Brake Help Please

[parklane]

I just recently had a car with a similar problem, with every thing right, it just didn't have enough brakes. In this case, it had a 7" single booster, and a 1 1/8" bore master cylinder. After changing the booster, and master cylinder, with no improvement, I changed to a 7" dual diaphram booster, and a 15/16" bore master cylinder. that solved the problem.

Frank...I can't understand why you would have brakes with a smaller master cyl. as it wouldn't move as much fluid when stepping on the binders :?  :?

John

[enjenjo]

Frank...I can't understand why you would have brakes with a smaller master cyl. as it wouldn't move as much fluid when stepping on the binders  

In this case, the master cylinder was too big to give an effective multiplication of force, which combined with the 7" single diaphram booster, also not know for good force multiplication, even standing on the brakes, you could not apply enough force to stop the wheels. The smaller master cylinder bore multiplied the force more, and the double diaphram booster, increased the force multiplication enough to make the brakes effective.

[40]

Mike...It is opening day in Nebraska as well....Katie is very excited as well.Worse than that,the Huskers play Oklahoma in Lincoln that day....my tickets are laying on my desk...unfortunately,I fear I may not be the ones in my seats come the 28th  :evil:

[40]

Decided to revamp the entire system and go with a 7/8" bore M/C and an 8" dual-diaphram booster if I can fit it into position without to much modification. There is an extremely well written,very informative 2-part article entitled "Brake Time" written by Ron Ceridono in the August and September issues of StreetRodder Magazine and a follow up on boosters in the December issue.It is full of illistrations,charts etc explaining clearly how an entire brake system works....one of the better articles in StreetRodder in a long,long time It is well worth the read....I learned a lot! I still HATE brakes but after reading the article....perhaps not as much The article Mike eluded to in his previous post is also a good read.Perhaps one of the Franks could include this info in the Tech section for future referance??

[34ford]

....it just popped into my head so I thought I'd mention it in case my "OldTimers" kicks in

Before I forget...I'm planning a surprise birthday party for the wifes 50th....I have rented the Knights of Columbus Hall near our house.It will be on Saturday,October 28th.



Worse than that,the Huskers play Oklahoma in Lincoln that day....my tickets are laying on my desk...unfortunately,I fear I may not be the ones in my seats come the 28th

Daryle,

Think the "OldTimers" already kicked in    

You might want to check your calendar as the 28th is on a Friday. The game is on Saturday the 29th.    Just had to give you a hard time. If you want to sell the tickets I have 2 son inlaws that would be interested in buying them from you   .

later

bob

[348tripower]

One of the biggest mistakes I have seen on brake set up is the lines are reversed on the master cylinder. Make very sure that the large resevor is hooked to the front!!!!!!!!! I did this wrong and I have fixed other cars that were wrong. For a while Speedway motors had a picture of a setup in their catalog that was wrong!!!!!!!!!! this is an easy fix before you go throwing everything away.
Don

Decided to revamp the entire system and go with a 7/8" bore M/C and an 8" dual-diaphram booster if I can fit it into position without to much modification. There is an extremely well written,very informative 2-part article entitled "Brake Time" written by Ron Ceridono in the August and September issues of StreetRodder Magazine and a follow up on boosters in the December issue.It is full of illistrations,charts etc explaining clearly how an entire brake system works....one of the better articles in StreetRodder in a long,long time It is well worth the read....I learned a lot! I still HATE brakes but after reading the article....perhaps not as much The article Mike eluded to in his previous post is also a good read.Perhaps one of the Franks could include this info in the Tech section for future referance??

[HotRodLadyCrusr]

Stacey on the HAMB just posted what her problems (issues) were.  She just figured it out after quite a while and lots of flustrations.  Quoted from her:

"Here's what was wrong..

#1 we had to reverse the lines on the master cylinder
#2 we had to make a threaded rod to take up the gap between the plunger rod and master cylinder.

Everything is GREAT with these changes, I can slam on my brakes and leave awesome skid marks!  

Stacey"

Hope it helps

[parklane]

Frank...I can't understand why you would have brakes with a smaller master cyl. as it wouldn't move as much fluid when stepping on the binders  

In this case, the master cylinder was too big to give an effective multiplication of force, which combined with the 7" single diaphram booster, also not know for good force multiplication, even standing on the brakes, you could not apply enough force to stop the wheels. The smaller master cylinder bore multiplied the force more, and the double diaphram booster, increased the force multiplication enough to make the brakes effective.

Yes, i understand that, but it seems that the brake pedal went to the floor when the engine was started, ASSUMED that a larger bore master was in order, not smaller.

