Light caliper drag on new rear disc conversion both sides. Can I just run it down?

[crazypete]

Hey guys. I finished my mc-2300c rear disc conversion: basically turbocoupe rear brakes on a mustang 8.8. Got me an SVO MC and prop valve. Took car for a drive and the rear brakes were lightly smoking. Rotors were really hot. Car didnt feel really bogged down so it must be on light contact. I remember the parking brake cables seemed really tight and were an enourmous b1tch to put in. The PB holds and releases.

As a quickfix, I sprayed the rotors with tire silicone, my favorite lubricant and took it for a drive. The smoking was gone completely but the rotors were still a bit hot. Later, after valiantly taking it up on the highway for a quick blast, the smoking returned a tiny bit...guess the silicone wore/spun off. No wheel blackness from brake dust though....odd.

Now I dont give a damn about rear brakes. Theyre bling as far as I'm concerned and their only real purpose is to make my parking brake do something. Front brakes do all the work and they are 73mm steel pistons with hawk pads. Stops the car cold solid. If it werent for the parking brake....I would be tempted to even remove the rear brakes completely for weight savings.

Could I just drip synthetic oil on the rear rotors and pads and let them "sand down" a bit or will the problem persist even after some material has been removed? I know the proper solution is to replace the calipers but at $64 EACH with like a $75 core EACH for 86 TC rear brakes, that is simply not going to happen.

Help me mickey mouse something together guys

 

[MrKwik]

Seems kinda silly to spend the time and money on rear discs and then oil them down ...but thats just me.

Did you gut the combination valve and then install the adjustable prop valve in the rear brake like at the firewall or did you use a combination valve off of an SVO?

Also, I seem to recall that you need to modify the parking brake lever to bypass the self adjusting mechanism or something along those lines. Im too lazy to go research it right now but you might check into that. Disconnect the park brake cables and see if it still happens, at least you would isolate the problem.

 

[crazypete]

I used svo front calipers, the factory brakelines, svo MC and svo proportioning valve (didnt they have these same brakes out back?) and then the 2300c kit which was brackets, rotors and the calipers from the 86 tc. I used the axle brakelines and flex line from an 86 turbocoupe. Ironically, there did not seem to be much fluid dripping out at all when bleeding the brakes, barely a drip or two. I was under the impression that the lines were not working. But then I had the tail in the air, put it in gear and stepped on the brake and the rear wheels stopped.

I used the old factory front DS pv->caliper brakeline as a hardline from that distribution block on top of the axle to the PS rear brake. I needed to adapt and it was the right threads on both sides. On the DS rear, I used the TC factory hardline/rubber line original combo. Neither bled more than a hesitant few drips with engine off and me busting a vein up front stomping the pedal.

When rebuilding tracloc, I could turn the rear wheels by hand with it in the air and there was only minor minor minor drag.

You need to take out the auto adjuster? Oh......is that unhooking the spring? Where is the autoadjuster?

This whole rear disc thing was a horrendous PITA expensive mistake to have done and so I am ready to oil the SOB's to get the car back on the road. Just wondering if there is like.....a break in period for brakes?

 

[MrKwik]

The brake lever mod includes cutting and welding the little catch mechanism if I remember. Do a google search and you will run across it I bet.

So the gold block below the MC...that came from the SVO?

 

[crazypete]

AHA!!!

This is my problem!! The spring would providde just enough force to cause the slight drag but not enough to slow the car down.

But I am confused.....with the ratchet welded.....wont the parking brake not stay up? I need to go take it apart tonight and look at the insides.

 

[MrKwik]

AHA!!!

This is my problem!! The spring would providde just enough force to cause the slight drag but not enough to slow the car down.

But I am confused.....with the ratchet welded.....wont the parking brake not stay up? I need to go take it apart tonight and look at the insides.

I dont think you weld on the part that holds it up. Seems like there is something else in there that only effects the self adjusting mechanism. Did you find the article?

Also...you DID use the FMS ebrake cables right?

 

[MrKwik]

I was also thinking about your bleeding issue. Did you bench bleed the MC before you installed it? If not, you will most likely have a hell of a time getting the system to bleed out right. Just thinking out loud here.

 

[tjm73]

All disc brakes drag slightly. This is normal.

 

[MarkFJ40]

Is that master cylinder for 4wheel discs ?
Drum brake master cylinders have a residual pressure valve that keeps some pressure in the line to keep the wheel cylinder setup.
Calipers don't need this pressure and that could be what is causing your drag.
don't oil your pads. You can throw them away if you did. They're done.

