Recomendations for Master Cylinder

Feb 25, 2002
I am getting all of the parts together for a mini truck disc brake conversion on my '72 FJ40. There is not much discusion on which master cylinder works best when doing this conversion. For those who have done this conversion, what did you use? I have read that a larger bore mc is required with disc brakes. I also have plans to put in rear discs later this year.

Thanks in advance.

Feb 13, 2002
Davis, CA
Hey Randy-
I just did the mini disc swap this past August- Pretty easy swap, with awesome results. My cruiser had a single reservoir master, with no booster- and it had a single brake line routed around, and branched off to each wheel. Well, that just didn't fly with me- so I got a booster/master from an '85 toyota 1-ton (15/16ths bore), and I got bulk brake line from Summit, and installed an almost new brake system. The brake line fittings were all the same- so that was nice- I just re-used the old fittings, because they were still good- just had to flare the new lines.
The diameter of the hole in the firewall wasn't big enough for the new master/booster- so I used a holesaw (very common, because it happened to be the same size as the hole you put in a household wood door, for the handle to go in). Let's see- I also had to grind a little bit off of a firewall brace- and had to shim under part of the booster against the firewall... &nbsp:Details, details... You just wanted to know what booster I used. Oh well. As far as going to rear discs, you can just remove the residual valve from the master, and everything should work out. There's a write up on that somewhere on this site. If you want more info on what I did, just ask. I think I might have some pics too- somewhere... I should just do a write up and submit it to Woody... All in good time. Anywhoo.
HTH- Zipp.


Staff member
Jan 15, 2002
Toquerville UT
<checking mail for writeups....>

Mine is setup with a 77ish master cylinder from the FJ40. Nothing fancy, I just removed the residual valve from the rear circuit and it works fine.

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