blue86iroc

iTrader: (2)

It took longer than I expected due to some parts availability issues, but overall, swapping LS1-style rear brakes to my '86 IROC was an extremely simple task. I'm really amazed at how straightforward the entire process was.



I was at my wit's end with the factory J65 rear discs. After investing far too much money in trying to get them to work properly, I broke down and started looking for better brakes. I was originally going to use '91-'97 PBR rears, so I bought all of the parts necessary, sans rotors and calipers. A trip to the junkyard a few days later (looking for front LS1s) yielded one heck of a deal on F-body parts. Aside from buying an aluminum driveshaft and some other goodies for next to nothing, I came across a wrecked Trans Am with rear discs in good shape. Needless to say, it was too hard to pass up. If anyone is planning on swapping the '91-'97 rear discs on their car, I can let go of the parts I no longer need. My friend got me an employee discount at the GM dealership, so they'd probably be cheaper than buying elsewhere. PM me if you're interested.



The following is a price breakdown of the parts.

Used calipers & backing plates, $50
Caliper rebuild kit (2), $10/ea.
New pads, $0
New rotor (2), $52/ea.
Banjo bolt (2), $3/ea.
Used brake cables & brackets, $5

I got lucky with the pads because the ones from the junkyard were lifetime replacement Carquest pads, so my friends at the auto parts store gave me a new set for free (and I have a receipt now!). I also decided to swap the thirdgen master cylinder for the fourthgen style, as well as replace the combination valve with one from a disc/drum (i.e. 1LE) car. These were $10 and $5, respectively.

The total cost for the brake swap came to right around $200, which is much less than I had anticipated. Since the axle shafts must be removed to install the backing plates, I decided to upgrade the stock shafts for higher-strength Moser pieces. This was done primarily because one of the existing shafts was slightly bent and caused some squeaking issues with the old disc brakes. The shafts, bearings, and studs were just under $300 from Summit Racing. I couldn't afford to go all-out and upgrade my 10-bolt to a 28-spline Posi, so these 26-spliners will have to do for now.





Overall, I'm quite happy with the swap. The stopping power has increased by what I would normally expect for upgrading the rear discs; that is, it didn't turn my car into a Corvette, but it's noticeably better. The free Carquest pads are actually made of the lowest-performing organic material, so ceramic pads might perform even better. I haven't gotten around to swapping my stock fronts for LS1 discs yet, but brake bias doesn't currently seem to be an issue with the 10.5" front discs and disc/drum combination valve. My previous disc/disc valve was brand new, so I just exchanged the metering spring from the junkyard valve (it's not quite as stiff; less k for all you engineers ). I may change out the spring again just to see the difference.

Regarding the parking brake, only minor modifications were required to get it functional. I've read numerous threads about people having issues with the LS1-style parking brake, but everything goes together smoothly if you can get the mounting brackets and cables from a donor car (or new from GM). The brackets bolt up to axle with the lower control arm bolt and the cables are routed under the panhard bar and above the axle using hangers attached to the differential cover.



The primary difference between thirdgen and fourthgen parking brakes is the location where the cables mount to the body of the car. On thirdgens, it's near the differential yoke; on fourthgens, it's right in the driveshaft tunnel. Using some scrap metal I had lying around, I was able to make a bracket that allows the LS1-style cables to bolt in the driveshaft tunnel. Fortunately, there's a little metal extension near the cable T-connection that allows the bracket to be bolted in place. It's off-centered, however, so I attached a small block of aluminum to sit flush with the edge of the extension, keeping the bracket straight.



The extension that the bracket bolts to isn't very sturdy, however, and began to deflect when the parking brake was applied. I added a piece of metal to the bracket that sits against the underside of the car, preventing the assembly from moving. It's shown by the red arrow in the following picture.



Note that I was able to retain the thirdgen cable that attaches to the parking brake hand lever, in addition to the T-connection.

