65 Mustang-Upgrading to a power booster dual MC

Ger47 · Jul 13, 2022

Fellow Members,
I am in the process of upgrading the car to disc brakes and would like to add power booster to the disc brakes.
The car is an automatic C-4 but it will be upgraded to a manual Tremec T5 in the near future.
I would like to add a power booster that would work on either transmission to minimize expense. Have two questions:
1. Has anyone done the upgrade to power booster that would work on Auto and Manual transmissions
2.. Understand that for auto transmission the 65 would require a pedal adapter so that the power booster would work.

Appreciate your comments.
Regards

wicked93gs · Jul 14, 2022

What would the transmission have to do with the power booster?(unless you plan on using a booster that is such a large diameter that it affects the manual transmission Z-bar setup)

Anyway...please do not this. A power booster does NOT improve braking...all it does is reduce pedal effort(assuming that it works correctly). Considering that the Mustang is a light car...power brakes are simply not needed. Back when they were sold no one had issues driving them with manual brakes to the point that very few chose the power booster option for 65-66 if it didn't come with the package they bought. Most of the people who buy an aftermarket power booster kit have trouble with them not working correctly...common complaints are increased pedal travel etc...the reason for this is that most aftermarket companies do not seem to have the correct pedal ratio required...their bell crank setup simply does not have the correct geometry to achieve the right pedal ratio. If you absolutely MUST have power brakes, my suggestion is to find an OEM power brake booster/linkage/bell crank setup and have it rebuilt. That way you can be ensured that the geometry is correct and avoid the pitfall that most people who user the aftermarket setups fall into. If a rebuilt stock setup is not an option and you must go aftermarket...I suggest the Mustang Steve setup. From everything I have heard, his power brake kit actually works correctly(no personal experience with it myself) and has correct geometry...but he uses a modified pedal hanger assembly to be able to use his booster and MC.

There is no issue with the dual MC and disc brake portion of your upgrade(even if you won't see a whole lot of difference over well maintained drum brakes except in increased resistance to brake fade and better performance in the rain) with most of the kits out there.

As for me...I actually want better PERFORMING brakes. SO I am going with the SoT front brake kit:

SOT 13x1.25" Rotor '4R' Forged Aluminum Caliper System - Leading Mount

This maximum performance system is a must for serious street machines and high horsepower track cars. Offering maximum performance this system is a must for serious street machines and high horsepower track cars. Utilizing a deeper hat offset this system is a direct bolt on to '65-73 Mustang...

streetortrack.com

Which is one of the few kits that you can find independent information on how it actually performs(numerically) after the install:

Street/Track Vintage Mustang Brake Upgrade

We install and test before and after effects of Street or Track’s brake upgrade for early Mustangs

www.motortrend.com

They essentially got a 33% reduced 60-0 over the OEM-style disc brakes(and much reduced fading) which is an impressive real upgrade that you can quantify....and still no power booster.

Of course....to be able to use that particular kit you need 17" wheels to clear the calipers...but that is something I have no problem with. I wouldn't bother buying a kit that you can't find any information on test result numbers myself though. Disc brakes sure look pretty...but in 95% of daily driving they don't make any difference....if you just want disc brakes for slightly better braking and dont care so much about performance...the stock Kelsey-Hayes style setup with more aggressive brake pads generally has good results.

Ger47 · Jul 14, 2022

wicked93gs said:
What would the transmission have to do with the power booster?(unless you plan on using a booster that is such a large diameter that it affects the manual transmission Z-bar setup)

