Super Duty Hydroboost and MC to Use

[Jambi]

I have a couple questions related to the Super Duty hydroboost: I have seen a few threads where the MC that was used was from like an '88 Dodge D150 and several other threads where the MC used was from like an '85 Dodge Diplomat.

Measuring the "bore" size of the Super Duty hydroboost unit (not sure what year it is), it looks like it's about 1 15/16" - 2". The D150 MC bore size is about the same. The Dodge Diplomat bore size is about 1 1/8".

Can a MC with a smaller bore size be mated to a hydroboost unit with a larger size or does the MC bore size have to more closely match the hydroboost unit?

 

[toddz69]

You can put any diameter master cylinder you'd like on the booster as long as they physically mate together. The D150 master cylinder that many of us use on the SD booster has a 1 1/8" bore.

Todd Z.

 

[pcf_mark]

I have a hydroboost from a 3500 GMC but the Bosch units are practically all the same. Select your booster based on the brakes you have disc/drum or disc/disc. My 80 Camaro MC was for a disc/drum car and bolted right up. After a test drive the brakes were dragging so I put a washer between the hydroboost and MC problem solved.

 

[Apogee]

...Measuring the "bore" size of the Super Duty hydroboost unit (not sure what year it is), it looks like it's about 1 15/16" - 2". The D150 MC bore size is about the same. The Dodge Diplomat bore size is about 1 1/8".

Pretty sure you meant 1-5/16, not 1-15/16, but they are big. The range of master cylinder bore sizes required/desired will be a function of the caliper piston area, booster gain, pad CoF, vehicle weight, pedal ratio, etc, so it's a bit more involved than just saying this Hydroboost gets this size MC. That said, most people use master cylinders in the range of 1-1/8" to 1-5/16" with the full-size truck (Ford/GM/Dodge all use Bosch units) HB units and what I would consider to be standard 1/2-ton type Early Bronco brakes.

Now if you have done a full-width 1-ton axle swap, and run the larger calipers associated with those brakes, then you may need the larger 1-5/16" bore MC just to get a pedal...someone on here had that issue with such a swap and couldn't get the rear brakes to actuate/bleed properly due to the component mismatch.

 

[trailpsycho]

You can put any diameter master cylinder you'd like on the booster as long as they physically mate together. The D150 master cylinder that many of us use on the SD booster has a 1 1/8" bore.

Todd Z.

Hey Todd! Are spacers needed between the D150 and the F250 units?

 

[ericwilkison]

As others have said, You can bolt any master cylinder to the front of the hydroboost and wit will work.

When I first installed my hydroboost, form and Astro, I tried using the Astro master cylinder. It has 1 1/4" bore. The brakes were super touchy. Push the pedal an inch or so and it STOPPED. I did not like the results. I ended up switching to a stock bronco manual master cylinder that has a 1" bore. Pedal effort is super easy and not nearly as touchy. I'm really happy with it now.

In my research there really is not much difference between manual and power master cylinder. Typically the manual master cylinders has smaller bore to keep the pedal effort down. In regards to stock bronco master cylinders, the manuals had the outlets on the left and the powers had outlets on the right. Pick the one that is going to make brake line routing easier.

 

[toddz69]

Hey Todd! Are spacers needed between the D150 and the F250 units?

Longtime no see! As memory serves, if you don't cut down the stock booster pushrod, you'll need to use spacers of some sort.

Todd Z.

 

[EPB72]

To jambi I think your measurments for the MC bores are wrong? are U measuring the the actual MC piston diameter ? or What I think your doing is measuring the diameter of the machined protrusion of the rear MC flange...,,,,,,and as far as bolting any MC to any hydroboost Is NO ,but is possible.with mods...