Another take on Disc Brakes - Rear

Builds, refurbishments, restorations, upgrades

Postby yitzac1990 » Wed Sep 11, 2019 10:31 am

DISCLAIMER: This post is for informative purposes only, do this work at your own risk. I am not responsible if you do this and your brakes fail and cause injury or damage to anyone or anything!

I just completed my rear disc brake swap last night (front still in the works) and wanted to post what I did. Here are the parts I used:

caliper - rear caliper and pads from S13 240SX (1989 - 1994)
rotor - rear rotor from 1995 Isuzu Pickup

I will jump right in:

First, you have to get the rotors machined. The center bore needs to be opened up to 4.2", and the lug holes need to be opened up to 0.609"

Second, the axle hub needs to be slightly ground or machined down. I was refurbishing my axles (new seals, axle nuts, lock washers, grease) so I already had the axle shafts out of the housing. I took them to a machine shop, along with one of the rotors and told them to machine down the hub enough to fit into the rotor "hat". You could also use an angle grinder to slightly grind down the outer diameter. This is the surface I am talking about, specifically:

Image

Third, the caliber brackets needs to be made. I have attached the PDF of the bracket, and I will attach a STEP file when I have it made up. CAUTION: THE ATTACHED PDF SHOWS THE BRACKET AT A SCALE OF 3/4! DO NOT JUST CUT IT OUT AND TRACE IT ONTO YOUR METAL TO BE CUT, IT WILL NOT BE THE CORRECT SIZE! It is to be made from 0.25" (1/4") steel plate. I was able to cut out each bracket using just an angle grinder, but obviously having a machine shop CNC it would be way nicer. I printed out the drawing at a scale of 1.0, cut out the shape, traced it onto the steel, and got to grinding/drilling. It came out very accurate the first time and slipped right on!

Forth, attach the bracket to the axle. I used new, shorter nuts on the backplate studs, still using lock washers. very simple and works great. that basically makes this a "bolt-on" disc brake swap :)

Fifth, install rotor and caliper. Do this as you would any other vehicle, however you need to come up with a spacer of about 0.28" between the caliper and adapter plate. I used Qty 4, M10 washers and it worked perfect. NOTE: I actually installed the calipers backwards; driver caliper on passenger side, and passenger caliper on driver side. This was so the e-brake attachment was behind the axle, instead of in front.

Sixth, plumb your new brake lines, however you see fit for your specific application, and bleed brakes!

Why did I choose that caliper?
A: because i come from the world of drifting, where nissan 240sx's are plentiful and cheap. I got a pair of calipers from a friend for $40 and got some rebuild kits for about $5 each. These calipers also have a built-in parking brake function, which I will work on adding at a later time.

Why did I choose that rotor?
A: because it was similarly sized (thickness) to that of a 240sx rear rotor, so I knew the caliper and pads would fit on it. The outer diameter was also not too huge compared to other rear rotors. It also had the correct lug pattern, obviously.

Good Luck!

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Postby yitzac1990 » Wed Sep 11, 2019 10:47 am

Here I have attached a 1.0 scale PDF of the bracket (if you want to print it out, cut it out, and trace onto metal, like I did). If you want the STEP file, please PM me.
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Postby r1lark » Wed Sep 11, 2019 12:34 pm

Good stuff yitzak, thanks!!!
Paul
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Postby Esteban » Wed Sep 11, 2019 3:07 pm

Well done Yitzak, and thanks for sharing the files and your insight into this matter. You work extremely fast also. Congratulations! :clap: :clap: :clap:
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Postby yitzac1990 » Thu Sep 12, 2019 8:09 am

One other thing I should mention: when I did my SPOA swap (as you can see in the pics), i rotated the axle to have more pinion angle for better driveshaft angles. MY axle housing, therefore, is rotated more than a stock patrol rear axle. The straight line between caliper mounting bolts is at a 14 degree angle from the straight line between backing plate mounting studs on the patrols axle. I'm 99% sure the caliper will work fine if its a bit higher and at an angle, however keep in mind that your angle may have to be less than 14 degrees in order to keep the caliper completely vertical (refer to picture 2, in the first post).
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