MC for T-bird calipers w/stock rear drums

[68ford]

That is correct, yes. And as Apogee has pointed out here in the past, the T-Bird calipers may be less of an upgrade than what you think depending on what you were running before the changeout.

Todd Z.

What MC bore dia do you use typically?
Sounds like if TBird calipers and a larger MC it really is not an upgrade, but a really expensive way of simply reducing the rear which a adjustable prop valve could have simply taken care of.

 

[68ford]

I will add to Todds info as for some technical details on the setup. Now just referring to the front only at this time, the large bore or T Bird calipers are very hard to beat. Even the aftermarket cannot compare. According to both Wilwood and Bear I contacted them looking to get a set private labeled for my company and wanted to be equivalent or exceed my current setup with the T-Bird calipers and in order to do so both of them required a 6 piston caliper and 18" rotors to equal the stopping power of the factory setup and they would not fit under anything smaller than a 20" wheel. This was the point I stopped looking for the aftermarket to improve on things for the bronco in this arena. As for the MC, take a look at Monster Garage videos on YouTube. They have done the research as well as demonstrations on what MC to use and why. I have found that an 1.125 bore is about perfect and I use them form a 95 F250 since they were the last years of the Disk/Drum setup. The MC utilizes a residual valve on the rear brakes for that application and the valve is no longer in production or available at this time. We are in the process of getting an adapter machined and hopefully tested that will adapt that odd fitting over to a -3AN fitting and this will be available at Duffs soon. As for the rear brakes, the math says with the increase in caliper piston vs the rear wheel cylinder displacement that it should be very close to a 70/30 bias however when we tested them straight up the rear would lock well before the front so we do install and recommend an adjustable proportioning valve to be installed when running Disk/Drum.

What's sound sketchy about running T bird calipers and a larger MC, being you're not improving the front brakes at all, is that you might be creating an opportunity for future reduction in braking. If the T bird caliper physically looks the same as stock and one or both get replaced with stock calipers, you now have reduced braking because of the large MC.
If you use stock 1in master with T bird calipers and down the road stock calipers get installed not knowing, worse case is equal to stock braking capacity.

 

[toddz69]

What MC bore dia do you use typically?
Sounds like if TBird calipers and a larger MC it really is not an upgrade, but a really expensive way of simply reducing the rear which a adjustable prop valve could have simply taken care of.

I switched to a 1 1/8" master cylinder back in the early '90s when I did my first 4 wheel disc swap (I never ran disc/drum - I went straight from 4 wheel drum to 4 wheel disc). In my particular case, I never could get an acceptable pedal height with the 1" bore masters (manual brakes) so I went to a 1 1/8" (many others did that as well). So I experienced an increase in front braking power when I switched from the Chevy calipers to the T-Bird calipers because all the other variables were the same. There isn't a hard and fast "no, it's worse" or "no, it's better". It all depends on your particular setup and what you're starting with and switching to.

Todd Z.

 

[toddz69]

What's sound sketchy about running T bird calipers and a larger MC, being you're not improving the front brakes at all, is that you might be creating an opportunity for future reduction in braking. If the T bird caliper physically looks the same as stock and one or both get replaced with stock calipers, you now have reduced braking because of the large MC.
If you use stock 1in master with T bird calipers and down the road stock calipers get installed not knowing, worse case is equal to stock braking capacity.

Apogee's excellent response (post #6) in this thread spells out the differences if you start with a 1" bore master and go to a 1.125" bore master while changing calipers without changing anything else:

https://classicbroncos.com/forums/showthread.php?t=276933

Todd Z.

 

[68ford]

ToddZ that was my concern with the T bird calipers and 1.125 MC actually having less braking than stock. If that is what was on someone's vehicle and they did not know it and went and bought 2 stock calipers, their brakes would really be worse,(or at least a lot harder to push the pedal) than stock by 26% per your link

 

[omureebe]

ToddZ that was my concern with the T bird calipers and 1.125 MC actually having less braking than stock. If that is what was on someone's vehicle and they did not know it and went and bought 2 stock calipers, their brakes would really be worse,(or at least a lot harder to push the pedal) than stock by 26% per your link

So what pads do you run with these? Just an off-the-shelf Napa part or something more robust?

 

[englewoodcowboy]

What's sound sketchy about running T bird calipers and a larger MC, being you're not improving the front brakes at all, is that you might be creating an opportunity for future reduction in braking. If the T bird caliper physically looks the same as stock and one or both get replaced with stock calipers, you now have reduced braking because of the large MC.
If you use stock 1in master with T bird calipers and down the road stock calipers get installed not knowing, worse case is equal to stock braking capacity.

I’m not sure you are grasping the values of the difference between stock and the T bird. The piston is 30% larger requiring more fluid to be moved by volume. The larger bore MC does this however when running drum rear it also pushes more volume there as well. This is why the APV is needed to get the bias back in check. Where you are thinking that it doesn’t improve the breaking overall has me confused. It does improve stopping distance significantly especially when you are running larger tires.
By design drum brakes do not require as much pressure to actuate as a disk system. Sourcing a true disk/drum MC helps this but we have found an APV to be the most crucial component in the system to get the breaking bias dialed in.

 

[68ford]

I’m not sure you are grasping the values of the difference between stock and the T bird. The piston is 30% larger requiring more fluid to be moved by volume. The larger bore MC does this however when running drum rear it also pushes more volume there as well. This is why the APV is needed to get the bias back in check. Where you are thinking that it doesn’t improve the breaking overall has me confused. It does improve stopping distance significantly especially when you are running larger tires.
By design drum brakes do not require as much pressure to actuate as a disk system. Sourcing a true disk/drum MC helps this but we have found an APV to be the most crucial component in the system to get the breaking bias dialed in.

