Disc Brake Swap Rotor 11 or 11.75?

[mrmolding]

Merry Christmas all! I think I've finally given in to a disc swap based on lots of posts here and the Disc O Tech article. Four years ago, I rebuilt everything from master cylinder to lines, to wheel cylinders, drums, etc. from mostly NOS parts. I did experience the incorrect shoe lining post in sticky thread Drum Grabbing Brakes -- SOLVED and wished I'd seen that years ago before I saw that thread recently. New shoes are junk and I found an older pair that had been relined -- worked great.

Anyway, driving in modern traffic with drum fade up and down canyon hills has become a little scary recently, so I'm going to give it a shot as a project over the winter. Oh well, no more red paint showing through my road wheels.

I've amassed all of the parts over the years from shows thinking that I'll just get things in case I do the swap. But I was wondering if anyone has any experience between the 11 rotors vs the 11.75 rotors? I have brackets for the 11 discs and the correct spindles from a 73 a-body, dual chamber booster, disc/drum master cylinder, different proportion valve, etc. I know I can get a bracket for the 11.75 rotors and I understand that there is more leverage, heat dissipation, etc., but has anyone noticed a significant difference that has gone from 11 to 11.75? I've gone to 15 in aftermarket Road Wheels, so I'm good with clearance based on what I've found for 11.75. But, I have all of the parts for the 11 and I'm ready to go. It would just be a matter of getting larger brackets and rotors.

Any help or thoughts are welcome!

 

[ckessel]

You've got the 15's so go biggie size with the 11.75's. Brackets and rotors. When I put the 15's on my 67 wagon, doing that plus swapping in the 11x2.5" drums on the rear. I like to have as much whoa power as possible.
But to one of your questions about comparison between regular and biggie, can't help yet.

 

[Nxcoupe]

I have the 11 in with 15 in wheels. I hadn't driven it with drums to compare, but I did drive it with manual discs before I had the old hemi booster rebuilt. I can say that it was like night and day going from manual to power and I love it now.

 

[mrmolding]

Ok, so now I find something! Looks like one person said just keep the 11s vs 11.75 but another said get DrDiff's slotted/drilled 11.75 rotors and noticed a big difference. Thanks everyone!
Inexpensive “Cordoba” Brake Upgrade for 70 Road Runner

 

[R413]

What car, what options, do you know the weight?

How are you going to drive it?

I use 11.00 on 36-3800lb B-bodies and they do everything I need, some power, some manual. I like manual better, but both drive nice.

 

[mrmolding]

What car, what options, do you know the weight?

How are you going to drive it?

I use 11.00 on 36-3800lb B-bodies and they do everything I need, some power, some manual. I like manual better, but both drive nice.

It's my 70 Road Runner. It came with 11x3 manual drums but everything was very original and tired with spliced line repairs etc. So I redid everything and added the single chamber drum power booster. It's been fine for the most part and I mainly cruise it on the back canyon roads where they filmed the 1971 Duel movie. It is a real blast driving the roads but I need to reenter modern traffic for quite a few miles to get home and lots of hills to get there. I've probably done 50-100 brake jobs as a helper at a gas station in my youth and maybe 10 rebuilds in the past 10 years for myself and friends. So I know everything is setup as well as can be. But in modern traffic with cars zipping around me and regenerative brakes in electrics, it can be interesting to figure out when cars are actually slowing down/stopping because the brake lights don't actually come on until the car is completely stopped. Not good for a lumbering mopar coming down a steep hill with brake fade. But, mainly cruising around for hours at a time, no racing, drag, etc. Just cruising around at normal speeds. So, another vote for 11 rotors. Thanks!

 

[Fran Blacker]

The Disco tech swap is expensive if you want 11.75 rotors unless you have the 11.75 caliper brackets. I did the swap it 2002 11.75 brackets cost me $135 or so.

 

[1 Wild R/T]

Red car is still running it's original 10.87 (11") discs, Green car has 11.75 discs (originally 10.87)
Only time you will notice a difference is a long down hill and you shouldn't be using the brakes that much anyway.... As long as the smaller rotors don't get hot they are fine....

 

[gkent]

Sent you a PM

 

[mrmolding]

View attachment 1778844

Red car is still running it's original 10.87 (11") discs, Green car has 11.75 discs (originally 10.87)
Only time you will notice a difference is a long down hill and you shouldn't be using the brakes that much anyway.... As long as the smaller rotors don't get hot they are fine....

