Beretta.net

Yeah but your thought of increasing the bore only fixes one thing, it shortens the pedal travel, it doesn't increase the PSI... it actually drops the PSI because there is much more surface area to spread it out over...

And no I have not posted this info yet... I just went through all of this stuff for the mod earlier this year and never got a chance to get something together on here... Plus I don't know the inner workings of the ABS master so I don't want to assume it's doing something it may not be, Once I get into one of mine and see what components are in use in there and can be changed/removed then I'll try to put something together for 4-wheel disc people to look over..

Remember what that other PDF showed though... 1/8" change was worth 25% pressure, so yes 1 from 7/8th's may shorten your pedal by a good amount but your sacrificing 25% of the pressure you once had, does your pedal travel that far? and have you increased the piston surface area by enough to justify that bore change? If you've increased the caliper size by enough to double the clamping force if not triple it, then you can increase the bore size to gain some pedal back but you'll loose a bit of that clamping force due to the pressure drop... See how its almost bass ackwards... it took me a week of reading and math to understand what we had on the mod and what the best setup was to run and how to setup the car with the pressure gauges we have... and to mix in even more, that car has dual master cylinders and a bias bar that's changeable by the driver with a knob, so on the fly he can adjust more brake pedal to the rear or front depending on what the car is doing.

I will get something together once I figure out how these masters bias the pressure to the rear, and how or if that can be eliminated.

That PDF has been saved. I read some of it though. Ok so it more like unequal pressure? The larger piston helps to make it more equal and not fight the pedal?
In other words the fluid is fighting the change in pressure and the energy is lost there?

My pedal moves too much. That could be from the age of the parts. New rubber lines may help. I did have the same trouble on the 90GT and everything but the hard lines and the booster had been changed. All I can find as far as the Booster is Dorman and I don't like that brand. That PDF said something about a mod for boosters, but I didn't catch what they were talking about.
So my Cavy's calipers must be larger, just trying to wrap my mind around this. That things brakes are almost too much stock.
Checked both Boosters and they are the same size 7x5. The Cavy seems to have the same brake system as the 95 Beretta. MS bore is also 7/8.

I'd love to run a hydroboost setup to gain some much needed engine bay space (depends on brake booster size), but that was never an option and I'd be afraid of the modifications I'd need to make to run such a setup.

You only need to plumb it in with the PS system and you'd have excellent clamping power in all conditions.

Ok so i bought an 89' master cylinder, i looked at it and its the same thing as my 95' cylinder..
As you can see in my pic, the 89'(top) has 4 tapped holes for the 4 lines all of which are different sizes,
And the bottom one you can see after you remove all the abs crap its the same thing except 2 holes aren't tapped,

So all that is needed is to tap 2 of the holes on the 95' master cylinder to use it without the abs..
Btw, the 95' master has 2 tapped hole sizes, 2 are m10x1 and 2 are 3/8-16 i believe which are the 2 that need tapped..

Slinky wrote:Ok so i bought an 89' master cylinder, i looked at it and its the same thing as my 95' cylinder..
As you can see in my pic, the 89'(top) has 4 tapped holes for the 4 lines all of which are different sizes,
And the bottom one you can see after you remove all the abs crap its the same thing except 2 holes aren't tapped,

So all that is needed is to tap 2 of the holes on the 95' master cylinder to use it without the abs..
Btw, the 95' master has 2 tapped hole sizes, 2 are m10x1 and 2 are 3/8-16 i believe which are the 2 that need tapped..

Nice to know that, Thanks

Slinky wrote:Ok so i bought an 89' master cylinder, i looked at it and its the same thing as my 95' cylinder..
As you can see in my pic, the 89'(top) has 4 tapped holes for the 4 lines all of which are different sizes,
And the bottom one you can see after you remove all the abs crap its the same thing except 2 holes aren't tapped,

So all that is needed is to tap 2 of the holes on the 95' master cylinder to use it without the abs..
Btw, the 95' master has 2 tapped hole sizes, 2 are m10x1 and 2 are 3/8-16 i believe which are the 2 that need tapped..

I was actually wondering that and you answered the question. I wasn't sure if they had the same threads needed to just plug everything in or if you were going to have to play games to get stuff to work.

Just remember though, you cant just "tap" the holes unless they have the correct flare fitting at the bottom... if not you have to do a pipe thread fitting to flare fitting to adapt to the brake line.

3X00-Modified wrote:

Slinky wrote:Ok so i bought an 89' master cylinder, i looked at it and its the same thing as my 95' cylinder..
As you can see in my pic, the 89'(top) has 4 tapped holes for the 4 lines all of which are different sizes,
And the bottom one you can see after you remove all the abs crap its the same thing except 2 holes aren't tapped,

So all that is needed is to tap 2 of the holes on the 95' master cylinder to use it without the abs..
Btw, the 95' master has 2 tapped hole sizes, 2 are m10x1 and 2 are 3/8-16 i believe which are the 2 that need tapped..

I was actually wondering that and you answered the question. I wasn't sure if they had the same threads needed to just plug everything in or if you were going to have to play games to get stuff to work.

