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Posted by: Qarl Jan 30 2004, 11:34 PM

I will be installing a 23mm MC to feed the bigger brakes on the new car. I have heard that their are plumbing issues, and clearance issues when installing the bigger MC.

I'm looking for feedback from those that have done this.

Here is a comparison of the new and old MC. I have some questions.

1) Ports 3 and 4 are the front and rear output ports. These correspond (location-wise) to ports 1 and two on the new MC. It seems that I can just transfer the hardware and lines over without any issues. Correct?

2) The locations of the feed lines are different between new and old. Is this going to be a clearance issue?

3) The hydraulic pressure switch (located between ports 3 and 4) does not have a corresponding location on the NEW MC. But there is another output port on the bottom of the MC (underneath port 1) that I can use? Any clearance issus here?

4) Does anyone know what the bolt on the top of the NEW MC is for? (between the red caps)... If I remove it, will a genie come out and grant me 3 wishes?

These would be easier to answer if my car body were in the same location as my parts. (hopefully in a couple of weeks!)

Thanks!


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Posted by: 0396 Jan 31 2004, 07:07 AM

kellzey,

I'll let you know,as Brad suppose to 'drop'one off for me
today or tomorrow.

To my knowledge, the only issue will be clearing the front
inlet . .Cuz the cross member will be in the way.
Also, I believe one has to use the alloy cross member to make this work.

Posted by: seanery Jan 31 2004, 07:09 AM

Karl, are you using boxster or 944turbo fronts? Let us know how this pans out.

Posted by: 0396 Jan 31 2004, 07:11 AM

I have a set of big reds 993 turbo on all fours.

Posted by: ArtechnikA Jan 31 2004, 07:42 AM

been a long time since i did this but it looks familiar. thanks for posting 'cause i'll be doing this in the 911 before spring ...

1) yes. i'd use the back port (2) for the front brakes. i don't recall any issues with the hydraulics.

2) only one inlet is different. i recall the steel lines that plug into the MC have a jog in them. i remember twisting those around so that instead of being parallel, there was an 'X'. but having done that, it fit fine.

3) i don't recall any brake light fitment issues, so if there were any, they were minor...

4) DON'T remove the bolt. you'll only want ONE wish, and that'd be that you hadn't removed it! the original MC's were pretty simple. if anything failed internally, everything failed, and you had no brakes. the bolt is a stop - if the front piston collapses completely, the aft piston will stop against the bolt that protrudes into the bore and give you SOME braking. this is why i recommend using the aft piston for the front brakes - it's your 'fail-safe' circuit. (please review the usual brake references and verify i'm right on this - i did research it, but it's been a while. if i'm wrong, i want to know it! 'cause i'll be plumbing my brakes too and i need to know!)

good luck ! if you find out something's different, pls report back. this time, you (instead of me) get to be the pioneer here ...

Posted by: ArtechnikA Jan 31 2004, 07:47 AM

i've heard this too, but i can tell you from personal experience i did it with a standard OEM 914.6 steel (911) crossmember.

914.4 uses the 914.341.013.03 auxiliary support;
914.6 uses the 901.341.013.03 auxiliary support.

you'd think there's be SOME difference or there wouldn't be two part numbers. i've never tried to put a 23mm MC in a /4 but it goes in a /6 just fine.

you probably need a 911 crossmember - alloy or not...

Posted by: Qarl Jan 31 2004, 08:47 AM

Thanks everyone.

The alloy cross member is not a problem...

Posted by: echocanyons Jan 31 2004, 09:33 AM

Karl,
How does the alloy crossmember mount?

The stock crossmember has tabs welded to it, Are the tabes shown in the picture mounted to the body and the x-member?

Posted by: echocanyons Jan 31 2004, 09:34 AM

IS the 23mm MC necessary for the monoblocks?

I ask cuz I will be running the same brakes.

I also noticed your cooling ducts for the brakes did you fab these yourself or are they a 911 piece?

Posted by: Qarl Jan 31 2004, 09:42 AM

Ducts are a 911 piece from AJUSA also available from SmartRacing.

The 23mm vs 19mm is sort of a tie. Either/or

If there would be a 21mm MC, then it would be perfect, or so I have been told!

