pmoose

For starters, i have a '93 Toyota 4x4 4cyl SAS'd running 35's. Since the 35's, the brakes have become inadequate, they won't even lock up on the street when I mash on them as hard as possible. After reading several threads on pirate4x4 as suggested by a thread on here, im confused on how to upgrade my brakes without buying new slotted/drilled rotors and doing the rear disc conversion. Ive heard about using the bigger 1in bore MC and a dual brake booster from a Tacoma. Does anyone from this forum have experience with this setup or any advice? Also, how do I identify a dual brake booster from a single if I was to go to a Toyota salvage yard to pick one up? Is it true that the V6 trucks had larger and better front calipers than the 4 cyl trucks? Again, I know this is alot but Ive heard so many different things and so many ppl say they "think" a certain part was found on a such and such truck but they really weren't sure. Any help would be appreciated, Thanks!

SCToy

Cheapest mod is T100 calipers, rotors and master cylinder. Best to time It when you need new rotors and pads anyways

SCToy

Oh excuse me SAS won't take t100 parts.
You need vented landcruiser rotors, V6 calipers and a good set of pads

xxxtreme22r

What did you do with the LSPV bracket when you lifted the truck?
Some 4cyls already had the "v6" brakes/1" or is it 15/16" master/dual diapham installed, just don't remember what year they switched over.

Single diaphragm booster



Dual Diaphragm Booster

pmoose

what is the LSPV? Load Sensing Proportional Valve? when I lifted the truck, the only thing I did to the brakes was put extended SS brake lines in the front and and rear. i guess im gonna have to pull the MC off to measure the bore. If its not 1 in, ill get one that is and find a dual brake booster and V6 calipers. The tacomas/T100s def had the dual brake booster and V6 style calipers right?

xxxtreme22r

If you didn't do anything to extend that LSPV (yes load sensing....) Then it thinks your "unloaded" and it relieves ALOT of the rear brake line pressure. It's probably why you have very little brake. Try unbolting the bracket and zipping the rod all the way up temporarily and see if your braking gets any better.

Personally I wouldn't leave it that way though. Some people have cut that rod and made an adjustable turn buckle for them to adjust the pressure to their liking. Problem with leaving it all the way up is if your in snow/ice the rear will lockup real easy.

If you don't have a dual booster then the MC is only gonna be like a 7/8's no need to measure it. This is assuming noone upgraded just the MC.

angrybob

The master cylinder size is cast in on the side of the master cylinder. Mine says "13/16" on the inboard side. Yours is a 7/8" for a standard or 1" for a 1/2 ton.

Check the pic above and confirm the size of your master cylinder and if you have a single or tandem booster. If you have the single, the dual upgrade could be a good fix.

Maybe. Drum brakes suck. Even a properly proportioned drum brake does about 20% of the work at best. Loaded, maybe a little more.

In this case, its all about money.

1. Check that your drum brakes are adjusted correctly - 0.6mm (0.024") running clearance. It will shorten your stroke if the running clearance is too large. Might help a little on the output too.

2. Bleed the brakes if the brake pedal feels spongy at all.

#1 & #2 you should do anyway.

3. Cheapest thing to upgrade is brake pads. Find a performance front pad (don't bother with the drum brake shoes)

4. If you don't have the tandem booster, this is an excellent upgrade and boneyard versions are $40 or so for the booster and probably $25 for the matching master cylinder. You must change both to keep a proper brake balance.

You may want to do #3 and #4 together.

5. As suggested above, bigger (landcruiser?) rotors, v6 calipers, and pads.

Good luck.

xxxtreme22r

My 2-3" homeade LSPV extension bracket made a huge difference in stopping my 33's after I lifted my back end. And because I was sagged before hand (loaded) I would actually lock up the rear brakes in snow if I gave it a tad too much brake. This was also after I put the dual diaphram booster and T-100 master in. I still haven't went over to the v6 style calipers as I had just did the front brakes less then 2 years ago with new rotors.

TNRabbit

The BEST pads I've used to date are the Hawk Super Duty. @ $90-100, but EXCELLENT pads. Combined with RotoPros (www.rotorpros.com) vented discs, I have the best brakes ever on my truck.

dropzone

iTrader: (6)

What axle is on your front end? If it's a 79-80 you will run into problems trying to get the vented rotors to fit, the FJ rotors won't fit,
If you have an 81-83 or 84-85 front end FJ rotors and v6 calipers are a no brainer.
4 cyl caliper suck compared to the bigger dual piston v6 caliper. Besides high steer, vented rotors and v6 calipers were the best upgrade I have done.

waskillywabbit

iTrader: (-1)

Rotors. Booster and MC. Bigger calipers.
It's that easy.

