loc: Bend,OR USA
If your using the stock B body master cylinder and it was for drum brakes for both front and rear then you need to remove the residual valve from the line that the front brakes are hook up to, which is normally the rear line and reservoir If it is the stock drum brake master cyliner remove the brake line and get a small # 6 or #8 sheet metal screw around one inch long and thread it into the brass insert inside that port, once it is theaded in two or three turns pry it out. The residual valve is behind the brass retainer, it looks like a rubber flapper valve with a small spring in it, remove it and reinstall the retainer and hook the brake line back up, make sure and tighten it real tight so the seal on the retainer will reseal in the master cylinder and on the brake line, bleed the brakes and let us know if that was the main problem or not
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#220053 - 02/10/09 11:31 AM Re: tricks to reduce drag on stock a-body discs? [Re: Cab_Burge]
dirtybee Offline
super stock

Registered: 04/14/07
Posts: 807
Loc: Toronto, Canada
when i did the swap about 5 years ago i got knuckles from a yard and everything else was '74 manual disc duster parts store stuff, master, calipers, pads, and rotors ,bearings, seals, and a repro front brake line kit.
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#220054 - 02/10/09 11:38 AM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
Lil Demon Offline
master

Registered: 04/02/07
Posts: 3746
Loc: Riverside, California
Buy Aerospace brakes.
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#220055 - 02/10/09 11:41 AM Re: tricks to reduce drag on stock a-body discs? [Re: Lil Demon]
Monte_Smith Offline
master

Registered: 11/10/04
Posts: 6890
Loc: North Alabama
On a strip only car, an old trick is to leave the spindle nuts a little loose. The added runout, helps keep the pads pushed back. Would not do that on a car that sees lots of street duty though.

Monte

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#220056 - 02/10/09 11:41 AM Re: tricks to reduce drag on stock a-body discs? [Re: Cab_Burge]
Phil Saran Offline
enthusiast

Registered: 11/22/06
Posts: 396
Loc: California, USA
Cab, what about on 73-76 A-body disc brakes?
I've got the later 2 bolt M/C and my fronts
are tight too.

I've also heard of racers adding springs between
the brake pads to help eliminate drag on the
rotors?

opinions?
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Phil Saran Parker, Colorado

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#220057 - 02/10/09 11:48 AM Re: tricks to reduce drag on stock a-body discs? [Re: Lil Demon]
dirtybee Offline
super stock

Registered: 04/14/07
Posts: 807
Loc: Toronto, Canada
if it was a race only car i would ( if i wasn't out of a job right now) but i heard that it takes a few pumps on the pedal till they stop the car( which is probably why they have ZERO resistance ) and this is basically my daily driver when there isn't 2 frikkin' feet of snow on the ground . seriously though aerospace look like a really nice setup
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#220058 - 02/10/09 11:55 AM Re: tricks to reduce drag on stock a-body discs? [Re: lewtot184]
dirtybee Offline
super stock

Registered: 04/14/07
Posts: 807
Loc: Toronto, Canada
i wonder if some emery cloth on the outer side of the piston would help it release better? or maybe it would just create a leak . sorry, it's winter and i am bored, AND broke
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#220059 - 02/10/09 12:09 PM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
Lil Demon Offline
master

Registered: 04/02/07
Posts: 3746
Loc: Riverside, California
Quote:

if it was a race only car i would ( if i wasn't out of a job right now) but i heard that it takes a few pumps on the pedal till they stop the car( which is probably why they have ZERO resistance ) and this is basically my daily driver when there isn't 2 frikkin' feet of snow on the ground . seriously though aerospace look like a really nice setup




You heard wrong on the pumps to stop the car. The first pump is softer as it is setting the piston but will stop the car just fine. I can nose dive my Demon at the stripe running 144 mph. The second pump brings the pressure to max (1100psi) and is very firm.

BTW - Aerospace makes a street kit as well that has no resistance.

