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Thread: 88 XR-7 and 11" brake upgrade :brake booster

  1. #1
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    Question 88 XR-7 and 11" brake upgrade :brake booster

    I was wondering, after doing a search of the past threads, if using the 88 5.0 Mustang GT/LX brake booster with the Cougar master cylinder would be beneficial with 11" Mustang front rotors, calipers and pads? I have the 10" drums in the back and do not plan any changes to those right now. I know the 5.0 fox Mustang (87-93) brake booster is smaller in diameter but longer than the Cougar's or the 2.3 Fox Mustang that came with the 10" rotors. Any ideas what would work best?

    My thinking was that the 10" front rotors got the larger diameter/shorter booster and the 11" front rotors got the smaller diameter/ longer booster?

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    No need to change the booster if the only mod you are making is swapping fro the 10" front brakes to the 11" front brakes. The booster change is basically when you swap over to the SN95 brakes.

    Darren

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    Changing over to the booster to a '93 Cobra booster just makes the car stop with less pressure applied to the brake pedal?

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    Its a little more complicated than that but in a nutshell yes. The booster is sized to the application just like the MC is. For your application they used the same booster for the 10" and 11" brakes.

    Darren

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    The upgrade from 10" front rotors to 11" front rotors requires changing spindles to Mustang spindles.
    Does that mean an change is needed to Mustang struts also?

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    More than likely the 87-93 5.0 Mustang spindles will be what you can source. The 87-88 Thunderbird Turbo Coupe spindles will work as well but are a bit harder to find.

    The difference between the struts is the mounting point to the spindle. The TC or 87-93 5.0 Mustang spindle is narrower at the strut mount versus the other spindle. You can get hardened washers to shim the gap if you want to reuse your existing struts. If you are going to replace your existing struts then get the 94-95 5.0 Mustang struts if the car is stock height or get the 87-93 5.0 a Mustang struts if you have the car lowered more than an inch. Some may say it is not necessary if the car is lowered but they do not understand that the SN95 struts are about an inch longer and will not compress as far as the Fox strut.

    Darren

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    I have fox Mustang spindles and did run T-bird struts for awhile. Like Darren said, you can just make up some spacers. Now I run Fox 'stang Tokico blue's front and rear (Chuck W adapters in rear). I also have Mustang 11" brakes w/Lincoln calipers and a TC rearend w/disks and am currently still running the stock T-bird booster and MC. Pedal is a little "spongier" feeling than stock but it does seem to stop shorter due to the larger rotors/calipers.
    '88 'bird, 1-family owned, original 302 converted to HO, T-5 swap, CHE upper/lower control arms, weld-in SFC's, BBK shorty headers & O/R H-pipe, Dynomax mufflers, fox GT tailpipes, Turbo Coupe 8.8 w/3.73's, 11" front brakes, lowered, Tokico Blue shocks/struts, Chuck W shock adapters and motor mounts, 15:1 rack & PS pump, custom alum. driveshaft, chrome '93 Cobra wheels, Falken tires, 20% tint, close to 190,000 miles!


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    The spongy pedal feel that 50tbrd88 is experiencing can be several things but one thing for sure is that it can be fixed.

    One thing to check is if you are getting full lock up on a panic stop. If you are not you may need to adjust the booster rod tip further out. 1/2 turn on this is a HUGE adjustment. My guess is that you still have air in the lines, water in the brake fluid, or you need a new/different master cylinder.

    The comment with regards to air in the line is one I make due to too many times I have heard that there is no way there is air in the system only to find there is. Power bleeders are the only way to go if you can get your hands on one or just buy one. I know $50 is expensive to some for one of these but I like to stop. I'm always amazed at how we will drop $500+ into a set of cylinder heads to go faster but the brakes get ignored.

    The master cylinder comment is from the plunger seals wearing and the brake fluid bypassing and the pedal getting that mushy feeling. Another problem with MC's is being improperly sized to the application. With the 73mm single piston front calipers and the TC rears you really need to run a MC with a 1" bore like an 85 Lincoln town car. That's just my opinion so do some research first.

    Darren
    Last edited by Aerocoupe; 11-23-2013 at 09:29 AM.

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    One other thing that may or may not be relevant to the OP's situation;

    For those (like me) that have a double adjustable clutch cable, you'd highly benefit from swapping the booster to a Mustang so that you can adjust the firewall end of the clutch cable. If you've got the SN95 brakes up front, it's almost a "must do" thing.
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    Depending on the age of the components, the spongy feeling can also be the result of old flex lines that swell under pressure. On mine, just upgrading to stainless lines made a noticeable difference.....and the rubber ones weren't that old.
    84 COUGAR/88HO, 1.7RRs, performer RPM,700DP, equal length shorties, stainless EXH ,T-5,Hurst pro-billet, KC clutch, 8.8/ 4.10s, line-lok, bla ,bla, bla.
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