Master Cylinder and Brake “Upgrade” Questions (1 Viewer)

[WoodnotRust]

Thanks @poptart for the thoughtful reply and details. I can see the logic behind larger calipers, rotors and pads with a hydraulic system to match...how does that not make sense?

I'm glad you posted the picture of your LSPV arm. Here's a picture of my OEM set-up which sits so much lower relative to the LSPV. I have the 2" OME lift and 265/75 R16 Bridgestone tires. That places the arm at center of the shackle bushing 10-1/8" below the bottom of my cargo tub. Your shackle is so much higher that it got me to thinking about how the LSPV works. There isn't some magic pressure sensor inside the valve...the arm open or closes a valve connecting the front/rear brake hydraulics in response to downward movement of the front of the truck (a response that might be expected with relatively stronger front brakes). It's a mechanical valve that tries to keep the vehicle level when braking I guess.

The LSPV seems like a key part that will likely need some adjustment. Without it properly tuned either the front or rear aren't contributing their fair share. When you read the FSM the initial set-up requires specialty pressure valves to set the relative pressure of the front and back brakes. Well, that's probably not even something my Toyota dealer will do much less a local brake shop...never mind me and my own garage. I'm guessing that if I can just get close to the stock position of the LSPV bushing arm (relative to the valve) then I'm in the ball park for the OEM set up after OME lift and can adjust based on "feel".

So...for those that have OEM brakes that seem nicely balanced, how far is it from the center of the LSPV spring-arm shackle pin to the bottom of the tub (see photo)?

I decided to go the OEM route on a "as-needed" basis, but I've gone ahead and collected all the currently available Toyota parts. Most of the critical parts like the Booster, MC, front calipers and LSPV aren't available from Toyota, but it does appear there are quality OEM aftermarket equivalents. Minus hard lines, all the parts to complete the OEM rebuild (including parking brake cable) will cost about $2,200. I've posted the list below with parts numbers, source and costs.

I'm going to start by replacing the Booster, MC, LSPV (along with new bushings and boots). I replaced front pads and rear shoes only a couple of 1000 miles ago, so I'm going to leave those alone for the moment and see what these changes bring.

The hard braking may be due to a bad booster, but it might also disguise unequal braking due to a poorly adjusted LSPV arm (as a result of my OME lift).

I'm not an engineer either, but a scientist at heart and I'm really tempted to do the brake distance test at 20, 40 and 60 mph (before and after). I'll probably need to buy a crash helmet and a Go-pro.

 

[4runner2FJ60]

Just to be clear on this thread. The 62s are the only series with the LSPV, unless they added it to the 60 in a late model?

 

[Godwin]

Just to be clear on this thread. The 62s are the only series with the LSPV, unless they added it to the 60 in a late model?

Yeah, only the 62.

 

[WoodnotRust]

I after I installed the OME 2.5” I raise the LSPV arm off the axle and I guess I was raised it a bit to much and was locking up the rears first. But I have since cut down my raised mount for that and solved that issue.

Apologies for continuing to beat this to death...

After reading the FSM and the comment above I'm confused about the effect of raising and lowering the LSPV spring arm. Here's the section from the FSM which indicates that if you raise the spring arm at the shackle (at the axle), then the pressure will drop. The FSM doesn't say so explicitly, but it seems they mean the "pressure going to the rear brake" cylinder.

Am I upside down on this?

 

[poptart]

Apologies for continuing to beat this to death...

After reading the FSM and the comment above I'm confused about the effect of raising and lowering the LSPV spring arm. Here's the section from the FSM which indicates that if you raise the spring arm at the shackle (at the axle), then the pressure will drop. The FSM doesn't say so explicitly, but it seems they mean the "pressure going to the rear brake" cylinder.

Am I upside down on this?

View attachment 3133097

I always think of it compared to the body of the vehicle. The closer it is to the body, it’s more like there’s a load in the back and increases the pressure to the rear brakes.

 

[WoodnotRust]

Thank you...I get it now. On the FSM is says "Low Pressure - Lengthen A"...meaning if you have "Low Pressure" to your rear brakes, then lengthening A (getting it closer to the body) will "Raise" the pressure. I misunderstood it to mean lengthening A would "LOWER" the pressure. That's why it's good to know people that are smarter than you.

 

[dogcruiser]

I’ll be honest, 4 years ago I did 4 runner calipers and 80 non ABS master on my 1989 HJ61 (brake system same as US FJ62). The brakes were ok to good, but not exceptional. I comprehensively redid the brakes and knuckles with OEM parts, and I even replaced the hard lines across the axles with brand new ones from @Rainman. It was pretty underwhelming…braking was ok, and like you I could never get it dialed IN in.

About six months ago I completely redid the brakes on my 1990 FJ62, with a City Racer brake booster, and OEM everything else including hardlines by Rainman, and the OEM Japanese loaded calipers from Cruiser Outfitters. I replaced everything except the rear drums and shoes as they were in great shape.

It was a revelation. It was the best braking 60 series cruiser I have driven. So much so that I am now redoing the HJ61 in the same way, ditching the 80/4runner combo to go back to stock.

Do you think it was the booster that made the difference? I have new OEM rotors, calipers, new pads and lines up front and drums/shoes in very good shape in back. But the pedal is soft. I can lock them up but it requires plenty of pressure on the pedal. I’d love it to be more sensitive.

 

[Spook50]

Do you think it was the booster that made the difference? I have new OEM rotors, calipers, new pads and lines up front and drums/shoes in very good shape in back. But the pedal is soft. I can lock them up but it requires plenty of pressure on the pedal. I’d love it to be more sensitive.

