23 mm Master cylinder?, From a 930? Options

[HalfMoon]

A friend of mine who owns a race shop that does alot of Porsche work said when queried about reducing travel on the 914 brake system that the 23mm master cylinder from a 930 would far better reduce the travel over a 19mm master cylinder.
Has anyone done this mod and if so, what were the performance gains/differences?
Thanks
D

[VaccaRabite]

A friend of mine who owns a race shop that does alot of Porsche work said when queried about reducing travel on the 914 brake system that the 23mm master cylinder from a 930 would far better reduce the travel over a 19mm master cylinder.
Has anyone done this mod and if so, what were the performance gains/differences?
Thanks
D

I'm assuming your brake system is nowhere near stock?

I'd not go bigger then 19mm for a stock or near stock braking system.

Zach

[HalfMoon]

A friend of mine who owns a race shop that does alot of Porsche work said when queried about reducing travel on the 914 brake system that the 23mm master cylinder from a 930 would far better reduce the travel over a 19mm master cylinder.
Has anyone done this mod and if so, what were the performance gains/differences?
Thanks
D

I'm assuming your brake system is nowhere near stock?

I'd not go bigger then 19mm for a stock or near stock braking system.

Zach

That would be correct sir, and I also run a sbc so "mo better" braking is always sought after.

[porschetub]

A friend of mine who owns a race shop that does alot of Porsche work said when queried about reducing travel on the 914 brake system that the 23mm master cylinder from a 930 would far better reduce the travel over a 19mm master cylinder.
Has anyone done this mod and if so, what were the performance gains/differences?
Thanks
D

Really to big ,running 19mm with huge brakes ,really too large for what ever brake setup you have,my car stops really well trust me running these on 19mm ATE cylinder;

I have these front and rear ,larger M/Cs are just a what folks talk about like the BS BMW caliper upgrade...waste of $$$$.
Cheers go well.

[Mike Bellis]

I'm running a 23 but I also have 930 brakes. It is a very stiff pedal. Not easy to modulate but I can put your head through the windshield if I slam on the brakes...

[shoguneagle]

Agree with all the above. I am running 23mm M/C with Carrera brakes; very stiff pedal which what I like; can put you through the windshield as Mike as stated; requires a strong leg pressure; 19mm would work with my setup but I do not like the pedal (had it on prior to 23mm).

[HalfMoon]

To clarify-

I run a 19mm too (as well as a variety of other big brake mods). The primary question I'm pursuing isn't brake "power" (performance gains/differences is/was ancillary), rather it's about "less pedal travel".
That's what the inquiry is really about as well as the advice I had been given.
So I guess the question is for folks who have ACTUALLY done the modification to a 23mm and if they have obtained less pedal travel as a result.
Not asking about theory or opinion, asking about actual experience. Many of us have done the 19mm change and their's reams of information on that mod but not much about the 23mm and pretty much nothing in terms of actual experience.
The main thrust of the question is "brake travel".

[HalfMoon]

I'm running a 23 but I also have 930 brakes. It is a very stiff pedal. Not easy to modulate but I can put your head through the windshield if I slam on the brakes...

Thank you for your report based in actual experience :-)

[HalfMoon]

Agree with all the above. I am running 23mm M/C with Carrera brakes; very stiff pedal which what I like; can put you through the windshield as Mike as stated; requires a strong leg pressure; 19mm would work with my setup but I do not like the pedal (had it on prior to 23mm).

Again, thank you for your real world experience report.

[infraredcalvin]

It’s not a 930 MC is a 23 mm ATE MC for a Mercedes, the 930 23 mm MC is for power assisted brakes. I did the conversion on my early 930, replaced the aluminum s brakes and stock 19 mm MC for turbo brakes and the 23 mm MC. It’s stiff with the 930 brakes, I wouldn’t want it on anything less, as for travel, yes less travel, but more pressure to achieve the same results. I also had to fab a spacer as the rod actuator needs to be longer to work on the 23 mm MC.

I can heel toe on about anything, but I always found it easier when there’s a bit more travel on the brake...

You can also adjust the pedal lower to reduce overall travel...

(Edited again after MC size confirmation) (IMG:style_emoticons/default/headbang.gif)

[infraredcalvin]

Sorry had to edit above...

