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8/09/2021 1:54 AM  #1


Plea for help! Mark VII rear disc issues.

I’m going to apologize up front if I start to ramble, my brain is on overload right now. Finally managed to squeeze a little free time into the schedule to work on solving this 9 yr, nagging problem that hasn’t been right since day one. I have the MkVII rear disc setup that started making a noise on day one of the install back in 2012. Sounded like a runout issue where the pads squeek a bit each revolution when the pads hit the high spot on the rotor. Took the rotors off, had them turned & had a mechanic buddy copy the ford manual pages on correct caliper adjustment. Double checked everything & still had the noise. Could back the pads off just enough to erase the noise, but then would lose parking brake functionality. A week later, before I could fiddle with it more, my father was killed & it just got shoved to the back of the to do list. Other than moving the car around, in & out of the shop etc, it didn’t get driven. In 2017 I moved & other than a couple trips to the main road & back, about 2 mi, it has sat covered up until today. Here’s what I have discovered & looking for advice on which direction to go to fix. 
1) took off wheels, disconnected driveshaft & was still very hard to turn until both calipers were removed.
2) spun rotors & marked the high spots where pads scraped on front & back. 

3) rigged up “redneck” dial indicator & Checked runout on rotors. Came up with roughly .030 between high & low areas. 
4) removed rotors & checked runout on axle flanges. One side was at .005, other pretty much 0. I did notice some other problems with the axles. Axles have long studs installed & noticed on a couple of the studs, the edges of the holes have bulges that interfere with the rotor. Also a couple other studs are long enough on the splined area to have splines sticking through & upon inspection, the lug nuts more or less press the rotor on when wheels are mounted & tightened. 
5) the axle that has a .005 runout when clocked with the high spot at 12 o’clock, doesn’t correspond with the high spot on the rotor which clocks at around the 3 o’clock mark. 
6) rotors and pads were SEVERELY glazed. 
7) I have pictures of everything, but assume I need a hosting service to attach here? 

I cleaned the mounting & pad surfaces on the rotors & mounting faces on the axles. I will address the bulging spots on the axle faces around the studs & exposed splines mount everything back up & recheck the run outs to see if anything improves... I will also go ahead & order a new set of rotors & pads. 

Is there anything else I need to check or be aware of/ do? I really want to get this working properly & this will be the last attempt before scrapping it & moving to a different setup. Besides life, this has pretty much kept me from being able to drive or enjoy the car going on a decade now. Any help will be greatly appreciated. With the way “life” has been the past few yrs, would do my soul some good to be able to get this thing out when time permits & just drive it a little! 

 

8/09/2021 7:46 AM  #2


Re: Plea for help! Mark VII rear disc issues.

Sounds like you still have the residual valve installed that is used with drum brakes.  This is there to maintain about 10 psi of pressure so the drum can grab quicker next time.  This valve should not be used with disc brakes.

 


1968 T-code Coupe with a 302.  Nice car, no show stopper for sure, but I like it.
 

8/09/2021 8:24 AM  #3


Re: Plea for help! Mark VII rear disc issues.

Rufus is right on the money here suggesting the residual valve might be the issue.
I have the MKVII rear set up on my 68 and other than a mediocre  e brake functionality I am pleased with the set up.
My  car has stock front disks and I used a stock 68 MC with no residual valve.

Last edited by Rudi (8/09/2021 8:25 AM)


Good work ain't cheap, Cheap work ain't good!   Simple Man
 

8/09/2021 8:45 AM  #4


Re: Plea for help! Mark VII rear disc issues.

Another suggestion, verify the calipers are centered on the rotor.  If these rotor and calipers are a 'custom' installation, the caliper bracket may need some adjustment so the caliper is centered on the rotor. 
What year is your car, and what rear end are you using? 


65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
 

8/09/2021 9:09 AM  #5


Re: Plea for help! Mark VII rear disc issues.

If you need to start replacing parts, I have a complete MK VII kit I removed from my 67/68. Sitting in a pile in the corner of the garage. Worked great--went with MSteve Cobra rears.

 

8/09/2021 11:01 AM  #6


Re: Plea for help! Mark VII rear disc issues.