John

[enjenjo]

You;re right, my pedal didn't go to the floor. It was just ineffective.

This goes back to air in the system, or bad residual valves, or maladjusted linkage. When you eliminate every thing else, the unlikely is the only thing left.

[40]

Bob...You're right....I think the "OldTimers" has already got me! Her Birthday is indeed Saturday the 29th not the 28th.I have a friend who has asked for  my Oklahoma tickets but is unsure if he can get away....If he can't,I'll shoot you an email if they are available.Should be one heck of a game  GO BIG RED!!!

[40]

I am thinking about using a remote fill for the M/C...mounting it fairly high on the firewall.....this will get it above the M/C and wheel cylinders and hopefully create a little additional line pressure.Any thoughts or experiences ??I have very little clearance under the floor so if nothing else...It'll make checking the fluid easier

[Bruce Dorsi]

You;re right, my pedal didn't go to the floor. It was just ineffective.

This goes back to air in the system, or bad residual valves, or maladjusted linkage. When you eliminate every thing else, the unlikely is the only thing left.

That was one of the things about Daryle's problem which I couldn't understand.

I can understand a smaller m/c bore generating higher fluid pressures, which in turn creates stronger holding power.

However the original post said the pedal was firm with the engine off, and the pedal would drop almost to the floor when the engine was running.  

Assuming all the air had been bled from the system, how would the m/c bore be a factor here?  ....Daryle  also said he set the pads against the rotors so the brakes were dragging slightly. ....Unless the booster applied more force to compress any air to a higher pressure, why would he lose the firm pedal, and where would the m/c move any additional fluid?  .....Ballooning brake hoses??

Please know I do not disagree with anything Frank said above.  

Under the conditions described, I don't see how decreasing the bore of the m/c would keep the pedal from dropping near the floor.  If anything, the larger bore will displace more fluid with less pedal travel, but will result in a lower fluid pressure at the calipers.

From what I have been able to learn, it doesn't really matter which port the brake lines are connected to, UNLESS there is an rpv or proportioning valve built into the master cylinder, or UNLESS a combination valve is used.   ....This is assuming the m/c has a straight bore, and is not a stepped-bore design.  

GENERALLY, but not mandatory, the front brake circuit is connected to the m/c port closest to the push-rod.   .....On a disc/drum system, the discs are usually connected to the larger reservoir.  

Master cylinders for a disc/disc system should have TWO large reservoirs.  ....According to law, the reservoirs must be large enough to hold enough fluid for a specified number of brake applications.  ....Disc brakes (generally) require more fluid volume than drum brakes, so the reservoir capacity is usually greater.

Laziness has its advantages! ...I won't change parts without knowing why!  

[ram-rod]

its easy to bleed all the air from the lines but should the calipers be swaped side to side during the build it puts the bleed nipple to the bottom leaving a huge resivor of air up behind the piston  

you can bleed three bottles of fluid through the system and if the air pocket is trapped above the nipple it wont expel with out

1 swapping them back to their original position / or
2 unbolting the caliper placing a block of wood between the pads and rotate bleed nipple to top dead center then get a friend to help bleed each one  then refit

using a piece of fish tank airline attached to the bleed nipple and a glass bottle is a great way to see what air is being removed

i have also seen guys get caught out buy swapping brake callipers from rear of front axel to frontof front axle  when fitting rear rack and pinion  this also orientates the nipples to the bottom
it easy to see why air gets trapped once you have a caliper apart and the piston out of it

[bucketmouth]

A quick test to eliminate the calipers. Clamp the front and rear brake hoses and see if you still have the same problem when you press the brake pedal.

[40]

I assure you that I have made nearly all of the mistakes mentioned in these earlier posts but in this case.....nothing appears to be amiss....everything is mounted correctly and I'm convinced we have all of the air out.I did manage to get a somewhat better pedal with the current set-up but nowhere near the braking ability I have with other cars I've done.Going from the current 1 1/8" bore to the 7/8" bore will increase my pressure at the wheel cylinders from somewhere around 450 PSI to nearly 750 PSI and I'm told the 8" dual diaphram booster will increase that pressure by another 15% or so.The M/C I'll be using has equal sized reservoirs and are somewhat larger in capacity than the current one.I am learning that disc/disc setups not only require more pressure but more volume as well.On my 40 coupe with a similar setup,I can touch my toe on the brake and lock up all four wheels.....that's what I'm after with the 36.When I get the parts and get it all assembled,I'll report back with the results.....In the meantime,I'll try and figure out what to do about the front wheels turning into the fenders   Aren't cars fun