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Guide to 13.1" 4-piston brakes for 1Gs on the cheap

Posted by wortdog, Jun 1, 2005

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  1. wortdog

    wortdog Proven Member

    172
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    Joined Jun 23, 2003
    Champaign, Illinois
    Please read the article through entirely before starting/purchasing anything. This setup has worked well on my car so far. This may work for 2G's as well, but I do not know for sure.

    First, here's a little background on what I did:

    The front brakes on early 1G AWD cars leave a lot to be desired for stopping a 3300lb car and driver from high speed. The later 93+ brakes are a huge improvement, and probably more than enough for the occasional track day and daily driving. I wanted something that would stop the car from 130mph+ everytime with no noticeable fade.

    The first part I got my hands on was a pair of 1G Stealth TT calipers from a friend who had upgraded the brakes on his Stealth. This caliper has a much larger clamping force than stock, but it carries with it the disadvantages of a softer pedal feel and more pedal travel. I knew that since the caliper wasn't going to just bolt up, I had my pick of rotors to use. I naturally gravitated towards OEM style brake rotors, as aftermarket 2-piece rotors are very expensive. I ended up settling on 97+ Mustang Cobra front rotors. They have the same bolt pattern as a DSM and very similar backspacing. They are also very thick and heavy, which is good due to the large amount of heat the rotor can absorb, but bad due to the extra rotating mass. The largest downside to these rotors is that they require a ring to center them on a Mitsu hub.

    Once I had the rotors, it was time to mock things up so I could design a bracket to mount the calipers. I used cardboard(pictured) and then wood to mock up the bracket, and took measurements off of it to make the drawing(pictured). It was immediately obvious that a large wheel spacer would be required during mockup, you'll need to measure it with your particular wheel/rotor combination.

    Now to the actual assembly/fabrication. You'll need:

    2 - Mustang Cobra 13.1" rotors, aftermarket or OEM style (OEM style are $20 a piece from certain online stores)

    2 - 1G 3000GT/Stealth TT 4-piston calipers (~$125 on Ebay if you're lucky, if you get 2G calipers, you'll have to design your own bracket)

    2 - sets of brake pads for above caliper

    1 - 1" bore brake master cylinder, for FWD only, AWD should already have this, some FWD cars will as well. The size of the master cylinder should be cast into it if you're not sure which one your car has.

    2 - wheel spacers

    a plate of metal large enough to cut two brackets out of, 3/8" thick steel or 1/2" thick aluminum will suffice, a little thicker won't hurt

    2 - hubcentric spacer rings -- I used the hightemp plastic hubcentric spacers for fitting aftermarket wheels to Mitsu hubs, metal would be better, but I haven't had any problems with the plastic yet. Baer sells the Track brake kit for DSMs that uses very similar rotors, so they may have metal spacer rings readily available.

    12mm mounting hardware of your choice(if using nuts instead of threading the bracket, make sure to get shear nuts, otherwise the nuts will hit the rotor)



    The first order of business is removing the old stock brakes, which can be quite time consuming. Once those are removed, you can mock up things to measure for the required wheel spacer.

    Next, if using the plastic hubcentric spacers, you'll need to trim them so that they fit tightly inside the rotor, centering it onto the hub. These spacers tend to come in packs of four, so you have some room for error. Metal ones will just be a matter of sliding onto the hub. At this point, you should have the rotor on the hub and centered by the hubcentric spacer ring.

    Making the adapter bracket is the toughest part. The unit in the drawing is inches. I used a band saw and a manual mill to make my brackets, which made things easier. If all you have available is a hand drill or drill press, you probably won't be able to drill the holes accurately enough to allow the bolts to thread directly into the bracket, and it will be much easier to use a nut and bolt at each hole. If you're threading into the bracket, use the drillbit listed on the tap for the final hole size, otherwise start at 12mm. If you do decide to use a nut and bolt at each hole, steel will give you much more room to work with, so keep that in mind when choosing the metal for the bracket. Be sure to trim the bracket such that it fits flush against all of the surfaces that it bolts to, otherwise the caliper will sit at an angle.

    Hopefully, your new brackets will bolt right up. If not, you can slightly drill out the various holes until it does. The bracket is designed to go in between the rotor and the mounting tabs, not on the backside of the tabs(pictured). Before you mount the caliper to the bracket, be sure to put the brake line on first. You can use washers to space the center of the caliper over the rotor, just make sure they are of the same thickness. You'll notice that the brake line no longer reaches its mount on the strut, so you'll either have to fabricate a mount for it or zip-tie the line to the strut. Stainless lines may be long enough to allow the stock mount to work.

    If you have a car with the smaller master cylinder, you'll need to install the new 1" master cylinder also.

    Now its time to bleed the new calipers(along with the rest of the brake system) and install your wheels. You should follow whatever break-in procedure came with your pads/rotors, if any. You will imediately notice a slightly softer pedal, which can be mitigated somewhat by stainless brake lines. The ultimate fix is to swap to a 3/S TT 1 1/16" master cylinder, but that would be the subject of a seperate article.

    At the time I'm writing this, I've put several thousand miles on the brakes, including a couple of autocrosses, and have had no problems at all with them.

    Please note that all of the pictures have the wheel spacer already mounted, the rotor is not that tall by itself.
     

    Attached Files:

    99gst_racer and wret like this.

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