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> Master Cylinder advice needed, for Boxster calipers
ChrisFoley
post Apr 7 2015, 02:38 PM
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A car we're prepping has Boxster calipers and a 19mm master cylinder.
While this is fine for a street car it doesn't provide the stiff pedal desired for competition.
What are people using for an upgrade with Boxster brakes?
I'm pretty sure the Mercedes 23mm master is too big.
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SirAndy
post Apr 7 2015, 02:45 PM
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I never heard of any size in-between 19 and 23 that would fit our cars.

I use the 19mm with Boxster calipers and you are correct, the pedal feel is OK for street driving and light track use but would probably be too "soft" with too much travel for a dedicated track car.

I'd go with the MB 23mm. The 911 race car i was working on ran a similar setup using the 23mm MC and the brakes felt great.
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ChrisFoley
post Apr 7 2015, 03:15 PM
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Thanks Andy!
I ran the numbers and the pedal stroke with a 23mm will be roughly 2/3 of the distance with a 19mm.
That's just within the range I had in mind.
I found a kit at PMS. Is there a better source? I need something quick.
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914Sixer
post Apr 7 2015, 03:33 PM
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At some point there was a 20mm master cylinder, I do not know where it came from but my car has one. Might be MB or BMW. Never was able to reference it from the stampings. Posted it here and Andy came up with what was thought to be a MB match.
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Luke M
post Apr 7 2015, 05:06 PM
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Get the 23 mm Mercedes master. You will need a longer push rod and need to modify the routing on some brake/feed lines. If I recall it's a tight fit or won't fit at all with the steel cross member but the aluminum style clears. It's a stiff brake pedal feel but I like it vs the 19 mm. I have a Boxster brake setup for the front/rear of my car and I also got a 23 mm Mercedes master to go with it. I'm using a 911 push rod which is a little longer then the 914.

I've had a Mercedes 23 mm master cyl in two of my other 914's and I liked it.
One car had the 930 4 piston calipers with 911 sc rears. The other was the aluminum S calipers with 914-6 rears. The brakes where great on both cars which where street and track driven. Hope this helps you out.
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Mike Bellis
post Apr 7 2015, 06:30 PM
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Not Boxster but I run a 23mm with my 930 calipers and I have a nice firm pedal, no prop valve and the car stops on a dime without any wheel lock up.
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Chris914n6
post Apr 7 2015, 06:31 PM
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RockAuto has a 23mm listed, by URO. Under 1975 911. $100 shipped. Looks right.
91135501202A

The one time a I had a warranty exchange with RA it was easy problem free. Sachs hatch struts if you were curious.

RA mystery... Clicking through their promo email link injected a 5% off code during checkout.
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screenguy914
post Apr 7 2015, 06:56 PM
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Read this thread:
http://forums.pelicanparts.com/porsche-911...tml#post6532921

My research for a much delayed brake upgrade and post (#14) suggests using a VW Passat MC w/o ABS (or equivalent). They have a 22.2mm bore. In addition, the overall length is slightly shorter than the more expensive 23mm M-B MC.

There are several 1990's VW models (Jetta GTI, Corrado and Passat) using the same MC. Compare and confirm reservoir inlets and outlet ports are oriented correctly for your application. Not sure if the brake pedal push rod needs to be shorter or longer. However, not insurmountable.

One 911 owner installed one with upgraded 4-piston calipers/larger/thicker rotors and reported all went well w/o any issues.

Notice the reservoir inlets are clocked differently on the same basic 22.2mm MC:
Attached Image Attached Image

This is a 914 MC for comparison:
Attached Image

Try this part number for cross-referencing:
Meyle 357611019BMY
Similar on ebay:
http://www.ebay.ca/itm/131-33408-New-C-Tek...20d9&_uhb=1

There's also a Porsche tax often levied for 914 parts.

Sherwood
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ClayPerrine
post Apr 7 2015, 09:05 PM
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I have the 23mm Mercedes master cylinder with the boxster calipers. Really good pedal feel, and it stops like it has anchors.

Betty thinks it feels like it has power brakes.
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ChrisFoley
post Apr 7 2015, 09:49 PM
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Thanks guys!
That's all good information.
I may just go to PMS for the convenience on this one due to time crunch.
Their kit includes special parts like a custom pushrod.
My customer plans on testing the car at Devens in less than 2 weeks.

But the VW option looks worth pursuing if I had a little more time.
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ChrisFoley
post Apr 8 2015, 10:36 AM
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D'oh!
I already have another car in the shop with Boxster brakes and a MB M/C.
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AndyB
post Apr 8 2015, 11:33 AM
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QUOTE(Racer Chris @ Apr 8 2015, 12:36 PM) *

D'oh!
I already have another car in the shop with Boxster brakes and a MB M/C.

(IMG:style_emoticons/default/drunk.gif) have another one Chris (IMG:style_emoticons/default/beerchug.gif) If you haven't had one then you may need one.

Andy
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MJHanna
post Apr 8 2015, 11:57 AM
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When I did mine I had interference with the steering rack moving connection from the brake filler to the master cylinder (it was pulling it out of the master) I used steering rack spacers to get the clearance
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ChrisFoley
post Apr 8 2015, 01:42 PM
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The other car I have here has the PMS kit installed, we looked at it.
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Paragon
post Apr 8 2015, 07:52 PM
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QUOTE(Chris914n6 @ Apr 7 2015, 04:31 PM) *

RockAuto has a 23mm listed, by URO. Under 1975 911. $100 shipped. Looks right.
91135501202A



URO master cylinders are junk. We learned our lesson early on. Not worth the hassle.
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