Posted by: ArtechnikA Jan 31 2004, 09:58 AM

are you using the blockoff plates too? i'm planning on using all that same stuff. does the kit come with fasteners to put your hubs back together, or are we on our own for that ?

the aluminum caliper cars came with a 20,55mm MC but those have been NLA for a while, i've been told. if you go to a dealer with one of those cars with a bad MC, i have no idea what they'd replace it with (if you could find a dealer interested in your '71 car these days ...). probably offer to 'upgrade' you to the 19mm for its "superior pedal feel and improved modulation" ... (the "sell what you've got" school of marketing ...

Posted by: Jeroen Jan 31 2004, 10:20 AM

The tabs that are welded to a steel x-member are bolted to a alu x-member
They're in the middle of the pic...

cheers,

Jeroen

Posted by: KenH Jan 31 2004, 10:23 AM

Replace the "feed hoses" with the flexible"blue hose" from PP.

Ken

Posted by: iamchappy Jan 31 2004, 07:45 PM

Karl
I can post a picture of it when I get back home, it does fit pretty tight as I remember it, and you will lose your brake failure idiot light as mine had no provision for it.

Posted by: Howard R Feb 1 2004, 12:32 PM

Karl,

You will have to file, cut, dremel about 6mm off the back of the bottom edge of the crossmember to clear the 23 mm master cylinder. Did it yesterday.

Posted by: ArtechnikA Feb 1 2004, 04:10 PM

interesting - i know i didn't have to do this. and i'm pretty sure i remember you saying you have a factory /6, yes ?

i have to wonder if we're now being sold a different 23mm MC than we used to get 30 years ago. i'm not even sure i moved mine out of NV for comparison purposes. i hope so ...

Posted by: Howard R Feb 1 2004, 05:54 PM

Rich,

In my case it might have something to do with being converted from left to right. The 23 master cylinder almost makes it but not quite.

Posted by: Qarl Feb 1 2004, 07:22 PM

Hmmmm.... I think I found an ATE 20.64mm Master Cylinder.

Part number 03.2120-8411.3

I found it here...

http://www.conti-online.com/generator/www/com/de/ate/ate/themen/kataloge/printkataloge/download/ate_hb5_de_en.pdf

Page 14.... Tandem Master Cylinders.

Posted by: ArtechnikA Mar 13 2004, 05:31 PM

i went to that site and didn't see any 20,64mm MC's -- but i didn't see any 23's either...

and here's an interesting note - earlier in this thread, when being faced with the difficulties some have been facing during installation, i had to speculate that perhaps we weren't being sold the same MC i used 25 years ago.

my new one came in a couple of days ago, from Dart Auto (after being jerked around a bit and facing a 25% (!) price increase over their published price by SmartRacingProducts...) sure enough - as you can see - the 'new' MC is not very close to what i used last - it is a MIRROR IMAGE to the part i bought at the Mercedes dealer all those years ago ...

that's gonna require some hardline changes, i bet, and what else i won't know until i get the car up and the access panel off ...


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Posted by: john rogers Mar 13 2004, 09:24 PM

When I bought mine several years ago, it came with new gromets and tubes for the fluid supply. I installed them before bolting in the m/c and then used new Parker kevlar hose from the top to the feed lines. I also had to make a new rod to go into the back of the piston since the stock 914 one was too short and I wanted to keep the pedal in the normal position. I did not have the pressure switch for the warning light either. You might want to use a residual valve in the line for the rear brakes to eliminate any change of lockup. I adjusted the brake lights so they come on before the m/c actually makes any pressure so the cars behind me will start braking but I'm not really braking yet. Good luck

Posted by: davep Mar 13 2004, 09:53 PM

I saw a car today, a converted 73, that had a booster assembly bolted to the trunk floor. It took up about 2/3 of the left half of the floor. I wish now I had taken a picture. I'm told it is quite effective. Don't know that it is necessary though.

I think that rebuilding my 20mm will be sufficient for several years. I'll have to try to find some more kits.
Note that the odd metric sizes are due to the fact that the true sizes are in 1/16 of an inch increments.

