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bigashlow
Samba Member
Joined: December 07, 2005
Posts: 88
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 Posted: Mon Apr 21, 2014 6:00 pm Post subject: Master Cylinder for upgraded brakes; AKA 4piston or 4 pot |
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OK...enough looking I have is bmw 2002 fronts 4 piston calipers & 914/4 rear brakes. MY QUESTION; There is a 23mm Porsche 914/911 early upgraded one , has anybody installed this master? Mercedes Benz unknown I think 22mm. For bug folks a 20.6?? mm one for type1 installs. Can the "rod" be made long & just use the bug unit? Or 914 master "appears" to close to type3 , maybe just by looking @ pix's. the type3 has a short neck & bug does not, I see that Lanner has deal for bug so I'm going e-mail him & see? SO whom has done a major mods to master brake & what calipers & what did the master start as or OEM part number & app.?? thanks type3 drivers.  |
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Nate M.
Samba Member
Joined: August 11, 2003
Posts: 1306
Location: Anacortes, WA U.S.A.
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| Posted: Mon Apr 21, 2014 6:57 pm Post subject: |
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I can only speak for what I've used and run to this point, but a 19mm Porsche 911 MC is a good upgrade for 914s and gives a firmer pedal while still allowing for good brake modulation and feel. A 23mm Porsche MC makes for a very firm pedal and you need to exert more force to exact the same results as the 19mm. I would not recommend a 23mm for this reason.
When I install the new MC on my Squareback that has 911"M" calipers front and stock 944 calipers rear, I plan on installing a 19mm 911 MC to run it all.
In general the smaller the MC bore = softer pedal, less force to actuate brakes and the more pedal feedback (feel) you get. The larger the MC bore = harder pedal, More force to actuate brakes and less feedback. It's really a balancing act.
Most MCs w/ bores larger than 19mm are power assisted. . .
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Regards,
Nate M.
Squarsche build
Heavy Metal Affliction feature
For heaven's sake, put a type4 and a Porsche 5-speed in there. . . It's the right thing to do!! |
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Erik G
Samba Member
Joined: October 16, 2002
Posts: 13280
Location: Tejas!
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| Posted: Tue Apr 22, 2014 7:15 am Post subject: |
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keep in mind the 911MC has less ports, and banjo style fittings. The early ones have one hole for the rear, one hole for the front with a banjo fitting and the electric brake light switch through the fitting. The later one has it's own hole for the switch, but still, just one hole for the front, one for the back, banjos and T's. Keep that in mind when planning your brake lines
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Erik G
Samba Member
Joined: October 16, 2002
Posts: 13280
Location: Tejas!
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| Posted: Mon Apr 28, 2014 1:53 pm Post subject: |
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| Nate M. wrote: |
I can only speak for what I've used and run to this point, but a 19mm Porsche 911 MC is a good upgrade for 914s and gives a firmer pedal while still allowing for good brake modulation and feel. A 23mm Porsche MC makes for a very firm pedal and you need to exert more force to exact the same results as the 19mm. I would not recommend a 23mm for this reason.
When I install the new MC on my Squareback that has 911"M" calipers front and stock 944 calipers rear, I plan on installing a 19mm 911 MC to run it all.
In general the smaller the MC bore = softer pedal, less force to actuate brakes and the more pedal feedback (feel) you get. The larger the MC bore = harder pedal, More force to actuate brakes and less feedback. It's really a balancing act.
Most MCs w/ bores larger than 19mm are power assisted. . . |
here's the math on this
pedal force = MC hydraulic pressure x MC bore area
Ipso facto, the stuff the MC needs to put out to stop
hydraulic pressure = MC pedal force / MC bore area
MC bore area = pi (bore diam ^2) / 4
To stop the same, the MC hydraulic pressure is equal for both the 19 and 23 mm bore MC.
hydraulic pressure = MC pedal force (23 mm) / MC bore area (23 mm)
= MC pedal force (19 mm) / bore area (19 mm)
Ergo ipso facto;
MC pedal force (23 mm) / MC pedal force (19 mm) = MC bore area (23 mm) / MC bore area (19 mm)
MC bore area (23 mm) / MC bore area (19 mm) = (23 mm ^ 2) / (19 mm ^2)
= 529 / 361
= 1.469
Abracadabra, et tu brute:
The extra leg force is 100 x (1.469 - 1) = 47%
Now you know how much extra leg effort it takes to stop the same and you also now know why.
I copied and pasted this. I'm not that smart (or maybe I am, because I copied and pasted?)
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