Brake Master Bore Size????

[Degnol]

I currently run a Corvette manual (UN-boosted) 4WDB master with 4WDB, rears are the metric GM calipers and the fronts are stock LC calipers. I am thinking about going to this master cylinder because it is ported on both sides and it is smaller (width-wise) than the cast iron Corvette master. It is available in 7/8", 1" and 1-1/8" bores. I think the Corvette cylinder I currently run is at least 1", maybe 1-1/8"

Bigger bore = more volume but less pressure
Smaller bore = less volume but greater pressure

Here is the link....Wilwood Aluminum Tandem Chamber Master Cylinders - JEGS


Also thinking about redrilling the brake pedal to increase leverage, too.

 

[Degnol]

He'p me here......

 

[osagecruiser]

too early ed...give folks a chance to wake up....happy 4th!

osagecruiser

 

[Degnol]

too early ed...give folks a chance to wake up....happy 4th!

osagecruiser

Marc, have you bought yer fireworks yet? I'm betting you are a big fireworks-guy?

 

[osagecruiser]

actually no i try not to purchase any...my neighbors across the street buy enough for the whole town....they have been driving me nuts since last sunday...i bet they spend at least a thousand bucks on that stuff...jake and i have a bet going to see which one of em blows there damn fingers off first...oh by the way...those sliders look good!...sorry for the hijack..

marc

 

[cruiserbrett]

std 76 and on disc masters from toyota were 7/8" bore IIRC.

I think early boosted drum masters were 15/16" and 75 drum masters were 1"

 

[Degnol]

std 76 and on disc masters from toyota were 7/8" bore IIRC.

I think early boosted drum masters were 15/16" and 75 drum masters were 1"

So, do you think 1" is what I should use? What's screwing me up is the whole "choice" thing.

Ed

 

[My wife said no FJ!]

I've been looking for a dual circuit master as the only up grade to my '64 restoration. I was going to see if I could use a new dual, from say a '71 to '74, and install it with out a booster. I know that Marc has the adapters, but I don't know which year masters he uses.

This being said, my question to you Ed is, wouldn't it be easier to use a newer dual Toyota master with out a booster instead of an after market master?

 

[BC40]

Not sure it helps the orig question, but I run a ford 1" bore dual circuit master/no booster/drums all around. I find that for my setup I would be happier with a 7/8" cylinder since the pedal effort is quite high (heavy).

Ed, I would think since the only part you plan on changing is the master, decide if you are happy with the current braking. Ie: is the pedal travel not excessive, effort not too heavy? I am guessing it must be a little heavy since you mention considering redrilling the pedal to get better leverage. In that case if it's a 1" and you still have travel left to work with, a 7/8" bore will lighten the pedal effort but at the expense of longer stroke.

 

[Degnol]

I've been looking for a dual circuit master as the only up grade to my '64 restoration. I was going to see if I could use a new dual, from say a '71 to '74, and install it with out a booster. I know that Marc has the adapters, but I don't know which year masters he uses.

This being said, my question to you Ed is, wouldn't it be easier to use a newer dual Toyota master with out a booster instead of an after market master?

Well, the reason I use the GM master is that it was designed to be used un-boosted. I don't know the difference so I thought using a design that was meant to be manual made sense. All the Toyota dual masters were designed to be used with a booster AFAIK. Besides, I have the adapter already and using a Toyota master would require another adapter. BTW, I think Mark A and others have said that the '71 has the largest bore.

Not sure it helps the orig question, but I run a ford 1" bore dual circuit master/no booster/drums all around. I find that for my setup I would be happier with a 7/8" cylinder since the pedal effort is quite high (heavy).

Ed, I would think since the only part you plan on changing is the master, decide if you are happy with the current braking. Ie: is the pedal travel not excessive, effort not too heavy? I am guessing it must be a little heavy since you mention considering redrilling the pedal to get better leverage. In that case if it's a 1" and you still have travel left to work with, a 7/8" bore will lighten the pedal effort but at the expense of longer stroke.