Anyway...please do not this. A power booster does NOT improve braking...all it does is reduce pedal effort(assuming that it works correctly). Considering that the Mustang is a light car...power brakes are simply not needed. Back when they were sold no one had issues driving them with manual brakes to the point that very few chose the power booster option for 65-66 if it didn't come with the package they bought. Most of the people who buy an aftermarket power booster kit have trouble with them not working correctly...common complaints are increased pedal travel etc...the reason for this is that most aftermarket companies do not seem to have the correct pedal ratio required...their bell crank setup simply does not have the correct geometry to achieve the right pedal ratio. If you absolutely MUST have power brakes, my suggestion is to find an OEM power brake booster/linkage/bell crank setup and have it rebuilt. That way you can be ensured that the geometry is correct and avoid the pitfall that most people who user the aftermarket setups fall into. If a rebuilt stock setup is not an option and you must go aftermarket...I suggest the Mustang Steve setup. From everything I have heard, his power brake kit actually works correctly(no personal experience with it myself) and has correct geometry...but he uses a modified pedal hanger assembly to be able to use his booster and MC.

There is no issue with the dual MC and disc brake portion of your upgrade(even if you won't see a whole lot of difference over well maintained drum brakes except in increased resistance to brake fade and better performance in the rain) with most of the kits out there.

As for me...I actually want better PERFORMING brakes. SO I am going with the SoT front brake kit:

SOT 13x1.25" Rotor '4R' Forged Aluminum Caliper System - Leading Mount

This maximum performance system is a must for serious street machines and high horsepower track cars. Offering maximum performance this system is a must for serious street machines and high horsepower track cars. Utilizing a deeper hat offset this system is a direct bolt on to '65-73 Mustang...

streetortrack.com

Which is one of the few kits that you can find independent information on how it actually performs(numerically) after the install:

Street/Track Vintage Mustang Brake Upgrade

We install and test before and after effects of Street or Track’s brake upgrade for early Mustangs

www.motortrend.com

They essentially got a 33% reduced 60-0 over the OEM-style disc brakes(and much reduced fading) which is an impressive real upgrade that you can quantify....and still no power booster.

Of course....to be able to use that particular kit you need 17" wheels to clear the calipers...but that is something I have no problem with. I wouldn't bother buying a kit that you can't find any information on test result numbers myself though. Disc brakes sure look pretty...but in 95% of daily driving they don't make any difference....if you just want disc brakes for slightly better braking and dont care so much about performance...the stock Kelsey-Hayes style setup with more aggressive brake pads generally has good results.

Thank you so much for your advise

WORTH · Jul 15, 2022

Depends on who you are, but I have a CJ7 that came to me with 4 wheel drum manual brakes, it weighs less than your Mustang. While it was definitely drive-able, and I think I would have kept it that way, my wife didn't like it so I added a booster. The booster is and always will be on any vehicle a big improvement. Also I have an Econoline pickup with manual brakes, That will also get power brakes as soon as I can figure out how to do it, it's a little funky being a cabover design.
PS. forgot to mention, I have a CDL-A and drive an 18 wheeler, and I also have a 1-A and 2-A hoisting lic. and can operate almost any machine made, so it's not like I'm afraid of a car.

wicked93gs · Jul 15, 2022

Well, a booster is strictly a quality-of-life improvement in that it reduces leg effort. It does not improve braking in the least little bit. In reality the only place a brake booster truly benefits you is if you are in a manual transmission car at a stoplight facing uphill. Then a power booster makes things somewhat easier. I don't have anything against power brakes per-se. My problem is that the aftermarket kits for the mustang are poorly designed...as such, virtually no one recommends them. After getting negative responses, people like the OP will then choose to ignore the advice not to get one they were given...then they go and buy a kit anyway. Next thing you know...they are back complaining it doesn't work right...pedal travel too long...too soft, not fully engaging etc etc. It a never ending stream of these threads because the manufacturers of these kits just don't do any engineering work. Which is why I recommend rebuilt stock stuff if you really want power brakes....or if you are going to buy some aftermarket kit of dubious quality...make sure to contact other customers beforehand to see if the thing actually works. I personally do not think Mustang manual brakes are stiff or undriveable by any means...but then I also have manual steering(16:1 box, shelby quick steer arms and 14" wheel no less driving 235 tires) and the only time I find it burdensome is parking in my driveway...other than that everywhere I go I simply park way out in the lot in pull-through spaces and its a non issue.

