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- #661
Seems like it. Now that I am sure all the other components are right I’ll jack it up again and start clicking turns to see if I can get some pedal back.
Build Goat. A 1967 survivor FJ-45 LWB
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Seems like it. Now that I am sure all the other components are right I’ll jack it up again and start clicking turns to see if I can get some pedal back.
- Thread starter
- #662
I’ll crack one open Wednesday. Take a pic.
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- #663
Man. No idea. That is something I did not look at at all. These are high quality Japanese ones from @cruiseroutfit and likely have ramps but I did not know to look for them to be oriented right.
Since I’ll have to crack open each wheel now to inspect I think I’ll take the drums
To be turned.
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The ramp on drum brake adjuster pistons oriented correctly:
For comparison, here's the ramp oriented wrong:
Slightly better view of piston without shoe in the way, showing high side and low side of ramp.
The ramps are oriented with the high side out, so the return spring tends to pull the shoe away from the drum. There should not be a big gap visible at the outside of the shoe/adjuster slot.
Go fix this at all 8 adjusters, then re-adjust brakes.
Don't introduce another variable by adding turning all 4 drums to the equation.
For comparison, here's the ramp oriented wrong:
Slightly better view of piston without shoe in the way, showing high side and low side of ramp.
The ramps are oriented with the high side out, so the return spring tends to pull the shoe away from the drum. There should not be a big gap visible at the outside of the shoe/adjuster slot.
Go fix this at all 8 adjusters, then re-adjust brakes.
Don't introduce another variable by adding turning all 4 drums to the equation.
https://www.mico.com/sites/default/files/document-pdfs/81001017Residual Pressure Valve.PDF
I found this text on an other forum, it explains things a bit better.
“Drum brakes have heavy return springs built into them. This is a result of wanting to prevent shoe drag. Drum brake shoes by design have a certain "power assist" affect due to the mechanics (servo action) and as a result having them drag even a little would generate a bunch of drag even moreso than you might think. This may sound contradictory (having a higher RPV valve rating here) but the saving grace is that that return springs are pretty heavy and therefore you don't get the full effect to the shoes - instead we are trying to maintain a minimal air gap - as a result the RPV and return springs need to be matched - we take this for granted with comments like "10# RPV's for drum brakes - period" well - like anything the 10# valve works a majority of the time - but it ISN'T magic - there are cases where it WON'T WORK.
The OTHER reason why we need a higher RPV in a drum brake is because when we retract the piston (brake release) in the absence of pressure the lip would allow us to suck in air EVERY time we released the brakes!!!! Maintaining a certain amount of line pressure PREVENTS this. So bottom line it is FAR MORE than just minimizing pedal travel in a disc system (although that'd be reason enough) but is even MORE important in a Drum System”
I would expect a RPV to be build in the MC already.
I found this text on an other forum, it explains things a bit better.
“Drum brakes have heavy return springs built into them. This is a result of wanting to prevent shoe drag. Drum brake shoes by design have a certain "power assist" affect due to the mechanics (servo action) and as a result having them drag even a little would generate a bunch of drag even moreso than you might think. This may sound contradictory (having a higher RPV valve rating here) but the saving grace is that that return springs are pretty heavy and therefore you don't get the full effect to the shoes - instead we are trying to maintain a minimal air gap - as a result the RPV and return springs need to be matched - we take this for granted with comments like "10# RPV's for drum brakes - period" well - like anything the 10# valve works a majority of the time - but it ISN'T magic - there are cases where it WON'T WORK.
The OTHER reason why we need a higher RPV in a drum brake is because when we retract the piston (brake release) in the absence of pressure the lip would allow us to suck in air EVERY time we released the brakes!!!! Maintaining a certain amount of line pressure PREVENTS this. So bottom line it is FAR MORE than just minimizing pedal travel in a disc system (although that'd be reason enough) but is even MORE important in a Drum System”
I would expect a RPV to be build in the MC already.
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Ramp orientation. Well there ya go, I never knew.
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That's all good info.
The stock RPV is right behind the big brass nut on the end of the cylinder. It is unlikely to cause the issue the OP is dealing with because a. they very rarely fail, and b. 2 OEM MC's have been tried with same result.
The stock RPV is right behind the big brass nut on the end of the cylinder. It is unlikely to cause the issue the OP is dealing with because a. they very rarely fail, and b. 2 OEM MC's have been tried with same result.
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- #669
Why does fluid not run out of an RSV equipped early master when the line is removed?
Seems this slight pressure we are talking about would have fluid going all over the place.
Seems this slight pressure we are talking about would have fluid going all over the place.
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There is no pressure reservoir, like a tank in a compressed air system or a pressure accumulator in a hydroboost system. As soon as a line is cracked open, the pressure in the system drops from a few PSI to zero. With no pressure reservoir there is no impetus for continuing leakage.
I agree.
Break bitch. I think that would get noticed on a resume. Nice.
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- #673
Popped it open. Was so excited to see the gap.
Flipped it.
Same.
Put a mic on the adjuster and it’s 3mm on both sides. So these aftermarket cylinders have no ramps.
And here are the cylinder orientation pics
Passenger rear over passenger front.
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I have both springs in the rear so that is one thing for sure that is not as the article states.
In the rear the opposite plugs have plugs in them. This is that way it was and seems to have been.
In the front I could have gone either way as there are slots both top and bottom on both sides all unplugged.
Also, my cylinders were not marked like that article says.
Finally, I’ve got 75% brakes on the first pump. It will stop but not lock. A quick pump and they lock so I got a bit closer this try.
Think the spring orientation will get me the rest?
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What’s the rest suppose to be? Lockup on first pump?
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The brake nails & retainer clips are missing? Very early Cruiser doesnt have them, but they are a later improvement. Since the shoes are drilled for nails, it would only be necessary to drill 2 holes in each backing plate to make that upgrade.
On the later drums, the frt to rear orientation of the return springs doesn't matter, but they should be installed one inside, one outside, so they cancel each other out. The missing hold-downs will have to be installed as part of this improvement.
The OE adjusters w/ ramps will screw into the aftermarket cylinders. I had to do it recently for an FJ40 that showed up with a set of new aftermarket cylinders and ineffective drum brakes. Fortunately, between his old junk that he had kept and the tiny bit of old drum junk I had, we were able to piece together new cylinder bodies w/ ramped adjusters and good cylinder springs & internal spring seats. Went from having 1-pump rear drums to having zero pump rear drums.
On the later drums, the frt to rear orientation of the return springs doesn't matter, but they should be installed one inside, one outside, so they cancel each other out. The missing hold-downs will have to be installed as part of this improvement.
The OE adjusters w/ ramps will screw into the aftermarket cylinders. I had to do it recently for an FJ40 that showed up with a set of new aftermarket cylinders and ineffective drum brakes. Fortunately, between his old junk that he had kept and the tiny bit of old drum junk I had, we were able to piece together new cylinder bodies w/ ramped adjusters and good cylinder springs & internal spring seats. Went from having 1-pump rear drums to having zero pump rear drums.
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- #680
Yeah. No nails or holes. I figured since they were not there they were not needed. I can add that.
I have piles of cylinders. I can harvest ramp adjusters I’m sure. Thought about it to measure the ones I had but did not know if that would break a seal and tear up my cylinders.
I have piles of cylinders. I can harvest ramp adjusters I’m sure. Thought about it to measure the ones I had but did not know if that would break a seal and tear up my cylinders.