Big Red problems!!!

[onixbonilla]

Hi everyone!
My 1303 uses front and rear 993 Big Reds with a 951 master unit. I had discover a very disturbing situation. The car brakes very well but the pads do not retract and mantain constant preasure on the rotors.When you jack the car, in order to rotate the wheels I have to push them fairly hard.
In fact when I drive it slowly and depress the clucth it stops by himself,I can feel the brakes working.
Previously I had the 951 calipers/rotors and have no problem, they turn easily.
The following are some things that I had try but no success yet;
-centralize better the caliper using different washers
-installed some used pads(half the width of the new ones) but once the pads
move farther and touch the rotors they do not retract and mantain constant pressure
Rechecked the pedal assambly brake pushrod, it have completelly free movement
As stated before the master unit is the same 951 used with the 951 brakes with no problem at all.
Anyone had similar problems?
Any ideas?
Thanks
Onix

[Sandeep]

Does your pedal return back to normal height after you apply the brakes ? What are the condition of the calipers ? New or used/cleaned ?

Have you made sure the brakes are properly bled with no air in the system ?

I noticed the same problem with my setup (993 TT front and 944T front on rear) when I first started driving my car and after a re-bleed ... the problem went away.

Sandeep

[onixbonilla]

The brake pedal does return to the normal position.
The calipers are used from LA dismantlers.
We bleed the brakes twice.
Yesterday I disassembly one front caliper(to my sorry) found nothing wrong, just ended with 4 piston that are nearly impossible to place back and a totally scracthed caliper.
Thanks
Onix

[onixbonilla]

I wonder if this had to be to the fact that these brakes were desingned for cars equipped with brake boosters. Do the brake boosters cause retraction of the pistons?
Onix

[volkdent]

I'm sorry to hear you guys are having troubles, but I'm glad you're discussing it here so we can all learn something hopefully.

Jason

[zen]

i have 951 m/c and calipers all around. i have not experienced this. i have the new pads touching a little, but all seem to retract fine. just have to break-in the first mm.

i have had an issue with the brake pedal pushrod not being long enough since my m/c piston seems to sit a little more forward than the stock unit.

[onixbonilla]

When I got the 951 calipers/rotors everything was fine. The problem is with the Big Reds calipers/rotors.
Onix

[Sandeep]

Could it be the size of the M/C ?

I'm running a 25.4mm front and 22.2mm rear with a balance bar for my setup, plenty of volume for the pistons .... remember, those Big Reds (f+r) have much larger pistons than the 951 setup.

Do you have to pump the pedal a few times to stop the car ? or do you have a firm pedal with just one push ?

Sandeep

[onixbonilla]

Oh, there is no problem to stop the car.With just one stroke it stop very well, better than the 951 set up.The master is from 951, but I do not have any balancing hardware.The calipers just mantain some considerable pressure/drag on the rotors.
Thanks,
Onix

[SilverBullet]

I have 993 c2 front and rear calipers n rotors with 951 m/c no problems. Any thing wrong with the pistons?

[onixbonilla]

I dissamble one of the calipers but not found anything suspicious.Will put them back tomorrow, will retry again.
Onix

Is the master cylinder used? This sounds like it might be a check value problem, getting stuck.

[onixbonilla]

Yes , the master cylinder is used, but it was working very fine with the previuos 951 calipers/rotors. I just changed for the 993 twin turbo calipers/rotors. Anyway it just matter of a little work to try another master.
Thanks,
Onix

[73notch]

when i installed my brakes, they binded for a while, then eventually broke free. if you can turn the wheel by hand, even with some force, then try driving around for a while with them, test em out.

i installed 4 piston wilwoods allround on my car for reference

[krukab]

I had a similair problem with a 67 notchback with 996 Turbo calipers,with also a 951 mastercilinder.

We found the solution in replacing the rubber brake lines,because they were old,and the hole in
the rubber hose became to narrow to have enough flow back into the mastercilinder !!
Now we're using Areoquip/Goodrigde stainless steel lines from m/c to caliper and our problem was over.

Good luck