onephatz Posted December 14, 2011 Share Posted December 14, 2011 Background: So I wanted to get better rear brakes on my car but didn't want to spend most of my paycheck on an off the shelf solutions already in play. The Modern Motorsport bracket looked really nice but resulted in less than bleeding edge braking performance. The 240sx caliper just wasn't big enough to lock the rear tires when sized to the Toyota 4x4 front upgrade. Brake pad compound could have been changed or other adjustments made but I wanted a rear caliper/rotor that would be overly large and need to be backed off with a proportioning valve of some sort. Result: Parts 84-86 300zx rear n/a calipers and pad brackets 84-85 300zx rear n/a rotors 84-86 300zx rear n/a pad one set of custom brackets new brake lines Now I'll go thru the process and show the results. I'll also post up the autocad DWG file needed to have it cut out. Step one, have the bracket cut out at your local waterjet using 1/2" steel. Chuck the top piece into a Mill and cut off 1/8" off the ears to set the pad bracket back far enough to clear the rotor. the bottom one is for the passenger side. as with most things in life it doesn't have to be perfect it just has to be close. I designed the top and bottom pieces so that the top of the bottom piece should line up exactly with the top of the top piece. clamp it together and weld it together. try and align the ears center to the lower piece but as before "close" is good enough. make sure to weld both the top and the bottom. How it looks attached to the car without the rotor. clearance between rotor and bracket. Clearance between rotor and pad bracket. as you may note, the bracket could have come back another couple of thousandths to center the rotor in the slot. Two thoughts. First, if this is a diy project cutting off 1/8" (0.125") is way easier than cutting off 9/64". second, as stated before, doesn't have to be perfect, just has to be close. Pad placement. With caliper. Now this is just a start, I'll update this thread as I get more data and more info on brake hoses and CAD files ect. Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted December 14, 2011 Share Posted December 14, 2011 (edited) If you make any more in the future to help with welding have the water jet guys cut 2 additional holes in each part of the bracket. If you make these alignment holes close to a diameter of a drill bit you can use them to line up the two pieces in perfect alignment making your job welding will be much easier. Edited December 14, 2011 by h4nsm0l3m4n Quote Link to comment Share on other sites More sharing options...
johnc Posted December 14, 2011 Share Posted December 14, 2011 And don't use 1/2" thick steel. You're not stopping a 747. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted December 15, 2011 Share Posted December 15, 2011 Looks GREAT! I am not familiar with the caliper you used, but I used a Maxima caliper and oriented it hoizontally as you did. Be prepared for trouble when you bleed this system, just as a heads up. You may be fine, but if you can't get a firm pedal, remove the rotor and bleed it while holding it at a variety of angles, using a block of wood as a mock-rotor, in order to make sure all the air comes out. The air will rise to the top. Since your bleeder screw is at the top, you should be fine, but just in case be prepared to flop it around a little. Also, watch for brake line to half-shaft clearance when you go to full squat of your suspension. Mine is close and may be a problem under hard accelleration, and I may have to move the bracket that holds the hard line at the frame rail. I also had trouble with the e-brake cable hitting the strut tube and the mustache bar and I had to spend a lot of time working to get the angle just right. See my Hydraulic Drifting Handbrake thread from earlier this year for similar arrangement. Really nice work. You can PM me if you run into any snags. Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted December 15, 2011 Share Posted December 15, 2011 (edited) Ive seen the late S130 brakes (essentially the same caliper as the z31, and the same brake pads) run in both the 12 o clock, and 3/9 o clock positions and am curious. The factory mounted the calipers at the 3 and 9 o clock positions. This is may be a more ideal orientation since it locates the bleed screw opening closer to highest point but locating it only horizontally. I run my brakes in such a setup and feel like I have trouble getting ALL the air out of the system without having to raise the caliper manually. I'm in the process of redesigning my brackets and wish to find a better orientation for the brake caliper. The 12 o clock position orients the bleed screw so it points straight up. However, is the 12 o clock position really the best orientation for these calipers? I dont think so since, if you look at the caliper from the rear (picture attached), it seems like the top of the hollow cavity behind the caliper piston (approximated in blue, note: this is outer wall, add 2-3 mm of wall thickness placing the actual inner wall a little lower) is still higher than the bleed screw opening (approximated in red). Wouldnt this area trap, or at least make it difficult for air to easily exit, the caliper out the opening? I personally was thinking perhaps clocking the caliper just less than 3 o clock position, maybe even as far as 45 degrees. This would point the bleed screw upward but not significantly raise the rest of the caliper to sit higher than the bleed screw opening. The air should naturally want to flow right to the opening and be much easier to bleed. Am I missing something? Edited December 15, 2011 by h4nsm0l3m4n Quote Link to comment Share on other sites More sharing options...
