Not wanting to cast any doubts on your mechanical ability (after all, you did build an entire car!) I was wondering if your bleeding technique could cause a problem. This may be stating the obvious but it is important to close off the bleed nipple before the pedal is raised at all. I even prefer to close it as the pedal is still being pressed so the person on the pedal feels it go hard.
Just my .02

 

On offense taken..... Ive bled them that way. Ive pressure back bled them. Ive bled them with a Minivac system.

same results.

earl

 

Earl
Although my brakes are still not as firm as I would like them I did replace the front lines with Tristates stainless braided lines-instant difference-eliminated 75% of the spongy feel-might be worth a try. Second thing I am now investigating in conjunction with the vibration caused by my newly installed FR rack is the runout in the discs-which, if excessive, will push the pads back in the calipers thus requiring more pedal travel to take up the slack. I mention this as I bought inexpensive Autozone replacement discs rather rather than performance discs-since they were made in China there maybe a runout problem
Good Luck

Dave

 

Originally posted by davem:
Earl
Second thing I am now investigating in conjunction with the vibration caused by my newly installed FR rack is the runout in the discs-which, if excessive, will push the pads back in the calipers thus requiring more pedal travel to take up the slack.
Dave

Dave, its good to hear that the stainless lines did help.

ABOUT THE RUNOUT problem Ive considered that.... BUT, that would only occur if you are going down the road. My brakes are just as spongy in the garage as they are on the road. AND, my brakes do not surge or wobble. SO im pretty sure my CHEAP Rotors are True.

 

Hey Earl,

Here's my 2 cents. Since you plugged the master cylinder and got a hard pedal it seems to be good. Now you only have lines and calipers left that could be the problem. If you are certain that the lines are not leaking then I would really take a look at the calipers (especially the seals). I had a bad caliper that cause a similar issue. It was the caliper seal that was leaking through a pin hole. The other thing that I do have is braided lines. They do make a big difference on the front brakes. If you don't have any leaks then replace the rubber lines with braided ones. BTW. I read your other post on the rear brakes. Wow, my biggest issue with braking were my SVO rear brakes. They always locked up before the fronts. The fix was a proportioning valve. Weird how similar cars can have so many different issues.

 

Earl- You didn't mention wether or not any air came out when you bleed. If you are still getting "champagne bubbles" then some how you are getting air into the system. If the fluid is clear and no bubbles at all, you may have a trapped air pocket somewhere. I would definitely change to stainless hoses.

I am also still fighting the spongies, but I have more bleeding to do. I am going to pressure bleed next, since the vacuum bleeder pulls air around the threads of the bleed nipple and I can't tell if it's "new" air or air from the system.

 

Originally posted by accobra:
Hey Earl,

I had a bad caliper that cause a similar issue. It was the caliper seal that was leaking through a pin hole.

Wow, my biggest issue with braking were my SVO rear brakes. They always locked up before the fronts. The fix was a proportioning valve. Weird how similar cars can have so many different issues.

IF my rears locked first, id go to the 73mm front calipers....

YES, Ive always been amazed at the huge differences people get with these cars that have similar brakes. It seems to defy logic.

about the pin hole..... Didnt yourcaliper leak fluid??

 

Originally posted by xracerbob:
Earl- You didn't mention wether or not any air came out when you bleed. If you are still getting "champagne bubbles" then some how you are getting air into the system. If the fluid is clear and no bubbles at all, you may have a trapped air pocket somewhere.

I would definitely change to stainless hoses.

I am going to pressure bleed next, since the vacuum bleeder pulls air around the threads of the bleed nipple and I can't tell if it's "new" air or air from the system.

The last couple of times ive attempted bleeding them, ive used the vac system. And you REALLY CANNOT tell about bubbles because of the leak..

earl

 

For quite a while I had spongy brakes and couldn't 'lock up' the tires. Over time I changed everything with no improvement. I finally decided it must have been the caliper design and/or piston size giving me the problem (single ~2.5" Ø). My solution was Wilwood discs and calipers all around. Same master, same lines, No More Problems!