My truck does stop just fine, but as you noted, my pedal is a little hard and the stroke is pretty short, so maybe I should go to the smaller one AND redrill the pedal.
Maybe you've seen my trailer build project in the trailer section? That is why I am interested in more whoa-power. Currently I do not run brakes on the trailer, so I'm relying 100% on the Cruzah to stop.

I think maybe I'll try the 7/8" master and if it does not work out I'll sell it and go bigger. The only thing that would kill the deal is if I run out of volume, but these are "High Volume" masters
BTW, there must be a difference in boosted vs non-boosted because the Wilwood can be used either way, but comes with some sort of plug that must be used if you use a booster.


Thanks for the replies!

Ed

 

[cruiserbrett]

I would install the 7/8" bore master and try that before drilling the pedal arm...

1" bore has .7825 inch^2 area

7/8" bore has .6013 inch^2 area, which is 76% as much area, so thats going to increase pressure for said pedal pressure by 1/.76 or = 30%

When I went to 7/8" bore from a 1" bore master cylinder, it made a surprising difference in the pedal, more than I thought.

 

[Degnol]

Thanks, that's the one I ordered over the weekend. I will install it and see if I need to drill the prake pedal.

Ed

 

[mr_manny]

if your thinking or already have rear disc brakes, I would go 1".
pretty much all toyota MC w/4wheel discs have a min. 15/16" bore.

hth,
manny

 

[Degnol]

Manny, yes I have 4WDB but I'm looking for more pressure. I'll try this 7/8 bore and see what happens. It is supposed to be "high volume" and losing volume is the only drawback to the smaller bore. As long as it will push enough fluid to put the binders on, I'm good

Ed

 

[tyama]

Any updates on this swap? I'm interested in putting in manual MC in my '69 and trying to figure out what MC to use. I'm stuck between early 80's corvette and mid 80's S10. Thanks for any info, ty

 

[PabloCruise]

How did the 7/8" bore size treat you?

I put disc brakes on a '74 Pig and kept the orig master, which I think is 1". Pedal effort is a little high...

 

[Degnol]

Any updates on this swap? I'm interested in putting in manual MC in my '69 and trying to figure out what MC to use. I'm stuck between early 80's corvette and mid 80's S10. Thanks for any info, ty

How did the 7/8" bore size treat you?

I put disc brakes on a '74 Pig and kept the orig master, which I think is 1". Pedal effort is a little high...

Sorry to say that the master is still in the box........I'm a looser with lots of projects and no spark
I'll report when it is installed......

Ed

 

[gid1972]

Degnol, I ran that same setup on my 69 FJ. I had a 76 front axle with toy discs, and GM calipers in the rear. I am pretty sure i had the 76 vette MC that was proportioned for 4 wheel disc. While this set up works, it didn't give me enough pressure. Not only did i have to leave a good amount of stopping distance on the road, but it wasn't enough pressure to hold me when wheeling.

I ended up getting a power booster from a 3/4 ton suburban and a m/c from a chevy rv van that was 4 wheel disc. Now, i can stop on a dime.

In my opinion, you might want to upgrade if you are looking for more pressure. I wasn't satisfied with that corvette m/c setup.

Just my .02. Good luck!

 

[Degnol]

I like that info AND your .02, but I am UN-boosted Old cruiser = firewall rib in the way......and I hate to cut it.

Ed


I'll post up the results of the swap to the 7/8" master.

 

[gid1972]

Ditto. the 69's have a rib too. That is why i went with the booster from a suburban. It is propped out from the firewall with a bracket that almost clears that rib. I had to add a spacer to fully clear it and my clutch m/c.

Here is a picture of it from advance auto parts.

http://shop.advanceautoparts.com/Pr...1C&MfrPartNumber=5471108&PartType=250&PTSet=A