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Bimmerguy2002
Joined: 03 Oct 2007
Location: Lodi, California
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 Posted: Feb 08, 2010 9:11 PM Post subject: |
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| bigger calipers and stock master WILL make the pedal mushy, those who say it doesnt are in DENIAL. Its simple hydraulics, i did the BBK and bled properly, the pedal is spongy with a factory master. |
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Scottinva
Joined: 07 Dec 2008
Location: Norfolk, Virginia
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| Posted: Feb 08, 2010 9:18 PM Post subject: |
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| I have a factory master with 750li brakes front and back, with 540i rear rotor. There is absolutely no mushy, it's very precise and normal stopping takes only like an inch of pedal. |
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Jeremy
Beamter
Joined: 12 Feb 2006
Location: Right on the CT/NY line somewhere.
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| Posted: Feb 08, 2010 9:23 PM Post subject: |
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| Bimmerguy2002 wrote: | | bigger calipers and stock master WILL make the pedal mushy, those who say it doesnt are in DENIAL. Its simple hydraulics, i did the BBK and bled properly, the pedal is spongy with a factory master. |
Yes, but he went back to the original brakes and still had issues. Therefore, it's not the calipers causing it.
Jeremy |
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Bimmerguy2002
Joined: 03 Oct 2007
Location: Lodi, California
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| Posted: Feb 08, 2010 9:58 PM Post subject: |
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oh, didnt read that
but with any bigger pistons at the calipers, it will always be mushy until the caliper fills-then firm. |
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Senorsuper
Joined: 25 Oct 2009
Location: south florida
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| Posted: Feb 08, 2010 11:28 PM Post subject: |
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Some thing miraculous has happened I took the car out for a drive and the first stop the pedal was still soft but at the second stop light the pedal was firm and hard I almost put my face in the steering wheel expecting a soft pedal. So the old brittle lines were just pinching air at the bends it just took them a few stops to get going I guess.
Thanks for all the input. problem officially solved by bleeding the brakes after taking off the calipers and stretching the lines strait |
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Coldswede
Joined: 10 Oct 2008
Location: Live in the UP, Stuck in Florida
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| Posted: Feb 08, 2010 11:46 PM Post subject: |
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| If the lines are that stiff and brittle it's time to consider new rubber lines. |
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Senorsuper
Joined: 25 Oct 2009
Location: south florida
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| Posted: Feb 09, 2010 12:01 AM Post subject: |
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| shopping for ss lines now on ebay. What are your guys opinion on the steel braided lines are they worth the money or should i just buy rubber lines for slightly cheaper |
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Bimmerguy2002
Joined: 03 Oct 2007
Location: Lodi, California
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| Posted: Feb 09, 2010 12:10 AM Post subject: |
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| bavauto.com or uuc have them, according to my sources, both are about 115 |
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Jeremy
Beamter
Joined: 12 Feb 2006
Location: Right on the CT/NY line somewhere.
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| Posted: Feb 09, 2010 12:17 AM Post subject: |
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Get coated SS if you're going that route. Rubber is perfectly sufficient for your needs, however.
Jeremy |
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Coldswede
Joined: 10 Oct 2008
Location: Live in the UP, Stuck in Florida
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Shawn D.
Beamter
Joined: 12 Feb 2006
Location: Alpharetta, GA
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| Posted: Feb 09, 2010 9:08 AM Post subject: |
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| Bimmerguy2002 wrote: | | bigger calipers and stock master WILL make the pedal mushy, those who say it doesnt are in DENIAL. Its simple hydraulics, i did the BBK and bled properly, the pedal is spongy with a factory master. |
Bull$hit. The pedal feel is excellent on my 535i w/ stock master and E32F/E34R brakes. So much so that when the original master cylinder went out, I replaced it with a new E28 unit. |
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tn535i
Joined: 14 Jul 2006
Location: Middle Tennessee
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| Posted: Feb 09, 2010 3:32 PM Post subject: |
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| Senorsuper wrote: | | So the old brittle lines were just pinching air at the bends it just took them a few stops to get going I guess. |
Sorry, I think that conclusion is nonsense... Maybe a bubble of air burped inside the master back to the reservour. that's the only logical explanation on a closed system.
