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Thread: Rear Disc Conversion Question

  1. #1

    Rear Disc Conversion Question

    I was talking to a buddy at work about this next mod/idea and he thought I should weld the bracket onto the housing itself. I was going to follow this thread more or less and actually run the parking brake since my truck is a DD.

    http://www.toyota-4runner.org/3rd-ge...on-pt-1-a.html

    Seems like he had a solid setup but I did not like the idea of washers in a final install. I was going to tack another 1/4" or 3/8" plate beside the 1/4 and grind it down to where it was spaced correctly without the use of washers.

    Lots of guys that have trail rigs just use pre-made brackets but they all use brakes designed for a much heavier vehicle whereas mine is almost stock.

    So my idea (since I have a non-abs axle) is to weld a 3/8" bracket directly to the housing with gussets to support the force the caliper places on the bracket. This should be safer and more effective. In addition after looking at the original caliper mounts on the Mustang GT this welded bracket should mimic the mount fairly well.

    Another thing that I noticed is that from a fat thumb observation the fact that I need to leave room for the nuts to be removed in the future should place the bracket in almost the perfect location to be a shimless bracket.

    Like the OP from 4runner.org I went with Mustang GT calipers ($40 out of the salvage yard) and I just scored Brembo 25200 94 Montero Rotors for $39 for the set.....and free shipping. So financially I'm doing fairly well. Here are some pics just to give a reference.

    My non-abs axle (which for once will make things easier)


    My mustang GT calipers with Toyota steel brake lines already installed (they were a perfect fit on the banjo fitting)


    Thoughts and/or comments? I will be primarily be working on the Monstaliner still for the rest of the week but I have a spare housing to which I can test fit the bracket to the housing so that when I go to install the calipers I simply line them up and drill the holes.
    98 3rz 4x4 5spd- Monstalined, 99 Talls, 4.30 E-locker, Extra Lights
    In Progress:
    Tundra/Rear Disc Brakes w/parking brake
    Roof Rack/Rear Ladder
    Sliders
    1st Gen Rollbar Shelf

  2. #2
    I was going to do this with the 4 pot stock front calipers, but figured it was more work than it was worth. Especially with the parking brake solution. It is still something I'd like to develop though, maybe when I have a bit more cash to spend prototyping it.
    2005 Lexus LX470 - Stock for now...

    1998 Toyota 4Runner SR5 V6 4x4 + a bunch of goodies. Lifted, Locked, Illuminated and Armored. Winner,"Best Offroad Truck" - 2010 Pismo Jamboree. It's been upside down and still drives me to work.

  3. #3
    Quote Originally Posted by Seanz0rz View Post
    I was going to do this with the 4 pot stock front calipers, but figured it was more work than it was worth. Especially with the parking brake solution. It is still something I'd like to develop though, maybe when I have a bit more cash to spend prototyping it.
    I was in the same boat as you till I was sitting in the salvage yard looking at the setup on the mustang. Their parking brake setup should be really easy to mimic. It is a simple Y pull design if I am not mistaken. I probably should have pulled the ebrake cable and just bought the system but I'm sure I can find one if needed. The question is how much tension/play will be necessary to work on our setups. So here are pics that might help the setup take shape.



    The force is exerted by the cable forwards through the caliper so the cable either has to be run under the axle tube.



    Relative placement (or the best I can do with what I have at the moment). So the cable would run very differently. I think taking the brackets off the back and tacking them on the front would give the ability to figure something out. Parking brake pulleys might help?

    I took a few pics of our stock setup just to compare and put everything out there and it's quite different but with a little work I think it would work quite well.




    So ours is a push pull but at least the main cable comes down on top of the center of the axle. Now it's just a matter of routing the cable reliably to that location.
    98 3rz 4x4 5spd- Monstalined, 99 Talls, 4.30 E-locker, Extra Lights
    In Progress:
    Tundra/Rear Disc Brakes w/parking brake
    Roof Rack/Rear Ladder
    Sliders
    1st Gen Rollbar Shelf

  4. #4
    I've seen a couple of conversions through the years. I built a 14 bolt with a Detroit locker on my last truck and considered doing a disc swap. The big caliper to use was the Cadillac El Dorado as it was appropriately sized and had a mechanical parking brake. I don't have a huge need to discs on the 4Runner but it would be cool. I'm looking forward to see what you come up with. A before and after weight savings would be nice to know as well.

