Problem with Rear Cobra Brake Installation - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 43 Old 09-08-2009, 10:44 AM Thread Starter
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Problem with Rear Cobra Brake Installation

Well after two years of sitting in boxes I finally got around to tearing the rear end down on my coupe and installing the rear axles and brakes. The axles are Moser's and I ordered them for a 95 GT and had the ABS rings and 3" ARP studs installed. I also ordered the FMS kit to install the rear brakes that came with the 11.65" rotors, dust shields, and axle brackets. I installed all of this and then decided I would go to Autozone and buy the caliper brackets for a Cobra instead of grinding on the stock GT units as they had some slider issues. For the sake of keeping all the bracket terminology straight lets say that the caliper bracket is the bracket the caliper bolts to and that the axle bracket is the bracket that bolts to the axle flange.

I measured the distance from the back of the rotor face (installed a couple of nuts on the wheel studs to clamp the rotor down to the axle flange) and the front face of the axle bracket. This came up to an average of 0.8125". I pushed the axle flange all the way in and and then pulled it all the way out and it moved about a 1/16" total travel. Here is the problem, I cannot install the new caliper bracket as the back rotor face makes hard contact with the opposing face of the caliper bracket. Another way of saying it is the rotor is too deep and it hits the caliper bracket. After using a set of mics and calipers to measure everything with the only solution I can come up with is to mill about 0.125" off of the mounting bosses on the caliper brackets.

I went to my dad's shop back in Oklahoma this weekend and measured the caliper brackets on my T-Bird (has the Cobra rears on it and the entire caliper and caliper bracket came from FMS) and they are within 0.015 of the ones I got from Autozone.

The only thing I can think of is that the new axles are just that much shorter. Has anyone else run into this and does it sound like I am on the right track to solve my fitment issue? I mean I could run a 0.125 spacer behind the rotor but I do not want my tires any further outward.

Thanks,

Darren


'83 5.8L TKO'd T-Bird on the bottle
'93 5.4L Mustang coupe that beat your mom's LTD

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post #2 of 43 Old 09-08-2009, 11:13 AM
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Sounds like a lot of variables...can you not just grind a little on the bracket?(thats what I had to do).

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post #3 of 43 Old 09-08-2009, 11:26 AM Thread Starter
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One of the reasons for buying the new Cobra specific caliper brackets was so I would not have to grind any clearances where the rotor passes through the bracket. Obviously this changed but if I have the bosses milled then there is no structural change in the bracket in the area a lot of people seem to have concerns with. The bosses are pretty thick, around 0.75".

I can see why some people have had issues in the past with using the GT brackets but using all Cobra specific parts I thought I had it made. The other things was I was seeing if anyone else has run into this with swapping out axles. I guess I am just trying to make sure I am not the only person this has happened to and something else is really wrong.

Darren

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'93 5.4L Mustang coupe that beat your mom's LTD

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post #4 of 43 Old 09-08-2009, 11:35 AM
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I understand your confusing with buying "the right parts"....as I would be too. I used my GT caliper brackets and just ground sensibly away the interferance. I've yet to have any bending/issue's. The pads are also quite aggressive in the rears as well.
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post #5 of 43 Old 09-09-2009, 08:05 AM
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I don't know what-all the various differences are between the axle tube lengths and axle shaft lengths on Foxes and SN-95s, but could it be an issue with your car being a Fox and the brakes being designed for SN-95s?
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post #6 of 43 Old 09-09-2009, 08:45 AM
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I also have mosers and rear cobra brakes. I used washers when mounting up my caliper brackets to get the rotor perfectly centered in them. I only had to do this on one side. The washers went between the caliper mounting bracket and the bracket that the caliper mounting brackets bolts to(hope this makes sense) I would get a picture for you but its raining outside!

Ross

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post #7 of 43 Old 09-09-2009, 09:28 AM
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Washers on one side here as well.
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post #8 of 43 Old 09-09-2009, 10:01 AM Thread Starter
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I am just the opposite here. If I washer the caliper bracket it will move the bracket outward which will cause even more interference with the inner face of the rotor. I am just going to have a local machine shop remove about 1/8" from the bosses on the caliper bracket and I believe that will take care of the problem.

Huesmann,
The rear 8.8 housing is the same from '86 thru '98 on the Mustangs. I think the '87 & '88 TC rear housings are the same as well but not 100% sure. The axles in the 8.8's are the same in the 86-93 Foxes and about 0.75" longer on the 94-98 cars. The additional 0.75" in length was to clear the ABS exciter ring on the end of the axle. I installed the ABS and the stock brakes including the rear axles out of a 95 GT in my Fox with the Fox 8.8 housing when I did the brake conversion four or five years ago. I have to have the longer axles in order to keep my ABS functional. Seriously, you knew all this man you have been posting here forever.

I will try and post some pictures at lunch to better illustrate what I am talking about at lunch as the servers here at work block all of that.

