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Brake bias

Discussion in 'E39 (1997-2003)' started by Touring525i4dawgs, Nov 26, 2017.

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    Touring525i4dawgs '02 525it M sport

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    After returning from my long trip and something I have noticed lately is that my real wheels have more brake dust on them then the front. I thought that the reverse would be true. All that weight up front would seem to create more dust. Any thoughts?
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    MGarrison

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    I guess I'd stick an inspection mirror in between the spokes to get a look & check the pads are wearing more or less evenly & no stuck calipers (or pop off the wheels for a look - use a torque wrench to torque lug bolts back to spec tightness). I presume E39's have 4-chan ABS, so if there's something going on w/ both rears and not the front, all I could guess there would be an issue w/ the rear channel of the master cylinder. Hard to guess what that might be though, if it were the case - would seem like an oddball issue though, at least to me.. but, I can't claim to know every vagary of BMW brake master cylinders either!
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    Touring525i4dawgs '02 525it M sport

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    Thanks for the feedback. Will inquire with mechanic. Just thought I would put it on the forum to see if others have had this issue
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    charlson89

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    Are the brake pads types the same front and rear? If the rear has different pads they could create more dust than the fronts depending on the materials.
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    Touring525i4dawgs '02 525it M sport

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    Thanks for that. Had not considered that. I believe they only changed the front pads last time. Btw do you have a pad you would recommend?
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    MGarrison

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    Stock pads should work fine for everyday driving; Axxis/PBR Ultimate Ceramics also (the Metal Masters are better for something like auto-x or light track, and not a good all-weather pad. I used to run them all year around, but there were winter days backing out of the driveway I wasn't sure I'd get stopped before getting to the street - cold stopping grip especially backing up... not so much!)

    http://www.importrp.com/manufacture...mmy_mode=apply&fmake=53&fmodel=356&fyear=2002
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    Touring525i4dawgs '02 525it M sport

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    K, Thanks. Was thinking about vented rotors. Trying to get wife as much stopping power as possible.
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    charlson89

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    Yes I agree if your doing regular driving just get OE pads. Vented rotors have there plus and minus if its never driven hard the stop brakes should have plenty of stopping power. Also with vented brake pads do not last at long one of the trade offs.
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    Touring525i4dawgs '02 525it M sport

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    Thanks for all the advice. Is there much bigger wear with vented rotors. Is the trade off worth it?
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    MGarrison

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    Vented rotors are unnecessary for daily driving. Yes, more wear, & no, not worth it. If it's an older car, maybe stainless steel brake lines. Otherwise, make sure the brake fluid's flushed at recommended intervals, at least once every 2yrs.
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    Touring525i4dawgs '02 525it M sport

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    So stainless steel brake lines would be the best way to improve braking?
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    charlson89

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    Yes they do help with brake pedal feel since rubber swells slightly under pressure and with older cars the rubber is older and swells more. I do recommend lines they really make the brakes feel much better.
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    MGarrison

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    In thinking about what it takes to minimize stopping distance...

    Tires - For street driving, having optimal tires for existing conditions; all-seasons vs. a 'summer' tire & cold weather/snow tire. If you're in a winter climate area & have snow/ice conditions, then a dedicated set of wheels w/ snow tires may not be a bad idea. When evaluating tires, the treadwear rating number is worth considering. A higher treadwear rating number doesn't necessarily correlate to less mechanical grip, but since tread compounding is a number of compromises geared towards a specific performance goal, it's a good idea to consider what's being traded-off for what. Get the best tires for your specific needs your budget allows.

    Your brakes, in a sense, are only as good as your tires. If you can engage the ABS system, that shows the brakes' stopping power is using all the grip the tire can deliver. The grippier/stickier the tire, given whatever road-surface conditions/temps, the higher the threshold for the ABS to engage (the harder you have to push the brake pedal). In modern-day cars & any BMW since the last time they might have had rear-drum brakes, the brakes are so powerful, relatively speaking, if you stomp on the brakes hard enough, ABS can be activated/engaged almost immediately, even if you're running race tires on a hot track.

    So, one way to help the braking situation, make sure your tires aren't old & worn out, & avoid using the cheapest crap tires if you're able.

    Pads & rotors - gets into the notion of clamping force. In street & highway driving, the brakes are essentially cold all the time (or perhaps just warm). So, the brake pad's performance characteristics come into play there. Similar to tire compounds, brake pad compounds are tailored to a specific performance goal - typically, as a pad is more geared towards hi-temperature racetrack performance, the less effective its cold performance. With the possible exception of dust production, BMW stock pads otherwise do everything they're designed for just fine - street & highway stopping, & the occasional emergency braking. All things considered, I don't find the stock pads on my E92 to be bad dust-wise, either; just about what I'd expect.

    Without doing something substantial, such a s a big brakes kit with bigger rotors, calipers, & pads, there's not much way with stock brakes to increase your clamping force. Different pads are what you can look at (ie an increase in the pad's friction on the rotor), and of course there's any number of options with stock pad replacements. Akebono, Hawk, Cool Carbon, EBC, Performance Friction, Axxis/PBR, etc. I tried slotted/vented rotors & the ATE 'power-groove' or whatever they are, I can't say I noticed any improvement in braking performance, but they were noisier & wore out pads faster.

    Having maximum emergency braking capability is good of course, although it's better to avoid having to use it. Don't tailgate, drive in a hurry, or distracted if you can possibly avoid it, & be looking up and out beyond the vehicle in front of you to help anticipate anything coming up that you need to respond to. On-the-road awareness can go a long way to minimizing the emergency braking & avoidance maneuvers.
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    Touring525i4dawgs '02 525it M sport

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    Thanks for all that info! As to tires I have always been one to buy a quality tire. On many occasion either a Road & Track or Club tire tests guided my choice of rubber. I rotate them and make sure pressure is correct. I have considered winter tires. As the climate has changed a bit over the years the need for true snow tires is seldom needed. When the big snow does come We sit in the house and watch movies! As my car is an '02 upgrading the brake lines might be a good option for me. As I have grown older my driving style has mellowed a bit. I do enjoy some spirited driving in the area I live. I pick my moments to have fun with this car. I was also lucky to have done some driver training at The Bertil Roos Driving School many yers ago. What he taught me has stayed with me for a lifetime of driving. Thanks agin for taking time to pass along some great info!
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