72 FJ40 Drum Brakes

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elgatoocho

10 Year
Joined
Apr 20, 2013
Threads
9
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35
Location
Redding California
just a couple simple brake related questions, firstly, I purchased a full "set" of 8 brake cylinders, they all have the same piston size, I know that originally had the fronts were slightly larger 1.11-1.12" , mine are all the smaller of the two sizes, .997". is this going to be a problem?? And secondly, the Toyota Repair Manual says,

"Caution, there are two kinds of adjusting nuts and the bolts. The adjusting bolt of the left-hand threads is on the right side of the rear brake, and the right-hand threads bolt is on the left side of the rear brake."

Does this means, that on the left side (U.S.A. Driver side) of the truck, the the left- hand treads would be toward the rear and on the vehicle, and on the right side (U.S. passenger) the left-handed thread would be towards the front of the vehicle, or are they referring to the sides of the axle???

also why? i assume its to simplify the direction of adjustment?

thanks
 
I wrote this up on the following post:

brake cylinders

Stock brake cylinders on my Jan 1973 FJ40 were 1.25" dia in the front, with only one piston per brake cylinder.

I don't have any idea how double pistons will work in the front.
 
is the place where you bought them from any help?
 
elgatoocho said:
just a couple simple brake related questions, firstly, I purchased a full "set" of 8 brake cylinders, they all have the same piston size, I know that originally had the fronts were slightly larger 1.11-1.12" , mine are all the smaller of the two sizes, .997". is this going to be a problem?? And secondly, the Toyota Repair Manual says,

"Caution, there are two kinds of adjusting nuts and the bolts. The adjusting bolt of the left-hand threads is on the right side of the rear brake, and the right-hand threads bolt is on the left side of the rear brake."

Does this means, that on the left side (U.S.A. Driver side) of the truck, the the left- hand treads would be toward the rear and on the vehicle, and on the right side (U.S. passenger) the left-handed thread would be towards the front of the vehicle, or are they referring to the sides of the axle???

also why? i assume its to simplify the direction of adjustment?

thanks
Click to expand...

I know this thread is old and you've probably worked all this out by now but here goes.

I believe you are correct in your assumption that the placement of the left versus right handed threads is to simplify adjustment.

If you visualize how the adjusters push the shoes against the drum they will always be moving closer to the drum when you turn the adjuster teeth in towards the axle (snugging up the brakes) and away from the drum when you move the adjuster teeth away from the axle.

Regarding the bore sizes I think the larger bores are to provide more stopping power up front where it is needed. I think (not 100% sure on the fronts - I haven't had them apart for a while) on my FJ40 the fronts are 1 1/8" and I know all the rears (except one) are 1". I'm guessing the 1 1/8" must have been put there by mistake (or because they didn't care) by a PO.
 
Last edited:
To confirm the OP had a misunderstanding regarding the adjuster threads (right vs. left hand threads) that was corrected when he read the post I referred him to, I am noting for the casual reader what the OP learned:

"Caution, there are two kinds of adjusting nuts and the bolts. The adjusting bolt of the left-hand threads is on the right side of the rear brake, and the right-hand threads bolt is on the left side of the rear brake." THIS MEANS THAT ALL OF THE BRAKE CYLINDERS ON THE LEFT SIDE OF THE VEHICLE HAVE RIGHT HAND THREAD ADJUSTERS AND ALL OF THE BRAKE CYLINDERS ON THE RIGHT SIDE OF THE VEHICLE HAVE LEFT HAND THREADS.

Does this means, that on the left side (U.S.A. Driver side) of the truck, the the left- hand treads would be toward the rear and on the vehicle, and on the right side (U.S. passenger) the left-handed thread would be towards the front of the vehicle, or are they referring to the sides of the axle??? NO!! SEE THE TEXT IN RED, ABOVE!

Using the above convention, turning the adjusting nut TOWARDS the axle will adjust the brake shoe into the drum, regardless of front, back, left or right brake.

Also, according to the Toyota part numbers, note that from 7109 to 7509, all stock OEM front brake cylinders were 1.25" diameter bores. For the rear cylinders, all were 7/8" (0.875") from 7109 -8007.

I can't speak for what is in anyone's brakes, I can only identify what the OEM part numbers indicate.

 
I just took my wheel cal apart this evening and can say the rears on my 71 are 7/8". Not to the fronts yet but I would expect them to be considerably larger.
 
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