BRAKE OPTIONS QUESTION

I found the text below from M1Dadio as part of the custom Chevy G10 posts. Can someone explain the reason why drum brakes in the rear would be good/fine but putting disks up front is better? I am looking at a V-8 and see the emphasis on disks for that motor. I am working on getting all the papers on what the owner has had done to the van other than engine and trans rebuild.

Would it be better to have disks all around? I am clear on the dual circuit concept.

And, since I am clueless, what is the difference between power brakes, disks, etc? I know this can all be found online, but I'd rather let the awesome folks here showcase their knowledge. Thanks!

"Well I would recomend firstly a duel circuit brake system is a must.
Add to that front disc brakes with that V8.
rear drum brakes are good.
Power brakes are another idea"

Think about high performance truck shoes from Ott's Friction
Supply.


63

I'm running manual 4 wheel disc and I like it fine. The next one however I am planning on going with a vac booster.
I am under the impression that front disc and drum rears may be easier to set up. There is some tweaking that has to be done to get away from a low-pedal issue with 4 wheel disc, but this is because of the geometry of our brake pedal set up. M1 has done an exstensive amount of research on the subject. Right now there are I think 3 set ups for the rear disc. 1 is a direct swap of an existing rear disc axle like M1s transam stuff. 2 a conversion kit like I am running. 3 a homebrewed set up using cadillac parts from a junk yard. Id say front disc would be great, rears would be a personal preference thing. I went with the rear disc because all of my stock parts were junk when I started the build.

I sure like my front disc brakes,should have done it sooner! Bill

I have run disc/disc and disc/drum in both manual and power on my van.

I will comment on that as soon as I get this new site to work. Right now your text runs off the right of my screen and I can't seem to get the new site to fit??

any Ideas??

M1D

All I can suggest is holding down the Control key and click on the minus sign once in the number pad, if you havent tried it

Hello Digz

I didn't get all that, I get
"hold down the ctrl key and click on ?????????????
number pad, if you havn't tried it"

I was able to figue out your sugestion. It does make the whole picture smaller onto my screen but the right side of this forum is still chopped off short and I don't see it. I don't even get the scroll bar on the right.

I can get this whole forum by increasing my screen resolution to max but then I can't see any other sites including all the other Vintage-vans pages, no can I see anything on my desk top because it ends up too small.

The problem has to do with this forum and this forum alone.

Dan the van man is helping me out over on the thread about this new forum site. so I won't hyjack any more of this thread.

Lazarusman: I will answer to the question of disc brakes, especialy rear disc brakes which I have much to say about and will save you alot of grief and unnessesary expence.
Just as soon as I can get this forum working.

M1D

OK, things are improving, Thank you Chebby for your hard work.

Lazarusman: I will divide the subject matter to answer your multiple questions.

First, the drum brakes on your van are designed for the weight class of the L6 engine. You can get better shoes as recomended by 63.

However, front discs are considered better because drum brakes need much more maintenance. You need to be onto adjusting your front drums about every three months and you must keep all thier components in near new condition to get best braking performance. And even at that drum brakes are notorious for inconsistant braking, due to uneven heat disapation, especilay lack of straight line braking as they are quite effected by environmental condisions, water, humidity all can affect the left or right side differently. and Drum brakes are more suseptable to "fade" form overheat on long hard brake applications. The drums on your van are adaquet for a factory van, maybe not so much for a modified van.
Thats why all car manufatures do disc brakes today.

Conversly disc brakes are known for being less secceptable to environmental effects, they don't need constant service and adjustment and they are cheeper to redo when worn out. All these characteristics amount to "Consistanly" better and more reliable braking each time they are used. And disc brakes are much more likely to provide even, straight line braking every time as an inherant nature of thier design.since they are out there exposed to the environmental condisions, both side are constantly effected equally making for consistant left and right side braking.
The disc brake designs we are all putting on our vans are of the correct size to handle the wieght of your van with a V8 doing the higher loads and speeds you are going to be doing with your V8 engine.

