The 1 1/16" BMC is installed in my '97 SAS'd Sport. That one runs the Chevy K10 callipers front and Exploder late '90s/early '00s callipers rear with Powerslot rotors and Hawk 'green' pads all the way around.
Everything installed as expected. Just a simple bolt in replacement for the OEM 15/16" BMC. The only thing of note was making sure to install the 'filter cup' right side up.
It has a top and bottom and apparently it came to me installed up side down which was why the fit was so loose. Having the Mitsu tool to adjust the booster push rod made the tech's life significantly easier. Another tool I'm not going to be without in the future is a brake pressure test set for testing brake pressure at the callipers and BMC. Its already proved to be a very useful tool.
I liked how my brakes were before with the OEM 15/16" BMC. The only real complaint I had was how much force it took to hold on a hill and that they had a VERY slight tendency to bleed down while sitting with a foot on the pedal. The latter seemed to be almost entirely due to the brakes not being bled completely or correctly - or both. The former was a real PITA if I had to sit for 20-30 minutes on the trail but thankfully that was a fairly rare occurrence. Otherwise, there was never an issue with stopping. The only complaint of others driving it was how squishy the pedal was and how much travel there was.
All of that is now gone. The feel is so close to an OEM Gen 1 Sport that if I hadn't been driving both my stock '97 and '99 for the last few days - both of which have had the entire brake system run through in the last three weeks - I don't know if I'd be able to tell any difference between the three.
The new BMC set up is more sensitive to foot pressure than the old set up but its absolutely rock solid stable and predictable. There is absolutely NO leak down. I tested that sitting in a drive-through for 20 minutes.
Hill hold is fantastic! It isn't necessary to actually press on the pedal. Just the pressure of resting my foot on the pedal is sufficient.
I did a couple hard 'highway' stops from 55-60 MPH. I didn't attempt a 'panic' stop, first because I don't lock up the brakes in lifted modified vehicles, but mostly because we have a LOT of crud on the roads since the last snow. Too much gravel and sand on the roads for it to be safe.
Anyway, brake performance is as good if not better than it was with the 15/16" BMC. Its hard to tell, but its definitely not worse and it takes less pressure on the pedal to brake the same distance. That's great - thatís the one thing I was afraid of changing since the bigger BMC bore produces less pressure and I wasn't going to tinker with the pedal ratio.
Front/rear pressure wasn't great with the 15/16" BMC. I had them do a steady, moderately heavy pedal press, not a panic stop so pressures are not maximum, but they are consistent. Something like 750/600 F/R with the stock OEM BMC. This isn't terribly accurate - I was primarily interested in getting the rear pressure as I already knew the front wouldn't be an accurate reading. The new BMC came in at about 1100/700 F/R. This is an accurate reading for both F & R.
Roughly the proportioning percentage F/R should be around 60/40 loaded and 70/30 unloaded +/-. The new 1 1/16" BMC with the OEM '97 Sport non-ABS valve and the above callipers/pads produces almost a 60/40 split - like 61/39. That's good with a heavy load in the cargo area - I normally have 500-600 lbs of gear in the back - but bad if the vehicle is empty.
Empty should be more like 70/30 with about 550 psi in the rear, +/- a little depending on the pad/rotor combination. Figure with my rotors/pads 550 should be pretty dang close. That'll send another 150 psi to the front which will actually improve the front braking a noticeable bit more.
So, the big '97 will stay on the OEM valve until it becomes strictly a DD. When that happens, all the gear comes out and goes in the new '99 and I'll change out the OEM proportioning valve for the Wilwood and set the pressure ratios to what I talked about above. The '99 will get a Wilwood when I pull the ABS here shortly and I'll set it to the 'loaded' values since it'll have a cargo bay full of gear all the time once its finished.
I'm a LOT less concerned with whether this set up will work with 37"s now. I think the most I'll have to do - if I have to do anything - is switch to a little more aggressive pad. I don't want to because I REALLY like the Hawk 'green' pads, but since the '99 won't be a DD I expect I'll live.
So, right now I'm ecstatic! This BMC is as close to a perfect match to the callipers I'm using as I can expect. Between the 1-ton steering last spring and this, its like driving a different vehicle.
Now, if the 3G BMC wasn't so insanely expensive!
1997 Montero Sport OEM Brake Master Cylinder
1997 Montero Sport w/ 3000GT VR4 Brake Master Cylinder
The booster hose is in a different location between the 'OEM' (stock 3.0L) pictures and the '3G' (transplanted 3.5L) pictures.
One more minor difference between the 3.0L and 3.5L.