The link ToddZ provides has the difference in bore sizes going from stock to T bird as well as difference on going from stock mc to 1.125.
Going to T bird caliper is 17% positive difference.
Going to 1.125 mc is 26% negative difference.
Clamping force is reduced 9% when going to this set up over stock with equal pedal effort.
Compared to stock, you are slightly reducing front braking and drastically reducing rear braking based of the given numbers.
Unless something is different because there is 2 calipers and 1 mc?

 

[toddz69]

The link ToddZ provides has the difference in bore sizes going from stock to T bird as well as difference on going from stock mc to 1.125.
Going to T bird caliper is 17% positive difference.
Going to 1.125 mc is 26% negative difference.
Clamping force is reduced 9% when going to this set up over stock with equal pedal effort.
Compared to stock, you are slightly reducing front braking and drastically reducing rear braking based of the given numbers.
Unless something is different because there is 2 calipers and 1 mc?

So we need to have an asterisk next to the T-Bird caliper swap that says it might work better in some instances, and in others it will not (~9% decrease in front braking force compared to stock configuration with discs and 1" master).

In those cases where a 1.125" master is already being used: some manual swaps, most hydroboost swaps, and BC's power brake kit, to name a few, it will increase the front braking force.

Todd Z.

 

[DirtDonk]

Seems like the biggest improvements in force would be in sticking with the existing size mater cylinder. But the question mark comes up as to whether the individual user will like the slightly longer pedal travel that theoretically follows the larger caliper.
Lots of systems are using the 1.125 size masters for a firmer pedal, but are almost always accompanied by a booster of one type or another.

Even with boosters though, Ford often did not feel this larger bore was necessary. We could look up the different sizes for different vehicles (such as the T-bird in question), but even my '79 F350 with big dual-piston calipers uses only a 1" bore master. Along with that huge vacuum booster that was such a desirable swap part.
Anyone know what the overall piston volume is for those dual-piston calipers? I wonder if it's more, less, or the same as the big single piston models?

I mention all that to see if anyone has used the bigger calipers with the smaller stock masters, and if so what they have to say about the pedal feel. Jdgephar and phyler seem to be happy with theirs. Did you notice a difference in travel and overall feel, or was it too close to call?
I remember lots of '70's vintage Ford cars having really long, soft pedal. Not spongy, but surely longer and softer than our standard drum, or disc brake setups. Especially the manual versions.

Paul

 

[nvrstuk]

DDonk... I remember!! Haha, easy memories. Couple quick dbl pump memories...

I kept my stock manual mc and swapped to first- 4 wheel discs and then t-bird calipers a few yrs later..

Great brakes after the first pump... I mean-huge difference in stopping distance. I was a brake tech at a GM dealership and I had my drums turned, adjusted and working great but the 4 wheel discs just clamped better and didn't fade...but, the answer is the mc didn't supply the volume w/o a quick double pump.

 

[toddz69]

Seems like the biggest improvements in force would be in sticking with the existing size mater cylinder. But the question mark comes up as to whether the individual user will like the slightly longer pedal travel that theoretically follows the larger caliper.
Lots of systems are using the 1.125 size masters for a firmer pedal, but are almost always accompanied by a booster of one type or another.

Even with boosters though, Ford often did not feel this larger bore was necessary. We could look up the different sizes for different vehicles (such as the T-bird in question), but even my '79 F350 with big dual-piston calipers uses only a 1" bore master. Along with that huge vacuum booster that was such a desirable swap part.
Anyone know what the overall piston volume is for those dual-piston calipers? I wonder if it's more, less, or the same as the big single piston models?

I mention all that to see if anyone has used the bigger calipers with the smaller stock masters, and if so what they have to say about the pedal feel. Jdgephar and phyler seem to be happy with theirs. Did you notice a difference in travel and overall feel, or was it too close to call?
I remember lots of '70's vintage Ford cars having really long, soft pedal. Not spongy, but surely longer and softer than our standard drum, or disc brake setups. Especially the manual versions.

Paul

The volume on the dual piston calipers is huge, as I recall, like 7.xx sq. in. I have it written down at home and don't have time to research it here on company time .

Todd Z.

 

[phyler]

The pedal is better than when I had drum brakes up front but I do notice a difference if I give it a slight pump then really push. It feels good to me but it's been so long since I made the change I can't say I remember accurately.

I do plan to do to hydro boost at some point but I'm not in rush given how the brakes feel currently.

Sent from my Pixel 5 using Tapatalk

 

[DirtDonk]

Thanks for the helpful feedback guys!

Todd, maybe the pedal ratio on the full-size is different then. I expected a larger master, but the listings I saw say 1" for the 350 as well. Might have to dig into more listings in case there was an error.

Paul

 

[toddz69]

Thanks for the helpful feedback guys!

Todd, maybe the pedal ratio on the full-size is different then. I expected a larger master, but the listings I saw say 1" for the 350 as well. Might have to dig into more listings in case there was an error.

Paul

There may well be a pedal ratio difference, I don't know. There is also some differences in the booster linkage on some of those trucks too that might help the 1" work ok.

Todd Z.

 

[nvrstuk]

... single piston Chebby JD 7's are over 7.5 sq in.

Volume of calipers (2 or 4) and max length of stroke for the mc and it still boils down to can you fill the caliper with a 1" piston w/o needing 2 pumps and 150# of leg pressure.