Are you saying it takes a good deal of actual force against the pedal, or a good deal of pedal travel for the brakes to lock up?

If the first, could be a booster issue. If the second, odds are you still have air in the lines and/or failing (soft) flexible lines.

 

[dogcruiser]

Are you saying it takes a good deal of actual force against the pedal, or a good deal of pedal travel for the brakes to lock up?

If the first, could be a booster issue. If the second, odds are you still have air in the lines and/or failing (soft) flexible lines.

It takes a good bit of distance, and at the bottom it takes more pressure than I think it should to keep the truck stopped. Ideally I’d like more brake at the top and less pressure required to hold it at a stop.

 

[cps432]

It takes a good bit of distance, and at the bottom it takes more pressure than I think it should to keep the truck stopped. Ideally I’d like more brake at the top and less pressure required to hold it at a stop.

Sounds like air in the lines.

 

[toy_tek]

FWIW I'm also in the thought camp of "keeping it stock". It astounds me how many people put faith in a backyard garage mechanic who posted on the internet with a "better" setup than the Toyota engineering department developed. While not overly complicated from a component standpoint, there are a lot of physics at play in a braking system. Ensuring the stock system is set up and operating at 100% would be my ultimate goal before trying out a bunch of parts that weren't originally engineered to work with each other as a system. And to that point, replacing and maintaining brakes are pretty simple, and even I've been guilty of skipping the manual details a few times. But usually, when I follow the manual to a T, I'll figure out something I've overlooked or done incorrectly, and I'm always able to learn a bit.

great thread, I've bookmarked for some parts info & sources.

 

[CruiserTrash]

FWIW I'm also in the thought camp of "keeping it stock". It astounds me how many people put faith in a backyard garage mechanic who posted on the internet with a "better" setup than the Toyota engineering department developed. While not overly complicated from a component standpoint, there are a lot of physics at play in a braking system. Ensuring the stock system is set up and operating at 100% would be my ultimate goal before trying out a bunch of parts that weren't originally engineered to work with each other as a system. And to that point, replacing and maintaining brakes are pretty simple, and even I've been guilty of skipping the manual details a few times. But usually, when I follow the manual to a T, I'll figure out something I've overlooked or done incorrectly, and I'm always able to learn a bit.

great thread, I've bookmarked for some parts info & sources.

2nd this. I did some brake work, new fluid, new calipers, flushed really well, everything adjusted. The 60 stops great. I was surprised at how hard it stopped without locking up - but I can still get it to lock up at the very end of the pedal throw. In fact I like where the “lock up” threshold is in the pedal travel. If it were higher up in the travel I’d be locking it up too often. Anyway, I have zero complaints about my brakes. I’ll be putting new OEM rotors on this winter when I do the knuckles and we’ll see if that nets any further performance.

I have a “Tundra brake mod kit” (really just all the necessary parts) sitting in a crate at home - rotors, calipers, MC, etc. I really don’t know what to do with them now.

 

[Spook50]

Sounds like air in the lines.

My thoughts too.

Also very possible there is air in the master cylinder and/or calipers and cylinders. @dogcruiser I would recommend doing a bench bleed on your master cylinder, then bleeding your brakes in the order of left rear, right rear, right front, left front, and finally the LSPV. As you do each caliper and cylinder, LIGHTLY tap each one with a ball peen hammer. The sharp taps will break loose any tiny bubbles that're stuck to the inner walls and let them be bled out. This is critical on new brake hardware.

 

[dogcruiser]

Thanks for the feedback, @Spook50 . This is helpful. I don’t know that I’ll get around to doing a bench bleed, but I can try the hammer tapping and bleeding at the brakes. Brakes were replaced very recently by CruiserMatt (only the calipers, rotors, pads and soft lines at the wheels, not the booster or cylinder), so I know the work is good, but it can’t hurt to check to see if any more air has presented itself.

 

[cruisermatt]

Do you think it was the booster that made the difference? I have new OEM rotors, calipers, new pads and lines up front and drums/shoes in very good shape in back. But the pedal is soft. I can lock them up but it requires plenty of pressure on the pedal. I’d love it to be more sensitive.

It takes a good bit of distance, and at the bottom it takes more pressure than I think it should to keep the truck stopped. Ideally I’d like more brake at the top and less pressure required to hold it at a stop.

Thanks for the feedback, @Spook50 . This is helpful. I don’t know that I’ll get around to doing a bench bleed, but I can try the hammer tapping and bleeding at the brakes. Brakes were replaced very recently by CruiserMatt (only the calipers, rotors, pads and soft lines at the wheels, not the booster or cylinder), so I know the work is good, but it can’t hurt to check to see if any more air has presented itself.

FWIW I thought your truck's brakes felt normal. 60 brakes can feel pretty bad especially if you just drove a modern car the day before.

We did all new OEM hoses and the brakes are bleed completely (we also always bleed brakes twice, immediately when the work is done, and again right before customer pickup)

What you are asking about changing the pedal feel can be accomplished with either a smaller or larger master cylinder bore, bigger bore will make the pedal firmer, smaller bore will make the pedal softer, but more sensitive.
Boosters are either good or bad - there isn't really and in-between there. It's just a rubber diaphram that either holds vacuum or doesn't.

however none of these will actually make the truck stop better - only bigger rotors will.

 

[dogcruiser]

however none of these will actually make the truck stop better - only bigger rotors will.

I figured. You know me, choosing to drive an old truck and always wondering how to make it drive more like a new one.