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TTB Thunderbird Caliper Upgrade

5.3K views 5 replies 3 participants last post by  SRWillis  
#1 · (Edited)
Hi all,

I recently finished my Thunderbird caliper install. I went through a few different how-to's, and felt that they all left out a few bits and pieces here and there that I had to research. So I thought I'd share my build and own how-to.

I'm working on a 1985 Bronco with the stock front brakes and TTB. The brakes were "good enough" but I was wanting something a little more without fully going to rear discs. I have 32" BFO KO2 tires and while they're nowhere near as big as some tires people put on, they're a bit heavier than the stock setup was ever designed for. On top of that, when I'm camping and loaded down with camping gear and 5 people and several dogs.... the Bronco can get pretty heavy.

Even with day-to-day driving, the brakes were good, but I would often find that after driving the Bronco for a few weeks and then getting in another car, I'd keep hitting the brakes and lurching the car, throwing everyone forward like a teenager just learning to drive. I really wanted the brakes to be much more like a modern vehicle in their stopping power.

The T-Bird caliper upgrade seemed like just the way to go. They fit right onto the TTB up until a certain year (not 100% sure which year is the cutoff), and have quite a bit larger piston. The single piston has more surface area than the dual piston that came in the larger f-series trucks. So they have some good stopping power.

After the install was complete and the new hardware was broken in, I have to say that the improvement was well worth it. Braking power is improved by a good 15 - 20%, and if I press the brakes hard enough, I'm thrown forward into the seat belt. It stops!

The biggest issue with this mod is that the t-bird calipers, while a direct swap, flip the sides that the bleeder valve and hose connect to. So, now the bleeder valve points outward, and the brake hose is up against the steering knuckle. There just isn't room to get the hose onto the caliper without modification, so some of the material on the knuckle needs to be ground away.

Then, due to the increase in fluid, a larger master cylinder up front and slave cylinders on the rear are required.

For starters, here is my shopping list:

Front Calipers (right/left)
Raybestos FRC 4083 / FRC 4084

Banjo bolts (7/16")
Crown Automotive J3225703

Copper Crush Washers

F-350 master cylinder with 1.250" bore
ACDelco 19176066

F-350 rear drum slave cylinders
Raybestos WC370042 / WC370043

Steel braided brake lines

I have no idea why those say 1980-1981 and 1988. They worked just fine on my 85.
Note that these are for 0" of lift, which mine has. They have some for lifts on the site as well.

I also bought an assortment of brake line fittings, since a lot of them will need to be cut off and swapped.
https://www.amazon.com/gp/product/B015YGRHXM/ref=ppx_yo_dt_b_asin_title_o00_s00

As such, you will also need a brake line flaring tool to cut off the brake line ends and swap on new ones.
Make sure it does double flare. I got mine on amazon.


The first step is to drill out the hoses. The Bronco uses a 3/8" banjo bolt whereas the T-Bird calipers use a 7/16". A drill press would make this a whole lot easier, but I don't have one. I just snugged it down in a vice and used a hand drill. I stepped it up in several sizes (3/8", 25/64", 13/32", 27/64",7/16"). This kept it from "biting" too hard and digging in. Take your time, so you don't mess up the hoses.

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Use a small dremel tool, or something similar, to clean up the ridge around the hole, so that it doesn't keep the crush washer from seating.

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Next step is to modify the calipers. The T-birds have a recessed hole, whereas the Bronco ones do not. So, the raised ridge around the hole will need to be ground down.

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Take your time so that you do NOT nick the mating surface. You just want to clear an area for the hose end to sit flush. I came in at an angle so that I could only remove material and couldn't hit the surface.
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The calipers are now ready to go.
 
#2 · (Edited)
Here's the stock caliper before diving in:

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The stock caliper (left) vs. the t-bird (right).
You can see how the bleeder and hoses switch sides:

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Once the T-bird calipers were in place, it was quickly evident just how close to the steering knuckle the hole for the hose sits. There's simply no room to get the hose in there. And even if you did, there's no room for the head of the bolt.