manicmechanic007 · Jul 15, 2022

Power brakes are a must
What you going to do with the clutch pedal when the automatic is in the car?
A booster that fits your 65 is a booster that fits your 65 and the trans is not a issue

wicked93gs · Jul 17, 2022

manicmechanic007 said:
Power brakes are a must
What you going to do with the clutch pedal when the automatic is in the car?
A booster that fits your 65 is a booster that fits your 65 and the trans is not a issue

Why are they a must? The car weighs less than 3000lbs and stops just fine with manual brakes. If you were talking abut ABS you might have a point...ABS is an upgrade in braking ability...but a power booster does not increase braking ability, it just makes you expend a little less effort. On a modern car, if your engine shuts off or your booster otherwise loses power...the pedal becomes rock hard and it a large increase in effort to stop. This is because the bore and stroke on a modern master cylinder are designed with power brakes in mind. The brake pedal feels normal under vacuum from the booster. This is NOT at all the case when talking about vintage cars. In a classic mustang, the brakes feel normal WITHOUT vacuum. Add vacuum to a master cylinder designed for manual brakes and the pedal is soft and feels like garbage,has unsatisfactorily long travel, etc...and that is if the geometry of the kit you got is right. Many the master cylinders included in the kits are simply not designed for power brakes...heck, half the time you can't even find a bore size and/or stroke in the description.

Also....be aware most of the power disc brakes require at least 15" of vacuum to function...so if you are running an aggressive cam they won't work anyway(or not without a vacuum resevoir at the very least).

In the end...the pedal pressure of manual brakes on these cars is simply not enough that it would ever make me go through the effort of sorting through 99 kits that don't work as expected to find the 1 that does. Even if you read the reviews for certain kits, most often what they talk about is the install, rarely mentioning how the finished product performs. These kits are buyer-beware for a reason. There is a reason so many people are unhappy with them.

manicmechanic007 · Jul 17, 2022

I guess it depends on what "stops fine" means to you
When I am doing 150mph I want power disc brakes to stop

wicked93gs · Jul 21, 2022

manicmechanic007 said:
I guess it depends on what "stops fine" means to you
When I am doing 150mph I want power disc brakes to stop

You are a better man than me if you trust a 50 year old car at 150mph!

Again though, power brakes do not increase your braking power, they only affect pedal feel. If you have bad knees as an example...they will help quality-of-life while driving, but remember...90lb secretaries drove these cars with manual steering and manual brakes in the 60s.

Back a couple months ago I was driving my daily beater(2005 Mazda6) at about 65mph and the engine cut out(I forget what it was now...something stupid that took about 5 minutes to fix)...there went my power steering, my power brakes, etc. Yes, the car was (marginally)harder to steer, yes, the pedal was stiffer....but it still stopped easily without issue.

The point is that losing power brakes did not affect the stopping power of the brakes in the slightest...it only affected the pedal feel. I agree that a working(I can't stress the work working enough) power brake conversion is a definite quality-of-life improvement(I myself can't use it anyway, the ITBs would not be able to generate enough vacuum, I think I pull something like 7")...but it is not a braking upgrade. If its a braking upgrade you want...then some type of ABS conversion would be better(pretty sure there only a few ABS conversions out there on classic mustangs...kinda hard to mount tone rings unless you have an 8.8" rear end....and you would still have to figure something out for the front)

65 Mustang-Upgrading to a power booster dual MC

Ger47

New Member

wicked93gs

SOT 13x1.25" Rotor '4R' Forged Aluminum Caliper System - Leading Mount

Street/Track Vintage Mustang Brake Upgrade

Ger47

New Member

SOT 13x1.25" Rotor '4R' Forged Aluminum Caliper System - Leading Mount

Street/Track Vintage Mustang Brake Upgrade

WORTH

wicked93gs

manicmechanic007

wicked93gs

manicmechanic007

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