Also agree with Shawn above. A bigger piston area on the caliper might equal slightly more pedal travel, but that should be about all. Maybe if you simultaneously also switched to a much softer pad, but probably a poor job of bleeding. |
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Senorsuper
Joined: 25 Oct 2009
Location: south florida
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| Posted: Feb 09, 2010 9:03 PM Post subject: |
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| I demonstrated how I was bleeding to a professional at brake shop and was given the OK. I really dont Give a $hit how or why it works now but it works |
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Bimmerguy2002
Joined: 03 Oct 2007
Location: Lodi, California
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| Posted: Feb 09, 2010 9:21 PM Post subject: |
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i just installed the 750 master and the mushiness went away, bled the same way, now the pedal is back where it was with instant engagement at the top of the pedal  |
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spinedocab
Joined: 12 Feb 2006
Location: Upper Bucks County, PA
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| Posted: Feb 09, 2010 11:41 PM Post subject: |
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| Shawn D. wrote: | | Bimmerguy2002 wrote: | | bigger calipers and stock master WILL make the pedal mushy, those who say it doesnt are in DENIAL. Its simple hydraulics, i did the BBK and bled properly, the pedal is spongy with a factory master. |
Bull$hit. The pedal feel is excellent on my 535i w/ stock master and E32F/E34R brakes. So much so that when the original master cylinder went out, I replaced it with a new E28 unit. |
Bigger calipers with stock master cylinder will result in a slightly LOWER pedal, ie more travel in the brake pedal, but mushiness is not an issue if only brake fluid resides in the hydraulics. So maybe we've got our semantics mixed with our metaphors, or something. But just because the pedal moves farther does not make it "mushy". |
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Bimmerguy2002
Joined: 03 Oct 2007
Location: Lodi, California
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| Posted: Feb 09, 2010 11:54 PM Post subject: |
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| Ok, terminology aside, the pedal had to travel a bit farther for the brakes to SAFELY start working. The pedal was still in its same range of travel, but had almost no braking until about half way down. With the 750 master, the pedal is hard as a rock like it was before i did the bigger calipers and have instant engagement of the brakes like normal, it definitely goes hand in hand with the calipers. |
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Shawn D.
Beamter
Joined: 12 Feb 2006
Location: Alpharetta, GA
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| Posted: Feb 10, 2010 9:26 AM Post subject: |
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| Bimmerguy2002 wrote: | | Ok, terminology aside, the pedal had to travel a bit farther for the brakes to SAFELY start working. The pedal was still in its same range of travel, but had almost no braking until about half way down. With the 750 master, the pedal is hard as a rock like it was before i did the bigger calipers and have instant engagement of the brakes like normal, it definitely goes hand in hand with the calipers. |
Your brake system worked that way. Mine gets braking just 1/4" off the stop. |
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Scottinva
Joined: 07 Dec 2008
Location: Norfolk, Virginia
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| Posted: Feb 10, 2010 11:24 AM Post subject: |
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| Shawn D. wrote: | | Bimmerguy2002 wrote: | | Ok, terminology aside, the pedal had to travel a bit farther for the brakes to SAFELY start working. The pedal was still in its same range of travel, but had almost no braking until about half way down. With the 750 master, the pedal is hard as a rock like it was before i did the bigger calipers and have instant engagement of the brakes like normal, it definitely goes hand in hand with the calipers. |
Your brake system worked that way. Mine gets braking just 1/4" off the stop. |
I am going to agree with Shawn on this one. My pedal is instantly very firm, and takes very little pedal effort to come to a stop. I planned on upgrading the master, until I put the calipers on. The stock master with the "upgraded" calipers, feels so good, I would go as far as to say upgrading the master is a waste of money. That is if the factory one is in proper working condition. I wonder if your master wasn't on it's last leg, and upgrading calipers made it worse. Then replacing to 7 series master helped, but I would bet putting a new factory master in would've done the same thing. Just my 0.02 |
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Blue Shadow
Joined: 12 Feb 2006
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| Posted: Feb 10, 2010 2:22 PM Post subject: |
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| spinedocab wrote: | | Bigger calipers with stock master cylinder will result in a slightly LOWER pedal, ie more travel in the brake pedal, but mushiness is not an issue if only brake fluid resides in the hydraulics. |
Mushiness can also come from a well-used master. One still capable of working but weeping a bit past the seals. This effective braking continues until the mushiness reaches the full depth of pedal travel. Well past the time to replace/rebuild the master. |
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