4 wheel disc brake conversion advice wanted.

[mburger]

Hey everyone.

I am planning a 5 lug conversion on my Mk1 the end of February and was originally going to go with the LMR conversion kit just to simplify the conversion keeping it disc/drum, but now I'm thinking about converting to 4 wheel disc during the 5 lug conversion.
The car stops fine as is but I never can leave well enough alone, so, my question:
What MC should I source for 4 wheel manual disc brakes? I THINK I need 5/8 bore but not sure, or, what model Ford had 4 wheel manual disc?
I could then source that replacement part.
The only reason to switch to 4 wheel disc is because I like "upgrading" and apparently spending money on lipstick for my pig.
Thanks!

[mike223]

What MC should I source for 4 wheel manual disc brakes? I THINK I need 5/8 bore but not sure, or, what model Ford had 4 wheel manual disc?
I could then source that replacement part.



What MC are you currently running?

What pedal are you currently running?


A 21mm bore MC works great with about a 4:1 pedal - that's what I'm running with 89 Tbird rear disks + 95 GT single piston fronts.

Your experience may vary depending on the specific bore sizes of the calipers you install, along with pad friction, disk size, and many other variables.


A conventional OEM MC that would work (and what I'm running) is Autozone part #NM1907 - this is a 21mm bore for 1982 Granada / Thunderbird / etc. This has two standard brake line flare fittings (9/16"x18, 1/2"x20).

If you're plumbed for more of a Fox body Mustang MC, try Advance Auto Parts / Carquest P/N MCA39637 - This is a 21mm bore MC that has the same metric brake line fittings (2- M10x1, M12x1) as most of the typical donor Mustangs. I don'r remember what that part number originally fit, I found it looking for additional 21mm bore MC options.


Good Luck.

[mburger]

Thanks Mike! I am running the complete 1990 Mustang/Fox body donor brake system including pedals and MC.

[Jeff Kleiner]

Pick up #31100 from Mark at Breeze and be done with it.

https://www.breezeautomotive.com/shop/master-cylinder-1994-mustang-cobra-new/

Jeff

[rich grsc]

I have a NIB Raybestos MC#390217. Plans changed and never used it, it's a 94-95 Mustang MC. I don't need it.

[mike223]

Thanks Mike! I am running the complete 1990 Mustang/Fox body donor brake system including pedals and MC.

Ok, LMR shows that as being a 21mm bore (maybe it is, maybe not): https://lmr.com/item/LRS-2140C/1987-93-Mustang-Brake-Master-Cylinder-For-23L-50L


I guess the key question at this point would be if your Fox brake pedal was modified or not - there have been instructions for cutting ~ 1- 1.5 inches out of the brake pedal and moving the pivot point for better leverage (in the build manuals).

If your current brakes work well it's probably a 21mm bore with a stock pedal, or a 15/16th bore with a modified pedal.


Either way you're probably good with what you've got for a pedal + MC...


Occasionally I have seen a check valve mounted on the MC to keep the rear wheel cylinders from compressing (drum brakes only) but I haven't seen this on Mustangs (but not sure if I ever looked at a drum brake Mustang MC that close) - if you see anything like that it may need to go away.

[Steve Powell]

Hey Mburger,

I've got some parts that may interest you. I changed from 10.5" rear discs to 11.65" on my race car. So, I've got the 10.5" discs, SN95 calipers, SS flex lines, North Race Cars caliper brackets (correct offset for standard Fox rear width). I also have a new 94 Cobra master cylinder set up for remote reservoir, plus the plastic reservoir and hoses. Only thing you would need to source is Fox width 5 hole axles. Let me know. If interested, call Steve at 503-nine70-319zero. I can better explain the situation.

[Jeff Kleiner]

Ok, LMR shows that as being a 21mm bore (maybe it is, maybe not): https://lmr.com/item/LRS-2140C/1987-93-Mustang-Brake-Master-Cylinder-For-23L-50L




Nope. The Disc/drum master is a stepped bore with 21mm for the front and 30mm for the rear. This won't be compatible with the rear calipers...the drum's wheel cylinder has fluid acting on .88 square inch while a SN95 rear caliper has fluid acting on 1.76 square inches.