Power vs manual: The first thing you need to understand is, power brakes do not make the brakes on the vehicle stronger or better or higher performance. The only thing a power booster does is make the brake pedal easier to push so your leg dosn't have to work as hard. Changing you van from a manual brake master cylinder mounted in the stock location to a power boosted master that has to be mounted some other place on the vans chasis is a job that takes much mechanical skill, enginuity and fabrication not to mention much more money and time. If you are paying somebody else to convert your van to power brakes, expect it cost you at least $1000 for power brakes alone.

Rear drums; On the subject of Disc/drum vs Disc/Disc. I have done and drove them all and I can now say, had I known before what is involved in getting rear discs to work right on these 10 bolt rear ends I would have stayed with rear drums.
I should first say, the rear drums on your van are all you are ever going to need. They are plenty adaquet for the wieght class, they are self adjusting (unlike the front drums) and because they are not on the "steering wheels" they don't produce as much problems with uneven braking like front drums do. This is why all throught the 70's and 80's the big three put Disc/drum set ups on everything. Further to this, when a disc/drum set up is used on these vans the "brake proportioning" is not as much of a problem like it becomes with Disc/disc conversions.

I will speek to rear disc isuse on a following post

M1D

how do you edit a post?

M1D

m1dadio wrote:how do you edit a post?

M1D

the edit button is next to the quote button below your avatar square

I'm not getting that picture guys!

When I'm on this web page my screen right side is cut off right down the right edge of the avitar picture. I get an almost complete quote button and everthigh right of that is black. i don't have the edit button you guys are seing.
I'm working with Chebby on this problem in another thread.

I will accept any sugestions, I tryed Dans earlier one of changing resolution and bits but that didn't work.

I I new how to take a snap shot of my screen I could show you what it looks like.

I thank you all for your help with this.

I have to sign off, My 10 year old girl and I are going to the race track now for an evening called "Weekend of Mayhem" total destrution, monster trucks demo cars, demo trucks, mini figure 8 demolision and demolision boat trailer races. Its a screem!!, last night was demolision school bus races.

M1d


M1D

SOUNDS LIKE FUN!

Ott's brake shoes do not fade; made of the same material used for semi trucks. They feel, by comparison, like power brakes. $80 per axle and
be sure to have the shoes arced to your drums.


63

Those brake shoes are great and do make a noticable improved braking performance. I have used them and yes they do make a change simular to power brakes "feel" because they are designed to grab better (have an increased coefitent of friction) at lower tempetures. The different material does wear out faster but who cares, its all about better brakes when you need them.

Contrary to what advertising says, Shoes and pads have nothing do with "Brake fade".

On "brake fade":

To understand brake fade you must understand a few facts.

These brake systems are the type design that "convert mechanical energy into heat energy" and they happen to use friction as the mode of energy transgresion. Thats what they do. They take the momentum of you van moving at 60 mph and change that energy into heat and disapate that heat into the atmosphere.

The function of the Rotor or Drum is to absorb that heat energy and more importantly disapate it into the surounding atmosphere at a rate faster then the heat is building. If the "Mass" of the material on the rotor or drum is not enough. (like when rotors or drums are machined beond designed limmits) the heat will build up faster then the rotor or drum can get rid of it. An undersized rotor or drum will eventually become so hot that it reaches its "thermal saturation point", meaning the friction of the shoes are generating more heat faster then the drum can get rid of it. Once the drum or rotor is heat saturated you get "BRAKE FADE" .

For those of you who have not expirienced this, basicaly the brake pedal stays the same at your foot but your brakes just "GO AWAY" and you have the sensation of the vehicle speeding up. You literaly have no brakes during Fade and pushing harder on the pedal only makes it worse and burns the pads ro shoe clean off. The drums or rotors must cool down in order for the brakes to begine working again.

