What car did the 23mm master cylinder that will bolt into our cars come out of?

John

Early Mercedes. You'll need the alloy front end support or what ever it is called as it is too long for the steel tube one, although I have seen a picture where someone put a dent in the tube with a BFH?

I believe it was a Mercedes truck. It's an ATE master cylinder. A search of the forum should give you a part number.

plain ol' Mercedes passenger sedan.

a few places have them (or claim to). i dealt with a couple of places that claimed to have them, but they meant they "could get" them. DART (they advertise in Pano and Excellence) had 'em in stock and will know what you need. you will need to mod the pushrod a little, has to be a little longer or shorter, i don't recall which. you can easily make one out of a cylinder stud by grinding a full ball radius on the 'working' end.

gotta ask: what are you doing to/with your calipers that makes you think you need such a thing? (there *are* correct answers to this question! but it's not something that everybody needs and it is NOT a "standard upgrade" to an otherwise stock brake system - even in a 914.6)

i've heard the stories of suspension crossmember mods too but i know for a fact i did NOT have to do that when i put my Mercedes MC in my 914/6 25 years ago. we'll see what happens when i p[op one into the 911 ...

I think the 914/6's came with the I-beam type front end support if I remember correctly? The 23mm m/c fits in there okay with that but not the 914/4 steel tube support. When I put mine in the 1973 race car I had to do a replacement. There is also an issue with the front line that feeds the brake fluid from above that it hits the bottom of the gas tank and the one I bought came with a short, bent adapter so the lines fit okay. I also had to lengthen the rod from the pedal to the back of the m/c.

John (stock93) will be my guinea pig for a Volvo brake upgrade. Want to test the 19mm and 23mm masters. Will probably be running Volvo vented calipers on the front and 320 calipers in the rear. Might do all Volvo calipers all the way around.

QUOTE (john rogers @ Feb 14 2005, 04:11 PM)

I think the 914/6's came with the I-beam type front end support if I remember correctly?

not sure what you mean by the I-beam support, but i did recheck the ETKA and sure enough /4's do carry a different part number for the rear crossmember - i always thought they were the same. 6's get a '901' number and 4's get a '914' number and you can't see diddly squat on the picture, and there's only one and you can't tell which it is anyway...

and i don't have a /4 crossmember to compare... i do recall having to re-twist / re-route the reservoir lines but it was ok with the stock parts in different places.

the aluminum crossmember arrived in "around" 1972 for the 911, "officially" for the 1973 911RS, but not all RS's got them, and not all "regular" 911's didn't. opinions vary as to why. almost certainly the first 500 homologation cars got them at first (lighter) and at least a few of those were refitted as roadgoing cars with heavier stuff. certainly some of the competition cars got the steel members (stiffer)... as for the rest - it was probably whatever was available in the parts bin that day, in the absence of a special order...

looks like my '71 911 carries the same part number as the 914.6 so barring pedal box dimensional differences i may be good to go!

thanks ! i learned something today !

Brett,

I think that the Volvo 240 used a 22 or 23mm MC with the 4-piston calipers--but they also had a vacuum assist. Wouldn't the 23 give you an awfully hard pedal?

I've got a set of vented volvo calipers and a MC hiding in garage somewhere if you need any dimensions (piston size, etc.).

Lemme know . . .

Best,

Steve A-

the 6 i parted out had a tubular crossmember

Thanks for the offer. I already have the calipers and stuff. just need the 23mm master.

With the proper proportions the pedal should feel like the stock brakes.

I've been looking at this on ebay for quite a time...the guy seems to sell these regularly...http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=7943123843&rd=1&sspagename=STRK%3AMEWA%3AIT
if anyone knows about these what modification for 75 914 1.8

What type of brake system do you think would require a 23mm master cylinder. I have all Carrera brakes on my 912 and I also have a 23mm master cylinder that I have not yet installed. Do you think that this is overkill or would it feel just fine?

-Britain

Britain,
Read Brett W's replys.

Ok guys, I got a mer truck or passanger sedan. I have access to several older Mercedes cars for parts. What does anyone know specifically what model this MC is out of?

QUOTE (rj777 @ Feb 15 2005, 02:19 PM)

if anyone knows about these what modification for 75 914 1.8

please learn how to use the "http://" button !

ok, rant over...

those look like the same ones available all over, over the counter, and at the typical price. DART isn't going to ask you to wait 21 days for shipment tho...

like it says, and every thread on this subject has said - you will need to clearance the suspension crossmember somehow, or use a 911/914.6 crossmember, or the aluminum 911 crossmember. you are going to have to re-plumb the reservoir lines. you are going to need to change the hard lines to the front and possibly to the first junction to the back. spend the $10 on a brake tubing bender tool and do the job right; brake hardlines are available at every FLAPS. you will need a new, slightly longer pushrod.

you're going to need at least 'S' or 'A' calipers front and 914.6 calipers rear or you'll have a pedal that is impossibly stiff to modulate and has about 1/8" travel, but you'll have spent $200 and a weekend getting there...

this is NOT a standard upgrade.

