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Excessive disc brake drag? #1700054
11/17/14 03:41 PM 11/17/14 03:41 PM
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
68LAR Offline OP
master
68LAR  Offline OP
master

Joined: Oct 2003
Posts: 4,013
South Park, Pa.
I've asked this question before and never did get an acceptable answer.
Stock drum rears
Stock disc front end (A body spindles and calipers // B body rotors)
Non power
Stock master from '95 Dakota. (aluminum body, plastic reservoir)

All pieces are in the stock location. Master is above the calipers and wheel cylinders.

Problem is,.. It seem like there is excessive pad drag at the rotors. Any body have a solution for this problem???????
Thanks for any constructive input.

4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
Re: Excessive disc brake drag? [Re: 68LAR] #1700055
11/17/14 03:45 PM 11/17/14 03:45 PM
Joined: Jan 2003
Posts: 28,067
Irving, TX
feets Offline
Senior Management
feets  Offline
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Irving, TX
The first question is how much drag do you get? There will be a bit of drag on them.

Do you have the springs installed over the pads? They help prevent unnecessary dragging.

In a properly designed brake system one inch of pedal movement only provides about .004" of pad movement. If the pads are too far away from the rotors you will end up with a soft or spongy pedal.

We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
Re: Excessive disc brake drag? [Re: feets] #1700056
11/17/14 04:45 PM 11/17/14 04:45 PM
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
68LAR Offline OP
master
68LAR  Offline OP
master

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South Park, Pa.
No springs on my calipers or pads. They are the slider type.
Brake pedal moves about 1" max. Nice high hard pedal.
I've had plenty of experiences with disc brake systems in my life time. My drag just seems to be a little more excessive than I've noticed on other cars.
I realize that there will be a certain amount of drag with disc brake systems.

Since I'm working with a conversion brake system, is this inherent of going this route?

4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
Re: Excessive disc brake drag? [Re: 68LAR] #1700057
11/17/14 04:52 PM 11/17/14 04:52 PM
Joined: Jan 2003
Posts: 25,785
Rio Linda, CA
John_Kunkel Offline
Too Many Posts
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Rio Linda, CA

Single-piston floating calipers depend on the distortion of the square-cut rubber ring to retract the piston ever so slightly, a small amount of disc runout helps...by nature they drag more than calipers with mechanical retractors.

If the rotors are really hot after a drive with minimum brake use there might be a problem.

The INTERNET, the MISinformation superhighway
Re: Excessive disc brake drag? [Re: John_Kunkel] #1700058
11/17/14 05:20 PM 11/17/14 05:20 PM
Joined: Aug 2005
Posts: 6,003
Salem
Grizzly Offline
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Salem
I pulled my hair out with the same issue as you, but all stock components.

It STILL drags to much for my liking.

Here is the thread, I start out just wanting to re-build a caliper, but if you read the whole thing it will at least give you an idea of what I tried.

Help.

Mo' Farts

Moderated by "tbagger".
Re: Excessive disc brake drag? [Re: Grizzly] #1700059
11/17/14 05:43 PM 11/17/14 05:43 PM
Joined: Jun 2014
Posts: 1,321
VA
D
dragon slayer Offline
pro stock
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Joined: Jun 2014
Posts: 1,321
VA
Stuck caliper, collapsed hose, stuck master cylinder piston. G
Re: Excessive disc brake drag? [Re: John_Kunkel] #1700060
11/17/14 05:59 PM 11/17/14 05:59 PM
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
68LAR Offline OP
master
68LAR  Offline OP
master

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South Park, Pa.
Quote:

Single-piston floating calipers depend on the distortion of the square-cut rubber ring to retract the piston ever so slightly, a small amount of disc runout helps...by nature they drag more than calipers with mechanical retractors.


This is exactly what I'm dealing with. Everything is new. Except for the calipers. They are NEW, in the respect that they don't have much mileage on them, but have been on the car for several years. I drive the car, maybe 1K a year. You see where I'm coming from??
I have heard that the Square Ring seal on the piston may cause an issue like this, but kind of discarded that thought because of usage.


4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
Re: Excessive disc brake drag? [Re: 68LAR] #1700061
11/17/14 06:10 PM 11/17/14 06:10 PM
Joined: Jan 2003
Posts: 4,573
...gently down the stream
LAR_414 Offline
master
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...gently down the stream
Just a quick thought. Could the wheel bearings be set with too little free play (too tight)? A little on the loose side where the bearings may have some play, would help push the calipers back in a little, as the wheel spins.

Just a thought.....
Re: Excessive disc brake drag? [Re: LAR_414] #1700062
11/17/14 06:19 PM 11/17/14 06:19 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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RapidRobert Offline
Circle Track
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Lincoln Nebraska
I had 74 A sliders & one of em (LF) had what I thought was too much drag. I replaced it with a $15 rebuilt caliper & problem solved. It had significantly less drag than the one it replaced did

live every 24 hour block of time like it's your last day on earth
Re: Excessive disc brake drag? [Re: RapidRobert] #1700063
11/17/14 07:31 PM 11/17/14 07:31 PM
Joined: Jan 2003
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Paul_Fancsali Offline
master
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Just fixed that issue the new calipers were NAPA and would barely spin. Took them off went and bought Advance Fixed do they drag yes, but not too bad Be careful that your master cylinder is not the source of your issue Many drum brake master cylinders passed off as disc in the reman world.