:wabbit2:

pmoose

thanks for all the help, this has really cleared my thoughts on what to do. I believe I will go to my local yota boneyard and find the dual brake booster and matching MC and also try to find the V6 style calipers as well. As for the LSPV, i forgot that I actually did put an extension to raise it up so I beleive the rears are working correctly. Also, my front end is from an '84 and the front rotors are the vented style that came with the SAS kit so I believe they are the landcruiser style

xxxtreme22r

You guys are practically making me wanna finish up on my brake upgrade. lol. How much of an improvement am I gonna see from where I am at now with the t-100 MC and DD booster?

TNRabbit

The problem here with the OP is that he's running 35s on a truck with brakes designed for what, 30" tires (& they weren't that great with the originals)?

The overall resistance has gone up TREMENDOUSLY with the over-diameter tires. Too bad there's not a 16" rotor/caliper combo you can upgrade to with 17" tires~

xxxtreme22r

Right, but..... I had the same issues on mine with 33's after upgrading to the 1"/DD and before I messed with the LSPV bracket. But since he corrected himself in saying he already extended that bracket you can disregard me recommendation on moving the adjustment rod.

Still curious though how much of an improvement I might see with the caliper/rotor swap. I know afterwards my pedal is gonna feel a little softer. I kinda like how it feels now. I had the 1" on just the single diaphram and the pedal was as hard as a rock. I know by upgrading the calipers now I will essentially lower the clamping force but up the pad friction so in theory my pedal should get a tad "softer"

SCToy

they work almost too well, it's very easy to lock up the front end of you're not careful on 31s.

Pad compound does make a huge difference. So, do some research before you pick a set up.

angrybob

What calipers do you have now? I had no idea that the pickups came with a single 57mm or the 4-pot for the 1/2 ton (according to rockauto.com at least). I thought only the 4-pot...

I learn something every day

xxxtreme22r

4cyl (small and large pistons) I am talking the switch from the 4cyl to the "6cyl" (all large).

I am assuming here he's got the "normal" 4 cyl calipers/rotors and retained the original calipers on his truck and not switched to the older style when he did the SAS. But since we don't know what year axle he used...........

xxxtreme22r

On a side note AZ is showing the same 4 piston caliper 79-85 but shows a different 4 piston for the IFS trucks. Then you got the v6 style.

I don't see a single or two piston anywhere for the SFA trucks. hmmmm.... lol.

angrybob

A little caliper 101:

To understand caliper sizes, the single piston equivalent areas must be compared. One thing to note is that even though the opposed caliper has 4 pistons, only one side is used for sizing because the other side just provides the normal force that the bracket provides on a floating caliper.

The math might surprise you:

The single 57mm has an area of 2552mm²
The single piston equivalent area of the 22RE 4-pot caliper (on my 87 4runner which is a 42.7 / 34mm version) is 2340mm² - 8.5% smaller than the single 57mm!
The single piston equivalent area of the V6 4-pot caliper (a 42.7 / 42.7mm version) is 2864mm² - 12% larger than the single 57mm.

All things being equal, the main advantages of a 4-pot versus floating caliper are smaller running clearance and usually way stiffer. A single piston 57mm floating caliper gives the same output as a 4-pot / 6-pot / whatever that has a single piston 57mm equivalent area. It just might ‘feel’ a little different.

In your case you would get 12% increase in capability, but with the same m/c your initial stroke it takes to engage the brakes will go up a little. You might feel a difference.

A little rotor 101:

The rotor size is a bigger output gain though. You go from a 257mm to a 290mm OD. The rotor dimension used for comparison is Effective Radius ~ from the center point of the rotor to the mid-point of the pad contact area along the radius. With a 33mm OD difference, the torque gain is about half of that…say 16mm. Torque = Force * Distance and since torque = force at the caliper * distance to the center of the rotor it’s a 1 to 1 gain with no loss, change in pedal feel, etc.

From a feel stand point, my guess is that the only thing you will notice is the slightly longer initial stroke since you already did the m/c & booster swap. Of course, with more output, you will probably not have to push the pedal as hard as before. That too should be noticeable. Throw sticky pads at it and you will probably get a big gain.

I’m in AZ so often forget to think about snow. Not sure how all of this would perform in snow and ice. My guess is with a little care it wouldn’t matter.

If you are looking to get more out of your brakes the V6 rotors and calipers seem to be a good option and will be well matched to the booster m/c you already installed.

Only reason to go with rear disc IMO is if you run loaded often, especially in the mountains. Disc brakes are way better for fade.

My $0.02