QUOTE (stock93 @ Feb 15 2005, 12:58 PM)

Britain, Read Brett W's replys. Ok guys, I got a mer truck or passanger sedan. I have access to several older Mercedes cars for parts. What does anyone know specifically what model this MC is out of?

I still don't get it??

if using the 23mm master cylinder with stock calipers you get what??

bragging rights to your buddies that don't know any better and the joy of spending a few hours under your car??

Adding a 23mm MC to a stock system is actually a BAD thing. You get a harder pedal and less pedal modulation of the brakes. Unless you get larger calipers it will be a lot of work for a less desireable result.

George

QUOTE (Brett W @ Feb 14 2005, 02:46 PM)

John (stock93) will be my guinea pig for a Volvo brake upgrade. Want to test the 19mm and 23mm masters. Will probably be running Volvo vented calipers on the front and 320 calipers in the rear. Might do all Volvo calipers all the way around.

Brett,

how soon will you have results on the test? I'm working with Volvo calipers also and was not sure what master cylinder to use.

John,

Did you ever get that V6 in your car or did you decide on something different?

SteveSr

I'm working up a spreadsheet now to help work out the ratios for MC/calipers. I need the following to finish it:

What is the diameter of one caliper piston on the Volvo 4-piston calipers?
How about the Carrera calipers, Britain? How many pistons are there per caliper?
Mike, what's the size of the caliper pistons on those 4-piston RX-7 calipers you have?

If anyone else has any calipers they'd like added, let me know. I just need the size of one piston and how many are in the caliper.

Carrera calipers (wide-A)

Fronts: 48mm piston bore (2 pistons per caliper)

Rears: 42mm pistons bore (2 pistons per caliper)

-Britain

Caliper


Piston Diameter

914-4


42 mm

BMW 320i


48 mm

911 - M caliper


48 mm

RX7=36mm (ea)

Big Reds=36/40

Boxster(F)=35

M-Caliper (early rear)=38

Everybody follow alonge here:

The 23mm master cylinder is not going in anything stock. I am well aware of the problem with upgrading the master on stock system.

I will get the Volvo piston sizes later tonight.

QUOTE (Brett W @ Feb 15 2005, 05:28 PM)

Everybody follow along here: The 23mm master cylinder is not going in anything stock. I am well aware of the problem with upgrading the master on stock system.

i'm not worried about you; you know what you're doing.

but you are not the only one asking questions in this thread...

and you are not the only one reading the answers.

QUOTE (Brett W @ Feb 15 2005, 03:28 PM)

Everybody follow alonge here: The 23mm master cylinder is not going in anything stock. I am well aware of the problem with upgrading the master on stock system. I will get the Volvo piston sizes later tonight.

i knew that

problem is, people see those eBay ads and get excited...."oh, it's a racing part, it'll make my car better"...

is your rotor hat off the shelf with no mods except the thru holes for the lug bolts?

how is the alignment with the caliper? is your pricing good? best pricing I found was with Pit Stop USA for the rotors..........still undecided which direction I'm going with mine....

got a volvo caliper question....

they bolt up fine. they can be centered on the rotor with a washer.... how much of the pad over hangs the edge of a rotor?

QUOTE (Aaron Cox @ Feb 15 2005, 03:40 PM)

how much of the pad over hangs the edge of a rotor?

something like 1/8" or a tad bit more...nothing to worry about unless you put on new pads and wear them down enough for the overhanging material to touch each other when you hit the brakes...you can always add a bevel to the edge to help minimize/eliminate the overhang

QUOTE (Mueller @ Feb 15 2005, 03:45 PM)

QUOTE (Aaron Cox @ Feb 15 2005, 03:40 PM) how much of the pad over hangs the edge of a rotor? something like 1/8" or a tad bit more...nothing to worry about unless you put on new pads and wear them down enough for the overhanging material to touch each other when you hit the brakes...you can always add a bevel to the edge to help minimize/eliminate the overhang

1/8th thats it???? i thought something like a quarter or something.....

hmmm..... maybe front and rear volvo calipers.... that could probably use a 23mm MC....

