87 XR-7 10" to 11" conversion - current plans; advice wanted!

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87 XR-7 10" to 11" conversion - current plans; advice wanted!

March 06, 2017, 10:48:41 PM

Hello Everyone, it's been a few years, but I'm back at it! Getting ready to do the 10" to 11" front brake conversion on my '87 XR-7, and the way I'm starting to source parts from all different vehicles, I'm a little worried I'm going to end up with a "frankenstein"! That said, you all have been tremendous help in the past, so I'm reaching out to you to see if I'm on the right track, or if I need to revise my plans. Here is the current plan:

The Car: 1987 Cougar XR-7 with HO 5.0, T-5, 17" X 7.5" Cobra R rims, TC rear end/disc brake conversion. I haven't done much on the front suspension yet, although I think I replaced the springs with used TC springs at some point in time - didn't make much of a difference in my opinion.

What I have: New slotted 11" rotors for a fox mustang, re-manufactured calipers from a Mark VII, stainless steel brake hoses for a fox mustang, all new bearings.

What I still need: Spindles: I should have my hands on some fox-body mustang spindles by the end of the week. I have sourced a pair from a 1990 Mustang GT.

While I'm at it: I figured it would make sense to do a couple other things while I'm at it. I am planning on installing new struts - but I have some questions. I have read that if you re-use your old Cougar struts with the new mustang spindles, you need to use washers/spacers. I would like to avoid this, and I need new struts anyhow, so I figured that if I purchased struts for the SN95, no spacers would be required. Is this logic sound? I'm looking at purchasing these struts from O'Reilly's: KYB Excel-G Part # 235060 - as it seems to have the most similar characteristics as the replacement cougar struts. I also ordered new strut mounts, but I got mounts for the '87 Cougar, as I figured they would be better suited: MasterPro Strut Mounts - Part # FM1061.
I am also planning on installing a new SN95 style Master Cylinder, as I'm hoping for better pedal feel: BrakeBest Select - Brake Master Cylinder
Part # NMC11349.

Please, let me know if I'm on the right track, or if I'm heading into a disaster! Any advice as to parts, etc. is much appreciated.

All the best

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #1 – March 06, 2017, 10:53:51 PM

Oh, and while you're at it, any recommendations on how to bring the front end down just slightly is much appreciated. Is there any way to also bring the wheels in further? I love the Cobra R's, but don't like how the fronts stick out. Thx!

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #2 – March 08, 2017, 04:15:52 PM

Man, you're still around, cool! I was wondering what had ever happened to ya. Glad to see you still have that beautiful Cat.

Your plans sound good to me...those are all good parts. The SN95 struts are the way to go...they hit the "sweet spot" in almost the same place as our cars.

As for the springs in the front, I had a bad time with TC springs myself (they actually raised the car up). Generally everyone seems to have more faith in SN95 springs. I'm sure someone will chime in but V6 convertible springs seem to be pretty good replacements.

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #3 – March 08, 2017, 06:49:11 PM

Thanks for the info, Eric! I saw you updated your site, and love it. I've used the site as a primary reference over the past 17 years, so thank you for the time, money and effort you put into it, as it is appreciated. I modeled my plans after the info about the brake conversion in your site, but I wasn't sure about the SN95 struts/springs, so thanks for clearing that up. I saw that you're planning on going to the 50th anniversary show up in Detroit - sounds like a good show, I might just have to go too. I think the last good show I was at was CatJam '03!!!

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #4 – March 27, 2017, 09:58:58 PM

Just an update for those that are also contemplating this swap. My parts list is located in the original post to this thread. First off, the swap is definitely worth it - braking power is much improved. I read about some people who used the Mark VII master cylinders, but didn't change the stock master cylinder had complaints of low pedal feel - and I had the same results. (I bought a SN95 master cylinder, but forgot to get the three to two brake line conversion so haven't installed it yet.) Even though I switched over to the stainless brake lines, pedal feel still went down. It's a weird feeling having better brakes but worse pedal feel. Really hoping the SN95 master cylinder fixes it.
While I was at it, I replaced springs and struts with SN95 springs and struts, and am very satisfied with the ride quality - it's a much more sporty ride, and the car doesn't bounce 5 times after every bump anymore! My car was instantly lowered at least an inch if not more (you can see how much room I had in the pic above!), and hopefully I'll post an after pic once the weather straightens up. I really like the stance now, but it's causing my tires to rub on the fenders whenever I hit a bump or brake hard. Now I'm looking at replacing the control arms with a set from a fox mustang to bring the wheels in, and hopefully keep the fender rub from happening. Info on that spin-off project in another post about control arm swaps.

