[fat40]

Well as for me I have had both on my coupe ,and I can say the disk brake set up is much better , it stops better and less work to maintain and I think they look better . But they both worked . So it's up to what you like and can afford .

FAT40

[xntrik]

Originally Posted by Triaged

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?

I apologize for the delay in answering. I will try to keep it short and simple.

BOTH,

Think how it would be if there were no springs but solid bars. No lift, no dive, no squat. But we must compromise.

If you ever have the opportunity to see pictures of a Fox or SN-95 Mustang doing a maximum effort stop (in lots of magazines) and then the new BMW video ad showing the Beemer stopping..... you will see that the Mustang pitches nose down 3-4 inches and the rear rises 3-4 inches and the Beemer stays almost level to maybe an inch.

Front and rear geometry are fixed by design, and by nature are a compromise of the lift and dive (squat) by their design. What works very well for drag launches is poor for stopping ability, etc.

When a front end nose dives the weight of the vehicle is being removed from the wheels on each end. Actually if the front end did not dive, the center of gravity would stay higher and there would be more downforce on the front tires. If during a stop the front springs were suddenly solid... there would be more downforce on the tires.

When the rear squats on launch, the weight bias is being removed from the rear wheels. Either way a stiffer spring or better geometry would improve the traction.

Suprisingly shorter ladder bars are are good for the rear. They lift the rear on launch, planting the rear tires, and when stopping, they are short enough to try to "pull" the rear of the vehicle downward when braking. But ladder bars are not the best for either situation and have other handling deficiencies.

When the front end drops and the rear rises during a stop, the rear tires are especially unloaded and traction suffers. Even with sticky rubber there is not enough weight on the contact patch to maintain reasonable traction.

Most stopping ability is determined by the tires themselves, by contact patch size and rubber compound. Skinny front runners are poor stoppers. If you have ever driven a drag race car on the street you could appreciate the deficiencies of the suspension settings.

Me? I drive a 5 series Beemer every day.

[xntrik]

Originally Posted by ramblin65

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.

I have had very good service with Wagner products.
If available I prefer the ThermoQuiet series.

Auto Zone sells a high performance brand that seems to work well for many people. Be advised that rotor material varies and so does the pad material... Not every pad is compatible with every rotor. I have seen new rotors installed with new pads and in 8,000 easy miles both were totally ruined.

So many people buy the cheapest pads they can get, insisting that lifetime guarantee is the important thing.. Cheapo NAPA or AZ pads are false economy. Buy good stuff that will STOP.

You can't imagine how many people I have seen convert to disk brakes and then buy $ 8 pads.... and later complain about increased pedal pressure and limited stopping ability.....they run around in circles chasing master cylinders, rubber brake lines, bleeding brakes. mmmmmm.

[chevymastermind]

do not get rear discs. you if its a street car then no you dont need it. if its for drag racing then maybe. rear discs take away power at the wheels. bottem line there not worth the 1000 dollars that it would cast.

[Moon]

Hi. Lots of opinions on this topic. Me, I would go to a deserted stretch of road, go about 30 mph, slam on the brakes and see if I could lock up all 4 tires. If all 4 tires don't lockup you don't have enough brakes. IMHO brakes and tires go hand in hand. Put some skinny bias plys on and see how easy the brakes lockup compared to a set of 60 series radials. It's my understanding that you get the shortest stopping distance by keeping the tires on the verge of lockup. Sooo if you can't lockup the tires then you don't know what the tires are capable of in terms of stopping power. If you can lockup all 4 tires then ( in my mind anyway) you've got enough brakes unless you upgrade the tires to the point where they overcome the brakes.

I've been trying to get the rear drum brakes ( 85 Monte Carlo rearend ) to lockup on my 38 Ford PU. The truck stops pretty good but I know it can be made better so that's something to work on this winter.

I have 255/15 70r tires on the back of the truck. My question is, does the large size make it harder to lockup the rear tire? It would seem like it would because of the slower drum rpm ( large dia tire ) which exposes less drum/shoe contact surface per road foot than a smaller dia tire. The tire also has more rotating mass. Also the contact patch of the bigger tire is naturally greater which makes it harder for the brakes to overcome the tire.

Well that's enough rambling for now.


Moon

[slowturbo]

Originally Posted by xntrik

.

If you ever have the opportunity to see pictures of a Fox or SN-95 Mustang doing a maximum effort stop (in lots of magazines) and then the new BMW video ad showing the Beemer stopping..... you will see that the Mustang pitches nose down 3-4 inches and the rear rises 3-4 inches and the Beemer stays almost level to maybe an inch.

Front and rear geometry are fixed by design, and by nature are a compromise of the lift and dive (squat) by their design. What works very well for drag launches is poor for stopping ability, etc.

When a front end nose dives the weight of the vehicle is being removed from the wheels on each end. Actually if the front end did not dive, the center of gravity would stay higher and there would be more downforce on the front tires. If during a stop the front springs were suddenly solid... there would be more downforce on the tires.

