Thread: Drum to disc brakes.

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I was just wondering how hard it is to switch from drum to disc brakes. Now its a rear end out of an 84 s-10. Its in fantastic conditon but I had planned on switching it out with a ford 9in. My frame has been backhalfed and my original rearend has been modified to fit. My truck has a small block 350 with a mild comp cam and camelhump heads but nothing special. Im currently building a 327 to drop in it but thats going to be a slow project because I want to build it to really thump, and I cant put a ton of money into it at once. So I was just trying to find out how hard it would be to convert from drum to disc. And another friend of mine had 2 different squarebody s-10s with small blocks in them and he used to run them at the track with its regular rear end but with a diff gear ratio and he used to smoke some people at that track in some pretty nice cars. Thats enough of me rambling I was just trying to get a few opinions on this subject

Lots of ways to put discs on a 9" Ford, Speedway has rear disc kits that use the metric GM calipers for under $300.00.

'84 S10 rear is a 26 spline 7.5.. disc brake can be fit but, that's a weakling.. and finding the 2wd 8.5" rear will be impossible.. 9" is a thought, but you can get just about the same strength AND disc brakes w/ a LSD if you get a Ford 8.8 out of an Explorer.. takes just a little coaxing to bolt them in an S10

Dics brakes aside,we found that by using a Buick roadmaster,Chevy Caprice taxi/cop car mid 90's backing plate,we could convert to 11" drum brakes in the Astro Van's 7.5 rear end.That is a major improvement in stopping power.Drum brakes don't drag like dics do and for my two cents are the brakes of choice in a drag car.

The other info I can offer is in a Astro site a member there at is a certified mechanic tried everything to O.E.M. swap dics brakes.After yrs of never getting it right,he determined it was a volume issue and converted to the above swap.The other thing you don't have to deal with is the e-brake on dics rear brakes "can be" a pain in the butt.Corrode over time,stick on,etc.

In terms of using Ford 9" and their dics brakes,you have to consider those systems are set up for a different wt than you truck.The bias is all different front to back.So now you are trying to adjust it with aftermarket proportioning valve which are really for race car use and not street use.Part braking being not the same as emergency stopping and soon becomes more trouble than it is worth.I give the US car manufacture auto engineers three thrums up for finding a good balance point.

So as far as a Ford 9 ",you could use the 11" brakes from that.

The main reason people have problems with brake balance is because they don't check the pressure at the wheels with a gauge.... Setting brake pressure by feel is like guessing at water temp by touch!!!!!!

Another reason I'm such a big 9" fan is the ease of changing gears...Just have your spare center section set up with your alternate gear choice.....

Another good item that just came out for braking systems is a junction block, proportioning valve and brake light switch all combined in one unit...Wilwood sells it, decent price, too.

Disc brakes front and rear, when sized, set up, and pressure balanced correctly offer a huge increase in stopping power over drum or drum/disc setups!!!

Originally Posted by Dave Severson

The main reason people have problems with brake balance is because they don't check the pressure at the wheels with a gauge.... Setting brake pressure by feel is like guessing at water temp by touch!!!!!!

Another reason I'm such a big 9" fan is the ease of changing gears...Just have your spare center section set up with your alternate gear choice.....

Another good item that just came out for braking systems is a junction block, proportioning valve and brake light switch all combined in one unit...Wilwood sells it, decent price, too.

Disc brakes front and rear, when sized, set up, and pressure balanced correctly offer a huge increase in stopping power over drum or drum/disc setups!!!

Dave-the pressure tests where applied and still it was a volume issue.

Here a article in part about proportioning valves:

Proportioning Valve
The proportioning valve reduces the pressure to the rear brakes. Regardless of what type of brakes a car has, the rear brakes require less force than the front brakes.

The amount of brake force that can be applied to a wheel without locking it depends on the amount of weight on the wheel. More weight means more brake force can be applied. If you have ever slammed on your brakes, you know that an abrupt stop makes your car lean forward. The front gets lower and the back gets higher. This is because a lot of weight is transferred to the front of the car when you stop. Also, most cars have more weight over the front wheels to start with because that is where the engine is located.

If equal braking force were applied at all four wheels during a stop, the rear wheels would lock up before the front wheels. The proportioning valve only lets a certain portion of the pressure through to the rear wheels so that the front wheels apply more braking force. If the proportioning valve were set to 70 percent and the brake pressure were 1,000 pounds per square inch (psi) for the front brakes, the rear brakes would get 700 psi.


The real question here is at wt of the vehicle and how to balance the system under a number of braking conditions.The wt transfer under those conditions vary so a trade-off is made with every dics/drum system.I gotta go right now,but will return to this topic later today.There is more to it than just setting pressures at wheel cylinders.

So to return to this topic,the amount of wt transfer that occurs varies given the type of braking being done.Where rear disc brake conversions fall's short is the greater amount of pressure needed for rear disc brakes to operate correctly vs's the balance needed front to back.It is very hard to judge volume vs pressure.Some rear dics systems require a larger brake master and line size.