Darren

'83 5.8L TKO'd T-Bird on the bottle
'93 5.4L Mustang coupe that beat your mom's LTD

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post #9 of 43 Old 09-09-2009, 11:06 PM Thread Starter
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Pictures...Finally




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post #10 of 43 Old 09-10-2009, 08:07 AM
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Quote:
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Seriously, you knew all this man you have been posting here forever.
LOL, but I haven't even owned a Fox for over 10 years. Who can keep track of it all?

So are you gonna have to grind the boss down on both sides of the car?

If'n you'd rather not grind the boss to bring the bracket closer, why don't you just use your Fox-length axles and use washers to space the backet out further as necessary?

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post #11 of 43 Old 09-10-2009, 08:39 AM Thread Starter
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If I use the Fox length axles then it would move the axle flange inboard an additional 0.75" and I would loose my ABS. If anything I need an axle that is 0.125" longer to keep from milling the bosses on the caliper brackets. Bigger problem is I sold my Fox five lug axles just the other day so that option is gone.

Darren

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'93 5.4L Mustang coupe that beat your mom's LTD
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post #12 of 43 Old 09-10-2009, 10:05 AM
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Can you measure the axle length? It sounds like Moser sent you axles that are too short.

--Vince

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post #13 of 43 Old 09-10-2009, 03:47 PM Thread Starter
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I would but they are already installed in the rear end (rear gear oil back in it) and have ARP 3" studs pressed in and new ABS exciter rings pressed on them. With all that I doubt they will exchange them and in all honesty the 1/8" they moved inward may keep the rears from rubbing the already trimmed fender lip under cornering.

Darren

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post #14 of 43 Old 09-10-2009, 07:04 PM
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In that case all you can really do is double (triple) check your measurements and then mill the brackets accordingly.

--Vince

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+ Tremec 3550, D&D shifter, 3.73:1 gears, & TrueTrac differential
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post #15 of 43 Old 09-10-2009, 11:25 PM
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Darren,

You can measure the axle length with the axles installed. Put a carpenter square on the wheel flange of each axle. Use a tape measure to measure the distance between the squares. Assuming you have a 28 spline differential subtract 0.75" from this length for the differential pin and then divide the result by two. That will give you the average length of each axle.

Whenever I order axles from Mosier, I always give them dimensions for every aspect of the axle. If you order the axle by application, you run into the problem of the accuracy of their data.

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post #16 of 43 Old 09-11-2009, 08:09 AM
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How are you running ABS on a Fox, anyway?
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post #17 of 43 Old 09-11-2009, 09:44 AM
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I have found that there seems to be some slight axle length differences between manufactures of axles. I compared my stock axles with a set of Mosers and a set of Supieriors and they were all slightly different. Just mill the bosses to the right size for your axles and be done with it.
Jim

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post #18 of 43 Old 09-14-2009, 12:52 PM Thread Starter
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Huesmann,
Its not that hard to get ABS on a Fox. Find an SN95 donor car and strip out the booster, MC, Brake lines from the MC to the ABS unit on the front right subframe, get the two pigtails from the main harness to the ABS module, and grab the four sensors from each wheel. One of the engineers from Ford did this years ago and a buddy knows him. I got the wiring diagram from him (its all over the net now) and wired it up. It even has the diagnostics working. This also requires the conversion to the SN95 brakes and having the front hubs with exciter rings and the rear axles with exciter rings.

Parts List for conversion:
https://www.corral.net/images/tech/abs/ABS_parts.pdf

Write up on doing the conversion:
https://www.corral.net/tech/handling/abs.html

Another good site on just about everything but particularly the ABS diagnostics:

http://www.veryuseful.com/mustang/tech/brakes/

Jack,
Thank you! I did not even think about the relationship between the axles and the differential pin.

Darren

'83 5.8L TKO'd T-Bird on the bottle
'93 5.4L Mustang coupe that beat your mom's LTD
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post #19 of 43 Old 10-06-2009, 03:22 PM Thread Starter
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Had the caliper brackets milled and installation is complete. Rotors are centered between the brackets just about perfectly. Had to space the ABS sensors away from the exciter rings but a couple of 10mm flat washers did the trick.

Darren

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post #20 of 43 Old 10-14-2009, 04:45 AM
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I am running Tom's KA 31 spline axles (based in Idaho now, but used to be a SoCal shop which is why I use them) and I had to grind my Cobra caliper brackets clear to heaven. Took a bunch of material off both sides. Seems that a lot if not most of the aftermarket axles are not 100% the same length as the ones they are meant to replace.

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post #21 of 43 Old 10-14-2009, 05:09 AM
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31 spline differentials use a larger diameter pin than 28 spline differentials. This effectively makes the 31 spline axles longer, since there is a larger diameter pin pushing them apart. When ordering 31 spline axles, you must compensate for this and get them with a slightly reduced length compared to a 28 spline axle. This is why I always order axles by physical dimensions, not application. I have yet to find any axle vendor that does everything dimensionally correct on them.

