1966 45lv rear wheel brake cylinders

[CRZR45]

Are the 45lv rear wheel cylinders same as fj40 on the stock 1966 rear axle? SOR say they have a different shoe and wheel cylinder and it’s no longer available but they have a rebuild kit. I was under the impression that the rear stock axle brakes and internals are the same as FJ40 (only difference is sway bar mounts?)so I could just get those?

 

[whitey45]

Same stuff, the hard part is the early rigs have 9mm fittings. All the newer wheel cylinders are 10mm. I used to just hone them and put new cups in, as long as they clean up without pitting.

 

[CRZR45]

Perfect! Thanks Whitey45! They have the early fj40 ones which I assume are 9mm. They said they were different but mr T did not change that much stuff! I’ll order the rear for 1966 fj40 and go from there.

 

[whitey45]

Pretty sure the 9 mm are no longer available, only 10mm which will require new fittings. Not sure why spector cant make that clear?

 

[CRZR45]

Just spoke to SOR again today and a different person. He said same thing that the LV and Pick up have different part number and no longer avail.I’m gambling and I Ordered the 58-70 fj40 rear wheel cylinders as the 9mm part is on the banjo so hopefully bolts in.. will report back when I get them.

 

[hdjtachtig]

Different bore. Found this in a a 60’s service manual:

Doesn’t mean the FJ40 cilinders won’t work.

 

[65swb45]

Correct. They will bolt in, but…the 45s are different diameter pistons, which was Mr. Ts way of achieving proportioning.

Sooo, if you put in a wheel cylinder with a smaller piston, logic says it’s going to engage faster. Worst case scenario: you’ll have to install a prop valve to slow it down.

But that’s really not likely to happen.

 

[CRZR45]

Thanks for the info! Got the parts and will start the install in the next couple weeks

 

[hdjtachtig]

if you put in a wheel cylinder with a smaller piston, logic says it’s going to engage faster

The other way around right? Bigger piston, more brake force.

With the same pedal pressure, you have the same brake fluid pressure. The larger wheel cyilinder has the same pounds per square inch, but more square inches so more pounds on the brake shoe.

 

[middlecalf]

Think about volume and it’s impact on fixed pressure system.

 

[hdjtachtig]

I don’t agree. More volume is more pedal stroke. Not more force.

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Force = pressure x area. More area is more force.

Think about a hydraulic jack. The master piston is small, the work piston is large. The larger the work piston the stronger the jack is. It needs more pumping but is stronger.

 

[middlecalf]

Which one rises faster? Mark @65swb45 refers to speed (timing) in his above post. That’s the key to proportioning fore/aft breaking.

 

[hdjtachtig]

Learning every day. Is the self energizing effect of drum brakes playing a role here?

I just thought: FJ45, heavier rear, need more brake force, mount stronger cilinder, voila.

Edit: it doesn’t make sense to have stronger rear brakes, you need the most brake power in front.

 

[middlecalf]

In general you want the front brakes to start braking first, then the rear - it's a stability and lockup thing - and all with enough force to stop of course. Toyota used smaller front cylinders in their 4-drum brake setup to make this proportioning balance. And the front brakes wore out faster because of this as they always engaged (if everything working right) but the rears not all the time for casual braking. On hard braking everything brakes, hopefully without anything breaking .

 

[CRZR45]

Rear went together perfect. Only difference is the piston size(Lv has larger one and the 40 ones I used were a little smaller) Next week or 2 get time for the front. Progress slowly but surely.