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07-08-2012, 10:32 PM | #1 |
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///m brakes inconsistent?
I finally got the z4m out to the track this weekend and it was fantastic! The suspension (ast) and alignment were great right off the bat and the oil temp stayed just a few degrees right of center despite the warm weather. The one thing that drove me crazy was the feel of the brakes. Once fully on the brakes they felt fine but part/light brake application was really inconsistent. Sometimes a light breathe on the brakes did nothing, sometimes it really grabbed, both feeling equally light on the pedal, to my foot anyway. They just didn't feel progressive or predictable. Anyone else get this? Would a bbk help with the feel?
Fwiw, I didn't have any heat problems running srf and pfc06 pads and the brakes performed great. My last track car was an e28 m5 with upsized rears and an upsized master cylinder which felt awesome - really stiff pedal, almost as heavy as the clutch, and progressive resistance through the whole pedal travel. Gratuitous 1M footage! Last edited by ajw45; 07-08-2012 at 10:39 PM.. |
07-09-2012, 07:49 AM | #2 |
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Thanks for sharing! Are you running OE pads?
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07-09-2012, 08:13 AM | #3 | |
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Hrm. Were these problems re-occuring in the same corner, or were they happening at different speeds? |
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07-09-2012, 09:33 AM | #4 | |
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Scrapped the OEM pads and running PFC 06/08 f/r |
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07-09-2012, 04:07 PM | #5 |
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Thought he was referencing his last car...
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07-09-2012, 04:39 PM | #6 |
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Brake pedals just move fluid. Master cylinders decide how much fluid is moved. Brake pads determine at what temperatures they grab at and when they don't. BMW electronics could do who knows what in a modern car.
But with my experience, you are having issues with the temperature of your pads. If I remember correctly, that pad (pfc 06) that you are running needs A LOT of heat, so they may be cooling down. Just a thought, but I am pretty sure it is not the brakes but rather your pads. |
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07-09-2012, 05:09 PM | #8 |
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Take a look at this thread. Sounds very similar to what you're describing, specifically see the posts by The Hack. Thread.
It could also be the active brake assist jumping in there as well. It tries to "help" when really jumping off throttle and onto the brakes. In my experience this seems to happen more when going from WOT to "light touch" braking transition. Not much can be done about the active brake assist, but if you noticing a less than stellar and firm pedal feel, "The Hack" method of removing air from the braking system is worth a shot. Can't hurt, and might help. Sean's input should be strongly considered as well, especially if it makes sense given it was the same corner consistently. Last edited by Finnegan; 07-09-2012 at 05:21 PM.. |
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07-10-2012, 12:06 AM | #9 |
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Get that all the time on downshifts. I call it "hyper brakes". My guess is it's the compliment of "dead pedal" throttle.
I think both are caused by the computers trying to make sure you don't jump on the brakes and the throttle at the same time and drive through a store front, but the system is too slow if you have fast feet. If I downshift without braking, throttle blips are predictable and effective. If I get on the brakes first, then try and blip for a downshift, throttle response is negligible, because it thinks I'm still braking and kills the throttle response. Have to smack it to the floor twice, then miss the apex because I've spent too much time fighting with the car. Once I do get it blipped and downshifted and get back on the brake, the slightest touch on the brake pedal nearly locks them up. Lift a little and reapply: back to normal brake response. It's too binary to be a hydraulic issue. I don't have a long spongy pedal. Brakes are firm, smooth, and predictable, except when getting on them fast after hard throttle. But even that's becoming predictable. The car's programming me. (2 blips for a downshift then eeaassyy on the brake, cause it's gonna grab like a pissed off cat. Lift a little and reapply. Damn, missed the apex again.) Last edited by StickMon; 07-10-2012 at 12:23 AM.. |
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07-10-2012, 10:47 AM | #10 |
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If I have to guess, I'm going to say this particular corner is at the end of a long straight? And the long straight is followed by a couple of potentially moderate to high speed corners that does not require braking?
I suspect it's a combination of brake technique and compound.
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