 

[jrichker]

I have the TC rearend in my car, & it caused the rear brakes to drag slightly if I ever used the parking brake. I did the parking brake lever mod, and my problems have cleared up.


See http://www.mustangcentral.net/tech/brake.html for help with the emergency brake - the stock setup tends to lock up and not release properly.

 

[crazypete]

The pads are not oiled but they have some residual tire silicone on them that will burn off with a little heat.

That link is gold. I now see what they are trying to do visually. Apparently you defeat the big loop spring then fuse the adjuster teeth together and cut a tab so it sits down......

My kit seems to have come with the exact same equalizer I already had and a set of ebrake cables that were identical to the ones already in the car. I swapped both in anyways.

About that procedure...

Does the parking brake still work that way, button and all? Can I still lift it hearing a ratchet sound then push the button to make it go down or is this now a yank and hold up e-brake for e-brake use and not parking brake use? Honestly.....after putting the equalizer in once....thats it. It's not coming off. It was such a pain I still vividly remember it. Will this work without the threaded bolt adjuster? Cant I just....torch the spring or unhook it and spin it one turn and hook it back so it has far less tension? I kinda like my ebrake since I live on a hill and all.

 

[Asha'man]

'86 TC had drums, just FYI. '87-'88 had the desirable discs.

Brian

 

[crazypete]

Woops, you're right!

Wow, the 87-88 rear calipers are even more expensive! 72$ each with $80 core each. And thats just reman stuff....

 

[vristang]

Just thought I would throw out a safety concern. I have been told that silicone cannot be removed from a material once it has been applied. This is from building 777s for 6yrs. If silicone has gotten onto the rotors or pads they will both have silicone on them forever. There was some debate as to how much material you would have to grind down on the contaminated part to reach virgin material (and whether it could be done at all).

I realize that the original poster does not care about rear brake performance, but for any car that is on the street this would scare me. If it were my car I would toss the rotors and the pads, as I would not trust their performance when I needed it (desperate braking in an emergency)

This is just my opinion, I'm not looking to start an argument. Just wanted to through out my experience and opinion.
Jason

 

[crazypete]

Well, the way I look at it:

1. The rear brakes do about 15-20% of the overall braking.
2. Lets say once the pad has heated through and burned off the silicone, I get back to 50% of their original effectiveness (which isnt much to begin with)
3. Effect: I'm at 90-93% braking efficiency

So yes, I am unconcerned with the loss of brake effectiveness. Based on their smoking and the car's excellent braking performance even with smoking rear siliconed pads, I'd say the brakes have plenty of friction left.

The SVO master cylinder is a dual reservior MC. Chance of me losing both circuits without noticing (if I notice, I'll use the remaining circuit to stop the car) and then having to rely on the ebrake is very very slim.

What you said about silicone is why I love, absolutely love to use it as a lubricant. Good stuff!

 

[jrichker]

About that procedure...

Does the parking brake still work that way, button and all? Can I still lift it hearing a ratchet sound then push the button to make it go down or is this now a yank and hold up e-brake for e-brake use and not parking brake use? Honestly.....after putting the equalizer in once....thats it. It's not coming off. It was such a pain I still vividly remember it. Will this work without the threaded bolt adjuster? Cant I just....torch the spring or unhook it and spin it one turn and hook it back so it has far less tension? I kinda like my ebrake since I live on a hill and all.

I used the FMS M-2810-A center Ebrake cable and modfied the ebrake handle per the instructions at http://www.mustangcentral.net/tech/brake.html. The brake handle works just like stock, the button unlocks it, the rachet allows you to set it where you want it. I used cutoff tool to remove the spring. Be sure to closely follow the instructions on how to weld the ebrake handle. I didn't and the first handle made it hard to get the proper cable adjustment.

 

[crazypete]

Well that was definately the problem! I didnt have a chance to roadtest it but the amount of force coming from that spring was definately pulling on the ebrake cables a bunch. I cut the spring off completely and the tab on top. I goofed and welded the adjuster on the second tooth from the beginning (looking at the picture this morning) but oh well. No adjuster underneath but lets hope this is enough to effect brake operation. Did it with the handle in the car.

Handle still ratchets and gives plenty of resistence so I think I am ok.

Thanks guys!!