You don't say whether you can lock up the tires or not. If not, then changing your flex lines will probably not cure your problem. That's more of a 'fine tuning' issue. As far as runout, if you can't feel pulsing in the pedal, then the discs are probably true. Also, if you have air in the system, you should still be able to pump up the brakes to feel firm, even if for only a minute.

I would have to agree with Arno, replace the calipers.

We should take a poll on brake systems. Collect info like caliper piston size and quantity (front & rear), disc diameter (front & rear), master diameter, pedal ratio, line size (1/4", 3/16"), proportioning valve (y/n), how good the system works (bad, okay, great), etc. There are so many brake questions that this could be a valuable resource for many people. I know I could have used it.

Good Luck,

Gene

 

Earl,

I don't my roadster on the road yet, but I now have quite a bit of experience with the Mityvac vaccuum bleeder and can offer you a suggestion. Remove your bleed screws and coat them with a light coating of anti-sieze. This will prevent the vaccum pump from pulling air from around the threads AND it will prevent the screws from ever siezing in the threads. I did this on ours and the pedal is rock solid. You could definitely see when you stopped pulling air. I don't think new lines are going to solve your problem if your rubber lines are in good condition.

Mike

 

What type of brake fluid are you using. If it is the dot 5 Silicon it would trap very tiny air bubles and take for ever to bleed on a new brake system. Different fluids will give you different properties. I have run into this quite often. Just an FYI I don't know if it will help you or not.

TK

 

Earl - I think you and I have the same car. I have spongy front brakes too and have just given up. They are fine for now. I have the Tri-states braided lines and that didn't help. I also replaced the calipers and rotors, that didn't help. I have replaced the MC three times, that didn't help.

So I give. I have brakes, that's what matters. I just want a rock hard pedal. Maybe they make viagra for brakes?

 

Originally posted by 6T5 Cbra:

Also, if you have air in the system, you should still be able to pump up the brakes to feel firm, even if for only a minute.

Good Luck,

Gene

If i PUMP the brakes, they do get MORE SOLID. They are uncomfortable enough that I habitually pump at least one time.

earl

 

Originally posted by Tom:
What type of brake fluid are you using. If it is the dot 5 Silicon it would trap very tiny air bubles and take for ever to bleed on a new brake system. Different fluids will give you different properties. I have run into this quite often. Just an FYI I don't know if it will help you or not.

TK

Good Point.... Im running Valvoline SynPower Syntheic formula High Performace DOT 3 / DOT 4 brake fluid. "Its compatable with conventional brake fluids ...exceeds DOT 3 & 4 specs... High poling point exceeds 500.. for abs, dixc and drum brakes".

However, thats what im using on the rear brakes also and they are ROCK HARD.

earl

 

No one has mentioned bench bleeding the MC. I too, am struggling with the spongy first pump, then rock hard pedal. I didn't bench bleed my MC and am hoping this will cure my problems.

 

Originally posted by FFR2781:
No one has mentioned bench bleeding the MC. I too, am struggling with the spongy first pump, then rock hard pedal. I didn't bench bleed my MC and am hoping this will cure my problems.

OH yeah, it was bench bled. , , , and with both lines disconnected and plugged, its like kicking a bolder..... so im assumeing the MC is properly bled.

but, after one quick pump, the brakes are better but not Rock Hard.

earl

[ October 01, 2002, 09:53 PM: Message edited by: CobraEarl ]

 

if you pump the brakes and it gets better, you have air coming in somewhere or already had air in the lines.

 

Originally posted by Bill:
if you pump the brakes and it gets better, you have air coming in somewhere or already had air in the lines.

BILL, I think you are right. Some one else sort of hit on this a few posts ago.

At this moment, I think two things.....
#1, the braided lines will help SOME...

BUT #2, THERE IS STILL AIR IN MY SYSTEM SOME PLACE. Im positive its in the front system.... because i can disconnect the front system and have a pedal that is litterally hard as a rock. I can disconnect the back and reconnect the front and its spongy, just like it is with everything hooked up.

It has gotta have air in the front system.

