Let's talk about Hydroboost Brakes (1 Viewer)

[J Mack]

Yes the rears are single piston and the front is dual piston.

You’re going to make me work for this.

OK, fronts and rears are the same but completely different so at least we have a starting point.

Sounds like you’ll want to match a 2007 Toyota 4Runner master cylinder size as close as possible, from what little digging I did I can only tell you they are hard to find. From what I could tell earlier 4Runners ranged between 21mm or 7/8” US sizing to 25mm or 1” US sizing but I came up blank for 2007.

A common master cylinder for an early Chevy truck will have a 1.3125” bore and is too big for your system if the 2007 4Runners used a 7/8” or 1” system like the earlier trucks.

Clear as mudd?

 

[scrapdaddy]

I believe the years I'm thinking 2000 and up use 1 1/8 or 1 1/4 bore masters. I'm using a 1" master now, so would .125 make too much of a difference since I have to go to the 1 1/8" for the hydroboost anyway. Might not be perfect.

 

[J Mack]

Just trying to keep all this straight in my brain.

1 1/8” = 1.125”

1 5/16”= 1.3125”

The early Chevy trucks (80’s) that used hydro boost used a 1 5/16” bore master from what I’ve found. YMMV. https://www.autozone.com/brakes-and...cylinder-brake-system/248443_478262_2558_3333

You would need to mix and match a hydro boost from an early Chevy truck and a master from an early Chevy car to get a 1 1/8” master.

This master will bolt to an 80’s Chevy truck hydro boost, it’s a 1974 Chevy Nova 1 1/8” bore master , https://www.autozone.com/brakes-and...ster-cylinder-brake-system/486228_0_2558_2867

If you want to stay with 1” you would need to research a factory application or buy aftermarket,

Remaster - Baer Brakes

No matter what you buy you’ll need to confirm the push rod length between the hydro boost and master cylinder.

 

[J Mack]

Like @cruisermatt said earlier a van setup might work better for you if you want to buy all new matched parts.



2002 Chevrolet Truck Express 3/4 ton Van 6.5L Turbo Dsl OHV 8cyl used a 1 1/8” bore master.

https://www.autozone.com/brakes-and...cylinder-brake-system/532399_0_2558_2060_3322



It also came with a hydro boost.

https://www.autozone.com/brakes-and...n-brake-power-booster/232651_534111_7889_5764

 

[Megadoomer]

I either got lucky or don't know any better, or maybe still Jmack is too smart for his own good. I have the MAF 4 piston fronts and a Mopar single piston in rear. I stuck with the 2002 3500 hydro and MC as is and only added a proportioning valve for disc-disc operation. The rear never locks up and pedal pressure is great and it stops on a dime and leaves you change. but I'm just a dumb ol' left-handed surveyor.

Also, Astrovans came with hydroboost and they match the same fittings as the 3/4 and 1 ton trucks.

 

[cruisermatt]

All the GM hydroboosters are the same, the mount brackets are different depending on the application but you don’t want to use the original mount brackets.
You can also look at Fords, I held the hydroboost I took out of a 2500 Express van right up to the one in my F350 and they're identical.

The Dodge versions look like they would interchange as well, the hose locations on it are slightly different but the fittings are probably the same.

 

[J Mack]

All the GM hydroboosters are the same,

FYI, all the GM hydro boost are similar, I have four GM units from different years sitting here and all four would need a different push rod to get the .005” to .010” clearance needed.

 

[scrapdaddy]

You guys are messing me up. How did we get on the old 80's stuff. I was looking at mid 2000s GM 2500, like megadoomer has. 1 1/8" bore on those and it should be fine with my 4runner brakes that work with my 1" bore master now. I found new OEM hydros on e bay. One problem I'm seeing is getting a new master with all the parts, rod etc. Most new masters don't come that stuff.

 

[scrapdaddy]

Hey J Mack,

question for you, are those push rod tools all the same. I've seen several and confused on vehicle application and what tool to measure with, if that made sense. Could I use one tool for say a GM booster and master, then use the tool for another booster combo.

 

[RUSH55]

More pressure should be produced by the front calipers, hence the 4 piston fronts and single piston rears, but I would reason that if you were using an adjustable proportioning valve, you should be ok if you were to have the 4 piston calipers in the rear.

