My Story - Brake/Hydraulic System Basics - Installation Details
The brakes on my 4runner never seemed to work that great with over-sized tires. When I first swapped in the D44, they seemed to get a little better, but then somehow went bad again. The pedal was very soft, the rear brakes were doing little or nothing at all, and I could mash the pedal all the way to the floor without even coming close to locking up the tires. Stopping distances were very long, even when the truck was empty. After a while I got fed up with it all and decided that it was unsafe to drive like this and I found some ways to upgrade.
Brake Pads: First of all, I was using Performance Friction
"Carbon Metallic" brake pads. Big mistake. These pads are designed
for high performance/racing applications. This meant that they only worked well when
they were hot, which for me was not very often (I didn't realize this when I
I swapped those out for some cheap NAPA semi-metallic replacements. These work well and have a MUCH better bite when cold.
Since then, I've seen that Hawk HPS pads are advertised to have 20-30% higher friction than OEM style pads, and they are supposed to grab well hot or cold. I may give these a try next time I need new pads. Raybestos "BruteStop" pads were another higher-friction pad recommended to me that are supposed to work well when cold.
Mushy pedal- The big Chevy D44 calipers need a whole
lot more fluid than the Toyota calipers. Knowing this, I upgraded from the stock 13/16" bore master cylinder to
a 1", but it still wasn't nearly enough. Searching
around the Net, I found that Scott at Rockstomper.com
on PBB about how to make an adapter to bolt a Chevy master cylinder into a
sells the adapters for about $40, or $95 with the new master. '70's and 80's Chevy masters
are readily available in 1-1/8" (1/2-ton), 1-1/4" (HD 3/4-ton) and
1-5/16" (1-ton) bores, and are relatively cheap too compared to Toyota
masters. Compared to a 1" bore MC, a 1-1/8"
pushes about 26% more fluid, and a 1-1/4" pushes 56% more. That's a huge
I put in the 1-1/4" master and this definitely got rid of the mushy pedal. My brake pedal was now rock-hard and could not be pushed all the way to the floor no matter how hard I tried. Locking up the front tires was now finally possible.
The only disadvantage was that it also increased the pedal-effort needed to stop the truck. So I found a work-around for that...
... A dual-diaphragm brake booster. Most earlier Toyota's like mine came with a single diaphragm booster. Around the early to mid '90's, Toyota started using dual diaphragm boosters, which provide even more vacuum brake assist. I picked up a dual-diaphragm booster from a '97 T100 4x4. It was the same over all diameter as my old one, but 1" thicker and still bolted right in. The bigger booster made the pedal feel a little softer again, and the pedal effort needed to stop the truck decreased quite a bit. The pedal only needs to be depressed a fraction of the effort and distance of what it used to.
Rear Brakes- I had tied my stock rear proportioning valve rod all the way up a long ago, as well as replaced it with a new one from Toyota, but the stupid/expensive thing seemed to have gone out again. I could stomp the brakes as hard as I could when pointed up a steep hill, but all that would happen is that the front tires would drag and the truck would roll backwards. So, I installed a Wilwood manually adjustable proportioning valve. This worked great. I can adjust it so the rear brakes lock up long before the fronts if I want to, but that's not a good thing because in a panic stop the rear end will want to come around. So I backed it off a bit and set it so that the fronts lock up just before the rears do. I can tell the rear brakes are actually doing something now.
All of this combined to give me AWESOME brakes. The pedal effort is much less than it used to be, my truck stops on a dime, and I can lock up all four tires if I want or need to. I feel much safer being able to stop the truck much more easily.
After I upgraded to 37" tires, I switched out the 1-1/4" master for a 1-1/8". This setup worked even better! (read on for the details)
Brake/Hydraulic System Basics:
Hydraulic pressure and leverage is directly dependant on the piston surface area at each end of the system (master end and caliper end). You have a relatively small piston in the master cylinder and large ones in the calipers. This gives your foot a leverage advantage.
If you want to increase your braking power for a given amount of foot power, then you can either increase the piston size of the calipers, or decrease the size of the master. This comes with a tradeoff though- your pedal will feel "softer," and if you make too big of a change, the master cylinder may not be able to push enough fluid to the calipers to build up full pressure before the pedal bottoms out. This is the problem I had with the big D44 calipers and small Toyota master.
Conversely, if you want a firmer pedal, then you can decrease the caliper size or run a bigger master.
