As a general rule YES......

That's why Ford and GM have went to 4 wheel disc brakes on most of the newer vehicles.

The lighter the vehicle....the less difference you will see between disc rears and drum rears. You will also need a different master cylinder for a 4 wheel disc brake setup.

It is generally accepted that the front brakes does 60 % of the braking and the rear does the rest ( 40 % ) .....on most vehicles.

 

It depends on how you define "better". It sounds to me that you have a fairly light weight car that you run on the street. If you're having no problems stopping I have to ask: Why change anything if it ain't broke?

 

I did a search on this but didn't get a definitive answer. Is it worth the time & money to convert my rear drum brakes over to disc? My rod has 11" front disc's, with a Ford 9" rear end & drums, power booster, combination valve and 205/65-15 tires in front, 235/70-15 rears.

Probably not.

The rear drum brakes that you have at present are originally designed for a much heavier car than what you have and assuming they are adjusted correctly will work great.

Some advantages of disc brake rear (for your consideration):

Will not fade as quickly as drum brakes.
Not easily affected when wet.
Ease of replacing pads versus doing a complete brake job with drum brakes.

Just for a side note. My latest project has 4 wheel disc brakes (9" Ford rear) and I am using GM rear disc brake calipers that have the emergency brake as part of the caliper. Running GM calipers on the front. Below the floor dual diaphragm booster and 1" bore Master cylinder. 2# residual valves in front and rear lines and adjustable proportioning valve on the rear line. So far I have been unable to get a good pedal. Takes two pumps. I don't think I have any air in the lines and recently read an article where it said to use a 10# residual on the rear with those calipers to correct the low pedal. I haven't tried that yet. My point here is that if I had left the stock drum brakes in place I would have good brakes and have saved a few hundred dollars. The rear calipers are $100 each.

As always, the final choice is yours to make. ENJOY!!!

 

Probably not.

The rear drum brakes that you have at present are originally designed for a much heavier car than what you have and assuming they are adjusted correctly will work great.

Some advantages of disc brake rear (for your consideration):

Will not fade as quickly as drum brakes.
Not easily affected when wet.
Ease of replacing pads versus doing a complete brake job with drum brakes.

Just for a side note. My latest project has 4 wheel disc brakes (9" Ford rear) and I am using GM rear disc brake calipers that have the emergency brake as part of the caliper. Running GM calipers on the front. Below the floor dual diaphragm booster and 1" bore Master cylinder. 2# residual valves in front and rear lines and adjustable proportioning valve on the rear line. So far I have been unable to get a good pedal. Takes two pumps. I don't think I have any air in the lines and recently read an article where it said to use a 10# residual on the rear with those calipers to correct the low pedal. I haven't tried that yet. My point here is that if I had left the stock drum brakes in place I would have good brakes and have saved a few hundred dollars. The rear calipers are $100 each.

As always, the final choice is yours to make. ENJOY!!!

I have seen 10 # valves on discs, but in general it is not recommended since it makes the brakes drag.

Could be air or bad master cylinder.

I also have heard that an adjustable proportioning valve to rear disc brakes will cause that. Try removing the prop valve just to see if the problem goes away.

Let me know. Please.

 

I did a search on this but didn't get a definitive answer. Is it worth the time & money to convert my rear drum brakes over to disc? My rod has 11" front disc's, with a Ford 9" rear end & drums, power booster, combination valve and 205/65-15 tires in front, 235/70-15 rears.

I have to agree with MM and frisco.
Depends on the WOW factor.

Discs will not stop faster..... that is determined by the tire traction and how good you can manipulate the pedal at the verge of sliding the tires = "threshold braking"... (ah anti-lock brakes) ... As for true stopping ability, fat soft front tires are the best. The more traction the faster you will stop.

Discs are easier to modulate and have advantages as per use in water, fade in the mountains, etc.

Newer cars with rear discs tend to stop quicker because the anti-squat is improved allowing more rear bias and consequently more stopping power by the rear tires.

Ever seen a late model mustang jam on the brakes?...... NOSE DIVE = rear tire slide.

Me? I stayed with the rear drums.

check out www.readershotrods.com drag cars/georges drag strip

 

If it stops well enough with rear drums, I wouldn't change. Drums work better as far as a parking brake, and if the hydraulics go out, drums don't take near as much pedal or manual effort to get the car stopped.