onephatz Posted December 15, 2011 Author Share Posted December 15, 2011 All good responses. This has been a first iteration and I'm sure there will be several versions as I go along. I was actually thinking about how to align the two pieces by having a v cut in the top to line the two pieces up. I'm not sure why most calipers are oriented as they are but it might have something to do with the internal structure of the caliper that facilitates bleeding the system. I haven't got the system completely plumbed up yet but as soon as I get the hose hooked up that clears the axles, wheels, and swap bar I'll post that up as well. John Yes. you are correct that 1/2" steel is a bit of an overkill but, to make the geometry easy to manufacture and assemble, 1/2" steel was the easy way out. you use a single sheet of steel and only have to machine strait cuts off the back piece to get the geometry that works. unless you know of a better way to get the setback from rear face of the bottom piece, the simplest solution that I know of is to take a overly large piece and cut it down. let me know what you think jesse Quote Link to comment Share on other sites More sharing options...
z240 Posted December 15, 2011 Share Posted December 15, 2011 (edited) It appears to me that no matter what stock thickness you use, (as long as its at least twice the depth of the relief you cut in the upper piece to keep enough for some strength), that you retain the exact caliper mounting face geometry/location as you have now. Stare at this doctored picture and imagine what happens if the stock is 1/2 the thickness in the picture, but built and attached the same way. The arrows point to the two reference surfaces involved. Seems to me that you remove material from the front (wheel side) and back (diff side) of the stock, that the position/location of the #1 arrow does not change.... You're simply positioning the caliper mounting face on the two upper ears back (toward to diff) from the bracket mounting surface by the depth of the relief you cut. Nothing more. Please tell me if I'm missing something here. I hope its that simple. Edited December 15, 2011 by z240 Quote Link to comment Share on other sites More sharing options...
onephatz Posted December 16, 2011 Author Share Posted December 16, 2011 There seems like there are three "simple" ways of making the attachement. number 1 is the current method using 1/2" material number 2 is the same method but using 1/4" material and number 3 is cutting off 1/16" material from both faces the get the same offset. I chose number 1 for a couple of reasons. first, the pad bracket is held to the hub by two ears. if you start with 1/4" material and cut off 1/8" you are left with 1/8" material left to hold all the braking forces. if using 1018 steel this should be able to take all the load with a factor of safety of at least 4. for some reason I get a little squeamish thinking about what might happen if the tabs bend instead of fail in sheer. I suppose we could start somewhere in the middle at say 3/8" material and go from there but we'll have to see. second, I wanted to minimize the machining time required to make the brackets. if I can make them with one or two passes on one piece, that saves money both in terms of time and equipment. if there is a better way to get the offset of 1/8" I'm open to discussion. also, I can provide a solid model for anyone who has access to FEA software that wants can find out how this responds to load at different thicknesses. Jesse Quote Link to comment Share on other sites More sharing options...
h4nsm0l3m4n Posted December 16, 2011 Share Posted December 16, 2011 (edited) My friend has the same brake setup on his 510. He used 1/8 in. steel, and has sold the kits to many 510 owners with great results. I would consider having the two pieces made out of 1/8" steel, then adding an additional 1/8 in. "spacer" plate in the middle. You can have the same alignment holes put in to jig each piece to the next one. With this design you have the added complexity of twice the welding, but you save yourself the added machining time, your call. As far as material thickness for your design, I wouldnt go with anything more than 1/4". If I had to guess I think the material will fail at the welds rather than where you are doing the machining anyway. You can run an FEA on the part but since you are doing welding you are throwing a lot assumptions into the analysis. Edited December 16, 2011 by h4nsm0l3m4n Quote Link to comment Share on other sites More sharing options...
letitsnow Posted December 17, 2011 Share Posted December 17, 2011 A proper weld should be stronger than the base metal. Post up the dimensions and I can see about plugging it into ANSYS, no guarantees though and probably not till after the holidays as I'm not planning on spending too much time at school. Quote Link to comment Share on other sites More sharing options...
Leon Posted December 17, 2011 Share Posted December 17, 2011 A proper weld should be stronger than the base metal. Post up the dimensions and I can see about plugging it into ANSYS, no guarantees though and probably not till after the holidays as I'm not planning on spending too much time at school. The weld itself is strong, but a welded joint is a stress riser. If failure occurs, it will be at the weld, not the weld itself, as Stepan already mentioned. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted December 18, 2011 Share Posted December 18, 2011 I agree, especially with something as overbuilt as this. With a part with a more reasonable thickness it's not as clear cut. Quote Link to comment Share on other sites More sharing options...
onephatz Posted December 19, 2011 Author Share Posted December 19, 2011 (edited) the link for the PDF of the part with dimensions is. http://finitecell.com/280z/bracket/280z-300zx-rearbracket-cut.pdf the link for the AutoCAD file for the waterjet is http://finitecell.com/280z/bracket/280z-300zx-rearbracket.dwg Also, as a bonus, I was looking around my garage for bolts to work with this thing to make sure it all fit right and found the bolts from my front brake upgrade. It seems that the bolts you remove from the front rotors to install the toyota 4x4 caliper upgrade for vented rotors are the exact right size for a 1/2" thick piece of metal. Not saying it's perfect or even lightweight, but it is mighty convenient. Edited December 19, 2011 by onephatz Quote Link to comment Share on other sites More sharing options...
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