Lack of brakes….

[Snek]

I understand that the need to stop my car from time to time may be in order.
I always figure that’s what down shifting is all about, but that’s just me.

Anyway the brakes work……. sort of.
They will stop the car, but for the life of me I can’t lock them up.
I was at a local Cars and Coffee and a fellow there who used to build CC cobras said that I should absolutely be able to lock them up.

He looked at the the brake masters and the little bar that goes between them (you can tell I’m new to this setup) and said something to the effect “that’s not right”.

I’m beginning to wonder if I’m just using the back set of brakes to stop.

Anyway I have Wilwood up front and a Jag rear end.

So I thought, before I kill myself and worst yet smash the car are there any articles I can read on these things and how to set them up?

I plan on bleeding the system, getting new pads, and turning the rotors.
That will get all the easy stuff out of the way.

By the way how do I bleed the Jag rear? It’s tucked way up there and I don’t have access to a lift.

Best,

Dave

[Tommy]

Given your starting point, you have a way to go. But lets get started with some basics.

• You should be able to lock the front brakes in an emergency stop.
• In an emergency stop the front brakes will do about 70% of the stopping and should lock up before the rears to prevent spinning out of control.
• Your car may need only some adjustment or it may need repairs or it may not have been assembled with the correct components in the first place.
• You'll need to share some more info for us to help you work through the process.

To begin with, please post a photo of your brake pedal assembly. We need to see if you have a brake bar adjustment system. Next, we need to know if your car pulls left or right during hard braking. And third, when you bleed the brakes, get a look at the brake pads and see if they appear wet or glazed. . . . Keep coming back here until it is stopping correctly.

[Tommy]

Originally Posted by Snek

By the way how do I bleed the Jag rear? It’s tucked way up there and I don’t have access to a lift.

A set of portable ramps similar to these might help.

[eschaider]

Over time, I have observed that many drivers frequently rub their worry beads over incidental things like parachutes, fire systems, and brakes. Mechanics, on the other hand, seem to focus on going quicker and faster. This is a curious distinction in priorities ...

[Alfa02]

Well Ed & Tommy, you two have been on a roll with your wit & wisdom lately I need to catch you up about the FI on the 514 cu in. Ford Motorsports in the West Coast Cobra come to find out, the running issues had nothing to do about the outdated FI, you won't believe what it was Cheers Buddy, Tom.

[mvanhorn8893]

Good evening,
I have a Contemporary with Wilwood front brakes and Girling brakes on the inboard rears. I upgraded to the larger front rotor diameter but it still uses the same Wilwood calipers. I also upgraded the rear to vented rotors instead of plates but I don't that either upgrade makes much of a difference in just getting the lock up.

If you shoot me an email I can send you photos of my brake balance bar set up.

I had to adjust may balance bar and bed my breaks in to get the fronts to lock up.

mvanhorn8893@gmail.com

Mike

[Snek]

Tommy:

Thanks for the reply.
Just as soon as I figure out how to post photos I’ll send them along, but for now it does not pull at all. Brakes in a nice straight line.
I did pull the pads and they were Wilwood.
Didn’t look glazed or wet or scored. Lots of meat left.
Do you have any recommendations on what I should use for street and the occasional motor cross event?

Let me ask you this question about the balance bar.
When I step on the brakes (they are CNC suspended from the top) should the angle of the bar between the front and rear master cylinders remain parallel or does that angle change?
I know some pictures would help. I’m working on that.

Thanks

Dave

[Tommy]

Dave,
Sadly there is more to it than the balance bar alone, but we can talk about it. When you press the brake pedal it apples force near the center of the balance bar. One side then presses in on the master cylinder for the front brakes and the other side for the rear. If the pedal point is closer to one side than the other, the short side will feel more force than the other. So if you want to try adjusting the balance bar, figure which master cylinder supplies the front brakes and adjust the balance bar so it is shorter on that side. . . The complication is that the front and rear brakes may use different size master cylinders, calipers and rotors. That can create a situation where the balance bar alone is not sufficient to balance the front and rear brakes. But it shouldn't hurt anything to try adjusting the balance. Just leave something for the rear brakes too.

