FJ80 Brake Upgrage

I've always dreaded how soft the brake pedal felt in my Tacoma, so for the longest time I did as much research as I could about how to remedy this - mainly master cylinder swaps. I'm not sure if this is as common as I thought it was, but I managed to upgrade the wimpy 13/16" master cylinder to a stout 1" master cylinder and dual diaphragm brake booster from a 1992 Land Cruiser (FJ80). I kept reading about this swap and was really excited to get it done, but once I got my hands on a FJ80 brake booster and master cylinder and attempted to simply "bolt it in", I realized there were some issues to overcome. I think a majority of the threads out there were for pre-Tacoma pickups that already had 4 bolt boosters, so I'm not sure if this is old news for some or I spent a lot of time in the garage for something that is a little less common. I didn't take too many pictures along the way, but here is what I did manage to take...

The first problem was the length of the pushrod. The Tacoma one is considerably shorter, so the FJ80 needed to be cut down along with having new threads cut further down it. I swore I took a side-by-side comparison shot of the difference, but I can't seem to find it. For the threads I used a Harbor Freight thread chaser (not a proper cutting tool). I didn't want the tool to have to cut through a ton of material, so I Dremeled the outer diameter of the shaft, almost all the way down to the actual booster. There was a section of the FJ80 pushrod that has a sort of knurled texture that was raised above the normal diameter of the rest of the pushrod. That was the main reason I went to town on it with a Dremel. I made sure not to take too much off though, because then there wouldn't be any actual material for threads to be cut into. Once this was done, I got the thread chaser started, and then clamped the very end of the pushrod TIGHTLY in the vise. The threads on the end get damaged, but the rod needed to be cut anyways. Once done, the thread chaser cleans the end when removing it. Overall, this was the most difficult part of the process. At certain times the rod needed to be clamped in different spots while making sure not to damage and of the threads. In the second picture, I used the "double nut" method to hold it, the second nut being the clevis from the Land Cruiser and put a punch through the clevis to hold it in place. It's important to note that if you were to use a clevis to hold anything in place while working on it, it should be the one from the Land Cruiser and not the Tacoma in case it gets damaged. There is a difference between the two, and the Tacoma one will be needed when it comes time to connect everything up to the pedal. The reason for not using the vice all the way through the process of cutting the threads was because this was all trial and error. I thought I had cut enough new thread, chopped the end off, only to realize I needed to cut more threads and had to get creative on how to hold it. It should also be noted that if anyone is wanting to do this, take your time with how much you cut off the end of the pushrod. I can't stress how much of a back-and-forth process this was to get the clevis in the right spot for the pedal to be adjusted.





The next issue (not as problematic) was the front brake line on the master cylinder. I probably could have made the existing one work, but I wanted to keep all parts in factory shape case this didn't work out and I needed to put the factory booster/cylinder back in. I went to Autozone, got a straight piece of brake line and a box of fittings, got a pipe bender and brake flaring tool, and made my own brake line. I was pretty stoked with how it turned out. The rear line can be forced into place without severely bending it.



There is a bracket that bolts to the factory master cylinder with a three-way fitting on it. The fitting is welded to it, so I forced the bracket out of the way. I'll probably eventually get around to getting a new fitting so I can get rid of the bracket sitting against the master cylinder.



I'm not sure which models come with it, but between the firewall and factory brake booster on my truck was an aluminum spacers. Through trial and error of taking the brake booster in and out of the truck, I realized the spacer was going to be too thick. So I improvised with some spare, weird looking oval washers from my dirtbike. It was all I could find laying around that had the thickness I needed. I was thinking of trying to get a machine shop to shave the factory spacer down, but again, I didn't want to ruin any parts in case I needed to put all the stock stuff back in. One of these days I'll come up with a better solution. Before anyone asks, yes there is some more noise coming from the firewall now since there is a void between the booster and firewall.



As stated earlier, the Tacoma clevis and pin are needed to connect the pushrod to the pedal. The Land Cruiser uses a larger diameter pin and won't go through the hole in the Tacoma pedal.



There is one quirky detail to all of this, and that is that the FJ80 booster has to be mounted upside down. I did this swap a couple months ago, and right now I can't remember why that was. I believe the vacuum line port was hitting something near the firewall. I can go look in the daylight if anyone is curious. Since it is flipped upside down though, a longer hose will also be needed to reach the vacuum port.

Verdict: STIFF PEDAL! I was amazed at what a drastic difference this made. The only downside is that since the pedal travels a shorter distance, it feels like you have to press harder. This is probably just a perceived feelings, but either way I prefer it over the old setup.

I apologize if this post was somewhat word heavy, but I like to try and give as much info as possible. Let me know what you guys think.

 

Well, here's what I think. You are not gonna like it.

I made the same mistake many years ago. I was convinced by online posters that a master cylinder with a larger diameter generates more force. However the opposite is true. I experimented with this so-called upgrade and immediately regretted it. Pedal was very hard, and my brakes were scary bad. I immediately replaced that caliper with a stock after market caliper and got my brakes back.

Google the principles of hydraulics. A larger piston moves more volume, but at a smaller force. The MC is carefully designed to fit our vehicles, to work with the stock calipers and wheel cylinders (that have appropriately sized bores).

 

People sometimes think that a firmer pedal feel means more power, but as stated above, that's not necessarily the case.

For better braking on the Tacomas, your best bet by far, is Tundra brakes, and that's really only if you put larger/heavier tires on.

 

I'm running Tundra 231 calipers and rear disc on my fzj80 axle and my stock booster and master are working fine.

 

Well that makes sense then. I had wondered if pushing more fluid would require "more force". I figured if nothing else the dual diaphragm booster would offset the a little, but that doesn't seem to be the case. Either way I'm okay with how the pedal feels right now. I am eager to do the Tundra caliper upgrade in the future.

Did you notice any difference in the pedal after you did this?

 

No, not really. If anything, I had better braking with slightly less pedal input.

 

Good to know. I got lucky with my Pro Comp 252's clearing my stock calipers, we'll see if I have the same luck with the Tundra calipers whenever I get around to doing that upgrade.

 

im running 16x8 Procomp wheels. they clear fine.

 

@SMKYTXN just put together some Tundra brake kits, wonder if they are applicable?

 

What style are they? I've read around that their steel wheels don't clear most Tacomas because of the calipers. 4 Wheel Parts even told me they wouldn't fit, but I had to find out for myself. I'm glad I did because they cleared mine... Barely.

 

Mine are the aluminium bullet hole wheels.