Other ways to increase the mechanical advantage of your brake system are smaller tires, bigger rotors, and increased brake pedal ratios (longer pedal).
Hydraulic "Leverage" Ratios (Mechanical Advantage)
NOTE: Since the front brakes perform the large
majority of the braking, I will concentrate on the front caliper size as it
relates to the master cylinder.
My recommendation when setting up your brake system is to set up master cylinder to front caliper ratio however it works best, and then use a manual proportioning valve to tune the rear brakes.
To figure how how much mechanical advantage, or leverage, the
hydraulic system gives us, we must first find out the piston surface areas at
each end of the system. Pistons are circular, and to
find the area of a circle, you take the square of the radius and multiply it by
Pi. [ A= Pi (r2) ]. For example, the piston surface area of a 1"
diameter bore master cylinder is (.5") x (.5") x (3.1416) = .785 square inches.
Notice that since the surface area is related to the square of the radius, relatively small changes in piston diameter result in significant changes in piston surface area. For example, increasing the piston diameter from 1" to 1-1/8" increases the piston surface area from .785 in2 to .994 in2 of surface area. The diameter increased 12.5%, but the surface area increased by 26.6%.
Master cylinder diameters are usually cast into the body
somewhere, but if not, you can always just measure the bore itself on the
backside of the master.
Common master cylinder piston diameters:
Toyota: 13/16" (.518in2), 7/8" (.601in2), 15/16" (.690in2), 1" (.785in2), and 1-1/16" (.887in2). (1-1/16" available on some T100's, maybe others)
GM: 1-1/8" (.994in2), 1-1/4" (1.227in2), and 1-5/16" (1.353in2).
For caliper effective piston area, you use the total combined surface area of the pistons in one side of the caliper. On a single piston D44 caliper, it's simply the surface area of the one piston. On 4-piston calipers like Toyota uses, you add surface area of the two pistons on one side of the caliper.
Toyota has generally used two different calipers on '95 and
earlier trucks and 4Runners. Sometimes
these are referred to as "4cyl" and "V6" calipers, however all
of them after about
'92 or so came with the larger ones.
Early Toy calipers had 2 small pistons (1.335") and 2 large pistons (1.685"). This gives an effective surface area of 3.63in2 .
Later Toy calipers used 4 large (1.685") pistons, for a surface area of 4.46in2 .
GM D44 calipers use a single 2-15/16" piston, which gives a surface area of 6.778in2.
GM D60 calipers use a single 3-3/8" piston, which gives a surface area of 8.946in2.
As you can see, the GM calipers have a MUCH greater piston surface area than the Toyota calipers. This is why your brake pedal will feel soft and low if you swap in a GM axle and don't upgrade the master to match.
Most early Toyotas came with 13/16" masters and the smaller
calipers. This gave a hydraulic leverage of .518 to 3.63, or about 7:1.
Later Toyotas usually came with 1" bore masters and the larger calipers. This gives a hydraulic leverage of .785 to 4.46, or about 5.7:1. The later trucks also usually come with the dual-diaphragm booster which helps make up for the reduced hydraulic leverage.
Hydraulic ratio changes can be compared by percentage to get an idea of how much the pedal effort will change if everything else is left the same. For example, when Toyota decrease the ratio from 7:1 to 5.7:1, they increased the pedal effort by about 23%. However, they made up for this difference by going to a dual-diaphragm booster.
|Early Toy = 3.63in2||Late Toy = 4.46in2||D44 = 6.778in2||D60 = 8.946in2|
|13/16" = .518in2||7:1||8.6:1||13:1||17.3:1|
|7/8" = .601in2||6:1||7.4:1||11.3:1||14.9:1|
|15/16" = .690in2||5.3:1||6.5:1||9.8:1||13:1|
|1" = .785"in2||4.6:1||5.7:1||8.6:1||11.4:1|
|1-1/16" = .887in2||4.1:1||5:1||7.6:1||10.1:1|
|1-1/8" = .994in2||6.8:1 +||9.1:1|
|* 1-3/16" = 1.1075in2||6.12:1 +||8.1:1|
|1-1/4" = 1.227in2||5.5:1 +||7.3:1|
|1-5/16" = 1.353in2||5:1||6.6:1 +|
|Pink area is most likely unusable/unsafe|
|Green areas are ratios I would recommend|
Stock ratios 7:1 (small booster) and 5.7:1 (big booster) are shown in BLUE
Ratios I've tried with the D44 calipers shown in RED
Different combinations I've tried with the D44
8.6:1 - My 4Runner would stop OK during normal driving, but the pedal felt soft and would hit the floor before I could build up enough pressure for a decent fast/hard stop. I definitely could not lock up the tires. I decided this was unsafe on my vehicle, however it might work OK for a lightweight buggy. This was with the stock single-diaphragm (small) booster and 35" tires.