Now, where the heck is it and why wont it come out??

earl

[ October 01, 2002, 10:32 PM: Message edited by: CobraEarl ]

 

Have you considered taper wear? Single piston mustang calipers are famous for this, the caliper twists along its sliders when the brakes are applied, the pads then begin to wear at an angle. The first pump of the brakes twists the caliper flush to the rotor, the next hit of the brakes feel better because the pads are closer, after driving a bit the caliper resumes its normal position - causing the long pedal. A number of mustang speed shops sell hardened brake caliper bushing that will help this problem, but once the pads begin to wear only replacement of them will really fix it.

 

lets see , youve isolated the mastercylinder, and the rearbrakes and during that you have a hard pedal. then you hook up the front brakes and it gets spungy, right? well obviously its in the front, is there anyway to eliminate the front calipers , leaving the flex lines and trying the pedal? i dont know much about the banjo bolts and how you could block them off. my point is maybe you could isolate the problem better, to either calipers, or prove the flex lines are the problem.i would say that you have already proved that 2/3 of the system is ok. i dont think this should be that big of a problem, basically cause theres only a handful of parts involved. when this problem is figured out, it will probably be something simple. the simple ones are always the difficult ones, goodluck, vince

 

Hey Earl,

Greytracer has a point. My Mustang has the 4 lug 87-93 brakes (my Cobra has the SN95 brakes) and it had some real issues with the pad wear/contact because of the crappy rubber/plastic bushings that the caliper rode back and forth on. I replaced them with Steeda caliper bushings and the brakes have felt a lot better. It's a cheap upgrade that will do nothing but help. It may not alleviate you issue 100%. I'm still thinking you have air somewhere. As for my caliper with the pin hole it leaked so little it was hard to find until it had been there a while. I also use the Mitivac for bleeding my lines and have never had a issue with air around the threads, etc. It's weird that so many people have problems with spongy feelin brakes. He's my setup on my Cobra:
Stock 1989 master cylinder, SN95 front calipers with Steeda SS caliper sleeves, custom braided front lines. The rears are 85' SVO rear calipers (with stock rubber connect lines). I run plain old DOT 3 brake fluid and use a Mitivac to bleed the brakes.

 

Originally posted by Greytracer:
Have you considered taper wear? Single piston mustang calipers are famous for this, the caliper twists along its sliders when the brakes are applied, the pads then begin to wear at an angle. The first pump of the brakes twists the caliper flush to the rotor, the next hit of the brakes feel better because the pads are closer, after driving a bit the caliper resumes its normal position - causing the long pedal. A number of mustang speed shops sell hardened brake caliper bushing that will help this problem, but once the pads begin to wear only replacement of them will really fix it.

MOST excellent thought and an excellent description of a problem that i will not dismiss catagorically... ..... BUT, My pads are just about new and I have those hardened brake caliper bushings. And the pads do not appear to be wearing funny.

I have considered taking a feeler gauge and seeing how much clearance there is between the pads and the rotors. Dont know if this is even checkable.......

earl

 

Earl,

I went to NAPA and got a pair of Speed Bleeders for the bleeding operation. These things are great when hooked to a vacuum pump. They will not let air back into the system since they have a check valve put in them. If there is anyone worse at bleeding brakes than me I'd like to meet them and I got this right the first time. They were $11.00 a pair.

Ben

 

originally posted by earl

I have considered taking a feeler gauge and seeing how much clearance there is between the pads and the rotors. Dont know if this is even checkable.......

earl

In my quest for better brakes, several people (at Wilwood, Tilton, etc) mentioned that when they compute brake system sizes (for master cylinder sizing), they allow for .030" to .040" of travel at the pistons. That tells me that if the pads are not touching the rotors all the time, you would have to push the pedal once to 'fill in the gap' and then push a second time to build pressure. I would measure the clearance between the pads and rotors before anything else. You may even be able to see the gap visually.

If the calipers are 'twisted' or 'misaligned' (as mentioned by Greytracer), they would return to this 'gapped' position shortly after releasing the brake.

Gene

 

Find you a stock rear end with drum brakes and throw up under it.. see what happens..
It seems that the more folks devieate from the ffr build plan the more problems folks seem to have... but what do I know... nutt'in...