Moparts

tricks to reduce drag on stock a-body discs?

Posted By: dirtybee

tricks to reduce drag on stock a-body discs? - 02/10/09 04:42 PM

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
Posted By: lewtot184

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 05:10 PM

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!
Posted By: Cab_Burge

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 05:34 PM

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
Posted By: dirtybee

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 06:31 PM

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.
Posted By: Lil Demon

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 06:38 PM

Buy Aerospace brakes.
Posted By: Monte_Smith

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 06:41 PM

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
Posted By: Phil Saran

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 06:41 PM

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?
Posted By: dirtybee

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 06:48 PM

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
Posted By: dirtybee

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 06:55 PM

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
Posted By: Lil Demon

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 07:09 PM

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.
Posted By: 68Fastback

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 07:10 PM

Here is something from the Tech Archives

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

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 08:13 PM

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
Posted By: @#$%&*!

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 08:34 PM

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?"
Posted By: Lil Demon

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 08:53 PM

http://www.aerospacecomponents.com
Posted By: JohnRR

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 08:57 PM

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 .
Posted By: CJK440

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 09:16 PM

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.....
Posted By: JohnRR

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 09:48 PM

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 ???
Posted By: dartman366

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 11:20 PM

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.
Posted By: oldiron

Re: tricks to reduce drag on stock a-body discs? - 02/10/09 11:52 PM

When I think of it, I turn the wheel back and forth a quarter turn, but its a stick car. It does work though
Posted By: Paul_Fancsali

Re: tricks to reduce drag on stock a-body discs? - 02/11/09 07:47 PM

My 4 piston disc brakes feel like unadjusted drums bet you have a piston or hanging up
Posted By: maximum entropy

Re: tricks to reduce drag on stock a-body discs? - 02/11/09 08:24 PM

you also may want to try rebuilding your calipers. old seals can cause alot of drag when they lose their elasticity, which is what minimizes drag. made a huge difference on mine!
Posted By: JohnRR

Re: tricks to reduce drag on stock a-body discs? - 02/11/09 09:27 PM

Quote:

My 4 piston disc brakes feel like unadjusted drums bet you have a piston or hanging up




the OP does not have a 4 piston setup , single piston slider and the slider is casting on casting .
Posted By: dirtybee

Re: tricks to reduce drag on stock a-body discs? - 02/11/09 10:57 PM

that's right single piston sliders and it's still fairly new but maybe it warrents a check on the seals and i wonder if smoothing down and lubing the casting to casting contact again would help some. anyways thank again all for the input.
Posted By: JohnRR

Re: tricks to reduce drag on stock a-body discs? - 02/12/09 02:42 PM

Quote:

that's right single piston sliders and it's still fairly new but maybe it warrents a check on the seals and i wonder if smoothing down and lubing the casting to casting contact again would help some. anyways thank again all for the input.




maybe you should try to find a set of the pin type caliper adaptors and switch calipers so you can try the spring trick ? the problem with lubing the sliders is you don't want the lube getting on the brakes .
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