6.8:1, small booster, 37" tires: Pedal was firm and relatively high, but the truck stopped just fine. Pedal effort was a little more than I liked for everyday driving. It took a lot of pedal effort to lock up the tires on dry pavement. Might have been OK with 35's?
6.8:1, big booster, 37" tires: Pedal feels a little bit soft, but I can bring the truck to a fast/hard stop with minimal pedal effort. I can lock up the 37's on pavement relatively easily (maybe even too easily on wet pavement?). This my current and favorite setup so far.
5.5:1, small booster, 35" tires: Pedal was very high and VERY hard. It took lot of pedal effort to stop the truck. This was unacceptable to me, but it was a step in the right direction, so I then upgraded the booster (below).
5.5:1, big booster: Pedal was high and somewhat hard. This stopped the truck pretty well with 35's. It took a lot of pedal effort to lock up the tires on pavement. Hard stops with a fully loaded truck and dirt bike trailer were a little nerve-wracking. However, this was a huge improvement over the 8.6:1 ratio I was initially running with the D44. It also seemed to work better than the stock IFS brakes ever had with 33 and 35" tires. I ran it this way for 2 years. When I put on the 37's, brake performance decreased a bit, so I then went to the 6.8:1 ratio, above.
7.5:1, small booster: Brandon Miller at River City Rock Crawlers runs a 1-1/16" Toyota Corolla master with a stock booster in his 5.0-powered '83 Toy. He says "Pedal is kinda stiff, but it works well enough for me." I would be curious to try this combo.
Brake Upgrade Details
Chevy Master Cylinder Install
The 1-1/4" master I used was from '76 Chevy HD 3/4-ton 4x4 w/
the bigger rear brakes. Autospecialty part # A-86008
The next problem is adapting the Toy
metric brake line fittings to the Chevy master.
The first thing I did was to reduce the 9/16" and
1/2" ports to 3/8".
The cleanest way to bolt the stock 3/16" hard lines to the 3/8" female ports would be to cut the metric fittings off, install 3/8" fittings, and re-flare the lines. However, I wanted to be able to easily go back to the Toy MC if necessary, and I also didn't want to bother with cutting and re-flaring my own brake lines, so I used extra fittings to make it all a bolt-together affair.
For the front brakes, I ran a 12" section
of standard 3/16" brake line with 3/8"-24 male fittings to a WH 1443,
to to the factory metric "T" fitting under the master. (Balkamp
(BK) 813-1203, to WH
1443 (3/8"-24 IF female to 10mm-1.0 male))
For the rear brakes, I ran an 8" section of
3/16" brake line to a WH 1443, to a factory 90 degree metric union
bolted to the factory hard line.
For some reason, the 1-1/4" and 1-1/8" masters have the 1/2" and 9/16" ports reversed front/rear. For both masters, I ran the front port to the front brakes, and the rear port to the rear brakes. I don't know if that is the "correct" way or not, but it worked.
This Edelmann catalog has a nice cross reference to
different brands of similar fittings, as well as a bunch of other useful
My local NAPA (Reibies) stocks the Weatherhead fittings and
Balkamp hard lines. I believe CarQuest carries Edelmann.
Bend your lines, bolt it all together, bleed your brakes, and you're ready to go.
The T100 booster upgrade is very straight forward. The booster I used was from a '96-98 or so T100 xtracab 4x4 without ABS. It bolts right in place of the old stock booster, but is about 1" thicker (due to the dual-diaphragm design). Be sure to re-check your push-rod distance.
Wilwood Rear Proportioning Valve
The Wilwood valve has 1/8" NPT female fittings, and comes
with two fittings to convert those to 3/8"-24 female inverted flare.
To plug the "T" in the front brake line that used to run to the old stock LSPV, I used a WH 1443 (3/8"-24 IF female to 10mm-1.0 male), and a WH 131x3 3/8"-24 plug.
See master cylinder section above for adapters/fittings links.
Then I bled the brakes, and did some testing to set the prop. valve where I wanted it. I basically set it so that the front brakes lock up just before the rears.
Grand Total- under $200
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