So my car came with power front disc brakes and drums in the rear. All of the conversion kits I've seen have the brackets and hardware to convert the rear to disc brakes but no mention of new booster or master cylinder. Are these components not required to replace if just switching to disc brakes in the rear and keeping the stock fronts as they are? I thought I read somewhere that a new proportion valve and master cylinder/booster were required specifically designed for disc brakes at all four corners.
First, if you have 15" Buick wheels, be careful. Many of the kits will rub the caliper. Been there, done that. Next, you might need a new master cylinder. Drums don't have enough capacity to full operate rear discs. Lastly, you will probably need a new proportioning valve as drums often have a residual pressure valve that holds the drums partially pressurized when you want discs to fully retract. I have a 70 with rear discs and it has no prop valve. I removed the hold-off valve up by the master, swapped masters and still have no prop valve. It will just barely start to slide the rear brakes in a panic stop. I have an adjustable prop valve but I've never plumbed it yet.
Thanks Greg. That info helps out a lot! I have aftermarket 18"wheels so I think I'm good there. But your comment about the master cylinder and prop valve are food for thought. The kit I was looking at from summit only had the hardware for the conversion without anything from under the hood. Which kit did you do your conversion with? Also, completely unrelated, how do you like the 3.73 gears with your 2004r? I have an extreme automatics 2004r with 3.42 gears but they wine like no one's business due to improper installation. I will swap to 3.73s soon since I need to replace them anyway. Just wondering how yours are treating you. I imagine I'll get a better off idle punch with the new gears.
I have the Right Stuff detailing kit. It works well now that it is on but using Buick wheels was a challenge. I bought deeper hat rotors and had them turned down to 11" and then modified the bracket by slotting the backing plate holes so I could sit the caliper lower on the rotor. Still needed a 3mm spacer with factory wheels. You should be in great shape with the 18" wheels. 17" where going to be my choice if I couldn't make it work otherwise. Yes, I have 3.73 gears and a truetrac setup and built by MonzaZ. He built it and shipped it to me for what it would have cost me to have my old housing blasted and assembled. Well satisfied. I had 3.73 before the overdrive and they were great but a little much on the road. When I went overdrive I toyed with 3.42, 3.55, 3.73 and even 4.10 before I settled on the 3.73. I think they are about perfect with the 275-60-15 rears. I turn about 31MPH per 1,000 RPM so just about 2200 at 65. 3,000 used to be 62 and now it is over 90!
If you already have discs in the front,then you should already have a master cylinder with a 1 1/8" bore. That might work,but you might need one with a 1" bore. When going from drums to discs,you want less volume and more pressure,do your master cylinder gets a smaller bore size. There are disc/disc proportioning valves available.If you have a 70,with two valves,try it the way it is,but with a smaller-bore master cylinder. If that isn't enough,then change the lower valve first,and go from there.
Duke350, Very interested with what you come up with. I have a 72 GS350 Convertible. Just pulled the rear out to rebuild it. Don't really want to put the drums back on. I had the front converted to disc last year. Not finding anything on the web and seen some other posts about calipers rubbing on the wheels or disc. take care, mike
Here's my original thread where I worked through the kit and 15" Buick wheels. They definitely rub. http://www.v8buick.com/showthread.php?219455-Right-Stuff-Rear-Disc-Brakes-amp-Buick-Wheels
Great, thanks Knuckle. I'm not too worried about rubbing on the original wheel...they were 14" rallye wheels that I had to give them up when I converted the fronts. Do you know the part or kit number for the Right Stuff kit you bought or where you got them?
I believe it was this kit. I got it with the rear end that MonzaZ built for me. https://www.summitracing.com/parts/rsd-afxrd01/overview/make/chevrolet/model/chevelle
That is the kit that I install on a lot of customer's rears,who want rear discs.Its a fairly simple kit. It consists of late70's Cadillac rear calipers,late-70's Camaro/Firebird rear rotors,and caliper brackets to mount to the A-body rears. You can get the traditional smooth rotors,or the slotted/cross-drilled rotors. Since they are copies of original parts from GM cars,you can get any spare parts from your local parts store,if needed.
Yes. The majority of the rears that I have installed them on were bolt-in axle. The inner diameter of the bracket is large enough to go over the l expanded section of axle tube,on a bolt-in axle style tube.
Yes, the have the parking brake integrated into the caliper. You may need to work on the existing cables to make it work. Mine hooked up pretty well with just some adjustment. Also, know that when you put this together, you have to actuate the parking brake once to set the brake shoes to the caliper or you will never get a good pedal.