 

[J Mack]

You guys are messing me up.

I’m trying to un-mess you.

You said truck hydro and master and you wanted to buy a complete matched unit.

Mid 2000’s truck master will have a 1.456” bore, way too big for what you want to do.

Mid 80’s truck will have a 1.3125” bore closer but again too big for what you want to do.



As @cruisermatt mentioned most of the GM hydro boost unit themselves are similar and master cylinders are interchangeable.

If you want to buy a matched unit “Hydro boost and master” and have a 1.125” (1 1/8”) you will need to follow cruisermatt’s lead and buy a complete early 2000’s Chevy ¾ ton express van setup.

NOT A TRUCK.

Hey J Mack,

question for you, are those push rod tools all the same. I've seen several and confused on vehicle application and what tool to measure with, if that made sense. Could I use one tool for say a GM booster and master, then use the tool for another booster combo.

As far as I know the tool I linked will work on all Ford and Chevy.

 

[scrapdaddy]

Mid 2000’s truck master will have a 1.456” bore, way too big for what you want to do.

Wait a minute... I thought the mid 2000s GM masters were 1 1/8" bore...I'll be back.

EDIT....OK, my notes were from the Wilwood page, they have 1 1/8" bore masters.

 

[scrapdaddy]

More pressure should be produced by the front calipers, hence the 4 piston fronts and single piston rears, but I would reason that if you were using an adjustable proportioning valve, you should be ok if you were to have the 4 piston calipers in the rear.

Rush55,

I have rear 4runner disc in the rear, they are single (dual if you want) and front 4runner disc in the front, they are dual ( quad if you want).

 

[RUSH55]

Shouldn't be any issues with that.

 

[scrapdaddy]

I didn't think so until this morning. I'm drinking my three Budweisers now, so all is good.

 

[Ol Yeller]

Well that was easy....just stick to

 

[scrapdaddy]

My only flaw was not starting in the morning.

 

[Megadoomer]

Can't drink all day if you don't start in the morning.

 

[J Mack]

Wait a minute... I thought the mid 2000s GM masters were 1 1/8" bore

I see how we got here now.
I apologize I was only trying to help not confuse the issue for you.

I learned the hydro boost lesson the hard way and I was trying to save you from going down my road. When I first converted mine to hydro boost I had read guys where using Chevy Astro van setups and like you I wanted to buy all new so I just picked a year and ordered the parts. First problem I encountered was the push rod was too long and brakes would drag, I didn’t think the new parts would be a problem so I chased my tail looking for the issue only to find the push rod was too long by just a few thousand’s. The Astro van master was a 1 5/16”- 1.3125” bore, I didn’t take the time to look into what it was or what I needed just that other guys said it worked for them, I always felt like the brakes worked good but not great and the pedal was a little on the hard side.

When I took everything apart to put the 4BT in I ditched the entire brake system and started over, I went to a pick and pull and bought 5 complete hydro boost systems for parts ($25 EA) but I was still shooting in the dark. That’s when I called Baer Brakes and talked to one of their engineers and he explained that to get proper brake bias you needed to run less piston surface area in the rear (just closing the proportioning valve alone wouldn’t do it) he also took the time to explain pedal feel vs line pressure vs clamping force vs stopping power and how you want a balance (it’s possible to have too much of a good thing) although most of it was over my head I understood enough to know I shouldn’t have built my first system based on internet forum information or hearsay, if I would have called to talk to an expert in the beginning not only would I have done everything different better but I would have spent less money doing it.



So with all that said if I were going to duplicate my current hydro boost/ master cylinder combo with new Chevy parts I would buy a mid-80’s truck hydro boost and a 1.125 – 1 1/8” master for a mid-70’s car like Nova or Camaro. I prefer the cast steel masters over the newer aluminum and plastic but at the end of the day they all work fine. This new combo on my 55 works extremely well and is night and day better than my first attempt.



Good luck.

 

[scrapdaddy]

I didn’t think the new parts would be a problem so I chased my tail looking for the issue only to find the push rod was too long by just a few thousand’s.

This is the main reason I wanted everything from the same vehicle, so no problems. With the measuring tool I'll be able to get it, so no concerns there now.

Never any apologies needed, I always learn something from you guys and that's why I'm here. You just make me drink a little more sometimes.