I find this quote misleading. It would seem that you are saying that weight transfer under braking is caused by chassis dive, which is incorrect. At the point that the chassis begins to pitch forward, weight transfer has/is already taking place. The only portion of weight transfer that can be assigned to chassis movement would be that caused by the vertical movement of the center of gravity (CG) under dive (or squat under acceleration). IIRC, in his book Tune To Win, Carroll Smith attributes something like 5% of weight transfer to movement of the CG. Additionally, from the formula HERE , weight transfer is purely a function of vehicle weight, CG height, wheelbase, and brake pad coefficient of friction.

Ramblin65,

There are several people on another board I frequent (Moparts), including a couple of autocrossers, who have used and recommend the Praise Dyno brake shoes. You might do a search over there for more info.

[Triaged]

Originally Posted by Moon

...If you can lockup all 4 tires then ( in my mind anyway) you've got enough brakes unless you upgrade the tires to the point where they overcome the brakes...

I've been trying to get the rear drum brakes ( 85 Monte Carlo rearend ) to lockup on my 38 Ford PU. The truck stops pretty good but I know it can be made better so that's something to work on this winter.

While I agree that if you can't lock up all 4 that you have serious problems, just being able to lock them up doesn't make for good (or even sufficient) brakes. Try stopping from 80 as fast as you can without locking up the brakes. Then do it again and again 'till the brakes fade and you can't even stop the vehicle. If you can't get at lease a few stops in without the brakes fading than you need more brakes.

As for your problem I think I have a solution. Try using rear wheel cylinders from a manual brake S10 of the same year. They came with larger wheel cylinders and will give you some more rear brakes.

[xautoracer]

Moon[/QUOTE]
I've been trying to get the rear drum brakes ( 85 Monte Carlo rearend ) to lockup on my 38 Ford PU. The truck stops pretty good but I know it can be made better so that's something to work on this winter.
Moon[/QUOTE]

Unless you like driving backwards at high speed, I would recommend abandoning this pursuit....Particularly since A/G GM rear brakes get really grabby in the wet....

[Moon]

QUOTE--"Unless you like driving backwards at high speed, I would recommend abandoning this pursuit....Particularly since A/G GM rear brakes get really grabby in the wet...."

I'd never try to lock them up going more than 30 mph. But I can't even lock them up going 5 mph on the grass in my backyard. That's not right. I've got the proportioning valve ( Speedway.. on the rear brake line ) wide open. My goal is to be able to lock the rears up at 30 mph and then I can start closing the proportioning valve down until they barely squeal. This should give me about the shortest stopping distance with the setup I have.

One possible problem I might have is the master cyl is a disc/disc and I have a disc/drum. I don't know if the internals are different than a disc/drum. Guess I'll have to call one of the brake vendors and ask the tech dept

Moon

[yesgo]

The 85 Monte rear cylinders are 3/4" bore. They might be too small for you. If you want more rear brake, try swapping in some 7/8" cylinders listed for a manual brake 84 S10. They are the same clip-in style, and should give about 25% more braking back there.

That is, if you haven't already done this

[Moon]

Yesgo, Triaged suggested the same thing, so I guess I'll have to go pick a pair up. It would be nice if that's all that's needed.

Moon

[Triaged]

IIRC the larger (7/8") wheel cylinders were about $5 each for new ones. When you have it apart you might as well spend another $12 and put new shoes on it.

I used them to balance out the 12" discs I put in up front and they worked great even with the stock prop valve.

As for master cylinders there is no difference between disc/drum and disc/disc except maybe bore and the size of the reservoirs.

[xautoracer]

Originally Posted by Moon

One possible problem I might have is the master cyl is a disc/disc and I have a disc/drum. I don't know if the internals are different than a disc/drum. Guess I'll have to call one of the brake vendors and ask the tech dept

Moon

What you're missing is the residual pressure check valve....I don't know if you can put one in a disc/disc master cylinder....I've removed them from drum/drum master cylinders to make front discs work better....I suggest you get an A/G body master cylinder and hook it up just like the service manual for a Monte Carlo or Malibu tells you....Then you'll have a built-in residual pressure check valve that you need for your rear brakes....

[Triaged]

Originally Posted by xautoracer

What you're missing is the residual pressure check valve....I don't know if you can put one in a disc/disc master cylinder....I've removed them from drum/drum master cylinders to make front discs work better....I suggest you get an A/G body master cylinder and hook it up just like the service manual for a Monte Carlo or Malibu tells you....Then you'll have a built-in residual pressure check valve that you need for your rear brakes....

I don't think GM has put the residual pressure valve in the master cylinder for a very long time (if ever). It will be in the combination valve (along with the proportioning valve, hold off valve, and idiot light switch).

[Dan B]

I've got the proportioning valve ( Speedway.. on the rear brake line ) wide open. My goal is to be able to lock the rears up at 30 mph and then I can start closing the proportioning valve down until they barely squeal.

Hello Moon,

I picked up on your statement above and I want to make sure I understand it correctly, I was struggling with my rear brakes and the proportioning valve until I discovered that the adjusting knob should be turned the opposite of what I thought. It should be screwed in (clockwise) all the way to give you maximum pressure to the rear lines and brakes. It should be backed out all the way open to REDUCE the rear brake pressure. You stated that you have the valve "wide open". If it is the same type of valve I have then this would give you minimal brakes in the rear. We talked about this at this link too with a picture of the valve I have:

proportioning valve

Dan B.