[flyer86d]

My old 911SC track car had turbo brakes front and rear with a 23mm Mercedes master cylinder. It was a great setup. Never had to worry about having enough brakes or fade. Look at the VCI website. Doug sells a 23mm master cylinder kit as well as lots of other brake candy. He is a member here.

Charlie

[mepstein]

To clarify-

I run a 19mm too (as well as a variety of other big brake mods). The primary question I'm pursuing isn't brake "power" (performance gains/differences is/was ancillary), rather it's about "less pedal travel".
That's what the inquiry is really about as well as the advice I had been given.
So I guess the question is for folks who have ACTUALLY done the modification to a 23mm and if they have obtained less pedal travel as a result.
Not asking about theory or opinion, asking about actual experience. Many of us have done the 19mm change and their's reams of information on that mod but not much about the 23mm and pretty much nothing in terms of actual experience.
The main thrust of the question is "brake travel".

The change in pressure and travel when you go to a larger MC isn't theory or opinion. Its a relationship/ratio between the size of the MC and size of the piston calipers. If you keep the calipers the same but increase the size of the MC, the MC will move more fluid with less pedal travel but at the same time, you will need more pressure on the pedal to achieve the same braking force at the caliper. Just like sitting on a see saw, shorten the lever on your side and it gets harder to lift the other end but the travel on your end is shorter. Go too short and at some point, you don't have the force available to move the lever. You also have to make sure the ratio front to back is correct. Its not just about going big, it's about the correct balance.

You won't see much information on World about 23mm MC's because most of the cars simply can't use a MC that large unless they've also switched to very large calipers.

[jd74914]

To clarify-

I run a 19mm too (as well as a variety of other big brake mods). The primary question I'm pursuing isn't brake "power" (performance gains/differences is/was ancillary), rather it's about "less pedal travel".
That's what the inquiry is really about as well as the advice I had been given.
So I guess the question is for folks who have ACTUALLY done the modification to a 23mm and if they have obtained less pedal travel as a result.
Not asking about theory or opinion, asking about actual experience. Many of us have done the 19mm change and their's reams of information on that mod but not much about the 23mm and pretty much nothing in terms of actual experience.
The main thrust of the question is "brake travel".

The change in pressure and travel when you go to a larger MC isn't theory or opinion. Its a relationship/ratio between the size of the MC and size of the piston calipers. If you keep the calipers the same but increase the size of the MC, the MC will move more fluid with less pedal travel but at the same time, you will need more pressure on the pedal to achieve the same braking force at the caliper. Just like sitting on a see saw, shorten the lever on your side and it gets harder to lift the other end but the travel on your end is shorter. Go too short and at some point, you don't have the force available to move the lever. You also have to make sure the ratio front to back is correct. Its not just about going big, it's about the correct balance.

You won't see much information on World about 23mm MC's because most of the cars simply can't use a MC that large unless they've also switched to very large calipers.

One small correction: You need to exert more force on the pedal to have the same brake line pressure due to larger MC area. A 23mm MC requires 1.47x more force for the same line pressure as a 19mm (needed if your calipers are unchanged during the swap). You also have 1.5x less travel.

[mepstein]

To clarify-

I run a 19mm too (as well as a variety of other big brake mods). The primary question I'm pursuing isn't brake "power" (performance gains/differences is/was ancillary), rather it's about "less pedal travel".
That's what the inquiry is really about as well as the advice I had been given.
So I guess the question is for folks who have ACTUALLY done the modification to a 23mm and if they have obtained less pedal travel as a result.
Not asking about theory or opinion, asking about actual experience. Many of us have done the 19mm change and their's reams of information on that mod but not much about the 23mm and pretty much nothing in terms of actual experience.
The main thrust of the question is "brake travel".

The change in pressure and travel when you go to a larger MC isn't theory or opinion. Its a relationship/ratio between the size of the MC and size of the piston calipers. If you keep the calipers the same but increase the size of the MC, the MC will move more fluid with less pedal travel but at the same time, you will need more pressure on the pedal to achieve the same braking force at the caliper. Just like sitting on a see saw, shorten the lever on your side and it gets harder to lift the other end but the travel on your end is shorter. Go too short and at some point, you don't have the force available to move the lever. You also have to make sure the ratio front to back is correct. Its not just about going big, it's about the correct balance.