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post #22 of 43 Old 10-14-2009, 05:56 AM
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Well that certainly makes sense. I've got 31's in mine and used a combo of grinding really good AND some spacers/washers.
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post #23 of 43 Old 10-14-2009, 01:19 PM
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Quote:
Originally Posted by Jack Hidley View Post
31 spline differentials use a larger diameter pin than 28 spline differentials. This effectively makes the 31 spline axles longer, since there is a larger diameter pin pushing them apart. When ordering 31 spline axles, you must compensate for this and get them with a slightly reduced length compared to a 28 spline axle. This is why I always order axles by physical dimensions, not application. I have yet to find any axle vendor that does everything dimensionally correct on them.
That is interesting, makes sense. Thanks for that bit of tech Jack, I learn something new every day!

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post #24 of 43 Old 10-15-2009, 02:18 AM
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Maybe you should post bigger pictures...

post #25 of 43 Old 10-15-2009, 06:12 AM
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When dealing with measurments such as .XXX, i'd say a large detailed picture is warranted.
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post #26 of 43 Old 10-15-2009, 02:45 PM Thread Starter
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Lima_Xray,

Take your post and shrink it up so I don't have to look at it. There is sooo much space in it due to it lacking any kind of technical data or valuable input that it is blinding my eyes.

Darren

'83 5.8L TKO'd T-Bird on the bottle
'93 5.4L Mustang coupe that beat your mom's LTD
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post #27 of 43 Old 10-15-2009, 02:54 PM
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post #28 of 43 Old 10-15-2009, 10:23 PM
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Quote:
Originally Posted by Jack Hidley View Post
31 spline differentials use a larger diameter pin than 28 spline differentials. This effectively makes the 31 spline axles longer, since there is a larger diameter pin pushing them apart. When ordering 31 spline axles, you must compensate for this and get them with a slightly reduced length compared to a 28 spline axle. This is why I always order axles by physical dimensions, not application. I have yet to find any axle vendor that does everything dimensionally correct on them.
Those are very good points.

The interesting thing is that based on this you would expect that his axles would have been too long. But that is not the case, they were too short.

Hmmm.....


--Vince

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+ Tremec 3550, D&D shifter, 3.73:1 gears, & TrueTrac differential
+ EVM watts & 3-link, Homemade LCA's, & Koni SA's
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post #29 of 43 Old 10-23-2009, 09:27 AM
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Quote:
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[
I'm working through the same scenario...I had to mill off the mounting boss to get adequate clearance. I'' then shim to get the correct rotor centerline. I had not notice the ridge inside the bracket though...I'll have o take another look, I'm having interference with the new pads fitting over the calipers, the weird thing is that the had fit fine before with my 95 axles...I have pic of my brackets etc. HERE

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post #30 of 43 Old 10-23-2009, 10:37 AM Thread Starter
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The Cobra rear pads are thinner than the GT/V6 pads. This is to compensate for the thicker Cobra rotors. Most parts stores will show all three as the same pad but that is not correct. Here is a really good thread on this particular subject:

https://forums.corral.net/forums/show...ear+brake+pads

Hopefully this is what you were referring to with your fitment issue.

Darren

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post #31 of 43 Old 07-12-2012, 01:07 PM
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Threadomancy, arise!

Does anyone have a part number for the 98 Cobra rear brake parking brake spring tensioner thingies? Shortly after I installed this setup on my '92, one of them disappeared. As a result, my parking brake doesn't work. I'm going to need to get that fixed to pass inspection.

TIA.

Casey
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post #32 of 43 Old 07-13-2012, 11:45 AM
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You mean the springs on the calipers that crank the doohicky the end of the parking brake cable slots into? I would imagine they are the same as the GT/V6 tensioners.
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post #33 of 43 Old 07-13-2012, 12:27 PM
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Quote:
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You mean the springs on the calipers that crank the doohicky the end of the parking brake cable slots into? I would imagine they are the same as the GT/V6 tensioners.
I don't know if they are the same or not but, either way, I'm having trouble finding a proper name or part number so that I can just order one. I found an image from a Chilton's online but the DPI was too low for me to read the part name. Sad to say, I've never bought my own copy (my buddy in Texas who has a shop had one that we always used).

Edit: Nevermind, my earlier Google-fu must have been weak. I just found a better image, it's called a "return spring".

Last edited by aurdraco; 07-13-2012 at 12:34 PM.
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post #34 of 43 Old 07-16-2012, 03:24 PM
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I haven't found a way of getting one of these return springs without ordering a caliper. Does anyone have a passenger side return spring they can send me from a busted caliper? It would be greatly appreciated.
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post #35 of 43 Old 07-16-2012, 04:06 PM
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Use a vise or a pair of vise-grips to hold the attaching point/ends of the spring together. Be careful, it can come loose-hurts like a bitch when it gets you, ask me how I know. When you get the spring compressed, use a strong tie strap to hold it together. After installing on the caliper, cut the strap. There may be a Ford tool for this but I've never seen it.
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