I haven't messed with boosters and only a little on non-Mitsu stuff.
I did some research last night. The booster ratio is 7:1 on all US Gen 1 Montero Sports. 2.4L, 3.0L and 3.5L - both narrow and wide, 2/4WD. I haven't checked the Gen 2 Sports or the Monteros.
I THOUGHT I had my brake issues on the '97 SAS Sport all taken care of with the BMC upgrade, but a week latter we replaced front pads and turned the rotors and now I'm back to where I started. Actually, in some cases its worse.
The BMC swap was goodness. Upgrading the bore to 1 1/16", irrespective of anything else, was necessary for the Exploder rear disks and GM D52 front disks to really work 'correctly'.
What I'm dealing with now is the same problem I've had for 10 years. Every time I or someone else has to replace a brake part, everything goes straight to hell and I end up replacing everything or close to it to get it all to work correctly again. The rear Explorer setup has been pretty bullet proof but the front GM setup has been a real PITA.
After doing a lot of research I figured out that there are a lot more different D52 parts than I was ever aware of. All of the pieces fit together but that doesn't mean everything will work correctly when you're done. So far, I've found three different piston bore diameters on calipers and almost half a dozen rotor thicknesses. Everything being 're-manufactured' now in China doesn't help at all, either, since no one there seems to know how to use a ruler.
This is a real PITA since this is the brake configuration I plan to use on this '99 build.
With the gearing I'll be running and 37"s, I need brakes that work correctly and well.
Anyway, I spent some quality time with Bill's 'Brake Bible' and his Xcel spread sheet trying to figure out if there was some inherent flaw in my brake design. (the download link for the spreadsheet is about half way down the 'Brake Bible' page)Pirate4x4 - The Brake Bible
As for an 'inherent flaw', the answer I came up with was no. I kinda figured that since I'm not the first one to run this setup and for the first 3-4 years after the SAS I had NO issues at all. Only after I had to replace pads, a frozen caliper and a master cylinder did 'issues' start cropping up.
My educated guess at this point is that I have 'mismatched' calipers and rotors. I think the rotors may be too thin for these calipers for everything to work correctly and we made it worse by turning them again last week. I'm not sure what the piston diameter on the calipers is or even if they're the same side to side. I specifically told the shop to replace both when it was in a couple years ago but they just replaced one. Both calipers are re-manufactured and are from different stores and are different brands, so ....
After plugging in a lot of numbers to Bill's spreadsheet, I should have more than enough pressure for everything to work even with the monster gearing and 37"s. Yea, well, I already knew that. When they're working correctly they're fantastic. Besides, his numbers are almost exactly the same as we got back when we pressure tested the brake system two weeks ago when the BMC was done. But, it was good to see some independent feedback.
I'm making the assumption that I'm running the 2.94" front D52 calipers now. Based on a lot of research, a lot of math, Bill's calculator, and a few educated assumptions, I THINK the front caliper volume is still a little out of whack - barely. It doesn't quite match up with the 1 1/16" BMC. From what I've read, the 1 1/8" would be the 'correct' BMC for the 1.88" rears and 2.94" fronts.
So, back into the shop on Tuesday. New rotors, new calipers, new front brake lines. Currently installed Hawk HPS pads. I found all the specs and matched up two sets of calipers to the Powerslot/Stoptech brand rotors I currently use.
- Rotors - StopTech Cryo Brake Rotors 127-68000CL, 127-68000CR (drilled/slotted, 1.25")
- Calipers - Wilwood GM D52 Dual Piston Caliper Kits, for 1.25" rotor 140-11290-R
Southwest Speed - NEW D52 Brake Caliper & Pad Set with Pins, for 1.28" rotor 203-6241
- Lines - Wilwood Brake Flexline Kits 220-11718 (20")
I've been wanting to try the frozen rotors, so this is just coincidental 'good' timing.
I can't find new calipers anymore and I refuse to buy re-man anymore, so I am pretty much stuck with after-market.
Piston diameter is 2"x2 for the Wilwood and 2.81"x1 for the Southwest Speed calipers. OEM is 2.94"x1 - which is what my existing calipers are supposed to be.
I'm 99.9% sure the Southwest Speed calipers would be perfect. I'm not as sure with the Wilwood calipers. I'm not yet quite comfortable trusting just the math.
Besides price, the downside to the Wilwoods are no dust boot which is not such a great thing for an off road vehicle. Otherwise, both are direct D52 bolt-ins.
Anyway, I have both sets of calipers ordered, new font lines and new front rotors. Tuesday we'll replace everything with the Stoptechs and the Wilwood rotors. If the Wilwoods work, I'll keep those on the '97 since that's almost entirely a DD now. The Southwest Speed calipers will go on this build with another set of Stoptech rotors. Otherwise, I'll pull the Wilwoods, return 'em and try the Southwest calipers. I'm going to stick with the HPS pads through this until I'm confident everything is good.
Provided all goes well, I have new cryo rotors for the rear and Wilwood D52 'E' pads and 667 pads for the rear almost ready to go. Figured if I was switching to cryo rotors, I might as well try to get something out of it and try the 'E' pads.
- Pads - Wilwood PolyMatrix E Compound Brake Pads 15E-6102K (D52)
- Pads - Wilwood ProMatrix Brake Pads 150-D0667K (Ford)
- Rotors - StopTech Cryo Brake Rotors 127-65052CL, 127-65052CR (drilled/slotted) (Ford)
Baby steps first.
I know how the Hawk HPS pads work, so change rotors and calipers first, see what happens and then go from there.