Inexpensive “Cordoba” Brake Upgrade for 70 Road Runner

[PurpleBeeper]

I’ve got a 70 Road Runner OEM power front disk car. I’ve already switched to ‘74’ish A-body disc front spindles & ‘73 1-piece rotors. I’d like to do the “Cordoba swap” on a budget and switch to 11.75” rotors (I have 15” factory steel wheels).

What cars/years should I find salvage yard caliper brackets from? I see references to pin-type calipers (like my OEM ‘70 single-piston) are preferred, but the pins are hard to find (?). I see Dr Diff sells aftermarket slider calipers/brackets. Thoughts? I will be getting part store calipers and rotors, so what year Cordoba/motor should I specify? I’d also like to upgrade my master cylinder with a parts store one….I see the ‘71 power disc master cylinder has a 1.03” piston (I think my ‘70 has a 1.125” piston). The ‘71 master cylinder has fender-side fittings like my ‘70 does. Both are 4-bolt. Can I just swap in a ‘71 disc master cylinder? THANKS FOR ANY ADVICE! and remember….budget

 

[WileE]

What's wrong with the setup you have now ?

 

[gkent]

Not worth the effort or expense to go from 10.87 to 11.75. Stick with what you have.

Keep in mind the calipers and most importantly the pads are the same size (surface area). The larger rotor will provide more leverage (but probably not noticeable) and "maybe" run a fraction cooler due to the larger surface area - again probably not noticeable. But heat in the pads is more of a concern thatn in the rotor and that won't change at all. In fact for every wheel rotation there will be more pad wear.

All things considered, really not worth the money, time or effort for that slight difference.

 

[bitterbelvedere]

'75 - '79 Gen 1 Cordoba's have the pin style caliper brackets for the 11.75 rotor. I presume bigger brakes were optional on any car regardless of engine delivered in vehicle because I've seen them on small block and big block cars. Dr. Diff's later style sliders are the affordable way to go. Agree with others benefits are minimal in normal use. I used this setup, with '73 only "C" body totors (1.25 wide) on my SCCA Valiant with Kevlar pads and was very pleased with function. Kevlar pads not recommended for street as they have to warm up before full/best function obtained. Hope that helps ?

 

[wagonman]

Not worth the effort or expense to go from 10.87 to 11.75. Stick with what you have.

Keep in mind the calipers and most importantly the pads are the same size (surface area). The larger rotor will provide more leverage (but probably not noticeable) and "maybe" run a fraction cooler due to the larger surface area - again probably not noticeable. But heat in the pads is more of a concern thatn in the rotor and that won't change at all. In fact for every wheel rotation there will be more pad wear.

All things considered, really not worth the money, time or effort for that slight difference.

I beg to differ, on my 68 non power going to the larger slotted and drilled rotors from Dr Diff IIRC made a substantial improvement. Less fade better bite and improved pedal modulation. Less Pucker Factor as well. Pin Calipers as well and I drove the snot out of it. Spendy Meh the peace of mind was well worth it. Don't cheap out on the pads and break them in correctly. Sadly sold the car. Still have the old setup if anyone is interested.

 

[autoxcuda]

The 11.75 Pin Calipers are hard to find in boneyards these days. Need to look for mid to late 1970's B-bodies. 4 doors and station wagons. Cop cars from that era (Hunter TV show like) were best. But what are chances of finding one in junkyard.

Otherwise, just convert to slider calipers and buy DrDiff's caliper brackets. They will bolt on to your spindles. Calipers are parts store cheap.

 

[autoxcuda]

'75 - '79 Gen 1 Cordoba's have the pin style caliper brackets for the 11.75 rotor. I presume bigger brakes were optional on any car regardless of engine delivered in vehicle because I've seen them on small block and big block cars. Dr. Diff's later style sliders are the affordable way to go. Agree with others benefits are minimal in normal use. I used this setup, with '73 only "C" body totors (1.25 wide) on my SCCA Valiant with Kevlar pads and was very pleased with function. Kevlar pads not recommended for street as they have to warm up before full/best function obtained. Hope that helps ?

@bitterbelvedere What spindle did you use? I thought the C-body inner bearing was larger than the 73-76 A/E-body setup.

And what caliper adapter did you use? A/E-body or the C-body one?

....hmmm. I have a '73 C-body setup on the shelf.

Pictures of Valiant?

 

[bitterbelvedere]

Gen 1 cordoba caliper brackets, late "A" BBP spindles, '73 (only!) Fury/Imperial rotors. These one year only "C" body rotors fit all late "A", "F", "M", and "J" body spindles. Standard calipers accepted these wider rotors without modifications. Can't say if they fit "E" body spindles because anything "E" body has been out of my price range since entering hobby in early 80's, and consequently have never used them.

