Disc Brakes

[goodnigh]

Considering installing rear disc brakes.

This would be for a '71 M-code Grande with comp suspension package

and toploader.  Any suggestions?  There are several kits available.

mike

 

[Stanglover]

Just my opinion, but why? Are disc brake really necessary on a car with such a light rear end. A good drum set up should be sufficient and again personally, not worth the expense to install discs. They might look cool if you're running open style rims where the brakes can be seen.

On my car, I have SSBC 4 piston front discs with an adjustable rear bias valve and drums. Even with a Track-loc diff, I can easily lock the rears and the bias valve is set as low as possible.

That said, it's your car, your way. Others will for sure have differing opinions.

 

[MikeGriese]

Disc brakes are more immune to water (ever try to brake a drum brake car after going through a deep puddle?), and are less likely to fade with heavy use.

 

[cwalker509]

i imagine it comes down to "What are your plans for the car?"  If you plan to autocross or other track type use then perhaps  4 wh discs make sense.  perhaps you like the look of them if you are putting wheels on where they would be visible.  that being said i am putting them on one of my cars that only meet the "looks good" criteria (557 BBF in a convertible) BUT I bought them with the idea of having better performance.  The folks here and on other forums changed my mind.  Your car, your money, your way.

 

[Lazarus]

I have a 72 that I put the rear discs on, and a 73 with drums still on the rear. Both are factory power disc cars. 
 

My 72 rear calipers look nice but the performance difference is negligible. The fact is that the factory front disc/rear drum is pretty good, and most of the braking comes from the front.
 

I personally would spend the money only if you have nothing else you need, or if you have fairly open wheels and the look of the drums really bug you. 

 

[c9zx]

A bit of a read but very fact based. Chuck

https://centricparts.com/getmedia/8aa0bf29-b986-48d4-a22c-adc4404081ba/Centric_and_APC_Technical_Whitepaper_A4-Rear-Brake-Upgrades-8-2018_1.pdf

Buy a set of semi-metallic rear shoes and call it good. Example: Porterfield Brake shoes

 

[tony-muscle]

As it has been said, rear brakes do very little of the actual braking. Factors to consider, as explained above, are intended use and looks. In my case I went to big brakes so they can handle track-day abuse. This means able to handle the heat generated by hard and constant braking cycles. As an example of balancing looks and application. For track applications drilled rotors are not recommended because they retain less heat and tend to crack easier due to the thermal differential of the rotor. However, a lot of people like the drilled rotors for the looks of it. They also "increase" braking ability slightly at the expense of faster wear, but if you size the brakes properly you don't need the "increased" ability. There are many factors to consider that you can only decide. Another one is easiness. For me it is easier to replace a disc brake pad than a drum pad, especially when on the road.

 

[detritusmaximus]

No expertise here, just thoughts...I've considered the rear discs because I like extremely good brakes, but that means a decent upgrade up front too.  As for rear discs on a car with stock front discs, the rest of the suspension can decide how effective they will be. If you have a fair amount of weight transfer under braking (nose goes down tail comes up) it may not matter what rear brakes you have. 

If you do it for looks and bragging, then get a kit that looks good. If you just want an increase in performance discs are not the only option. There are a couple options with larger Ford drums. I think there is a late 60's Lincoln/Galaxy/something or other that provided 11" drums the racers used to fit to the Mustangs (some redrilling is necessary, plus the matching backing plates and probably cylinders). The easier option is the Aerostar/Ranger 10"x2.5" drum swap. This gets you 1/2" wider rear shoes and the bolt pattern is the same.

For me, I doubt I will swap to discs unless I do the Explorer 8.8 swap. Then it becomes too easy as they come with them.

 

[tony-muscle]

No expertise here, just thoughts...I've considered the rear discs because I like extremely good brakes, but that means a decent upgrade up front too.  As for rear discs on a car with stock front discs, the rest of the suspension can decide how effective they will be. If you have a fair amount of weight transfer under braking (nose goes down tail comes up) it may not matter what rear brakes you have. 

If you do it for looks and bragging, then get a kit that looks good. If you just want an increase in performance discs are not the only option. There are a couple options with larger Ford drums. I think there is a late 60's Lincoln/Galaxy/something or other that provided 11" drums the racers used to fit to the Mustangs (some redrilling is necessary, plus the matching backing plates and probably cylinders). The easier option is the Aerostar/Ranger 10"x2.5" drum swap. This gets you 1/2" wider rear shoes and the bolt pattern is the same.

For me, I doubt I will swap to discs unless I do the Explorer 8.8 swap. Then it becomes too easy as they come with them.

Definitely a saggy suspension will make things worse, but even if you had a solid suspension with no nose diving, still weight gets transferred to the front due to the car "trying" to rotate around the mass center of gravity.

 

[Don C]

Definitely a saggy suspension will make things worse, but even if you had a solid suspension with no nose diving, still weight gets transferred to the front due to the car "trying" to rotate around the mass center of gravity.

+1, that 3 or 4 degrees of dive isn't enough to make an appreciable difference in the weight transfer, over and above what you described.

 

[Don C]

The easiest way to upgrade the rear drums is to put on the Fairlane station wagon rear drums:

How-To: Shelby Rear Brake Trick on Early Mustangs (motortrend.com)

You can get new ones from NPD

DRUM, BRAKE, REAR - #1126-4 - National Parts Depot (npdlink.com)

These will give you about a 25% increase in braking surface area, plus the added cooling, and they'll look a little better than the plain drums.

 

[MooseStang]

Why does the MotorTrend article show 3" and the the NPD state 2.5"?

 

[Don C]

Yeah, that article was a little misleading. The lining doesn't contact the full width of the machined area of the drum.

Here's what a stock drum looks like, you can see the wear pattern and where the lining doesn't make contact. Also, the width of the 2" drum is almost 2 1/2".

 

[detritusmaximus]

That was it, the Fairlane drums. More 'mysts of time' recollections. 

There are still lots of cars out there with original springs and shocks of questionable age and/or quality. I would presume anyone asking about a disc swap would have already dealt with the suspension, but someone else reading this might not have thought about it.

 

[Carolina_Mountain_Mustangs]

There is absolutely nothing wrong with drum brakes. We use to build race cars and use drum brakes before disc. If you run through water just touch the brake pedal and dry in seconds. One issue is that nobody grinds the shoes to fit the drums anymore. I have a brake shoe grinder for that reason. You can slide all four tires with drum brakes all around. disc will not make the tires stick better. Unless racing not really a benefit.
Disc drag all the time and actually if you go back to factory info I think a disc brake car has 1mpg less mileage than drum. Here is picture of a shoe grinder you can pick one up for $350 if you look around.
If you do not grind has to wear in to fit.
The brakes are just one component in stopping tires are what grips the road.