  5. #5
    I have seen more third gen rear disc brake conversions lately. I see a popular combination uses Mustang calipers and Montero rotors on a custom bracket.

    Here's another iteration, Toyota rotors and calipers on a custom bracket:


    People generally struggle to get the pedal modulation to feel right.

  6. #6
    On the full size Chevy's it was manditory to use a proporitioning valve. Not a huge deal but it did add cost to the project. It did however allow adjustment to make everything operate perfectly.

    I know I've seen some caliper ripped off their mounts while wheeling. These are usually aftermarket or DIY setups. In a DD it's one thing that would concern me, especially in an accident. If they ripped off it would be bad news. The picture above might work but looks half the thickness I'd want.

  7. #7
    When I was looking at doing mine, I was considering 3/8" thick for the mounting brackets, and using 3 of the 4 bolts on the axle. That right there made it a bit thicker than I could really cut with what I have on hand. Sending it to get laser or plasma cut made it too expensive.

    For me, brakes are the one thing that should never be anything less than 100% perfect.
    2005 Lexus LX470 - Stock for now...

    1998 Toyota 4Runner SR5 V6 4x4 + a bunch of goodies. Lifted, Locked, Illuminated and Armored. Winner,"Best Offroad Truck" - 2010 Pismo Jamboree. It's been upside down and still drives me to work.

  8. #8
    I'm with ya on the 100% part. Even if it was stout if the pedal didn't feel right I'd be pissed. Stuart has a plasma and there are a couple of shops around here that do drop in work. I'd pay their hourly instead of trying to wing it myself.

  9. #9
    Quote Originally Posted by paddlenbike View Post
    I have seen more third gen rear disc brake conversions lately. I see a popular combination uses Mustang calipers and Montero rotors on a custom bracket.

    Here's another iteration, Toyota rotors and calipers on a custom bracket:


    People generally struggle to get the pedal modulation to feel right.
    I am doing the mustang/montero setup. The way I figure it the OP that I am following did the Tundra brake upgrade first so when he did disc in the rear he ran out of pressure (it's a theory at least) creating too soft of a pedal. I want to do the rear disc setup to see whether I really need the bigger brakes up front. I think converting the rear will probably be all I need (at least for the time being).

    Quote Originally Posted by Seanz0rz View Post
    When I was looking at doing mine, I was considering 3/8" thick for the mounting brackets, and using 3 of the 4 bolts on the axle. That right there made it a bit thicker than I could really cut with what I have on hand. Sending it to get laser or plasma cut made it too expensive.

    For me, brakes are the one thing that should never be anything less than 100% perfect.
    Right now I have access to a torch and welder capable of 3/8" so that's what I'm going to try and do. I want to truss it a little as well but I agree that the DIY kits are too fragile. I think a 3/8" with a truss or two should be pretty bulletproof. That's what the mount on the mustang was.

    For the parking brake I think I am going to go grab a mustang setup and see if I can route it up and out of the way to simplify the parking brake. It might just be the best answer to a simple problem.
    98 3rz 4x4 5spd- Monstalined, 99 Talls, 4.30 E-locker, Extra Lights
    In Progress:
    Tundra/Rear Disc Brakes w/parking brake
    Roof Rack/Rear Ladder
    Sliders
    1st Gen Rollbar Shelf

  10. #10
    FWIW, the Tundra brake mod is really only good at preventing fade and the inevitable warping of rotors. I haven't compared piston sizes, but I suspect they are very very close in size.

    To avoid locking up the rear brakes, I think a proportioning valve is a requirement. If you feel adventurous , you could go with an LSPV from a later 4Runner.

    Oh, and make sure you get the bleed screws at the top. If not, bleeding will drive you up the wall...
    2005 Lexus LX470 - Stock for now...

    1998 Toyota 4Runner SR5 V6 4x4 + a bunch of goodies. Lifted, Locked, Illuminated and Armored. Winner,"Best Offroad Truck" - 2010 Pismo Jamboree. It's been upside down and still drives me to work.

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