double -pump the brakes - Subaru WRX Forum
 
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#1 Old 10-05-2005, 01:30 AM
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double -pump the brakes

some drivers always double -pump the brakes, they give the pedal a quick push and release it before pushing on it for real.this comes from one too many expeiences of pressing on the brake pedal and finding very little pedal there, if your brake fade, this one way to keep safe while you get back to the pits.brake in good working order shouldnt require this, such a tech also requires you to lift your foot from the throttle earlier than otherwise necessary.


is anyone can tell me more details about this tech?
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#2 Old 10-05-2005, 07:50 AM
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I have always noticed the pedal goes down very far when you press it for the first time. I also pump it once of twice and then you get a very firm pedal that has minimal travel.
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#3 Old 10-06-2005, 11:22 AM
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if you have less pressure under your foot the first time you depress the peddle, then either one of two things is hapaning

a) your racing and your experiencing brake fade

b) you have air in the system, and you need to do a bleed.

you shouldent have to depress the peddle more then once, to have a solid feel.
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#4 Old 10-06-2005, 07:02 PM
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Its not that it isn't a solid feel or pedal fade, its that the pedal depresses more then it should. If you pump it once then the pedal doesn't travel nearly as far. I've drive multiple WRXs and all felt about the same. Mine did this from the factory.
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#5 Old 10-06-2005, 07:28 PM
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you have air in the system
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#6 Old 10-06-2005, 11:30 PM
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Quote:
Originally Posted by Nose Nuggets
if you have less pressure under your foot the first time you depress the peddle, then either one of two things is hapaning

a) your racing and your experiencing brake fade

b) you have air in the system, and you need to do a bleed.

you shouldent have to depress the peddle more then once, to have a solid feel.

I understand that if the brake is in a good working order, we shouldnt press more than one time, but if the brake fade do happen while racing, should we double pump it?
I tried that, use my left foot press the brake slightly on the straight line right before I have to brake, just like what i saw from the JGTC driver, and the brake did less travel about a inch.
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#7 Old 10-07-2005, 11:39 AM
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Quote:
Originally Posted by kawaigng
I understand that if the brake is in a good working order, we shouldnt press more than one time, but if the brake fade do happen while racing, should we double pump it?
you can pump it all you want, it wont make any diference.

Quote:
I tried that, use my left foot press the brake slightly on the straight line right before I have to brake, just like what i saw from the JGTC driver, and the brake did less travel about a inch.
A JGTC driver told you he brakes slightly with his left foot, on a straightaway before the braking zone? You shouldn’t be doing any braking before the brake zone, that’s why its called the brake zone. The only think you should be doing right before the brake zone is keeping your foot pegged to the floor WFO.
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#8 Old 10-07-2005, 04:19 PM
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Quote:
Originally Posted by Nose Nuggets
you can pump it all you want, it wont make any diference.



A JGTC driver told you he brakes slightly with his left foot, on a straightaway before the braking zone? You shouldn’t be doing any braking before the brake zone, that’s why its called the brake zone. The only think you should be doing right before the brake zone is keeping your foot pegged to the floor WFO.

I saw that from a video. I will try to post that vedio on later.
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#9 Old 10-07-2005, 04:58 PM
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thats crazy.

do you remember the drivers name?
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#10 Old 10-07-2005, 06:43 PM
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Quote:
Originally Posted by Nose Nuggets
thats crazy.

do you remember the drivers name?
actually is more than one driver do that, and I will post that video next week i hope
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#11 Old 10-10-2005, 09:35 PM
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i talked to a subaru tech about the double pumping thing, he said it has something to do with when u first press the pedal and let go, the brake pads are slowly letting out, and because its slow, when u go to press them a second time, they feel firmer, because they were closer to the rotor than usual...
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#12 Old 06-30-2006, 02:54 PM
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http://www.stoptech.com/tech_info/wp_knockback.shtml

Check this out. It should answer all your questions.
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#13 Old 06-30-2006, 04:12 PM
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Quote:
Now, the Cobra had never exhibited knockback around town, regardless of how hard it was driven.

you have air in your system
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#14 Old 02-23-2009, 09:16 PM
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Double pump brake YAY!!

HEy this thread is mad old but oh well, i too have the awesome 1st pedal hit fade. looking at all of our posts i can reply on this. YES there is DEFINITLY AIR IN THE SYSTEM!!!!!!

yes i know that clearly now, ive bleed my brakes probly 3 times getting a spongy 1st hit on the pedal about 1-2 days after bleeding the system. So i now have replaced the master cylnider thinking the seal was bad and it was taking on air since, i never lose brake fluid. I bleed the whole system again. IT seemed it was ok, hard to tell with tons of snow. by the next day it faded some more and having better conditions to test it. and now the 3rd day it has went back to it's original problem. the 1st hit of the pedal, depresses way to far, the 2nd hit like the best brakes in the world never fades at all, ever on the biggest hill trying to stop at over 120mph, the 1st hit is only the weak one.

SO anyone got any ideas? replace rubber lines with braided? or maybe calipers? im just trying to fix this and not spend 2 grand replacing every single part untill i get it right. OH and yes i am a mechanic by trade, so im well knowledged on bleeding the brakes correctly, but please any suggestions are welcome.

Caleb Gere
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#15 Old 02-24-2009, 09:23 PM
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I've heard that a quick light press of the pedal before braking seats the pads. Dont know if this wouldbe necessary though. It seems to me the pads would already be seated from the last time you used the brakes.

Adair
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Phatbotti tuned!
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