This truly is a great swap and really modernizes the braking system on our older cars. Without Thirdgen.org it would have been much harder to piece everything together. Thanks, guys!

Z28guy83

i just got all the parts for my camaro i cant wait to get rid of those crappy disks that the car came with

AJ89Irocz

Looks awsome man I cant wait to do my brake upgrades.

ABJ88

iTrader: (3)

Is the fourth gen master cylinder a simple bolt in? I have Front Ls1 disc brakes and stock rear drums.

blue86iroc

iTrader: (2)

Yes, the bolt pattern is identical to the thirdgen style; the only difference lies in the thread type. Thirdgen master cylinders used two different thread pitches for the front and rear fittings, but the newer style uses the same for both (the coarser one, in this case).

I got a coarse-to-fine adapter (red) for the master cylinder, and a small-to-large adapter (blue) for the combination valve, connected by a regular piece of 3/16" bubble flare line. I'm not being too technical because I don't know the exact details of the adapters, just that they work. You can see the fittings in the master cylinder picture above.

Orinackra

looks great, love the info with the e-brake bracket. I'm gonna be doing my ls1 front/rear swap in 2 weeks, and it'll be nice to have that reference.
btw...where did you get a prop valve for 5 bucks? junkyard?

ebmiller88

iTrader: (7)

Very nicely done..

Ed

blue86iroc

iTrader: (2)

Thanks. Yep, I got the valve at the junkyard out of a disc/drum car. If you go that route be sure to find one with bubble flare fittings if you don't want to redo the lines (I've seen early-model thirdgens with standard flare lines).

Dyno Don

iTrader: (7)

My e-brake cable bracket:

https://www.thirdgen.org/forums/brak...ny-tricks.html

bingo

iTrader: (2)

Do you have a part number for the M/C adapter fitting, the red one.

blue86iroc

iTrader: (2)

Nice bracket, Dyno Don. I must have missed that post when I went searching. Welding it was definitely the way to go... one more tool that I need to buy .

bingo, the red fitting adapts 11-1.5MM threads to 10-1.0MM (i.e. 3/16" bubble flare line). The part number depends on manufacturer, but most parts stores should be able to cross-reference.

Edelmann: p/n 266000
Everco: p/n 3021B
Weatherhead: p/n 7935

bingo

iTrader: (2)

I am wanting to put this type od M/C on my car, but I will have to adapt one of the lines. My M/C has a M11 X 1.5 port and the LS1 has a M11-1.25. The other line is the same. I was wondering if you found a fitting that changes these without changing lines.

blue86iroc

iTrader: (2)

Are you sure the fourthgen master cylinder has 1.25-pitch threads? Mine had 1.5, the same as the rear output of the thirdgen master cylinder.

I retained the thirdgen combination valve, so I reused the line with 11-1.5MM fittings on both ends (rear output of the MC). My front output of the fourthgen MC also had 11-1.5MM threads (unlike the thirdgen MC), so that was adapted to 10-1.0MM threads (red fitting) so I could use 3/16" bubble flare brake line. I also had to use a (blue) 12-1.0MM to 10-1.0MM adapter on the combination valve.

I would have preferred to retain the thirdgen line and not use 3/16" bubble flare line, but I couldn't find an adapter. That would have been something like 11-1.5MM to 12-1.0MM, I think.

Maybe that helps?

86Z

iTrader: (4)

nice job, what did you use to mount the caliper mounting brackets to the axle? i'm doing this swap right now, i need to get my ebrake working as i have a manual

blue86iroc

iTrader: (2)

If you have rear discs, the thirdgen caliper brackets can be directly swapped out for the LS1 style. This backing plate includes the internal brake shoe mechanism for the parking brake, too. If you have rear drums, you'll need to drill the four holes yourself, but it doesn't appear to be that difficult. There's a tech article on Thirdgen.org if you need to do that.

The parking brake is mostly useless since I have an automatic, but hopefully that'll change someday!

