 The 20.5mm 911 Master Cylinder Myth, A Real Factory 1969 Part |
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| 914Sixer |
 Dec 29 2025, 05:47 PM
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#1
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914 Guru  Group: Members Posts: 9,380 Joined: 17-January 05 From: San Angelo Texas Member No.: 3,457 Region Association: Southwest Region 
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Found this and passing info on. I have one of the 20mm on the 1975. Never could prove it was a factory part. Article clears up myth that the larger master cylinder came from Mercedes.
Attached thumbnail(s)   
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| sixnotfour |
Dec 29 2025, 06:46 PM
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#2
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914 Wizard Group: Members Posts: 11,079 Joined: 12-September 04 From: Life Elevated..planet UT. Member No.: 2,744 Region Association: Rocky Mountains 
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no myth, just NLA
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| 914Sixer |
Dec 29 2025, 07:06 PM
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#3
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914 Guru Group: Members Posts: 9,380 Joined: 17-January 05 From: San Angelo Texas Member No.: 3,457 Region Association: Southwest Region
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Not totally true, I have a 2nd one that is NOS.
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| Ninja |
Dec 29 2025, 08:16 PM
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#4
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Member Group: Members Posts: 63 Joined: 25-September 25 From: Granbury Texas Member No.: 29,004 Region Association: Southwest Region |
What calipers are you running Mark?
That looks like a good MC size for Boxster calipers. I wish they were more readily available. Have you researched what the NOS one you have is worth to the 911 crowd? |
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| sixnotfour |
Dec 30 2025, 04:39 AM
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#5
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914 Wizard Group: Members Posts: 11,079 Joined: 12-September 04 From: Life Elevated..planet UT. Member No.: 2,744 Region Association: Rocky Mountains
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QUOTE(Ninja @ Dec 29 2025, 07:16 PM)  What calipers are you running Mark? That looks like a good MC size for Boxster calipers. I wish they were more readily available. Have you researched what the NOS one you have is worth to the 911 crowd? modern adaptation.. http://www.914world.com/bbs2/index.php?s=&...t&p=2500996 |
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| davep |
Dec 30 2025, 09:10 AM
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#6
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914 Historian Group: Benefactors Posts: 5,352 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada  |
I have two examples of the 20mm and one rebuild kit sourced from Stoddard's 25 years ago. Since the 19mm is actually .75", the 20 would be 13/16".
Yeah, the 20 did not last long in production or spare part supplies so very rare to come across one in the part 50 years. Let me know if you replace the old 20 with the NOS 20, I could use the kit on your old one instead of trying to resurrect my two old parts. |
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| Jack Standz |
Dec 30 2025, 12:12 PM
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#7
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Senior Member Group: Members Posts: 650 Joined: 15-November 19 From: Happy Place (& surrounding area) Member No.: 23,644 Region Association: None
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If you want a new 20mm master cylinder (currently as low as $6.78), maybe one of these in the photo? Not 100% sure this works, but have just ordered one to see.
It will require rebending a couple brake lines, as documented here: http://www.914world.com/bbs2/index.php?sho...p;#entry2500996 Attached thumbnail(s) 
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| Ninja |
Dec 30 2025, 12:45 PM
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#8
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Member Group: Members Posts: 63 Joined: 25-September 25 From: Granbury Texas Member No.: 29,004 Region Association: Southwest Region |
Thanks for the heads up guys!
A modern solution at the size I wanted. Even real ATE stuff is still available! SKU ATE-010532 @sixnotfour @Jack Standz |
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| tomeric914 |
Dec 30 2025, 01:43 PM
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#9
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One Lap of America in a 914! Group: Members Posts: 1,302 Joined: 25-May 08 From: Syracuse, NY Member No.: 9,101 Region Association: North East States
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QUOTE(Ninja @ Dec 30 2025, 01:45 PM) Thanks for the heads up guys! A modern solution at the size I wanted. ...or you can follow the How-to in my signature below (IMG:style_emoticons/default/smile.gif) |
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| Ninja |
Dec 30 2025, 07:16 PM
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#10
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Member Group: Members Posts: 63 Joined: 25-September 25 From: Granbury Texas Member No.: 29,004 Region Association: Southwest Region |
@tomeric914
Thank you for the detailed write up! Well done sir! Even included PT# for the needed feed line connections... I will be using what you posted to source parts. I should have thanked you FIRST! I don't look at signature links as much as I should. Bad ninja, bad bad ninja. (IMG:style_emoticons/default/ninja.gif) |
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| Jack Standz |
Dec 31 2025, 02:30 AM
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#11
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Senior Member Group: Members Posts: 650 Joined: 15-November 19 From: Happy Place (& surrounding area) Member No.: 23,644 Region Association: None
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(IMG:style_emoticons/default/agree.gif)
You have my thanks and appreciation too for a very helpful writeup and photos. |
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