Rear disc brake upgrade?

Are rear disc brakes a big improvement over drums?
I know up front they are a big improvement, but the fronts do most of the work.
My car needs help in the braking department...it's right at 3800 lbs and runs mid 8s.
I have Aerospace Components front discs, but I'm thinking of using Wilwood for the rear. Does anyone foresee any issues mixing the two?
I have the MP master cylinder...can I still use this if I switch to the rear to discs?

My only “experience” was when I had wilwood fronts and drum rears I absolutely decimated my rotors at an 1/8 mile track with a short shutdown. That hasn’t occurred since going disc on the rears. I went with Strange brakes on the rear. No proportioning valve although I did buy one in anticipation of needing it.

I don't know if your 'Cuda sees any real street use these days, but I see the "race" disc brake kits are very clear about being track only. I'll take a a s.w.a.g. that repeated stops with short cool-down intervals warp the rotors on those lightweight parts.

Chip,

If you don't have a trans brake you might want to consider dual rear calibers if you switch to rear disks.

After switching to four wheel disk from drums many years ago I always had trouble holding the car on the line. Once I went to dual calipers in the rear no problems at at.

I don't this you would have any issue mixing brands front to rear.

Good luck,

Bill

Which aerospace kit? I just put the Strange 4 piston kit on the front, I’m a good bit lighter, 3300 lbs going down the track. The kit weighs 18 lbs total per wheel.

Made a huge difference to mine, once I fitted the correct master cylinder. Pretty sure I changed from 1" to a 7/8ths", needed too much pedal pressure with the 1" master cylinder. I knew I'd made a 140+ pass when I had to use two feet on the pedal at the end of the track No problems now

Edit: I used a wilwood street kit with parking brake BTW.

I will most likely get a "street" brake kit for the rear.
I do have a transbrake.
The front has Aerospace Components' pro street brake kit. They can be a pain to deal with and I've had some issues w/ the calipers. That's why I'm wanting to use a different brand now.

What's on it now is marginal. Most of my racing is 1/8 mile, but at 1/4 mile tracks. Obviously shutdown isn't an issue there...which is why I've let it go this long.
Trying to haul this thing down at an 1/8 mile track can be tricky.
It needs a parachute, but the car needs a lot more before I can put one on...so that won't happen anytime soon. It still has the stock fuel tank and no bracing from the cage to attach a chute too.

My brother put a Wildwood rear disc setup on the back of his car that runs close to 120 in the 1/4 and it made no difference over the rear drums. I think he said the calipers and pads looked very similiar to Ford Thunderbird Super Coupe units? Drum brakes do have more contact area than discs so it's going to take a good disc setup to surpass properly working drums that are sized right for the car.

Guys in the handling forum are pretty knowledgeable about high performance brake setups so perhaps do some reading in there, or ask them for some suggestions?

The old rule of thumb was that rear discs didn't improve braking until you were stopping from 150 mph or higher. Drum brakes are really good at slower speeds but they heat up fairly quick. Disc brakes run cooler so they'll do a better job at a high speed stop, or repeated stops. On a drag car the weight advantage of disc brakes, and the easier maintenance can tip the balance. Dual calipers on the rear can help holding a car on the line.

Whatever you do, you have to make sure that the piston sizes are balanced front to rear with the master cylinder. It is a hydraulic system and the caliper pistons will move according to piston ratios. If you mess up the balance between front and rear piston size then the car will never stop very well.

I just noticed there is a pinned brake math thread at the top of the handling forum that might be worth a read.

I saw a noticeable improvement going from drums to the basic 11" rotor Wilwood kit on the front of mine, and then a little improvement going from drums to the 11" street Wilwood kit on the rear. The bigger 12.19" rotors don't always fit under 15" wheels so I erred on the small side. Mixing front and rear manufacturers shouldn't matter, but like Andy said it is dependent on caliper piston size and rotor size too. You can fix mismatches with a proportioning valve as long as it isn't too far out front to rear.

once I hit 125+ I found 10"rear drums were not happening anymore . Cadillac style rear discs fixed that .

Tex

Yeah 10 inch drums might give up at 125. We ran the larger 11 x 2.5 station wagon drum brakes on the back of a Valiant road race car and they worked fine well past 125. Finally moved to rear discs once the car was going more than 150 mph on the straights.

I have Strange front and Aerospace rear on my 8 second Valiant with Mopar master cylinder and no proportioning valve and the car stops fine from 155 mph in free neutral. The front pads get changed every season because of heat cracks. Make sure you use the soft compound pads or your rotors will become scored.

Mixing and matching properly sized components from different Mfg' shouldn't be an issue, The key is properly sized components. I have even swapped one MFG caliper on to a different MFG brackets without any issues. The master cylinder dia needs to be sized correctly for teh amount of piston area being installed. You may get lucky with the one you have but more than likely you will need a new (different size) one. Drum brakes require more fluid volume than a disk system.

On my Cuda, I am a tad lighter than you. I am at 3450lbs with me in it. I have Wilwoods on all four, and no proportioning valve. Works awesome. And mine sees more street than track. Same setup on my Duster, and we have a short 1/8th we run on, and I have not had to change a set of pads yet. That car traps 115mph usually, and I am on the brakes hard.

FWIW, I’m only hauling down from 111 MPH or so, but the car is pretty heavy @ 4100+. And it’s mostly a street car, with a good amount of Autocross during summer. I’ve been using Doctor Diff’s 11.7” rear disc brake kit for 60,000+ miles and has worked great through all the above. Proportioning valve installed, but it’s wide open, and 15/16” master cylinder

I added willwood discs to the rear of mine in 2018 when I put the Dana in. I have had the front forever. The front kit has vented rotors the rear kit is a drag race kit with drilled rotors. On the street there is not a huge difference in braking. At the track it is substantially better. I made the first turnoff at the house of hook, that turnoff isn't meant for people running the 1/4 mile lol but I was committed so I stayed with it and had no trouble.

These rears have been on since 2018 and have done 4 drag weeks, the pads and rotors still look great. The fronts also seem to be lasting longer with the rears added.