 

rear discs

I spent a lot of time and money switching to rear discs and didn't notice any difference on my daily driven streetrod. Maybe if I drove it harder I would have. Bill

 

Thanks to all for your replys, as usual here very informative & helpful. acr

 

Frisco, I have almost the identical setup as you do except I have Wilwwod calipers. I used a 67 Corvette 427 manual 4 wheel disk master cylinder and my pedal feels good, no need to pump. Me thinks you have either some air or a faulty m/c. I don't see the prop valve or the 10# residual causing your problem.

Vince

 

Newer cars with rear discs tend to stop quicker because the anti-squat is improved allowing more rear bias and consequently more stopping power by the rear tires.

Ever seen a late model mustang jam on the brakes?...... NOSE DIVE = rear tire slide.

I take it you are talking about anti-dive in the front end?...or are you talking about anti-lift at the back end?


Care to explain any of this to me? Why would the nose diving cause the rear tires to slide? How much anti-dive are we talking about?

 

From what I have seen of rear disks on the newer GM cars, they are a PITA...................

 

From what I have seen of rear disks on the newer GM cars, they are a PITA...................

By newer do you mean what GM used up to the mid 90's that had the e-brake as part of the caliper or the newist ones that use a small drum inside the rotor as the e-brake and a standard caliper for the main brake?

What exactly is a PITA about them?

 

YEAH...THE EARLY 90S....NOT SO MUCH TAHT THEY WERE SO HARD TO WORK ON, BUT THE FACT THAT THEY DON'T LAST AND YOU ARE REPLACING THEM EVERY YEAR.

Whoops...cap locks on.................

 

YEAH...THE EARLY 90S....NOT SO MUCH TAHT THEY WERE SO HARD TO WORK ON, BUT THE FACT THAT THEY DON'T LAST AND YOU ARE REPLACING THEM EVERY YEAR.

Whoops...cap locks on.................

I wasn't a big fan of those either. I didn't like how the e-brake needed to be used to adjust the brakes.

I have a set of 2000 s-blazer brakes on my s10. I still haven't hooked up the e-brake part but I like the newer design with the "bridge" that holds the pads in place allowing the caliper to float better (no force on the sliding pins).

 

I run 4whl drums on both of my cars, stock and I have no intensions of changing them, they stop fine for being over a ton.

 

I run 4whl drums on both of my cars, stock and I have no intensions of changing them, they stop fine for being over a ton.

Both of my projects are 4 wheel disks - if I can help it I will never run drums again. Disks are soo much simpler, and on top of that.. they actually stop! :thumbup:

 

BTW the main reason I swapped is I got sick of adjusting them or having them adjust on their own or blowing wheel cylinders or...

Just too much to go wrong with drums.

 

Hydroboost Systems

The reason most hot rods have poor brakes is the lack of vacuum in high performance engines. Othe changes have come up from modernizing older cars. The older cars had manual trans, for the most part. With auto trans, hot cam, f.i. turbos, overdrives, etc. the car can not stop the way it came from the factory. Another problem is valve cover clearance. As far as the question; are rear discs better than drums, rarely are they. Air brake trucks still use drums, because the rotors will melt going down a mountain with 80,000 lbs. The drums can and will "lock up" because of their self-energizing action. Discs, by design don't lock. To make a disc brake work, the piston size is increased from the basic 1.125" to 3" piston, and requires a 1200psi booster. drums usually lock up at 600psi. That is the function of the proportioning valve, to hold down the rear line pressure from a disc brake booster. Rear disc brake systems require the same high pressure as a front disc, but with the increase from a 1" rear wheel cyl to a 2.5" rear caliper, the piston size (volume) of the master must be increased to fill them. Increasing the piston size lowers the line pressure. The power booster output must be increased to bring the pressure back up. All new cars with 4 disc have huge vacuum boosters. Not good for hot rods. The best alternative now is the Hydroboost system. It runs off of the power steering pump, and requires "no vacuum" It can generate up to 2000psi, push a master cyl up to 1.625" and clear the valve covers of a hemi or 572 Chevy.

 

Why to consider rear disc brakes....

1. Rear drum brakes have a non-linear response to fluid pressure, so the proportioning valve needs to be matched to all of your vehicle characteristics including the rear drum brake design.

2. Rear drum brake linings often become "grabby" when wet or in a high humidity environment. The resulting rear brake lockup is particularly nasty in slippery conditions.

