[Keith Seymore]

Originally Posted by Scarebird

To the OP; in short, no.

.

Originally Posted by geeteeohguy

THIS^^^^. As a retired automotive professional with 42 years in the business, this is absolutely true. IMO, rear disc brakes are especially wasteful, and usually have inferior parking brake operation compared to drums.

Same here, only 44 years in the biz, 40 of those with GM and 4 of those as a brake development engineer in Full Size Truck.

Most vintage front disc/rear drum systems regulate the rear brakes down through the proportioning valve.

My question is this: if a person was desperate for more braking in the rear (for whatever reason) - why make any hardware changes at all? Why not simply allow more pressure to the rear system, open those puppies up and let them hunt?

What am I missing?

K

[JLMounce]

I think the misconception comes from taking all the marketing hype from manufacturers like Wilwood, Baer etc.

For 90% of the people on this forum that drive around on 7" wide all season style rubber, good functioning stock brakes (even manual 4 wheel drum) is more than adequate for their purposes. The misconception is that bigger brakes will stop the car quicker. It's just not grounded in reality. Tires stop the car.

There are legitimate reasons to switch to big 4 wheel disc brakes. The juice just isn't worth the squeeze for the vast majority of people however. Unless you just like the look, which in that case, go for it!

[Formulabruce]

Couple facts.
1. Factory front disc/ rear DRUM on say a 79 trans am
WILL STOP faster than same car with 4 wheel DISC.
2. Factory 4 wheel disc WILL SLOW DOWN faster than a disc/ drum set up.
Stop= 40-0 drums will lock up and car will stop.
Slow 40-5 mph. Discs resist locking, dissipate heat
And slow car faster while moving.
Worth it on a weekend cruiser? NO.
This is a STOCK analysis, not bigger stuff, Not bigger wheels to fit over it, STOCK.

[jerry455]

I upgraded the brakes on my Firebird first, since they needed a little attention. The tires are going to be this winter's project.

[R 70 Judge]

Originally Posted by The Champ

This was a serious reason for adding rear disc brakes to my wife's '72 Camaro after we upgraded to her current Billet Specialties 17" wheels from her previous 16" Centerlines.

The Centerlines - you didn't really see the rear drums. But with the BS Win Lites, the drums stood our like a sore thumb in my opinion. The photos below show it with the original factory front disc/rear drum.

We used The Right Stuff rear disc kit and then ordered front disc/rotors to match the rears.

What is your tire size on the front? Wheel specs?

Thanks

[Formulas]

I like the idea that Jerry455 put forth in post 8

mix match stock OE parts to get a little extra performance with modest pricing

only problem is finding a donor for such items
my last 10 or so years in CA i barely saw cars that were not front wheel drive in pic a parts

now that i am in WV its even worse

[Formulajones]

The 11" drum brake kits are sold new for both GM and Ford housings.

[hgerhardt]

....And then there's my experience. On my own '66 GTO, I installed 4-wheel discs back in the mid 80's by using '70-81 F-body fronts and '78 Cadillac Seville rears which was a significant improvement over the 4-wheel drums (although how much the rears actually helped, who knows).

Those early rear GM calipers with integral parking brake of course sucked as most of us know. I installed them because they looked cooler than rear drums, but also provided axle retention. No need for aftermarket axle retention systems with rear discs as there's no way the broken axle/rotor will make it past the caliper.

When I re-rebuilt the car in the early Aughts, I tossed the GM discs and went to the later PBR brakes as used in 4th gen LS F-bodies. The fronts are 12" dia and will work with 16" wheels. The rears are also 12" dia with drum-in-hat e-brake which were easy to adapt in my GTO with a pair of simple brackets made from 1" angle iron bolted to the rear axle lower control arm bracket. And the e-brake works really well.

The performance of the PBR brakes is leaps and bounds better than the old GM discs. Not so much in absolute brake power which is largely bound by tire traction, but the pedal FEEL and initial bite and being able to judge the threshold of max brake effort before lockup is HUGELY better. And ultimately makes the car more satisfying to drive.

[NeighborsComplaint]

Originally Posted by Formulas

I like the idea that Jerry455 put forth in post 8

mix match stock OE parts to get a little extra performance with modest pricing

only problem is finding a donor for such items
my last 10 or so years in CA i barely saw cars that were not front wheel drive in pic a parts

now that i am in WV its even worse

Most kits come with GM style replacement calipers and rotors for the front. It's also easier to swap in disc style spindles rather than modify your non-disc ones. The parking brake for the rear is the issue when swapping to 4 wheel disc. These kits use the Eldorado style caliper with it's built-in e-brake and even come with the parking brake cable adaptors. They work fine but you must set the rear caliper pre-load per the specs or you get excessive pad travel before braking. Also, If you use the parking brake infrequently, the "pad gap" becomes excessive and you wind up with diminished rear braking pressure.

[The Champ]

Originally Posted by R 70 Judge

What is your tire size on the front? Wheel specs?