Jeff

[mike223]

Nope. The Disc/drum master is a stepped bore with 21mm for the front and 30mm for the rear. This won't be compatible with the rear calipers...the drum's wheel cylinder has fluid acting on .88 square inch while a SN95 rear caliper has fluid acting on 1.76 square inches.

Jeff

If you say that exists - I certainly believe you. It might even be widespread (I haven't seen it all).

I have heard of stepped bore MCs, but never actually found one that was when I took it apart and measured it.

Nothing could surprise me much in MC's - that's why I've taken apart several (and some weren't what they were supposed to be).


I took apart the NM1907 I'm currently running before I put it in - 21mm front + back - that's from "a" (different) OEM Ford disk/drum application.

I have a (NIB) Advance Auto Parts / Carquest P/N MCA39637 on the shelf (contemplated swapping over to something more conventionally Mustang, someday). I'm pretty certain I already took it apart and measured it too - but I will take it apart tomorrow and measure. I think that part # probably relates back to the LMR part number (and/or application), but I'll look into all that more tomorrow and report back.


Like I said - nothing would surprise me much either way - just a matter of curiosity + interest at this point.

[mburger]

Thank you all for the help! (again)
I'm working on a plan to upgrade this to 4 wheel disc with the info you all have given me.
Going to change to coilovers in the rear at the same time as the 5 lug conversion, but that's another thread...
While a better ride, I don't see a need to change the rear susspension to 3 link etc. at least for my use.
After all this is done, I want to add ~50hp as while it's a fun car to drive, I'm finding myself wanting just a little more. Don't want or need anything much over 300hp at the flywheel. (another thread!)

[Ray]

Take a look here: https://www.ffcars.com/FAQ/brakes.html

Lots of great info especially for the older model FFR's

Ray

[CraigS]

If you are going to 5 lug up front and have Fox spindles here are notes I have saved to use Lincoln rotors.
89 mark 7 rotors, 89 mark 7 grease seals, 90 mustang bearings, 90 mustang calipers
and
Aimco # 5449 Fits 89 mkvii W/O abs. Seal 9150s Timken or National same #.
and
Lincoln grease cap is shoter than Mustang so fits our wheels better.
I bought all of this at the local parts store 10 yrs ago because the weight is so heavy that shipping would have been prohibitive. Now, w/ so many having free shipping or even $10 shipping it probably isn't a big deal.

[luvaz]

Mark,
Lots of good info here. I completed this swap last month on my Mark 3. It had an '89 fox 4 link and front brakes. If it were me, I'd jump on the phone and call Steve Powell who already posted about all of the rear brake parts he has available, sounds like they're from NRC, and speaking from experience, that's the set up I have and you can't go wrong for the price.

I think Jeff's recommendation for the Breeze M/C is a no-brainer, too!

As far as 5 lug front rotors and 5 hole rear axles, I got them at rockauto.com for $183 delivered!
Here's what I ordered to complete the swap:

Dana 2022601 '92 Ranger 3.0 V6 left side axle shaft (2 each) @ $50.99/ea.
WJB Wheel seal WS9150S (2 each) @ $0.62/ea. '89 Lincoln Mark VII 5.0
Durago BR5463 Front brake rotor (2 each) @ $26.79 '89 Lincoln Mark VII 5.0

These bolted right in and were a perfect fit, all for under $200 delivered.

HTH,
Will

[mike223]

I'll look into all that more tomorrow and report back.



Alright, that required more research than I anticipated, but I got to learn something, lol.

Measuring the seals on the MCA39637, I found there is a 30mm element that I did not recognize.

In the first photo below, on the left (rear of MC) circled in red is a 30mm o-ring, circled in yellow is the 21mm primary piston seal for the front brake circuit, in green is the 21mm seal that separates the front circuit from the rear circuit, circled in blue is the 21mm secondary piston seal for the rear brake circuit.

In the second photo circled in red is the only port in the 30mm portion (returning toward the reservoir).

Third photo is the fluid control valve in the top of the MC (between reservoir + MC).