CODE

914/4 & A rear  320i/M front   RX-7 4piston  Boxster front  M rear                                   42x4                 48x4              36x8               35x8               36x4 stock 914/4       17      24                    32                   36                  34                  18 stock early 911 19       20                    26                  29                  27                  14 mercedes          23       13                    17                  20                  19                 10

If the table above looks all messed up, it's Andy's fault.
I could attach the spreadsheet, too, I suppose.

Down the left are the three most commonly used MCs. Across the top are the brake calipers I have data for.

The numbers in the table are the ratios of the MC piston area to the total caliper piston area for the front or rear half of the circuit. Note the stock 914/4 ratio of 24:1. With a smaller number, pedal effort increases for a given braking force, but pedal travel decreases. If the number gets too small, you need more pressure than you can physically exert on the pedal to lock the tires. If the number gets too big, the pedal hits the stop before you're generating max braking power (actually, before it gets there, the pedal will usually feel all mushy, like it needs bleeding). So, you're trying to strike a balance between pedal effort and feel. Most people like a harder pedal (smaller number), but most people don't have the leg muscles of a Mr. Universe qualifier (number too small). For non-servo'd brakes, the range 19-26:1 seems to be a good one, with personal choice determining where along that line you want to be.

See that the 19mm with stock 914/4 calipers requires more pedal effort, but less travel. Some people like this setup, with a 20:1 ratio, and I can say it's adequate but not ideal (PO fitted this to my car). I can just barely lock the tires with big effort, but day to day the brakes feel OK.

Note that with with the 320i/M fronts/A fronts (the 48x2 calipers), you get more braking force with slightly longer travel using a 19mm MC. This is why so many people like this setup. Less pedal effort than stock, but not so little you have to practically push the pedal through the floor to get full braking.

The RX-7 or Boxster calipers require a 23mm MC just to get down to the 19mm/stock setup. With a 17mm MC, I'd expect this setup to be very touchy and feel awful, requiring a looong pedal to get braking effort. The Boxster fronts with the 19mm MC will feel a bit more powerful than the 320i/M caliper w/ the 19mm setup. I would think a 21mm MC (if such a beast exists or could be made) would be about ideal for these calipers.

Some rear calipers are also included, and you'll note how small the numbers are. This indicates much less braking force for those calipers, which is how you get front/rear brake balance w/o a prop valve. Also note that adding a bigger MC with bigger front calipers REDUCES rear braking even more, moving the brake bias forward. This is why removing the prop valve is usually helpful in such cases. To keep brake balance, you need to increase the size of the rears as well as the fronts when upgrading.

QUOTE (ArtechnikA @ Feb 15 2005, 03:24 PM)

you are going to need to change the hard lines to the front and possibly to the first junction to the back.

why would you need to do this?

caliper spec sheet

and brake bias sheet

QUOTE (ein 6er @ Feb 15 2005, 04:34 PM)

and brake bias sheet

here is a great link with tons of Porsche caliper and brake information

Porsche Brake page

QUOTE (nsyr @ Feb 15 2005, 05:55 PM)

QUOTE (ArtechnikA @ Feb 15 2005, 03:24 PM) you are going to need to change the hard lines to the front and possibly to the first junction to the back. why would you need to do this?

you would need to do it because the lines exit on the opposite side of the MC vs the OEM, and it is longer, so the hardline might not be long enough to reach the outlet port in the MC.

second pdf file screen shot:

I installed a 23mm M/C this winter and have one test day at Willow to evaluate the difference. Previously I was running a 19mm and always had too much pedal travel when the pads wore anything beyond about 75%. I would only have a good firm pedal after a new pad change. Calipers are Carrera front and SC rears so I was on that margin between the 19 being too smalll and the 23mm too large. After a couple of hours testing, I can modulate this combination of the 23mm and the Carrera/SC calipers OK, but its probably not for everyone. Pedal pressure is significantly higher. I plan to upgrade to Boxster fronts so this should bring the overall ratio into a more optimal range. My first race with this setup (23mm, Carrera/SC) is this coming weekend in Phoenix (if we don't get rained out). I let you know how it went.

BTW, I did install with the steel crossmember, but had to take off about 1/8 inch dimple with my grinder and and another 1/8 inch off the casting bump on the M/C. It fit but had me exercising my four letter word vocabulary. Not a fun job - the fluid supply lines were tricky to insert into the M/C. I loosened the crossmember and dropped it and the front suspension arms about 2 inches to get the M/C in.