You won't see much information on World about 23mm MC's because most of the cars simply can't use a MC that large unless they've also switched to very large calipers.

One small correction: You need to exert more force on the pedal to have the same brake line pressure due to larger MC area. A 23mm MC requires 1.47x more force for the same line pressure as a 19mm (needed if your calipers are unchanged during the swap). You also have 1.5x less travel.

Right. There's no free ride. The later 911's (at least most of the air cooled cars) with bigger brakes used a vacuum assisted brake booster.

Too big on the MC and you loose the ability to modulate the brakes. They become an on-off switch because you have to use your quads to force the pedal down instead of your smaller foot,ankle and calf muscles.

[DBCooper]

And, important to note, with just a larger m/c your brakes will NOT have any additional braking force, the car will stop exactly the same, brake fade will be exactly the same, the pedal will simply be harder to push.

I come from sport bikes. Have you seen them do stoppies, a wheelstand on the front wheel while braking? Requires a HUGE amount of control to keep it right on that edge, and the only way that's possible is with modulation, i.e. a long lever (or pedal), which is the exact opposite of what you get with a larger 23mm master on the same calipers. Nothing's free, so with a harder pedal and less modulation what you give up is control. You have the same amount of brake so you can still "go through the windshield" but it's more binary, on-off, and that's not usually desirable. For me, anyway. Tastes differ, as always.

[ChrisFoley]

We just swapped out a 23mm M/C for a 22 mm VW unit in a V8 track car we have here with BIG brakes.
I thought the pedal could be modulated fine, with good toe-heel control for downshifts, but the owner wanted it to be a little easier on his leg.
The other option was to install a vacuum brake booster but that would have been more work.

[HalfMoon]

To clarify-

I run a 19mm too (as well as a variety of other big brake mods). The primary question I'm pursuing isn't brake "power" (performance gains/differences is/was ancillary), rather it's about "less pedal travel".
That's what the inquiry is really about as well as the advice I had been given.
So I guess the question is for folks who have ACTUALLY done the modification to a 23mm and if they have obtained less pedal travel as a result.
Not asking about theory or opinion, asking about actual experience. Many of us have done the 19mm change and their's reams of information on that mod but not much about the 23mm and pretty much nothing in terms of actual experience.
The main thrust of the question is "brake travel".

The change in pressure and travel when you go to a larger MC isn't theory or opinion. Its a relationship/ratio between the size of the MC and size of the piston calipers. If you keep the calipers the same but increase the size of the MC, the MC will move more fluid with less pedal travel but at the same time, you will need more pressure on the pedal to achieve the same braking force at the caliper. Just like sitting on a see saw, shorten the lever on your side and it gets harder to lift the other end but the travel on your end is shorter. Go too short and at some point, you don't have the force available to move the lever. You also have to make sure the ratio front to back is correct. Its not just about going big, it's about the correct balance.

You won't see much information on World about 23mm MC's because most of the cars simply can't use a MC that large unless they've also switched to very large calipers.

Yep, already knew all that thanks.
So, have you done the conversion and have actual road experience with same and if so did it reduce your brake travel?

[HalfMoon]

We just swapped out a 23mm M/C for a 22 mm VW unit in a V8 track car we have here with BIG brakes.
I thought the pedal could be modulated fine, with good toe-heel control for downshifts, but the owner wanted it to be a little easier on his leg.
The other option was to install a vacuum brake booster but that would have been more work.

Thanks for the valuable feedback Chris.
Your opinion is appreciated (and further valued in that it's backed up with ACTUAL experience)

[DBCooper]

OK, when I got my car the pedal was way too hard. It sucked, made the car unpleasant to drive and the braking less accurate, so I changed it back to a 17mm m/c. That's my ACTUAL experience.

irony is that I later changed to Tilton pedals (for a hydraulic clutch), and the brakes are back to too hard. So it sucks again.

One more note, this is my opinion based on my experience. And I think that's what most of the advice you've gotten is, opinion based on experience. Bottom line is that I'm right and anyone who disagrees with me is wrong, so factor that into your thinking.