[twobjshelbys]

Aren't different cylinder sizes used for front and rear too? I don't remember a proportioning valve. (My brakes were great only had probs with clutch cylinders do don't remember the brake details)

[Snek]

Tommy:
Is there an easy way to isolate the front from the rear brakes?
That way I can see if the front vs. the rear are actually engages?
Or is that not necessary?

I think I figured out how to upload photos.
I will take some tomorrow.

Thanks again.

Dave

[Tommy]

Originally Posted by Snek

Tommy:
Is there an easy way to isolate the front from the rear brakes?
That way I can see if the front vs. the rear are actually engages?
Or is that not necessary?

It is possible to isolate the front from the rear, but it should not be necessary to diagnose your problem. . . Based on your earlier comments and the age of the car, here are the steps I suggest:

• Service your brakes as they are (i.e., inspect and replace rubber hoses and pads, replace fluid and bleed the brakes, inspect the master cylinder, ALL hoses, lines and calipers for leaks).
• Test to see if the front brakes lock before the rear. (I do this by finding a safe dry road where I can apply full brakes from about 35 MPH. It helps to have an observer at a safe place watch from the outside to see which wheels locked up first.) If the front wheels do not lock first, adjust the balance bar and repeat.
• If acceptable braking cannot be achieved using the balance bar, evaluate the brake pedal geometry and master cylinder sizes.

[1985 CCX]

Dave

Sent you manuals!

[saltshaker]

Dave, I had the same problem with my Contemporary, wilwood dynamites in the front. I made 2 changes toget the brakes to lock up…EBC yellow brake pads and I moved the brake pedal forward 1.5”. I’m 5’7” and I couldn’t push the pedal far enough… worked for me. don’t remember if I’m using a 7/8 or 3/4 mc
Jon

[Snek]

Jon:
How are the EBC Yellows working for you?

How do I know what to order that will fit my Wilwood?

[saltshaker]

Originally Posted by Snek

Jon:
How are the EBC Yellows working for you?

How do I know what to order that will fit my Wilwood?

it depends on which caliper you have…, which caliper do you have?

[Snek]

Good news everyone!
I bled the brakes (twice actually as I was looking at the wrong master and bled the correct one dry) but live and learn.
Anyway, I bled the correct MC then changed the pads to Wilwood BP20’s.

What a difference!
I bedded in the new pads and tried a panic stop to lock them up.
Got the back to lock, but not the front.
I thought it was time to start adjusting the balance bar (Tommy, thanks for the explanation as it all makes sense now), but the front MC is as far inboard towards the center as possible so maybe it’s time for a new larger master?

What do you think?

Next up I would like to tackle the rear pads.
I’ve got a Jag rear with inboard disks.
Would any of you know what kind of Jag it came from or what I should ask for as far as the pads are concerned?
I think I would like to get the equivalent composition as the Wilwood BP20s so it would eliminate that variable.

I’m not sure what to tell them to get what I want.

Anyway, thanks for all your help.
It’s nice to be able to really feel the stopping power.

Dave

[Tommy]

If you can't lock the front brakes before the rear with full adjustment on the balance bar, you need a SMALLER diameter front master cylinder. More than likely one step smaller will do (e.g., from 3/4 to 11/16 or 5/8). Applying the same pedal pressure to a smaller diameter cylinder results in a higher fluid pressure (PSI) in the brake fluid going to the calipers. But the master cylinder has to be large enough to provide the volume of fluid needed by the caliper. That is why you want to step down only as much as needed. . . . BTW, if you do swap out master cylinders, be sure to follow the instructions about bench bleeding the MC BEFORE you install it. Skipping that step has caused problems for many DIY mechanics.

[saltshaker]

I have Wilwood Dynalites w/1.75 pistons and I use a 7/8 in the front and a 3/4 in the back and I can lock up all 4 wheels
Jon

[Tommy]

One more thought - When I was having a similar problem with my Cheetah I reached out to the Master Cylinder manufacturer, Tilton. They sent me a data form where I provided lots of detailed information about my car. They analyzed it and concluded I needed to replace my 3/4" front MC with a 5/8" piece. I did and it worked just right.

[eschaider]

Originally Posted by Tommy

...to begin with, please post a photo of your brake pedal assembly ...

And that photo is where ...