lbhsbZ Posted February 18, 2007 Share Posted February 18, 2007 I couldn't bring myself to buy Ross's $500 hubs and the rest of the stuff needed to do the cobra upgrade, and I'm in the brake business, so I picked up some 300ZX hubs, took some measurements, and hit the rotor spec sheets. I found one that is almost perfect. Almost perfect means that it doesn't need to go to a machine shop to make it fit, its readily available, relatively cheap, and all the dimensions are pretty close to perfect. I wanted something that I can go to the parts store and buy whatever replacement parts I needed. Here it is: The rotor is from a Lincoln Aviator. 13" diameter, and the pilot hole is about 0.5mm larger than the pilot on the back of the 300 ZX hub. No problem, I welded a small bead around the hub pilot and turned it down to perfect....I'll never have to touch it again. The only thing I had to do was redrill the 5 bolt pattern to mount the rotor to the hub. I used lug studs through the rotor holes and hub lug holes to center everything, then used a transfer punch to mark the new holes and drilled them with my battery drill (it wouldn't fit on my drill press). Now to make the caliper fit. I toyed with the idea of making a bolt on bracket, but the bracket would have to be pretty big because the existing caliper ears on the spindle interfered with the holes on the new caliper carrier. I would have had to position the caliper about 30 degrees farther up the rotor in order to have everything clear. A larger bracket wouldn't resist the twisting force of the caliper as well as a smaller bracket, so I opted to do it this way. I cut the ears off the spindle, then with lots of measuring and spacers at work, properly located the new bracket (3/8"x1.5" 1018 steel) and Tigged it on. I did some test samples on the welding with another strut I had and cut it up to verify proper penetration. this is about the thickest material I've ever had to make a structural weld on, so I did a few practice runs first to find the proper settings and technique. I was most happy with 180 amps on my little TA185 welder. One of the problems was distortion of the bracket after/during welding. The first weld didn't upset the alignment of everything. When I flipped it and made the second weld, the bracket pulled toward the second weld and hit the rotor. I ran a second pass over the first weld and it pulled the bracket back straight....this was a frustrating lesson to learn, but I'm glad I figured it out. I'd like to add gussets, but I'm scared that the welds will misalign my bracket again. I've got to talk to the engineers at work on monday before I go screwing it up again. My main hurdle with the brakes was making the pieces fit. I plan on using a chrysler aluminum 1 1/16 bore cylinder (same bore size as the cobra master) and also cobra rear calipers. I have an adjustable prop valve that I can use to limit pressure to the rears, but it shouldn't need too much limiting, as the rear rotor will be slightly smaller than the cobra rear rotor. How'd I do? Quote Link to comment Share on other sites More sharing options...
Cal Poly Zmanaustin Posted February 18, 2007 Share Posted February 18, 2007 I love it when a plan comes together. Quote Link to comment Share on other sites More sharing options...
LS1 240Z Posted February 18, 2007 Share Posted February 18, 2007 you think those front rotors would work without spacers with the toyota front calipers? Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 19, 2007 Author Share Posted February 19, 2007 I don't think so, the rotors are 6mm thicker than the 4 runner vented rotors so they probably wouldn't fit inside the calipers. BUT, there's always the landcruiser calipers, which use a much thicker rotor. I don't have the thicknesses off the top of my head, but the problem you'd run into would be once the pads wear more than 60% or so, the only support would be from the pins, which would be bad. I'll check on monday, I've got another set of struts that I haven't cut up yet. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted February 19, 2007 Share Posted February 19, 2007 I like home-made solutions. Great job! When I was putting the C5 rotors on, the very first rotor I experimented with had the bore slightly too large (machining mistake), so it was not a tight fit. I took a center punch and peened just next to the edges of the center bore in four equally spaced locations. It allowed the bore to fit tightly over the hub and remained perfectly centered as well. Quote Link to comment Share on other sites More sharing options...
Kennysgreen280zt Posted February 19, 2007 Share Posted February 19, 2007 that works pretty slick. how thick are the rotors? Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 19, 2007 Author Share Posted February 19, 2007 Rotors are 25mm thick...same as the Cobra rotors. The only difference is the offset and the vanes. The cobra rotors have directional vanes, the lincoln aviator rotors have radial vanes. But the aviator rotors have more vanes than the cobra rotors do. I plan on building some proper brake duct registers that will bolt onto the spindles, so I think I'll be able to keep cooling under control. I plan on this car going 160+ on the long straights in Tecate and Tijuana, which are very hard on brakes...we'll see. I'll put a parachute in the back just in case..LOL. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 19, 2007 Share Posted February 19, 2007 One of the problems was distortion of the bracket after/during welding. The first weld didn't upset the alignment of everything. When I flipped it and made the second weld, the bracket pulled toward the second weld and hit the rotor. I ran a second pass over the first weld and it pulled the bracket back straight....this was a frustrating lesson to learn, but I'm glad I figured it out. Don't weld in one long bead. Alternate short 1" backstepped welds on each side (flip the strut over). Don't weld too much (heat and filler). Bevel the joint. http://www.lincolnelectric.com/knowledge/articles/content/distortion.asp Quote Link to comment Share on other sites More sharing options...
blueovalz Posted February 19, 2007 Share Posted February 19, 2007 Excellent link! Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 19, 2007 Author Share Posted February 19, 2007 John, I'm familiar with backstepping, I did the welds in 3 sections on each side. I did the one end, then the other, then the center, flipping the parts and alternating sides between each weld. Every time I made weld on the front side, it pulled the bracket. I had to make a partial second pass on the backside to pull it back straight. Thats a good link though. Miller has some excellent information on thier website as well, as does Hobart. Every amature welder should read up on these sites....there is a lot of helpful information out there. Quote Link to comment Share on other sites More sharing options...