So what's happening here is they're using the 30mm section to both pull the (front) pads off the rotors as the brake is released, and as a quick take up (on the front calipers) until the 21mm area (front brake section) seals itself off.


These guys explain it better than I can, look at their illustration (at top) and read the part about "On many late model vehicles, a special "quick take-up" master cylinder is used to reduce brake drag for improved fuel economy":https://www.aa1car.com/library/brake_master_cylinder.htm


So anyway, on the MCA39637, the 30mm area only has to do with quick take up, the front + rear brake MC bore sizes are 21mm. The application for this MC is Mustang 87-93, TBird + Cougar 87-88.


Again, I am running a NM1907 MC without the quick take up feature, and never even knew that feature existed. Works great as a manual MC with a 4:1 pedal / OEM 89TBird rear / single piston OEM SN95 fronts. The application for this is 1982 Granada etc.


The 21mm bore MCs require about 25% less pedal effort than 15/16th, but require more pedal travel for the same fluid volume.

So if your pedal is modified for a higher ratio you're probably going to be happier with a 15/16th, a stock pedal is probably going to be better with a 21mm (but the OEM pedals also vary in ratio, especially SN95 pedals - at least 3 or 4 different pedal ratios).


Good Luck.



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[mburger]

Everyone, great info and thank you! I'll be calling Steve and reaching out to Mark Reynolds at Breeze. I learn something almost every day on the forum.

[Richard Oben]

http://www.northracecars.com/Brakes.html

We have been doing this for 20 years. We can and have answered any question out there. Richard.

[R. Button]

:) Been there and did that on my Mark 1 based on a 1990 GT donor - 3 link, coil overs - best upgrade for drive and ride! You may consider replacing the lower front control arms from the Mustang to the FFR ones. I also cut the rear coil tubes off the old frame too no going back to the old Mustang coil springs!!
But I liked my 4 lug wheels so much called Gordon. He set me up with a complete system to keep the 4 lugs and install disk brakes all around. I keep looking at Richards stuff and thinking … maybe it's time to make the switch over to 5 lug and even larger brakes!
Then there was the upgrade to power steering, then the upgrade to a supercharger with aluminum heads, then the upgrade to... :) and the list goes on...

[mburger]

Ralph,
I just bought Steve’s parts will change to rear FFR coil overs. I already changed to FFR lowers on the front. WAY more turning radius. I’m going 5 lug FFR wheels. Just preference.
I’m also going fake billboards and meatballs.
It’s my car so .....

[R. Button]

The most "dificult" part to changing over to coil overs on the Mark I's is drilling the rear upper hole for the coilover shocks! I bought a 90 degree adapter and then cut down a drill bit, to fit up in the rear wheel well, so I could drill out the hole. But that was now years ago that I made the change. Incredible ride difference - so worth it! combine with 3link and the car will ride and handle so much better! enjoy!

[mburger]

Pick up #31100 from Mark at Breeze and be done with it.

https://www.breezeautomotive.com/shop/master-cylinder-1994-mustang-cobra-new/

Jeff

Just ordered to complete my 4 wheel disc brake conversion. Thanks Jeff.

[mburger]

Mark,
Lots of good info here. I completed this swap last month on my Mark 3. It had an '89 fox 4 link and front brakes. If it were me, I'd jump on the phone and call Steve Powell who already posted about all of the rear brake parts he has available, sounds like they're from NRC, and speaking from experience, that's the set up I have and you can't go wrong for the price.

I think Jeff's recommendation for the Breeze M/C is a no-brainer, too!

As far as 5 lug front rotors and 5 hole rear axles, I got them at rockauto.com for $183 delivered!
Here's what I ordered to complete the swap:

Dana 2022601 '92 Ranger 3.0 V6 left side axle shaft (2 each) @ $50.99/ea.
WJB Wheel seal WS9150S (2 each) @ $0.62/ea. '89 Lincoln Mark VII 5.0
Durago BR5463 Front brake rotor (2 each) @ $26.79 '89 Lincoln Mark VII 5.0

These bolted right in and were a perfect fit, all for under $200 delivered.

HTH,
Will

I purchased and received what you suggested from Rockauto, Thak you!