Orinackra

thats exactly the only reason I care about getting mine done.

86Z

iTrader: (4)

do you have a picture of how your rear hard lines mount to the calipers? i need to change my drum ones and was wondering how the disc rear hard lines will work, also my parking brake is rubbing, i can hear it when i turn the wheel, it doesnt feel like resistance, just that i can hear it and it's not every time on the rotation. only at a certain point

V6sucker

I am looking at this swap now as I find more and ore damage that the previous owner has done to the car.

This time the rears are just not acting like they should. I cannot even drive up onto ramps even using a board extension as the fronts lock and push everything. This is absolutely INFURIATING! as all I wanted to do was replace the knock sensor plug...

So I started pricing calipers... yeah after seeing them for 170 (both)something I decided to start looking at LS1 rears.
The calipers, caliper mounts and rotors are 150ish used.
That kinda made the decision alot easier.

blue86iroc

iTrader: (2)

V6sucker, this swap really is top-notch and simple to do... much easier than I originally thought. As you said, there's no point in spending money on the crappy stock brakes if you can upgrade to these (or the LT1s) for a little bit more.

86Z, here are a few pictures of the brake lines on the rear axle. I was upgrading from factory discs and the original lines would have worked (with a bit of fanagling), but I chose to run new ones because they weren't in the best of shape. I did not use the hard lines from the donor vehicle. The rear axle on fourthgens is a little wider, but it shouldn't make much of a difference if you're going that route. Depending upon the length of your drum brake lines, you might be able to make a loop or two to use up some of the excess (provided you don't kink the line). I had to do that when I ran new hard lines.

As you can see in the pictures, I ran the lines right into the parking brake bracket, using the LS1-style hoses. I had a set of Earl's braided hoses on my car with the J65 brakes, but they were too long to use with the LS1s... you can see how there is very little room between the bracket and the caliper. The hoses are only a few inches long.

Don't say anything about the nasty shocks and undercarriage... I know I gotta redo that someday .

86Z

iTrader: (4)

ok cool, i ordered some stainless steel pre bent brake lines for a disc camaro, only 35 bux so i should be able to get them in the holes of the brackets, theres no way i can move my drum lines they are rusted and i was going to replace them anyhow, nice job again, i'm still in the process of mine, i'm going to have to make a bracket similar to yours for the e-brake, as i use it everytime i stop especially with a manual, i have the ls1 e-brake cables, how is your fabricated mount holding up? thanks again.

blue86iroc

iTrader: (2)

Yeah, the pre-bent lines should fit up reasonably well to the LS1 brackets. On the driver's side, you'll have to rework the bend that would typically go into a thirdgen rear caliper, and on the passenger's side you'll have to run the line over the top of the axle tube, as opposed to the rear.

I haven't been using the parking brake too much since my car has an auto, but it's been holding up just fine. The cable needs a minor adjustment but I haven't the energy to crawl underneath and tighten the bolt .

8898z28

here is my set up with 17 inch wheels
i had problems with the cable as well and i just pulled longer cable threw the hose and re-did the conections and it wasnt easy
i also had make all new lines because the nuts where all froozen on because of minor salt damage from being up north, but napa had the line and auto zone had the tools to rent and it wasnt so bad

blue86iroc

iTrader: (2)

I hear you on that one! My Camaro isn't so bad since it's only driven in clement weather, but my two Jeeps are a pain to work on. You know it's bad when the roads turn white from all that salt in the winter time...

Looks good, 8898z28.

8898z28

yeah every thing under the car is new (almost), and all those old bolts where a pain to get off.
shes setting in the garage right now with rusteater on the front control arms and spindel. shes getting a clean one of a texas car thats been up graded with LS1 brakes
----------
what master cylinder did you go with, ive heard people say put the LS1 on and some people say that the one for rear disc works fine
mine was a rear drum and the pedal is a little soft but she stops pretty fast, saved me from a wreck, but like i said im up grading the fronts this weekend