JustinOlson Posted February 19, 2007 Share Posted February 19, 2007 Napa information on the aviator rotors. Item#: UP 880166 Price: $76.49 tax and shipping not included Disclaimer: The stated price may vary from the in store price and may change at anytime. Attributes: # of Bolts:5 Bolt Circle Diameter:4.5" Brake Rotor Type:Rotor Discard Thickness:1.043" Height:2.290" Outside Diameter:13.000" Vented / Solid:Vented Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 19, 2007 Author Share Posted February 19, 2007 If anyone else wants to do this, you can get all the parts from me. (I work for a brake parts manufacturer). I can get the rotors for less than 1/2 that price. Quote Link to comment Share on other sites More sharing options...
JustinOlson Posted February 19, 2007 Share Posted February 19, 2007 Can you get cobra calipers for cheap? Justin Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 19, 2007 Author Share Posted February 19, 2007 I can do the cobra calipers with brackets for about $150 each, brand new, but it will take me a couple weeks to get them. Pads are another $20 or so for street pads, and $60 for entry level track pads. I also have PFC and Hawk race friction. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted February 19, 2007 Share Posted February 19, 2007 Are these rotors ON the car at this time. I'm curious about the rotor offset and where the rotor ends up on the inside of the rotor adjacent to the lower contorl arm (specifically, the area between the ball joint and the rotor. On my rotors it was so close that at full droop, the two (rotor and CA) cleared well enough (about .200"). but once the suspension was compressed to normal ride height, the two made hard contact. Just a heads-up of this in case you've not looked into it yet. Factors to consider that may help or hurt here: My measurements from the outside face of the wheel mounting flange (where the wheel actually touched the hub when bolted on), to the inside face of the rotor (that face that faces the control arm and ball joint) is 3.060" on my set-up. When I ran the '87 Supra rotors on the front (12"), I still had this problem (but much less severe), but because the rotors were only 22mm, the interference was much less. My GUESS is that if you exceed 2.75", then you may need to check for this clearance issue BEFORE you drive the car. It will not be obvious during assembly because of the full droop relationship. ALSO, if you use the roll-center spacers (mine are 1"), this will also close this gap up as well because with these spacers, the spindle is moved inward (or you could look at this as the control arm is moved outward in relationship to the spindle) about 1/4" due to this spacer. Thus, the spacers will agravate this problem as well. Lastly, I used four piston calipers which required lots of space between the rotor and the wheel spokes. To gain this additional spacing I used the thick-flanged 280Z hubs (1" flange), BUT the C5 rotors only have .560" step (or offset) between the flange and the rotor (which appears to be a lot less than your rotors have). Lastly, the lower the car's ride height, the worst this issue will be. So take all of these factors into account on this project. Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 19, 2007 Author Share Posted February 19, 2007 Hmmm... good point. I kinda eyeballed it and it looked like it would clear fine. Didn't think about the bump steer spacers though. I'll have check it out tonight. Damn, I thought I had it for sure. Leave it to a ford guy to pee in my Koolaid Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 19, 2007 Author Share Posted February 19, 2007 Ok, just measured things up. The rotor height is 2.29", and the hub thickness is 0.67", bringing the total hub face to back of rotor distance to 2.96". BUT, you used 280 hubs. From what I've read, the 300ZX hubs are offset another 3/4" outward....so my 2.96" is equal to your 2.21", provided that the thickness of the hubs is the same. Here's hoping. Quote Link to comment Share on other sites More sharing options...
V8_DatZun Posted February 19, 2007 Share Posted February 19, 2007 you say you can get calipers cheap.. what about 280zx calipers? can you check on a price for them and racing pads Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 20, 2007 Author Share Posted February 20, 2007 you say you can get calipers cheap.. what about 280zx calipers? can you check on a price for them and racing pads No, I said I could get rotors cheap. The core charge on the calipers is what kills the deal most of the time....but here it is. $35 each for rebuilts, with a $20 core charge. So $70 for the pair if you send me your old ones back, or $110 if you keep your old calipers. I also have seal and boot kits so you can rebuild them yourself for $5 each. Unfortunatly, I don't have any race pads for these calipers....the best thing I've got is an Axxis (PBR) Deluxe pad, for $35. Quote Link to comment Share on other sites More sharing options...
lbhsbZ Posted February 20, 2007 Author Share Posted February 20, 2007 SWEET! I bolted up a ball joint and control arm and I've got 1/2" of clearance with the arm in the full compression position (limited by the ball joint). Quote Link to comment Share on other sites More sharing options...
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