The problem of brake fade is more prominent in heavy vehicles and faster speeds and occures during long hard braking, like you see on the race track. Or an overloaded vehicle speeding down hill with the driver "riding the brakes".

This in fact is why they went to "Finned drums" on bigger cars in the late 60's.

This also is the main reason disc brakes are better then drum brakes and are now the main stay for new vehicles.
Drum brakes trap the heat inside the drums and are much slower at disapating the heat then rotors are.
Conversly, the big three (making faster heavier cars)found drum brakes had to get too big and too heavy comparatively speeking to disc rotors which could be much smaller and lighter in weight in order to absorb and disapate the same amount of heat energy.

One other note: the material rotors are made from has everything to do with heat disapation. race cars today use "Carbon fiber rotors" that esentialy do not store any heat, they disapate it all instantly. Some race cars even have liquid cooling systems for their brakes.But thats too expensive for us. I bring this point to you because you should know that when you buy cheep ass rotors made in China for your daily driver. You get a cheep steel material composition that just barely meets the minnimum thermal standards set out by DOT. Where most all "made in USA or made in Canada" rotors and drums are made with much higher quality steel that absorbs and disapates heat much more rapidly then those made with cheeper metals.

M1D[img][/img]

Now that's a great explanation in detail!!

yup I agree. I thought it was when the brake fluid got to hot and pedal went to the floor. I pressed the + button.

M1D, great detailed input.

I would also mention that aluminum drums on some models of late 60's Buicks (front) and 70'/80's Camaros (rear) will fit our vans.

I agree that drums near oversize should not be used.

However, it is a popular misconception that OEM discs weigh less than
drums. Consider the additional weight of the caliper alone as well as the
disc. Some drag racers (including me) run drums because of this. Less unsprung should be considered too.

We have 3 types of shoes/pads to choose from:

Metallic (agressive wear)

Semi Metallic (moderate wear- brass/bronze )

Stock (low friction)

I use the ones in the middle for a street/strip application.

63

Lazarusman: here is my expirience with rear disc brakes for these vans.



I said earlier that your rear drums are good enough. To expand on that I will say the rear drum brakes on your van are plenty of brakes for the weight of the rear of that vehicle. When you add front disc brakes in combonation with the factory rear drum brakes; the proportioning valve ballance requirments are close to correct for the vans weight distribution.

I have installed disc brakes onto two ford 9" rear ends, one buick 10 bolt and 3 chevy 10 bolts of various years.
If you want to go to disc brakes on the rear, Here are some of the unkowns and mistakes.
The most commun mistake people make with rear disc conversions is putting too large a disc brake system on the back causing brake proportioning to be difficult if not imposible to manage. Many people put too big a rotor on the back axle which will hardly ever get used because the proprotioning valve has to be set for almost no brake action to the rear discs or they will always be locking up. You can see this at car shows where rear rotors of some cars have much surface rust on the friction surface of the rotors because they are not being used enough to keep them shiny steel.

Especialy on these vans that are quite light on the back axle, it is very difficult to find a rear disc system small enough to be of correct size and that can be easily addapted.

I am using a rear disc size commun to many lighter four wheel disc GM cars. I have the 10.5" dia by 1" thick rear rotors but that is allready too big for the back of my 90" 65 with a V8 and 700R4 trans and heavier 1979 10 bolt rear end. Currently my adjustable proportionign valve is cranked all the way to minnimise rear brake action. This 10.5" rear disc system found on many mid 80's camaros and firebirds is fairly easy to addapt to your current early 10 bolt but also requires you to have the axle flanges machined down to fit inside the rotors (just like GM did to put them onto the Camaro). There are some even larger rear brake systems with rotors that will fit right over the axle as it is, designed for heavier GM cars but I think that is way too much for these vans.