17.46 = 11/16
19.05 = 3/4
20.64 = 13/16
23.81 = 15/16

Posted by: SirAndy Mar 14 2004, 03:05 AM

wow, now we're talking!

anyone who wants to buy a alloy cross-member that's already cut/notched for the 23mm MC ????

i have one on my car currently and i want to go back to the steel crossmember!
Andy

Posted by: ArtechnikA Mar 14 2004, 07:22 AM

i won't really -know- what's required until i get in there; last time i did this, it was to the 914.6 but this time, it's the 911. installing the feed lines -before- bolting up the MC is definitely the hot setup, having done it the hard way once too...

i don't think there will be an issue with bias, this is close to the size the car should have had originally with the aluminum calipers, and there's a significant weight and tire-size bias to the back. early 911's never had proportioner valves and i'm not expecting to need one now. (i do, however, have one on the shelf if required...)

i'd heard the bit about the brake pushrod too, and while i've BTDT, i just don't remember doing it. but i did pull the pushrod from the 914.6 last time i was there so i have that one to be pressed into service if required (as everyone says it will be.) i probably ought to measure it real good so i won't have this issue the next time :-)

Posted by: blabla914 Mar 14 2004, 07:52 AM

A little off topic, but why do you want to go back to a steel cross member? I've been thinking about going to alloy. Should I rethink that?

Kelly

Posted by: ArtechnikA Mar 14 2004, 08:30 AM

the steel -is- a little heavier, but the weight is so low that it doesn't have the effect on handling of weight up high (which is bad). it is MUCH more rigid than the aluminum crossmember.

Porsche had really good experience with the aluminum 'bananas' (trailing arms) on the 911 in ~'74 -- they were lighter -and- more rigid than the steel ones. win/win. since the aluminum crossmember is a one-piece part rather than a fabricated weldment like the steel one, it's probably much cheaper for them. they were starting to get excited about going Group 4 and Group 5 racing again with the I-series cars in 1976 and wanted to homologate a bunch of light parts since they knew the 934 was going to have a weight problem...

i was hot to make the change when i thought the alloy crossmember incorporated a suspension pickup ahcnge, but it turns out it was in the I-series tub instead, and the crossmembers are dimensionally identical. that cooled me on that idea. the suspension change was good, but the crossmember wasn't going to get me there.

if for some reason your steel crossmember is bad, and you have a street-driven car, and you got a killer deal on an aluminum part, i wouldn't turn it down if it'd keep the car in service. but i wouldn't be going out of my way to replace a good steel one.

(although as seen in Kellzey's pictures, they do look so darned cool....)

Posted by: thesey914 Mar 14 2004, 08:49 AM

Karl can you show a close up of how the callipers mount on the struts? Just want to see what kind of spacers/brackets are required. Where are they available form?

Posted by: blabla914 Mar 14 2004, 11:53 AM

Thanks, you just saved me time and money. I am going to pull the front end to do bushings and check the rack (something is clunking down there when i hit big bumps on autocross courses) and I was going to swap to an allow cross member while I was at it. I think I'll stick with what I got.

Kelly

Posted by: ArtechnikA Mar 14 2004, 12:08 PM

go back and re-read the thread from the beginning (i just did) ...

there are those who say you need to modify the crossmember to accept the 23mm MC (if that'd in the cards for you) and while i didn't on my car (914.6 with 911 part number crossmember) we just established (a couple of posts ago) that the current crop of 23mm MC's is different from what i used way back then - so i donno what kind of modification will be required. (the 911E i'm prepping uses exactly the same crossmember part number ...) ports coming off the 'wrong' side could definitely make a difference. some day, i'm gonna hafta take my old part to a Mercedes dealer with an old-guy parts counterman and see what the old one used to be ...

oh - clunks are ball joints, tie rod ends, damper inserts loose in struts, really, really badly adjusted steering racks (i think you'd feel that...). in my car the antiroll bar used to slide from side to side until i made some little travel-limiting collars out of PVC pipe. could be wheel bearings too... very slightly possibly a loose steering rack mounting bolt - i'd think you'd feel that one too...

Posted by: SirAndy Mar 14 2004, 02:58 PM

what rich said. the steel CM is more rigid than the alu one.
it's also heavier, but because the weight is so low, that doesn't make much of a difference.

Andy

Posted by: SirAndy Mar 14 2004, 03:00 PM

i had the same. the car also started to "jump" either left or right when hitting the brakes hard.

turned out to be the ball joints. they were completely toast and allowed the struts to move about 1/2" up/down when unloaded.

i (well, brad and i) replaced them yesterday and all is good now ...
Andy