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I got a carbide bit and a grinder and went to work. I recently got an air compressor so I bought a cheap $15 harbor freight "dremel" style tool that really helped. After some grinding, the hose fit:

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However, there are still two more factors to consider. The first is that the caliper MOVES. Super important! It slides back and forth as you press the brake. Last thing you want is to press the brake and the head of the bolt hits the knuckle and impedes the travel of the caliper and it doesn't engage.
The second issue is that the knuckle stays still while the caliper swivels as you steer.
You need to grind enough material that the caliper can slide as you press the brake, and that the hose end doesn't pinch as you turn.

Without grinding, the hose end will get pinched when you steer to the left, and will limit how far you can turn.

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I didn't have to remove a lot on mine, but I did have to carve the arm back to make some room:

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The passenger side required a lot less material removed.

Just enough to let the bolt head slide. The hose didn't hit the TTB arm so there was no grinding required there.

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#3 · (Edited by Moderator)
F-350 master cylinder with 1.250" bore
ACDelco 19176066
Any reason you did not go to the F350 brake booster? I guess there is some debate maybe on if the swept area on F350 booster is really
any better than your 85. It always looked thicker to me, but don't know that that matters much. Dia looks close. \

I figure there had to be a reason Ford used that booster over the F150/bronco one's. The middle one in pic just so happens to be
from and 85 (left is 93 F350, right in 79 which is single diaphragm).

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#4 ·
I don't recall, but I think I read a few places that it was optional, and most didn't notice a difference. I figured I'd wait to see how it felt without the bigger booster and go from there.
I've also toyed with the idea of a hydroboost so I was leaving my options open.

Either way, after it's all said and done, I don't think it's necessary. The pedal feels great.
 
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#5 · (Edited)
Onward:

Steel braided hoses, T-bird calipers, and fresh pads, and rotors. If you install new rotors, there are other writeups on that so I won't go through the steps here.

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Next was getting the master cylinder set up. I decided to go with a 90s era master cylinder since I was fed up with the older style always leaking. I've had several of these on 3 different Broncos, and there always seems to be brake fluid down the sides of them. The lids just don't seal! So I figured this would deal with two problems at once.

From the data that I found online.

The old style master cylinder has the following fittings:

Primary Port (front): 9/16" - 18
Secondary Port (rear): 7/16" - 24

The new style master cylinder:

Primary Port (front): 7/16" - 24
Secondary Port (rear): 9/16" - 18

It seems like they just swapped the thread sizes. You can't just swap the lines or you'll have more fluid going to the rears than the fronts. You'll need to cut off the ends and swap the threaded fittings.


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Some speed bleeders make quick work of bench bleeding the master cylinder.

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A regular 3/8" drive extension fits right into the plunger hole:

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Afterwards, the new master cylinder drops right in.

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The rears will then need to be modified. The wheel master cylinders use the larger fittings as well, so the originals will need to be cut off and new fittings put on:

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The driver's side line is easy to remove and the fittings can be done on a bench vice, but the passenger side is a bit longer and is clamped to the axle. I didn't want to mess with removing it, so I was able to flare it with it on the vehicle:

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With the steel braided lines I got, both sides of the rear hose had the same thread size. On the original, one side was small and one side was large. This was only to make sure it was installed a certain way (and not for fluid flow).

Since the new hose had the same size on both sides, I needed to cut another of the ends off and swap it as well. If you use original hoses, you won't need to do this.

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And that sums it up. Now to just bleed the whole thing and give it a test drive.
If you put in new rotors and pads, break them in.

Be sure to stomp on the brakes hard a few times. Then check for leaks and repair as needed.

You now have bigger T-bird calipers on your Bronco. :D
 
#6 ·
Thanks for another excellent write-up. Something I may have to consider in the future, and now I have info at hand to do it.(y)
 
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