There is another big problem with putting rear discs onto thes 10 bolt rear ends. That is axle end play. Many other rear ends like the ford 9" and the buick 10 bolt and some dodge rear ends have the axle held in by a pressed on bearing that is bolted to the axle at the backing plate with a four bolt flange. These axles can move in and out by about .005" on hard cornering which is acceptable for disc brakes. The problem with the GM 10 bolt is the axle is held in with "C" clips to the spider side gear. Unless your 10 bolt rear end is in nearly new condition, it will have axle end play up to as much as .050" which is excesive for disc brake function. This is a problem because on cornering the axles move in or out and the rotors will force the caliper pistons to retrack more then should be and then the next brake application will feel low and need a pump to restor pedal hight.This is further agrivated if the rotors are not perfectly true and straight and especialy if the calipers are dragging on the brackets at all. This can be avoided by having a "tight" rebuilt of the rear end. This standard usually requires replacment of all bearings, spider gears, gear Pin and sometimes new axles. Or you can get a kit that converts the 10 bolt from a "C" clip type to a flange mount axle bearing. A tight posi rear end is less seceptable to this problem because the side gears are spring loaded keeping the end play to a minimum.

In a nut shell, these 10 bolt rear ends where not designed with the intension of disc brakes being installed.
I completely rebuilt my 10 bolt to the tightest standard I could get away with and my rear discs work prety good.

Another requierment to having a succesful rear disc installation is the parking brake. You will have to redesign and modify your park brake cable set up to work correctly on the rear calipers. These rear callipers depend on a properly operating park brake system "BEING USED ALL THE TIME" to keep the rear calipers properly adjusted. If not your brake pedal will get lower and lower over a few thousand miles of driving and you will have to manualy manipulate the the caliper park brake lever adjustment to restor the pedal hight.

When it comes to building up your rear discs system, You will get what you pay for. That law is as consistant as the law of gravity. It is recomended you buy two new American built calipers, they are expensive but will save alot of greif when it comes to bleading, adjustment and continued adjustment while in service. I know two people in a local car club ( one 67 Camaro and one 57 Chev) who bought that rear disc kit (made in China)from a big name aftermarket brake kit suplier ( the one where the bracket comes in three parts so it is a one kit fits many GM rear ends). After a few weeks of ripping their hair out of their head trying to get it to work right, they both went back to their original drum brakes. There is also several vanners from this club myself included who had alot of hastle getting their rear discs to work properly.

I spent more money converting to rear disc brakes then it cost for the front disc brakes. front disc conversion should come in at around $475 in parts, the rear conversion cost me about $800 in parts, park brake system included.

I am not trying to discourage anybody who wants rear discs from doing it. These are just the facts of the conversion on my van, and for what??? they are not better then the rear drums that came factory on the van. They need about the same amount of maintenance as the drum brakes.

Honestly: the only advantage to rear disc brakes on my van is I have the bragging rights at car shows to say "Yep she's got four wheel disc brakes".

If you want to go rear discs I will be happy to help you in whatever way I can.

m1D

Well when it come to brakes there's no denying M1D, you have it figured out!! Another great explanation!

If I could give you x2 "+"s I would for that one!!!

Dan

Alright!


63

M1, Awesome explanation. Deserves a sticky...That really sums it up and makes sense (most of it, even to a mechanical novice). I never knew what rebuilding a rear end meant or why it's important. It sounds like too much "sway" in the rear w/disks if not perfectly tight.

It sounds like putting disks up front is a straight ahead deal vs. what would need to happen by placing them in the rear. Again, I am looking for good solutions that minimize expenses since I likely won't tackle them myself.

Another simple question: Does "posi" rear end mean anything other than "position?" Just trying to figure out why it's called "posi" and if it's different than another type of rear end.

lazarusman,

Posi is an abbreviation for positraction; power to both rear wheels.
A nonposi is only power to the passenger side rear wheel.

Other names for posi are limited slip, posi trac, power lock and others.