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> Brakes don't Bite
bkrantz
post Sep 1 2022, 08:16 PM
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As part of my rebuild I completely replaced the brake system:
calipers and rear pressure valve rebuilt by PMB
new ATE 19mm master cylinder
new hard and flex lines
new disks and Porterfield R4-S pads

I went through many (many!) episodes of bleeding, with different methods. The pedal feels very firm from the first push, and does not pump up. Rear clearance is set at .004". I went through the PMB bedding process, and have driven around a bit.

But the braking force seems weak. When I get on the brake pedal, I do not feel any "bite". Another 914 friend drove the car and also agrees.

Any suggestions?
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jim_hoyland
post Sep 2 2022, 09:57 AM
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What MPH would the front lock-up test best be done ?
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Superhawk996
post Sep 2 2022, 10:06 AM
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QUOTE(jim_hoyland @ Sep 2 2022, 11:57 AM) *

What MPH would the front lock-up test best be done ?


30- 40 mph is sufficient. Dry pavement. Safe area to do so.

You want the vehicle to have enough momentum so that it will take quite a bit of line pressure to lock the brakes but not end up stopping the vehicle completely.

A light squeal or heavy scuffing from the tire is all it takes to confirm No need to keep it locked for any time/distance that would cause a tire to flat spot.
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Posts in this topic
bkrantz   Brakes don't Bite   Sep 1 2022, 08:16 PM
Superhawk996   Brake feel is highly subjective. The obvious thi...   Sep 1 2022, 08:51 PM
mgphoto   19mm master cylinder, push the pedal harder, they ...   Sep 1 2022, 09:54 PM
barnfind9141972   I did the same thing and also couldn’t get much ...   Sep 1 2022, 10:27 PM
Mikey914   The system is notorious for holding bubbles. You w...   Sep 1 2022, 11:07 PM
ChrisFoley   As part of my rebuild I completely replaced the b...   Sep 2 2022, 07:55 AM
Superhawk996   Adjust the rear brake regulator to begin regulat...   Sep 2 2022, 09:24 AM
ChrisFoley   [quote name='ChrisFoley' post='3026647' date='Sep...   Sep 2 2022, 10:58 AM
Superhawk996   [quote name='Superhawk996' post='3026665' date='S...   Sep 2 2022, 11:17 AM
Superhawk996   Add a master cylinder brace to prevent floorboar...   Sep 2 2022, 09:28 AM
JamesM   As part of my rebuild I completely replaced the b...   Sep 2 2022, 09:27 AM
Superhawk996   Can you lock the brakes up if you stand on them? ...   Sep 2 2022, 09:31 AM
jim_hoyland   What MPH would the front lock-up test best be done...   Sep 2 2022, 09:57 AM
Superhawk996   What MPH would the front lock-up test best be don...   Sep 2 2022, 10:06 AM
emerygt350   I just went and tried Locking them up tonight (hav...   Sep 2 2022, 06:32 PM
bkrantz   Thanks for all the replies. Yes, I can lock up th...   Sep 2 2022, 07:38 PM
Superhawk996   But I still think I should feel more bite and urg...   Sep 2 2022, 08:41 PM
JamesM   Thanks for all the replies. Yes, I can lock up t...   Sep 3 2022, 12:44 AM
Van B   I love the motive pressure bleeder. I don’t kno...   Sep 2 2022, 08:23 PM
bbrock   I have essentially the same setup as you and get r...   Sep 2 2022, 08:26 PM
iankarr   It takes several bleeds to get air out of a totall...   Sep 2 2022, 10:34 PM
Geezer914   Pressure bleeding is the best way to bleed the Bra...   Sep 3 2022, 05:20 AM
jim_hoyland   Pressure bleeding is the best way to bleed the Br...   Sep 3 2022, 06:23 AM
gereed75   Different car but maybe a useful data point - I ha...   Sep 3 2022, 09:51 AM
Superhawk996   Not sure what type of compound the R4S is, but ...   Sep 3 2022, 10:07 AM
bbrock   FYI - get ready for things to get worse. Copper...   Sep 3 2022, 11:12 AM
930cabman   FYI - get ready for things to get worse. Coppe...   Sep 9 2022, 01:16 PM
bbrock   Sounds as though the consensus is having the abil...   Sep 9 2022, 03:16 PM
Superhawk996   It was the early version of ABS @Superhawk995 :...   Sep 9 2022, 04:47 PM
PatMc   [quote name='bbrock' post='3026923' date='Sep 3 2...   Sep 15 2022, 10:06 PM
jim_hoyland   What's a recommended for light daily driving ?...   Sep 3 2022, 12:25 PM
JamesM   What's a recommended for light daily driving ...   Sep 3 2022, 12:49 PM
bkrantz   Thanks, again. I will try bedding again with some...   Sep 3 2022, 08:09 PM
michael7810   Thanks, again. I will try bedding again with som...   Sep 4 2022, 06:36 AM
ChrisFoley   I used to sell KFP pads because I liked their perf...   Sep 4 2022, 05:02 AM
bkrantz   I ordered a set of Textar OEM style pads for F and...   Sep 5 2022, 07:57 PM
jim_hoyland   I just ordered the Pagids from PMB, Here’s the i...   Sep 5 2022, 08:46 PM
Montreal914   Mentioned before but the stock system was designed...   Sep 5 2022, 09:12 PM
robkammer   This is a thread I thought I would need to start. ...   Sep 8 2022, 01:25 PM
ChrisFoley   venting clearance of 3mm. Hmm, what?   Sep 8 2022, 03:17 PM
Superhawk996   On my last spirited drive with lots of hard braki...   Sep 8 2022, 03:50 PM
robkammer   Guys: Oops, not 3mm, .003". Clearance between...   Sep 9 2022, 07:39 AM
bbrock   Hmm. I have PMB plated calipers that I rebuild my...   Sep 9 2022, 08:12 AM
robkammer   Thanks All: Good comments all around. Still not su...   Sep 9 2022, 01:14 PM
bkrantz   I replaced the pads with "stock" Textars...   Sep 15 2022, 07:48 PM
robkammer   All: This is all great info. So, an update, last S...   Sep 16 2022, 04:11 PM
bbrock   All: This is all great info. So, an update, last ...   Sep 16 2022, 06:41 PM
Superhawk996   Going on two years and getting tired of screwing ...   Sep 17 2022, 11:05 AM
michael7810   For $35 you can try a set of Textar pads for ...   Sep 16 2022, 04:25 PM
ChrisFoley   New caliper seals cause a long pedal which will pu...   Sep 17 2022, 07:02 AM
PatMc   I would try a conventional bleeding method…one p...   Sep 17 2022, 07:47 AM
robkammer   Thanks All! Have not checked the pedal box, bu...   Sep 17 2022, 01:32 PM
Literati914   Man this is frustrating, hate that you’ve not go...   Sep 19 2022, 09:20 AM
Superhawk996   Man this is frustrating, hate that you’ve not g...   Sep 19 2022, 09:48 AM
rfinegan   Last week I rebuild all 4 calipers, Potterfield pa...   Sep 19 2022, 10:08 AM
scott_in_nh   I very recently got around to installing the KFP 1...   Sep 21 2022, 12:48 PM
bbrock   I do notice they are getting better, but my quest...   Sep 21 2022, 01:44 PM
NARP74   The numbers are on the round barrel, mostly on the...   Sep 21 2022, 01:59 PM
NARP74   For the pedal box flex, I had someone press the pe...   Sep 21 2022, 02:04 PM


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