No picture of car, pitched off Mulholland Dr. playing with a Porsche between I-405 and Cold Water Canyon ? Rd. on my 21st b-day. Wasn't a total loss, I got to meet Jay Leno that night !

 

[autoxcuda]

Gen 1 cordoba caliper brackets, late "A" BBP spindles, '73 (only!) Fury/Imperial rotors. These one year only "C" body rotors fit all late "A", "F", "M", and "J" body spindles. Standard calipers accepted these wider rotors without modifications. Can't say if they fit "E" body spindles because anything "E" body has been out of my price range since entering hobby in early 80's, and consequently have never used them.

No picture of car, pitched off Mulholland Dr. playing with a Porsche between I-405 and Cold Water Canyon ? Rd. on my 21st b-day. Wasn't a total loss, I got to meet Jay Leno that night !

late "A" BBP spindles are the same part number as 73-74 E-body spindles. Nothing special about using them on an E-body.

I have all 3 of those parts to mock that combo up. Thanks.

About what year did you loose your Valiant up on Mulholland?

 

[moparedtn]

According to Professer Ehrenberg (the acknowledged expert), the spindles are key to everything:
"The knuckle you need for our primary swap is from any ’73-’74 E-body, or, believe it or not,
any ’73- ’76 disc-equipped A-body (Valiant/Dart/Duster)."
Doing this maintains the original steering geometry of our older b-bodies.
The rest of his now-famous DISC-O-TECH article:
Disc-O-Tech
or
DISC-O-TECH: Stop on a dime from Mopar Action and Rick Ehrenberg

 

[moparedtn]

I beg to differ, on my 68 non power going to the larger slotted and drilled rotors from Dr Diff IIRC made a substantial improvement. Less fade better bite and improved pedal modulation. Less Pucker Factor as well. Pin Calipers as well and I drove the snot out of it. Spendy Meh the peace of mind was well worth it. Don't cheap out on the pads and break them in correctly. Sadly sold the car. Still have the old setup if anyone is interested.

What "old setup" is it you have, exactly?

 

[autoxcuda]

According to Professer Ehrenberg (the acknowledged expert), the spindles are key to everything:
"The knuckle you need for our primary swap is from any ’73-’74 E-body, or, believe it or not,
any ’73- ’76 disc-equipped A-body (Valiant/Dart/Duster)."
Doing this maintains the original steering geometry of our older b-bodies.
The rest of his now-famous DISC-O-TECH article:
Disc-O-Tech

Original poster has those spindles on his 70 Road Runner already.

 

[moparedtn]

Original poster has those spindles on his 70 Road Runner already.

Prof. Ehrenberg's article (as I linked to above) will have the rest of the info needed then.

 

[PurpleBeeper]

What's wrong with the setup you have now ?

Soft pedal, bled 3 times & shop says the master cylinder doesn’t have enough force. It won’t lock up the brakes

 

[gkent]

Soft pedal, bled 3 times & shop says the master cylinder doesn’t have enough force. It won’t lock up the brakes

Larger rotors aren't going to fix a master cylinder issue !!!

 

[440+6]

Still have original disk drum on my 70 gtx, it stops just fine, I have a hard time understanding upgrades. Please explain why the need?

 

[WileE]

Soft pedal, bled 3 times & shop says the master cylinder doesn’t have enough force. It won’t lock up the brakes

Locking up brakes is not a desired result, ergo why anti-lock brake systems were invented. If you perceive system pressure as a problem , that's the focus of your troubleshooting. Are your soft hoses balooning ? What proportioning valve are you using ?

 

[PurpleBeeper]

Larger rotors aren't going to fix a master cylinder issue !!!

True, but I figured if I upgrade the master cylinder I could upgrade the rotors too

 

[PurpleBeeper]

Locking up brakes is not a desired result, ergo why anti-lock brake systems were invented. If you perceive system pressure as a problem , that's the focus of your troubleshooting. Are your soft hoses balooning ? What proportioning valve are you using ?

Good point. I should replace the brake hoses regardless. It has some weird Speed Master proportioning valve in it. When I put inline Tube SS brake lines on and used their proportioning valve, I lost brakes completely. A shop installed the oddball proportioning valve

 

[440 PHIXX]

I remember reading back in the late 80’s the R body setup was the one to pull from the junkyard. The only problem was not many were made. I never saw one in the yards.

Mind you, this was before the aftermarket kits that have all the parts for the conversion.