The other day I was going up whites canyon road and coming down plum canyon road after an hour driving in the canyons and a slow electric was in front of me (no brake lights until a real stop) and another electric tailgating me and pointing at the car giving me the thumbs up. Then a guy in a BMW was riding along side of me to wave and yelling about how he loved the car. Very flattering, but people don't understand the old rule of 3 car lengths to follow a car (at least in my driver's ed it was that in the 70s). I was driving a buddies 72 Mustang fastback on the same road with period correct discs in front and drums in the rear. Night and day difference in stopping after same amount of driving. It's not easy to be an offensive driver in a classic with all drums without less congestion, so looking to stop being a defensive driver. Thanks as always! Figured I'd add a pic of the runner in front of the "Duel Tunnel" where the Truck and School bus scene was in the movie.

 

[mrmolding]

Alright everyone -- thanks for the help! I just ordered the 11.75 brackets. I'll report back when I'm done! Much appreciated!

 

[autoxcuda]

It’s just extra insurance.
The cost of bracket for 11.75 vs consequences.
No one will ever notice the difference looking at them vs 10.75” disk.

Come out to a Spring Fling Malibu Friday Cruise through Santa Monica mountains

 

[1 Wild R/T]

It just extra insurance.
The cost of bracket for 11.75 vs consequences.
No one will ever notice the difference looking at them vs 10.75” disk.

Come out to a Spring Fling Malibu Friday Cruise through Santa Monica mountains

View attachment 1778884

View attachment 1778885

The Friday Cruise was a blast... Planning to do it again in a few months...

 

[tonysrt]

Going with the 11 3/4 is a smart move especially for the hills. I did the big disc conversion along time ago, probable in late 80's on 71 Cuda. You'll probable get longer life out of the pads with bigger disc. Too much brake is not a problem, lesser could be.

 

[mrmolding]

Ok, wondering if I should start a new thread, but this will probably work as well. I'm making progress on my tear down, and have all of the parts here or on order. Reading different opinions in regard to front or rear caliper mount on a 70 B Body is to put the caliper in the front, but looks possible in the rear as well. I'm planning on front. I got a 73 a body remain caliper that has the same connection location as in the Disc O Tech article and while the picture in the original article is decent enough, I was wondering if anyone just used stainless hoses vs the flex hose like in the article pic I highlighted? I got a stainless pair from Cass (DrDiff), but then I also found a hose from Autozone (should arrive tomorrow) that looks to be exactly like in the original article with the banjo/metal line from caliper and then flex hose.
Does anyone have a pics of a front mount conversion from the back view and how the hose is routed? Maybe I'm overthinking this.

Two more things, I've been wanting to do the C-Body Tie Rod end upgrade and have parts for that and also I have a Hellwig 55904 1 1/4 sway bar that came with the car. I've been thinking about doing both during this swap and it does not appear that front vs rear will make a difference? Thanks as always everyone!

 

[gkent]

Front-mount your calipers and save yourself some hassles. Stock lines will also remove guesswork.

What's the "c-body tie rod upgrade" ?? What's the advantage over stock tier ods ?? Never heard about that one!

 

[1 Wild R/T]

Front-mount your calipers and save yourself some hassles. Stock lines will also remove guesswork.

What's the "c-body tie rod upgrade" ?? What's the advantage over stock tier ods ?? Never heard about that one!

C body tie rods are 11/16 in diameter B&E are 5/8 so the C body parts flex less..
If your changing them anyway there's no reason not to upgrade...

 

[mrmolding]

Front-mount your calipers and save yourself some hassles. Stock lines will also remove guesswork.

What's the "c-body tie rod upgrade" ?? What's the advantage over stock tier ods ?? Never heard about that one!

Stumbled on the c body upgrade a few years ago. I got parts last year but the tie rods themselves were hard to find reproduced. Not sure currently. I actually got proforged for the tie rod end over current moog since I’ve had great luck with their ball joints.

 

[mrmolding]

Progress! Waiting on 11.75 silder brackets but test fit and turns well. Seriously looking forward to much better braking!

 

[mrmolding]

Comparison of b body to c body tie rods…sleeves and diameter of tie rod ends are thicker for the most part. C body on right.