Thanks for the replies! There are no residuals in the system. Everything was built brand new with the exclusion of the pedal. Car is a base model 69 sportsroof with 94k original miles. Rear is the original 8” with an added Eaton posi 3.73 gears. Here’s a parts list of the brake system:

Reman booster
Approx 2000 V6 master cyl. 
Wilwood adjustable prop valve. Not a single in/out but the combo one with the distribution block
All new stainless lines & hoses. 
Front is 05 GT using MS conversion brackets & new takeoff calipers/ rotors/ pads purchased from Shelby
Rear MKVII was salvage yard purchase, used calipers for cores, new pads & turned the original rotors. Also used MS bracket kit to mount. 

Going to start by addressing the issues I found on the axle around the lug studs & do some testing, now that I have the high/low spots marked. Ordering new set of rotors today. Only $18 ea thru rock auto & have a guaranteed lateral runout of .004 or less. Will also check for centering of the calipers, but think it’s good based on wear patterns on pads. Once I get the runout issues somewhat under control Will test with parking brake cables disconnected to make sure those aren’t creating a drag. Should I also back off the bias a little on the prop valve and see what that does? 

     Thread Starter
 

8/09/2021 5:54 PM  #7


Re: Plea for help! Mark VII rear disc issues.

I did not know that MS had MK Vll rear brake brackets. Ultrastang had these for a while but no longer see them.
I sourced the MK Vll calipers, caliper mount and hardware from a salvage yard and used calipers as cores for rebuilt ones from a parts store.
I made my own mount brackets to fit an 8” rear end, splash shields don’t survive in northern climates so those were custom fanned as well, also had to make my e brake cable bracket.
I was very careful when making the mount brackets, setting the calipers and mounts on the axel mounted rotor and measuring the mount points directly to ensure accuracy and operation.
I think that you should jack up the car and with the wheels removed ensure that all the mount brackets are aligned properly.


Good work ain't cheap, Cheap work ain't good!   Simple Man
 

8/09/2021 6:11 PM  #8


Re: Plea for help! Mark VII rear disc issues.

I’m pretty sure they came from MS, but could have been Ultrastang. Bought the car in 07 & started picking up parts soon after, so has been a good bit of time. 

will double check those calipers/brackets, but think it’s more of a runout issue. Did a little more monkeying around today & found that no matter how I clock the rotor on the axle, the high spot always stays in the same spot on the axle, doesn’t move with the rotor. Guess I’m going to have to start with the axles & work my way out. 

     Thread Starter
 

8/09/2021 6:15 PM  #9


Re: Plea for help! Mark VII rear disc issues.

Here are some pictures of my MK Vll concersion for this picture starved forum.








e bnrake bracket

 


Good work ain't cheap, Cheap work ain't good!   Simple Man
 

8/09/2021 6:16 PM  #10


Re: Plea for help! Mark VII rear disc issues.

Here are some pictures of my MK Vll concersion for this picture starved forum.
 


right side assembly



right side e brake detail



bending the splash shield 


splash shield mock up




band sawing the 3/8" steel bracket mount

e bnrake bracket

 

Last edited by Rudi (8/09/2021 6:32 PM)


Good work ain't cheap, Cheap work ain't good!   Simple Man
 

8/09/2021 6:49 PM  #11


Re: Plea for help! Mark VII rear disc issues.

Nice! I’ve made much of my stuff too. Made all my hydraulic clutch brackets & crossmember for the T5 swap. I also make the shock tower reinforcement kits. Just developed a new kit for 65-66. 

     Thread Starter
 

8/10/2021 8:07 PM  #12


Re: Plea for help! Mark VII rear disc issues.

Tinkered around today with the right side & made some positive progress. Addressed the issues on the axle where the studs had pushed up the edges of the holes. Dressed everything down with a file, took the old rotor from the left side that didn’t have the stud issues & lightly hit the backside of the lug holes with a 45 degree tapered reamer. Also noticed the aluminum rotor centering rings had a very sharp edge On the inside where it seats on the axle. Axle wasn’t machined to a precise edge where they meet so chucked the ring up in the lather and put a light 45 degree cut to that sharp 90 inside edge. Put the rotor on, torqued it down & first reading has the runout down to .004 at the rotor. Won’t mess with it any further until I get the new rotors in. If there is no improvement with the new rotor, one of the .003 runout correction shims would bring it in to .001. Don’t think I could ask for any better on that side... 

     Thread Starter
 

Board footera


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