The issue is if you have a adjustable proportioning valve set to panic stops,it doesn't work well for part brake stops because the setting is static.The same holds true for O.E.M. all wheel dics brake systems.Honestly,The system of front dics/drum brake systems,the drum brakes are more forgiven in the balance issue.

The truth is the ABS systems and for all their misgivings was the OEM's systems answer to those balance issues.It doesn't work very well because at times the ABS systems do kick in when not needed.

The latest innovation is a system that senses the type of braking and the wt transfer of braking condition that is being applied.So it adjusts pressure depending on the type of braking being done.Panic stops vs normal braking.

My two cents is when guys try to adapt dics brakes using existing brake line sizes and master cylinders.Then volume issues do occur and that can get complicated is a hurry.

By using drum brakes in the rear(11" drum updates)it is more closely to the OEM design and is still a upgrade from the stock system.In fact you can get a 1" rear wheel cylinder inlet and run the same 1" brake line for super results that don't drag like disc brakes do for drag racing.And yes you do see in the super dragster classes disc brake systems,but given the engines outputs it is not a great concern where the braking power is more important than the loss of it because of a disc brake system.In fact you see proportioning valves on solid mounted rear axle dragsters to try to control the brake line pressure so to "try" to eliminate wheel hop issues while trying to stop them.


I totally agree with Dave in regard to a 9" rear end.In fact in my Ole Yellar project,I have planned for a Ford 9" so I can play the center chunk gear changes to the best over all results.

I have more documentation about this topic if needed.

First, you will not gain by putting disc's on the rear!, It's more for looks unless you plan on doing some road course driving! Same with drilled or sloted rotors.
Drum brakes will Always have better stopping power over disc's because of the locking feature of the shoes to the drum, versus clamping of a disc.
And yes drum are better for drag racing and they will not fade for the time you use them. and they will stop you better.
If you want dics on your S-10 rearend you can get them from a Bravada, most (not all) had them or get them from a '98? and newer.

A proportioning valve is not what you want, you want a combination valve . A combination valve has a proportioning valve, A metering valve, and a pressure differential valve all built in one.
A Metering valve puts the pessure to the rear brakes first untill they just basiclly touch the drums or disc's, and then allow full pressure to the front for a second and then puts the pressure to the rear, because the rear take less to lock and it sets them ready and when your braking with the front for that instant, then the rear can tighten down without locking up.
There is 2 basic proportioning valves, one for Front disc/rear drums is set for 70% front brake, and 30% rear brake pressure.
One for disc front & rear is set for 50% front brake and 50% rear brake pressure.
You could use a adjustable one to fine tune your brakes if your going to road course or circle track, or if you don't have the right master cylinder bore sizes and you lock the rear to easy. you don't ever put on in the front to stop if your locking the front easy! Get the right MC!
You will NOT! have a volume problem if you get the right mc for your setup!
The pressure differential valve is a valve that will move from center to a side and and close off a side if you get a leak and trip a light, and allow you to still have front or rear brakes to stop with a leak in the line with a dual master cylinder

There 1000's of people out there that have done this change to rear disc's and have no problems doing it.
I don't know anyone that has used a pressure gauge to check what they have though. Not saying nobody does it, I just never seen or heard anyone do it.

I do not like the brake light set up that Wilwood has, because you get a leak in the rear brake portion, you loose brake lights! It's a pressure switch and I only use mechanical brake switchs.

The weight of the vehicle comes into play with the size of brakes you use, not by the pressure!

You would think the engineers at Ford all got drunk one day at work and came up with the 3 line master cylinder on the Mustang from '87 to 93. They thought they needed a 3rd line from the master cylinder to go to the left front brake only! the rest went to the combination valve

Pat

To be fair about this topic.......I am supplying this link that is the opposing point of view than my own.Just be very aware it's source is a Carcraft article which by the nature of the magazine is to promote the sale of parts of sellers that buy ad space it reviews.

http://www.carcraft.com/howto/ccrp_0..._adapters.html

I have not put it together yet but on my 85 s10 frame I put a explorer disc brake rear with posi on. 53 chevy body to follow. The with was correct but not sure what I need to do about the master cyclinder. from the s10 which was disc / drum. maybe i will try it and put in a adj. proportioning valve ED

Thanks guys I appreciate it a bunch. My truck isnt necessarily going to be a drag truck and I dont plan on driving it long distances so ill probably just stick with what I have untill I decide to drop a bigger powerplant under the hood.

Disc brakes are generally considered superior to drum brakes for several reasons. First, they dissipate heat better. Under severe usage, such as repeated hard stops or riding the brakes down a long incline, disc brakes take longer to lose effectiveness. Disc brakes, like ate brakes, also perform better in wet weather, because centrifugal force tends to fling water off the brake disc and keep it dry, whereas drum brakes will collect some water on the inside surface where the brake shoes contact the drums.

had a caliper seize on my 96 s-10 had to drive it to get it home took side streets 10mph to get it home melted the brake pad into fiberous material and the rotor was orange

my nova has 4 wheels drums granted only mid 12s but i always make the return road??? never had an issue

Kinda old thread guys - I hope he took the advice we gave him early last year