Just remember though, you cant just "tap" the holes unless they have the correct flare fitting at the bottom... if not you have to do a pipe thread fitting to flare fitting to adapt to the brake line.

Its countersunk at the bottom for a double flare.. So just tap it to what ever size fitting you have, i used 3/8-24 because my shop didnt have any m11x1.5 taps(which are factory size for 2 of the lines)

Slinky wrote:

3X00-Modified wrote: I was actually wondering that and you answered the question. I wasn't sure if they had the same threads needed to just plug everything in or if you were going to have to play games to get stuff to work.

Just remember though, you cant just "tap" the holes unless they have the correct flare fitting at the bottom... if not you have to do a pipe thread fitting to flare fitting to adapt to the brake line.

Its countersunk at the bottom for a double flare.. So just tap it to what ever size fitting you have, i used 3/8-24 because my shop didnt have any m11x1.5 taps(which are factory size for 2 of the lines)

That's more awesome information

Slinky wrote: Its countersunk at the bottom for a double flare.. So just tap it to what ever size fitting you have, i used 3/8-24 because my shop didnt have any m11x1.5 taps(which are factory size for 2 of the lines)

Countersunk would be for a bubble flare... not a double flare.

Wish I had checked this sooner, could have just sold you my malibu master/prop valve. For right now i'll be sticking with the ABS. I was able to get the downpipe to fit under the abs module. As long as the bottom doesn't melt out, all should be well. If I convert to rear disk, I'll be going back to non-abs with a prop valve made for rear disk.

I'd love to see these prop valves that you guys are using. From what I've been seeing the proportioning is done inside the master.

http://www.amazon.com/ACDelco-22701249- ... s=22701249

There you are.

And to help with further questions.. It's used with this Master Cylinder, not the ones seen above.

http://www.amazon.com/Delco-18M983-Brak ... s=19175921

This is the setup used on 00'-03' malibu, grand am, alero, etc. without abs. I speculate that they use the same master cylinder in both the abs and non-abs units. This is due to the abs module being separate from the master cylinder and located in the same spot that the prop valve would be.

If one plans on doing a rear disc brake swap in the future, id go with this set-up. That way you can easily change out the prop valve for one that's made for rear disc. Since the pressures are different from disc to drum.. There are also various aftermarket prop valves that are front/rear bias adjustable. IE: http://www.jegs.com/i/JEGS+Performance+ ... 5/10002/-1 <-- though you'll need to search for one that will work with the master cylinder that you're using. That's just one from a quick search.

If you notice the Prop valve you pictured is used on a cast iron front disc/rear drum setup from 03-05. There isn't anything listed for proportioning on a Disc/Disc setup, at least not for that car, just the ABS unit is in that place which we can't use.

You can calculate Bias simply by the piston size that your using and the output pressure (which no one has ever tested), The reason for a proportioning valve is the fact that a rear drum setup requires more fluid flow, but LESS pressure in comparison to a Disc setup where more pressure is required...

So as I've said in the past many times our setups are proportioned INSIDE the master somehow and the issue we will have is not enough pressure to the rear discs to help a lot, so I will continue to plan on pulling a full setup apart to see what I can find inside the ABS system regarding proportioning.

Yes, it would appear that the proportioning is done internal in our master cylinders, that's why for this set-up you need to replace both the master cylinder and install an external prop valve. Yes again, the prop valve I posted is made for disc front and drum rears. However, if you do want a braking system designed for disc-disc, all that you would need to change would be to remove the external prop valve, and install an adjustable prop valve/distribution block. For bias, since compensation isn't required on disc/disc like it is for disc/drum. That is, if you can find one that has 2 in, 4 out. I haven't looked super hard, but can't find one. If people are at all interested come November, I can ask around when I'm at SEMA.

But the reason I started this thread was to find something smaller than our stock master cylinder mounted EBCM. The malibu master/prop valve is much smaller, with testimony that it works better than our stock brakes. (possibly due to them being from "ten years in the future" for our cars). They're also relatively easy to locate at junk yards and fairly inexpensive.

I still doubt that you would even need the prop valve or bias valve for a stock vehicle. I think once the factory drum limitations are removed you will have a more neutral brake setup because of the equal sized bore and then the smaller pistons being in the rear giving you a natural front bias over the rear. As I've seen with the Modified you want to run identical pressure front and rear as well as equal bore sizes on the masters, and then simply the fact that the rear caliper has XX amount of surface area less than the front gives you a static 65/35 bias to start. And with that we have a bias bar on the pedal so we can transfer force from one master to another adjusting the pressure on the fly.

The Modified's example

Front caliper has a piston surface area of 5.1785665 sq/inches
Rear caliper has a total piston surface are of 2.989908 sq/inches

So at a perfect 50/50 PRESSURE split, example 500psi going to each end of the car you're getting;

Front braking force 2589.28 lbs of force
Rear braking force 1495.95 lbs of force

Equal master cylinders and equal pressure you have a Static Balance of 63.3% front and 36.6% rear.

So if we knew pressures we could calculate this and know a real answer.

And here is the answer on the master Proportioning... Its inside as I expected.
http://parts.nalleygmc.com/showAssembly ... evel=15622