Thanks

235/45/17 with 17x8's with, IIRC, 5" BS

[JLMounce]

Originally Posted by NeighborsComplaint

Most kits come with GM style replacement calipers and rotors for the front. It's also easier to swap in disc style spindles rather than modify your non-disc ones. The parking brake for the rear is the issue when swapping to 4 wheel disc. These kits use the Eldorado style caliper with it's built-in e-brake and even come with the parking brake cable adaptors. They work fine but you must set the rear caliper pre-load per the specs or you get excessive pad travel before braking. Also, If you use the parking brake infrequently, the "pad gap" becomes excessive and you wind up with diminished rear braking pressure.

If you have the option to do a drum hat e-brake, it's well worth the upgraded price.

Getting the metric e-brake calipers setup properly is incredibly difficult. If you don't get them setup correctly, you get a low, soft pedal. While I'm not a professional mechanic, I do know my way around a brake system. I struggled for about a month on my wife's car to get those things setup perfectly and gain a re-assuring pedal. In the end, it was an auto car and I swapped the calipers for a non-ebrake style.

[Skip Fix]

Keith I'm hoping you did not engineer the POS late 90s ABS truck brakes! My 97 is terrible I don't think just because of the drums. Most folks feel the self adjusters don;t work due to lack of pressure and need lots of routine manual adjustment and that ABS system is a lot of the problem. Mine once it gets engaged I have good pedal and stopping for a few hours!

I know some of the late 90s GM trucks had rear discs but then went back to drums .

[RocktimusPryme]

I have 4 wheel manual disc. It didn’t really improve the stopping power over the disc drum setup I had. BUT when I switched rear ends I needed complete brakes. It was arguably cheaper to buy a disc kit then it was complete drums. It was inarguably an easier install.

I should probably switch my MC. I didn’t change it from the one that came with my front disc kit speced for rear drums.

[Keith Seymore]

Originally Posted by Skip Fix

Keith I'm hoping you did not engineer the POS late 90s ABS truck brakes! My 97 is terrible I don't think just because of the drums. Most folks feel the self adjusters don;t work due to lack of pressure and need lots of routine manual adjustment and that ABS system is a lot of the problem. Mine once it gets engaged I have good pedal and stopping for a few hours!

No, but one of the guys in my group did.

In his defense - he could never get out on the basalt tiles to do actual testing. The facility was always unavailable because they were using for marketing photo shoots.

I (me personally -) I don't DO electrons. Just mechanical stuff.

K

[Keith Seymore]

Originally Posted by Skip Fix

I know some of the late 90s GM trucks had rear discs but then went back to drums .

Due to cost.

They would introduce the product with discs for the perceived benefit, then during periods of cost reduction they would go back to drums for the piece cost savings.

K

[NeighborsComplaint]

Originally Posted by JLMounce

If you have the option to do a drum hat e-brake, it's well worth the upgraded price.

Getting the metric e-brake calipers setup properly is incredibly difficult. If you don't get them setup correctly, you get a low, soft pedal. While I'm not a professional mechanic, I do know my way around a brake system. I struggled for about a month on my wife's car to get those things setup perfectly and gain a re-assuring pedal. In the end, it was an auto car and I swapped the calipers for a non-ebrake style.

This^

It took me forever to get them sorted out. I found you couldn't bleed the rears without partially unbolting the calipers and swinging them down on the rotors. There was a spot inside the caliper higher than the bleeders where bubbles would trap in the upper corner and leave you a low, spongey pedal no matter how much you bled them. I can't tell you how many times I bled the brakes until someone tipped me off to that trick. I'd never do that rear disc conversion again.

[77 TRASHCAN]

The aluminum 9-1/2 drums were on many GM makes. It might be difficult to find 2 good used ones. I've not known any aftermarket brake manufacturers to make them in aluminum. I'd run them on my TA, if I could find 2 usable specimens...

I currently run D153 pads on my stock calipers. These pads were used on 3/4 pickups in the 80's. 3/4 tons had light and heavy duty brakes. The D153 pads are the light duty pads.

[Scarebird]

Originally Posted by JLMounce

If you have the option to do a drum hat e-brake, it's well worth the upgraded price.

I usually do not like to push our stuff on a sponsored forum, but we are closing down at the end of the year.

We make a setup that is externally adjusted drum-in-hat and uses a bigger caliper than GM does - also allows the use of bolt in axles as a proper BOP should without spacers.



A bodys: http://scarebird.com/index.php?route...&product_id=68

F bodys: http://scarebird.com/index.php?route...product_id=178

My Trans Am has an earlier version for the last 6 years - no issues and track proven.

[Skip Fix]

I can say my 2015 Silverado has the best braking pedal effort, stopping ability of ANY vehicle I have driven. Not sure how much is computer assist. 4 WD.

I know some of the guys use a later model MC on the 90s . Did not make much difference on mine,Some guys delete to ABS and like that with just a prop valve.

I've been lucky with the 81 TA setup on my 78 never had much issues over 30 years with it. Adjustable prop valve and I think the silicone fluid keeps the ratchet working better.

[ta man]

My stock 80 brakes on my rear wheel disc car work great..crossing the traps at 127 never any issues. I know all the issues with these brakes..but the best brakes ever on a second gen.