If you want drag free brakes use four piston disk brakes They are like unadjusted drum brakes and stop fine I rebuild my own
Re: Excessive disc brake drag? [Re: Paul_Fancsali] #1700064
11/17/14 10:31 PM 11/17/14 10:31 PM
Joined: Jan 2003
Posts: 15,350
Omaha Ne
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TJP Offline
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Omaha Ne
open a bleeder and see if it squirts fluid and then see if the drag is significantly reduced.

If so now you have to establish why,
1. Internally collapsed hose
2. Wrong residual valve in the master
3. M/C pushrod too long.

www.tandmautomotive-omaha.com
Re: Excessive disc brake drag? [Re: 68LAR] #1700065
11/18/14 01:17 AM 11/18/14 01:17 AM
Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
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Rick_Ehrenberg Offline
top fuel
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Marlboro, NY, USA
Also look for worn adapters (brackets). Sometimes the pads wear a groove that hinders retraction. Mill basturd (hadda misspell, Moparts would not allow correct!) file fixes that, also provides more inner pad clearance causing inner shoe to seize and crack pad material off when very hot.

Rick
Re: Excessive disc brake drag? [Re: Rick_Ehrenberg] #1700066
11/18/14 01:53 AM 11/18/14 01:53 AM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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RapidRobert Offline
Circle Track
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Lincoln Nebraska
Rick is that correct or not correct that you want the one pad to have some side to side clearance (so it can float)? And the other pad you want to bend the end L tabs so you have to snap it into place on the caliper?

live every 24 hour block of time like it's your last day on earth
Re: Excessive disc brake drag? [Re: 68LAR] #1700067
11/18/14 01:57 AM 11/18/14 01:57 AM
Joined: Mar 2013
Posts: 197
Nor-Cal
L
loaderpro Offline
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Nor-Cal
Check the residuel valve. Most disc systems use a 1-3 lb valve for disc systems and some do not use any. Put in the lighest valve, if that doesn't do it then remove it alltogether. Check though to make sure after doing this you do not lose the pedal. Apart from that as others here have mentioned, be sure the pistons will retract fairly easy with the bleed screw open. if not then you need to disassemble/clean and rebuild your calipers.

8334673-pomona.jpg (58 downloads)
Re: Excessive disc brake drag? [Re: loaderpro] #1700068
11/18/14 11:51 AM 11/18/14 11:51 AM
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
68LAR Offline OP
master
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Let me take all the suggestions one by one.
1. Wheel bearings are adjusted properly. With no pads the rotors spin freely.
2. Brackets are brand new. Purchased from Dr Diff and installed last week. Had the same issue B4 that.
3. No residual valve that I'm aware of. Standard A Body to B body disc brake conversion.
4. Inside pad is floating on bracket. Outside pad snaps into caliper.
5. Everything you guys are suggesting is pointing to the calipers. I find that hard to believe, but facts is facts.

Thanks for all the input.


4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
Re: Excessive disc brake drag? [Re: loaderpro] #1700069
11/18/14 11:58 AM 11/18/14 11:58 AM
Joined: Sep 2007
Posts: 14,889
up yours
Supercuda Offline
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Posts: 14,889
up yours
Quote:

Check the residuel valve. Most disc systems use a 1-3 lb valve for disc systems



Residual pressure valves are used in some DRUM setups, not disc.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
Re: Excessive disc brake drag? [Re: Supercuda] #1700070
11/18/14 12:44 PM 11/18/14 12:44 PM
Joined: Oct 2005
Posts: 902
S.E. Minnesota
gtsdude Offline
super stock
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S.E. Minnesota
Maybe you checked already, but make sure your pedal is coming back all the way. When I changed over to manual brakes and aluminum master on my 68 dart my front brakes were dragging too. After bleeding them half a dozen times I just happened to grab the brake pedal and pull it up. Over the years it wore into a spot and would not come back on it own.

8334872-dart1.jpg (63 downloads)
Re: Excessive disc brake drag? [Re: gtsdude] #1700071
11/18/14 01:42 PM 11/18/14 01:42 PM
Joined: Jan 2003
Posts: 15,350
Omaha Ne
T
TJP Offline
I Live Here
TJP  Offline
I Live Here
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Joined: Jan 2003
Posts: 15,350
Omaha Ne
GTSDUDE, I know the history on your Dart,

www.tandmautomotive-omaha.com
Re: Excessive disc brake drag? [Re: 68LAR] #1700072
11/18/14 02:44 PM 11/18/14 02:44 PM
Joined: Jan 2003
Posts: 28,067
Irving, TX
feets Offline
Senior Management
feets  Offline
Senior Management

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Posts: 28,067
Irving, TX
I'm still not sure what you call excessive drag.

Is there some way you can quantify the problem? Can you turn the wheel by hand? Can you spin the wheel without it stopping immediately upon release?

We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
Re: Excessive disc brake drag? [Re: feets] #1700073
11/18/14 03:20 PM 11/18/14 03:20 PM
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
68LAR Offline OP
master
68LAR  Offline OP
master

Joined: Oct 2003
Posts: 4,013
South Park, Pa.
Quote:

I'm still not sure what you call excessive drag.

Is there some way you can quantify the problem? Can you turn the wheel by hand? Can you spin the wheel without it stopping immediately upon release?



If I spin the wheel with a good hard spin, it will rotate on its own for about one revolution.

4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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