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #5 – March 29, 2017, 12:36:29 PM

So I did the 73mm Lincoln caliper conversion after I had converted my 93 Coupe to the 11" brakes on it and it was the dumbest thing I ever did due to my lack of brake knowledge at that time.

My Coupe was originally a four cylinder car so it had the 10" brakes stock. When I originally did the 11" brake swap I used the stock Mustang GT 60mm calipers. I later swapped them out in favor of the 73mm Lincoln calipers with the Maximum Motorsports stainless steel guide sleeves for the caliper pins and SS braided brake lines. What I did not take into account was the master cylinder differences. The brakes went from a low effort pedal to a high effort pedal and less braking power. This was due to the Lincoln Mark VII having a 1-1/8" bore where my stock MC had a 13/16" bore. The choice I had was to install a Mark VII MC or put the GT calipers back on.

The 4 cylinder and GT's had the same MC so I opted to put the GT calipers back on and get better brake pads which helped immensely. Some of the Mustang guy's have opted to go to the SN95 MC and have indicated good results and better brake pedal feel. I think this is due to the larger piston size of 1-1/16" so this would help with the Mark VII calipers if you have drum rear brakes.

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #6 – March 29, 2017, 06:19:14 PM

I actually did the TC rear axle swap, so I have the rear discs. Does that make a difference?

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #7 – March 29, 2017, 09:42:21 PM

The rear 45mm calipers will require more fluid to actuate them than the slave cylinders on the drum brakes. So with that I would highly suggest that you get a Mark VII MC as you now have a Mark VII spec brake system and that MC was designed by Ford Engineers to go with it. Again, the 95-94 SN95 MC has been used and will work but my guess is that with the smaller 38mm rear calipers and 66mm front calipers is why they went with a 1-1/16" MC on those cars.

Also, I believe the Mark VII MC is SAE threads and will basally bolt up to your car but I cannot remember there. The 79-86 Mustangs do not require the 3-2 conversion like the 87-93 Mustangs but I am not sure with the 87-88 Birds and Cougars. I am pretty sure the Mark VII MC is a straight bolt in on the 83-86 Birds and Cougars but I have not done one so not sure.

I do know you will need to gut the proportioning side of the combination valve and get the plug for it as well as install a manual proportioning valve. I posted a diagram of the stock PV/SV assembly here (post #7):

http://www.foxtbirdcougarforums.com/...php?31037-1987

Also, Maximum Motorsports sells all of this conversion stuff and remember the SVO MC is the same as the Mark VII MC:

http://www.maximummotorsports.com/1-18-1986-SVO-master-cyl-C539.aspx

So my call here would be the Mark VII / SVO MC, gut the proportioning side of the stock combination valve, install a manual proportioning valve, buy some good pads, bleed the hell out of the system which includes property bench bleeding the MC, and then bed the brakes. IF you are not sure what bedding the brakes means then go here:

http://www.stoptech.com/technical-support/technical-white-papers/bed-in-theory-definitions-and-procedures/stock-brake-system-bed-in

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #8 – March 30, 2017, 11:16:47 PM

So, since my Thunderbird still has the stock 10" front brakes, when I upgrade to 11" brakes the 87-93 Mustang 60mm calipers should be fine? What I plan on running is:

87-88 Thunderbird master cylinder (same as 87-93 Mustang GT), already on my car

87-93 Mustang 60mm calipers and 11" rotors

10" rear drum brakes, already on my car

Seems like that should all work together fine.

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #9 – March 31, 2017, 11:32:48 AM

There is no difference in MC's between the 11" and 10" brake cars except the SVO, 1993 Cobra & Cobra R, and the Mark VII. The calipers are all 60mm pistons with the exception of the SVO, 1993 Cobra & Cobra R, and Mark VII. They used different castings with the same 60mm piston diameter to accommodate the difference in the rotor diameters.

Hopefully that answers your question or to put it bluntly you are good to go.

87 XR-7 10" to 11" conversion - current plans; advice wanted!

Reply #10 – April 01, 2017, 03:42:44 PM

Quote from: Aerocoupe;460111

There is no difference in MC's between the 11" and 10" brake cars except the SVO, 1993 Cobra & Cobra R, and the Mark VII. The calipers are all 60mm pistons with the exception of the SVO, 1993 Cobra & Cobra R, and Mark VII. They used different castings with the same 60mm piston diameter to accommodate the difference in the rotor diameters.

Hopefully that answers your question or to put it bluntly you are good to go.

I figured as much. Thanks.