Sorry about the job and the snow.
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#220060 - 02/10/09 12:10 PM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
68Fastback Offline
master

Registered: 07/13/03
Posts: 2637
Loc: Western Michigan
Here is something from the Tech Archives

http://www.moparts.org/Tech/Archive/brake/13.html

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#220061 - 02/10/09 01:13 PM Re: tricks to reduce drag on stock a-body discs? [Re: 68Fastback]
dirtybee Offline
super stock

Registered: 04/14/07
Posts: 807
Loc: Toronto, Canada
demon, is there a link for aerospace just to see the street kit, even if i don't buy now. 68fastback thanks for that link, interesting, i was thinking about a spring to separate the pads and all around informative bit of info. thx very much guys for informing me
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#220062 - 02/10/09 01:34 PM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
@#$%&*! Offline
New user name, Same old jerk!

Registered: 05/03/08
Posts: 1058
Loc: 1940 North Victory Boulevard ...
The piston shouldn't touch the bore, it's surrounded by fluid and just slides in the seal.

"i wonder if some emery cloth on the outer side of the piston would help it release better?"

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#220063 - 02/10/09 01:53 PM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
Lil Demon Offline
master

Registered: 04/02/07
Posts: 3746
Loc: Riverside, California
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#220064 - 02/10/09 01:57 PM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
JohnRR Offline
I Win

Registered: 01/20/03
Posts: 73560
Loc: U.S.S.A.
Quote:

demon, is there a link for aerospace just to see the street kit, even if i don't buy now. 68fastback thanks for that link, interesting, i was thinking about a spring to separate the pads and all around informative bit of info. thx very much guys for informing me




do you have PIN type calipers ??? I think you'll need those to do the spring trick if I am reading the link above correctly , you'll need a pretty hefty spring to get a sliding caliper to move .

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#220065 - 02/10/09 02:16 PM Re: tricks to reduce drag on stock a-body discs? [Re: JohnRR]
CJK440 Offline
master

Registered: 01/20/03
Posts: 9980
Loc: Ansonia, CT
What keeps the coil spring on the pin from pushing the piston too far back??

I'm sorta thinking that you could get that scary feeling that you get when you forget to pump the pedal on the daily driver after a pad swap but at 120mph.....
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Just enjoying the drive...... Back to basics with a little boost thrown in.

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#220066 - 02/10/09 02:48 PM Re: tricks to reduce drag on stock a-body discs? [Re: CJK440]
JohnRR Offline
I Win

Registered: 01/20/03
Posts: 73560
Loc: U.S.S.A.
Quote:

What keeps the coil spring on the pin from pushing the piston too far back??






No idea , the links above says to do it , I think you could play with spring tension ??? BUT you need to be careful of coil bind as the pads wear ???


Edited by Johnahah (02/10/09 02:49 PM)

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#220067 - 02/10/09 04:20 PM Re: tricks to reduce drag on stock a-body discs? [Re: JohnRR]
dartman366 Offline


Registered: 01/18/04
Posts: 13185
Loc: Mt. Vernon, Ohio
If the caliper's are hanging up any they will drag, I fixed mine a few years ago by putting new caliper's on it,,,,and yes Monte's Idea work's, but the ultimate answer is Aerospace.
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Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.

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#220068 - 02/10/09 04:52 PM Re: tricks to reduce drag on stock a-body discs? [Re: dirtybee]
oldiron Offline
mopar

Registered: 11/08/05
Posts: 656
Loc: New Hampshire, USA
When I think of it, I turn the wheel back and forth a quarter turn, but its a stick car. It does work though
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66 Belvedere Vert, 4 Speed/Jerico, slowly, very slowly, getting faster - NA LD Wedge
New New Best: 10.56 @129
68 B'cuda 4 gear Jerico - Another New Best of 9.86 & Trying to slow up
https://www.youtube.com/watch?v=T4jDLKwd9Gs

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#220069 - 02/11/09 12:47 PM Re: tricks to reduce drag on stock a-body discs? [Re: oldiron]
Paul_Fancsali Offline
master

Registered: 01/21/03
Posts: 2929
My 4 piston disc brakes feel like unadjusted drums bet you have a piston or hanging up

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