3. The people making rear disc brake conversion kits could use the money.

 

The reason most hot rods have poor brakes is the lack of vacuum in high performance engines. Othe changes have come up from modernizing older cars. The older cars had manual trans, for the most part. With auto trans, hot cam, f.i. turbos, overdrives, etc. the car can not stop the way it came from the factory. Another problem is valve cover clearance. As far as the question; are rear discs better than drums, rarely are they. Air brake trucks still use drums, because the rotors will melt going down a mountain with 80,000 lbs. The drums can and will "lock up" because of their self-energizing action. Discs, by design don't lock. To make a disc brake work, the piston size is increased from the basic 1.125" to 3" piston, and requires a 1200psi booster. drums usually lock up at 600psi. That is the function of the proportioning valve, to hold down the rear line pressure from a disc brake booster. Rear disc brake systems require the same high pressure as a front disc, but with the increase from a 1" rear wheel cyl to a 2.5" rear caliper, the piston size (volume) of the master must be increased to fill them. Increasing the piston size lowers the line pressure. The power booster output must be increased to bring the pressure back up. All new cars with 4 disc have huge vacuum boosters. Not good for hot rods. The best alternative now is the Hydroboost system. It runs off of the power steering pump, and requires "no vacuum" It can generate up to 2000psi, push a master cyl up to 1.625" and clear the valve covers of a hemi or 572 Chevy. Check them out at POWERBRAKESONLINE.COM

I don't think most hot rods ever came with power brakes at all so none of that really matters unless you are talking about adding power brakes. I hear what your saying but on the two vehicles I have swapped from four wheel drum to four wheel disk there was a significant difference - and both remained NON power.

I come from the off road school where your not making vacuum simply because your barely moving so hydroboost is nice..

 

Hope This Helps

IT was a hard choice to convert to disc brakes in the rear on my suburban rod--which tows a 12kl,lb trailer to boot.....However after all the proper evlauation of both systems, i went with all disc's .....

at the junk yards i got a set of front 77 chevy truck disc and 69 cady elderado rear discs with ebrake built in.....i got the bracketts to hook it all up to the dana 60 axles from ccp in calif as well as the 1' master cylinder and a 8' stainelss double booster....the ebrake cable came from lokar--but the real secert to having it all work great was a stainless vacum can from summit.....this stores all the vacum i could ever use and really helps pedal pressure.....it is pluged in directly to the vacum port under my stealth ram throttle body....

also going to a 1'' bore mc really helped pedal presure greatly and i ended up with more stopping-then the stock 12'' booster with the 1.5'' bore mc....and i kept the p-valve were it was with the original adjustments-60 up front 40 in the rear......and with a lil bardering got everything for under 500 dollars--that is before i chromed it all......But with it all chromed--lines and mc and booster and calipers, vacum tank and all braided ebrake lines and an vacum lines--i would put it up against any system costing thousands in any show.....

when you look at my system it is small enough to look great on a roadster but has the stopping power for a tank.....ALL MY TEC INFO CAME FROM REALLY GREAT FOLKS AT SPEEDWAY MOTORS--THEY SPENT MORE TIME HELPING ME GRASP WHAT WAS NEEDED-THEY ARE TOP SELF FOLKS INTO HELPING PEOPLE....AND ALSO THE FOLKS AT CCP WERE ALL KNOWING ABOUT WHATS NEEDED.....CHECK THEM OUT IF YOU NEED HELP....

Anyway i hope this helps and remember you do not have to spend alot of money to do this....BUT YOU DO HAVE TO INVEST SOME TIME TO GET IT RIGHT :thumbup:

ALASKAN

 

Added the SSBC rear disc conversion for our 98 Durango, after adding 20" rims. The Durango had marginal braking before, and with the heavier rims (73lbs per corner as opposed to 54lbs) braking upgrade was necessary.

The brakes are 200% better now, and it stops effectivly even when we are towing (7000lbs)

I would call the braking on this suv almost acceptable, as opposed to marginal the way it was from new.

Incidentally the proportioning valve had the spring removed for equal pressure to all 4 corners, as instructed by SSBC.

 

Pads are 90 % of stopping ability.

 

Xntrik,

Who makes the best shoes in your opinion? Has anyone tried these folks? http://www.praisedynobrake.com/index.htm

I've got 4 wheel non-power drums on my 65 Rambler Classic, and just want to find the best shoes for it.

 

It's easy to upgrade the front brakes of the Rambler to discs, provided you can find a 79-83 Concord or Spirit to rob the brakes from. Get the spindles and all, then bolt to the Rambler. Almost that simple! There's a small brake line issue, and you need to remove the residual pressure valve from the front brake portion of the master cylinder, but otherwise it's pretty easy. You don't have to have a power brake system either, but you will notice a slight increase in pedla pressure is needed with non-power front discs.