Steve

QUOTE (lapuwali @ Feb 15 2005, 05:54 PM)

...I would think a 21mm MC (if such a beast exists or could be made) would be about ideal for these calipers. ...

there *used to be* a 20,5mm MC used with the early 911E and 911S with aluminum calipers front but the rear brakes unchanged. those have been NLA for years.

BTW - we call these MC sizes by their nearest metric equivalents, but they're *actually* English-system measurements. 19mm is really 3/4", that 20,5 is really 13/16", and the 17mm is really 11/16" (11, 12, and 13/16")

Just a note here, the master cylinder sizes are actually in increments of 1/16 of an inch, they are not metric. The '19' mm is actually 3/4 inch. Moreover, the 911S used a 20 mm master with the aluminum 'S' calipers. It would be really nice if it was still available.

17.46=11/16
19.05=3/4
20.46=13/16
23.81=15/16

QUOTE (slivel @ Feb 15 2005, 06:43 PM)

...the fluid supply lines were tricky to insert into the M/C....

here is the trick on that that i learned only after having struggled with it - once.

put the reservoir lines in the MC while it's still sitting on your bench and you have good leverage from the top. some brake assembly grease helps, but mostly it's just a matter of being on top of the problem rather than it being on top of you.

then snake the lines up to the reservoir as you install the MC onto the studs ...

QUOTE (ArtechnikA @ Feb 15 2005, 03:47 PM)

QUOTE (lapuwali @ Feb 15 2005, 05:54 PM) ...I would think a 21mm MC (if such a beast exists or could be made) would be about ideal for these calipers. ... there *used to be* a 20,5mm MC used with the early 911E and 911S with aluminum calipers front but the rear brakes unchanged. those have been NLA for years. BTW - we call these MC sizes by their nearest metric equivalents, but they're *actually* English-system measurements. 19mm is really 3/4", that 20,5 is really 13/16", and the 17mm is really 11/16" (11, 12, and 13/16")

Something handy to know.

On Honda motorcycles (using Nissin brake parts, Nissin is owned by Honda), they cast the size of the MC into the body of the MC. However, some are shown as metric (11mm for a particular 400), some are English (0.5 for a popular 600). I'll bet the 11mm isn't really metric, either, but 7/16" (only 4 thou different: 0.433" v 0.437").

Wilwood makes a "21mm" (13/16") and a "22mm" (7/8") MC with a remote setup. They're only single circuit, though. They make some dual circuit MCs, but they're big (smallest is "25mm" or 1").

I have Carrera (wide-A) calipers all around and according to that link above the stock set-up was a 20.64mm MC vaccum assisted. Do you think that a 23mm MC would be too large for this set-up when not using vaccum assist? Also, should a proportioning valve be used?

-Britain

QUOTE (Britain Smith @ Feb 15 2005, 04:20 PM)

I have Carrera (wide-A) calipers all around and according to that link above the stock set-up was a 20.64mm MC vaccum assisted. Do you think that a 23mm MC would be too large for this set-up when not using vaccum assist? Also, should a proportioning valve be used? -Britain

With A fronts and A rears (I'm assuming this, not the same sizes all round), the split you have is 17:1 front and 13:1 rear with a 23mm MC. This would have fairly heavy pedal. A 19mm would be pretty close, though. A 21mm w/o a servo would probably be spot on. Both might be close enough to be workable, and will come down to your personal preference.

I'm not going to speculate on brake bias, since this is on your unfinished 912, and there's no knowing what your front/rear weight distribution is going to be when you're all finished.

I wonder if a new piston could be machined up to fit a bored out 19mm (3/4") MC. Seals would be interesting, though using 13/16" seals from a Wilwood or other MC might work, which would give 20.62mm. Are rebuild kits for those NLA "21mm" MCs still available? If so, do they include new pistons, or just seals?

Sorry Mike, didn't mean to jump your shit.

My hats are off the shelf bolt on. Have to drill the lub holes though. With the vented rotor and vented caliper the caliper will need about .75-.100 off the inside mounting ears. I beleive. I need to machine and measure and machine an measure.

The Hat is something like 50 and the rotor is about the same. Calipers are 13 apeice. Haven't priced studs yet.

For the guys running Fuchs or other hub centric wheels then the hat will have to be machined slightly otherwise I am going to turn the ring off all together.

Audi RS2 and some Quattros has 23 and 25mm masters. I have Quattro version from -92. It has two different size of pistons. other is 25,5mm and the other is 19,8mm. Bigger is for rear and smaller for front calibers. It's quite hard to use but with 996 monoblocks it is awesome in 914...


lower part is somekind of pressure balancer between rear and front

I have a 23 mm master and a 19 mm master for sale both are new. they come with the matching pus rod for the pedal.