I'm switching my car over to four wheel disc brakes. I know the proportioning valve is different, but is there really any difference with the master cylinder? I have front disc/rear drum on it right now.

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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

 

It depends on which disk brakes you're putting on....

If you're putting on the newer style with the aluminum PBR calipers, you don't have to change anything. If you're putting on the older inferior kind that usually doesn't work, specifically the ones that came on a 9-bolt or 80s 10-bolt, then you will have to change both of those things.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Just made that swap 87 drum to 89 disc rear.
Only changed the emgr. brake cables and the
proportioning valve and some fittings. Did not have to change the master cylinder. The new rear was a B-W
9 bolt with the 11.655 rotors and the alum.PBR calipers everything works great.



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1987 Black Camaro IROC-Z (original owner) Replaced LB9 @ 86100 miles.
New 350 Crate engine
Balanced & blueprinted
WP 67cc Heads 9.6:1 C.R.
Cam: 454lift,216dur@50,110ls
TPI Induction(from 305)
22# Fuel Injectors,AFPR&Gage
SLP Intake runners
New GM 1988 chip
K&N filters & Air Foil
Hothkis STB
SLP 1 3/4 Headers
CATCO 3" Catalytic conv.
SLP 3" Cat Back Exhaust
700R4 Auto
SLP Torque Converter (2400 stall)
B-W 9 bolt rear 2:77 Possi. Four wheel disc brakes,245/45/ZR-17 Tires
17x8.5 ATI 5 Razze Wheels
Dyno results: 211 RWHP & 282 RWTQ.
264 HP & 352#/ft at flywheel. NEW TOY

 

Cool, that was the answers I was hoping to hear! I'm putting on the aluminum PBR calipers off a 91 GTA. Actually, it's the whole rearend from that car. I've got the proportioning valve and the e-brake cables as well. I just didn't think to grab the master cylinder. I'm glad to know they should be the same. Thanks guys!

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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

 

I put a 91 rear in my 83. The only thing I had to deal with was the metric / std line issue: I got the end of the steel line off the 91, cut the same amount off the end of the line in the car, flared the ends, and used a union to hook them up; and then used the rubber line for the 91 rear. If you're doing this to a 89 car, you won't even have that much trouble, it should just bolt right in without having to change anything else. In mine, the 91 rear's parking brake cables hooked right up to the car side of the cable, it hardly even required adjusting.

I was not aware that 9-bolts ever came with the PBR calipers, although that system should swap right onto one since the axle housing flange is the same between the 2 designs... the older system that they (and the pre-90 10-bolts) came with is famous for not working because of the poor adjuster system design. And of course, its hydraulic requirements are different, so it requires the different MC & PV, where the PBRs use about the same amount of fluid as drums do, so all the hydraulics can be the same as drums.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Yeah, nine bolts having PBR calipers is a new one on me too. I guess I'm lucky mine's already metric. I didn't think about that when you're installing one in an earlier car. I'm glad I bought the whole rearend too. I noticed the axle housing flange is different between drum and disc housings. It looks like you could probably modify a drum housing to accept the disc mounting plates if you had to. Fortunately, that's one headache I don't have to deal with! I made a point of it to get an 89 or newer rearend because I've also heard the self-adjusters on the older ones were basically worthless. Once again, thanks for the info. A site like this one would've been great to have around when I was building my first gen!

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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

 

1989 was the first year for the updated disc's on the B-W 9 bolt, came with 11.655 rotors
and 2-piston Alum PBR calipers. I think this set up was used only on the 9-bolt rears from Borg-Warner until it was dropped in 1991
then put on the 10- bolt.

[This message has been edited by Z28DJP1987 (edited August 31, 2001).]

 

Would I have to change it going with a Baer setup? :P