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> 17mm vs 19mm Brake Master Cylinder, again!
87m491
post Jul 24 2023, 05:32 AM
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With the prospect of incoming rotten tomatoes forefront, I wade in here looking for a little BTDT.
Background, just got the 74, 2.0 back on the road after a 7 year hiatus. Over the years,, I did fuel system, brake system (19mm master(ATE) /calipers (PMB rebuilt fronts, stock rears) /rotors/hoses) engine mechanicals and cosmetics.

I haven't driven the car during that time and I only had about 150 miles on it before it came off the road and memory ain't what it used to be.

I did the 19mm MC many years back because it was way less expensive than the 17 and the forum feedback seemed fine. I also have a mid 80's Carrera (with turbo brakes) against which many folks relate the 19mm MC pedal feel. I like a firm pedal and the 911 is pretty easily modulated, heavy but responsive.

Fast forward to this past week and some short shakedown runs. The 914 pedal is "right there" and noticeably firmer than the 911. But while being firmer, the braking is far from commensurate with pedal input. Yes, the 911 pedal is firm, but with the right effort, the car will slow/stop NOW. Been on the track with it no problem. On the 'teener, I feel like I am about to bend/break the pedal and the car seems to barely slow. No way I can lock up these brakes at any road speed, nor do I feel I could lose momentum in a hurried stop situation, even at in town speeds.

I'm wondering if I have missed something or is this type of pedal feel/action is "typical" of the swap? Shamefully, I honestly can't recall if I did pads, but the rotors are spotless and look like they're getting good pad contact but would love any pad advice as well.
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87m491   17mm vs 19mm Brake Master Cylinder, again!   Jul 24 2023, 05:32 AM
914Sixer   Typical response with 19mm master cylinder. Go ov...   Jul 24 2023, 06:40 AM
87m491   Thanks been all through that but didn't run ac...   Jul 24 2023, 07:24 AM
SirAndy   Thanks been all through that but didn't run ac...   Jul 24 2023, 12:17 PM
mepstein   Make sure you bed the pads to the rotors. Do it ag...   Jul 24 2023, 06:48 AM
87m491   Very good idea. I sourced some of the very popula...   Jul 24 2023, 07:23 AM
mepstein   Very good idea. I sourced some of the very popul...   Jul 24 2023, 08:34 AM
flipb   I've got the 19mm and I can definitely lock th...   Jul 24 2023, 06:49 AM
Shivers   I had a stock system with a 19mm. I submarined my ...   Jul 24 2023, 08:24 AM
MM1   Re: Porterfield R4-S brake pad OFFICIAL break-in p...   Jul 24 2023, 11:28 AM
87m491   Sweet! That'll up my 20 mile per year, th...   Jul 24 2023, 12:14 PM
mepstein   How do you bed in the rotor if that’s new as wel...   Jul 24 2023, 12:10 PM
76-914   @Eric_Shea Shea it or don't say it!   Jul 24 2023, 12:51 PM
Eric_Shea   We always bed Porterfields. We're their secon...   Jul 27 2023, 12:44 PM
bkrantz   To get good braking response I needed to bed my R4...   Jul 27 2023, 07:43 PM
Dave_Darling   So, do you know you can't lock up the brakes i...   Jul 28 2023, 06:01 PM
87m491   First, thanks for all the thoughts so far. As I m...   Jul 29 2023, 05:58 AM
914sgofast2   What kind of brake pads are you running? If they a...   Jul 28 2023, 06:15 PM
87m491   With the prospect of incoming rotten tomatoes fo...   Jul 29 2023, 05:59 AM
87m491   Data point please for those w 19mm MC. What is yo...   Aug 1 2023, 06:19 PM
davep   That is way too much free play. I think spec is 1-...   Aug 1 2023, 06:33 PM
87m491   A quick adjustment of the push rod to ~1mm spec an...   Aug 2 2023, 11:40 AM
87m491   Finally got into the hydraulics to see if the MC w...   Aug 14 2023, 05:52 AM
VaccaRabite   Bleed more. Use a power bleeder to pressurize the ...   Aug 14 2023, 06:41 AM
87m491   Looking forward to it. As mentioned did use a pow...   Aug 14 2023, 09:26 AM
87m491   I finally got back to these over the 3 day weekend...   Sep 5 2023, 06:05 AM
VaccaRabite   There is weirdness going on for sure. Is the vent...   Sep 5 2023, 06:59 AM
mepstein   There is weirdness going on for sure. Is the ven...   Sep 5 2023, 07:12 AM
87m491   I just wanted to give a final update for those who...   Sep 5 2023, 08:42 AM
Shivers   I just noticed your home state. Rotors and a lot o...   Sep 5 2023, 09:15 AM
bkrantz   Some speculation: If you have a firm/hard pedal t...   Sep 5 2023, 07:24 PM


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