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11-10-2015, 06:30 PM | #1 |
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BMW M Performance BBK RETROFIT
Hello all,
I have an amazing opportunity to pull the trigger on an M Performance BBK originally designed for the new F series vehicles at a crazy price. I am aware that these were not designed for our cars and that custom brackets will have to be made to get them to fit, however I am confident that I can get them to work. All that aside, considering that these are not fully floating discs and not drilled (only dimpled), would anyone be able to chime in on whether this would be a significant upgrade from our stock setup. I am interested to see what everyone's opinion is on this. Specs are: 370x30mm and 345x24mm rotors with four piston front and two piston rear. This is the kit in question below: https://www.ecstuning.com/ES2587022/
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11-10-2015, 11:34 PM | #2 |
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If the overall piston area is equal to or within 10% smaller than the OE piston area, yes it can be an upgrade. If not, no.
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11-11-2015, 02:16 AM | #3 |
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it works out then that would be a nice upgrade but, as theirs already kits based on the earlier bmw brembo callipers id stick with that as they are tried and tested....
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11-11-2015, 03:05 AM | #4 |
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You can always fit the calipers onto the stock z4m discs.
Then you have both semi floating discs and lightweight aluminium mulitpiston calipers. With the 370mm discs you probably need 19" rims. Also you have to check the hat depth from the new discs that that fits with the stock hat depth. Otherwise you may need to compensate with spacers or a different ET value but you risk the tyres touching the bodywork. The 6 piston 135i m performance brakes have significantly larger pads than the ones on these 4 piston calipers. These have pads that are 11,4cmx7,1cm The 135i calipers have pads that are 16,5cmx7,3cm A much longer pad so 6 pistons (to give equal pressure on the pad surface) the 135i pads are roughly brembo 6pot GT pads. A typical stoptech/ap racing 4 piston pad is 13cm long and typical 6 piston pads 15cm long for comparison (width is all about the same)
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11-11-2015, 07:37 AM | #5 | |
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Good argument and I agree with you on the superiority of the 135i kit versus the one I am presenting, however I am looking to compare strictly against the stock setup on the Z4M. My current 18" wheels can clear up to a 380mm Brembo BBK so I am not too worried about wheel clearance.
By looking at numbers alone going to multipiston and from 345mm rotors to 370mm there is definitely an upgrade there, but I am not able to find the exact sizing of our OEM pads, there seems to be a definite decrease in the overall surface area of the brake pad from OEM to this kit. Quote:
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11-11-2015, 09:58 AM | #6 |
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Sigh.
If the piston surface area is not equal or slightly smaller, you will significantly downgrade the braking performance. If you can't find out what the total piston surface area of each side of the caliper is compared to the front and rear, it's a worthless exercise.
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11-11-2015, 12:50 PM | #7 | |
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Maybe it's me being a bit thick, but from what you are saying I am gathering that the piston surface area needs to be within 10% smaller to see an improvement ? Well just with the fact that it is now 4 piston instead of 2 piston on the front, that surface area would be almost doubled (right?), At the same time however the surface of the pad is smaller than the OE pad so the contact patch between the pad and rotor would still be smaller.
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11-11-2015, 02:30 PM | #8 |
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Piston area is only important if you have trouble achieving the point of lockup.
There is no need to press the brakes harder than locking wheels Just press the pedal a bit harder if there's a little bit less piston area.. Lots of racecars have really hard brake pedals (little brake boost) and need a firm drive. The real braking performance, that is the stamina, is dictated by pads and disks (it's all about heat management). For large pads they use mulitple pistons to achieve a pad pressure that is as evenly as possible.
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11-11-2015, 03:20 PM | #9 | |
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That sweet spot of the same overall size, while adding more pistons to spread out the forces AND increase frictional area, is where going to a bigger caliper with more piston count really matters. Here's where it gets tricky. A 5% larger piston area can make the pedal so soft it'll feel like there's an opening in the brake line. A15% decrease in piston surface area can make the pedal so stiff that 10% travel will make the pedal rock solid without even engaging ABS. If you're going to "upgrade" to fixed calipers, do it smartly and do it right. The size of the master cylinder and the slave cylinder(s) are vital to the operation of the brake. Do not eff up that relationship unless you really know what you're doing.
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11-11-2015, 03:40 PM | #10 | |
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Take the 6 piston caliper in the 135i for example. I happen to have the piston diameters on hand, because I asked my buddy who races one long time ago when someone were interested in getting some take-offs from the 135i and custom fabricating a bracket to fit it on his 335i. I did the calculation for him to show that the 6 piston calipers on the 135i has a significantly smaller piston surface area than his sliding 1 piston caliper OEM set-up and would result in the brake pedal being so insanely stiff that you wouldn't be able to push it past more than it's 1/2 travel point, and that such a system would be hazardous to drive because it's impossible to modulate the brakes. Just for sh*ts ang giggles, I'm going to repeat that calculation for the thousandth's time, but this time, I'm going to do it against the front calipers of the MZ4 Coupe. The MZ4 Coupe has a sliding caliper with a 60mm diameter piston. The 135i 6 piston caliper has a progressive caliper piston diameter of 28, 32, 36mm. The MZ4 number I can pull out the back of my head. It's 2827mm^2. The 135i I will have to calculate again, but it's simple. It's ((D/2)^2) * Pi, or Pi*r^2. Given the 28, 32, and 36mm diameters, the overall clamping side piston surface area of the caliper on the 135i is: (14^2)*Pi + (16^2)*Pi + (18^2)*Pi = 2438mm^2 (no you do not calculate all 6 piston, the ratio of slave pistons to master cylinder is per CLAMPING SIDE ONLY) That's a 15% decrease in piston surface area, which, like I said, will lead to a rock solid and useless brake pedal. Here's a thread where I installed the RacingBrake 4 piston front, 2 piston rear caliper upgrade kit for the MZ4 Coupe, in it I also detailed how piston surface area affect pedal feel in a sliding vs. fixed caliper system: http://www.zpost.com/forums/showthre...ht=RacingBrake RB's 4 piston calipers measured with a progressive piston setup of 38mm and 44mm. Unless you an find out what the piston surface area is on the kit you're looking at, and do the calculations above, *I* wouldn't touch the kit with a thousand foot pole. But it's your choice. You can easily go in blind and hope that BMW uses the same ratio of master cylinder for ALL their cars, which, actually, has been the case for the last 20 year or so of non-M 3 series. Although, even within the same 3 series family, there are variations between M and non-M models, and even with M models, the ZCP and the nonZCP E46 M3s have different sized master brake cylinder. Last thing I will add. If you don't care whether or not your brakes function properly, feel free. I have absolutely zero objections for you to modify your critical safety system on your car, provided you don't live anywhere near me or share any of the same roads I drive on.
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11-11-2015, 04:05 PM | #11 | |
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I see a statement but no physical/mathematical deduction. Anyway, tons of people use the 135i calipers on m3's/z4m's on track and have no problem what so ever. It's a really common mod. There are multiple suppliers here (mostly germany) that make brackets or complete kits. Also if you look at a tried and tested set for the z4/m3: the ap 6 piston bbk, that has 2x 27mm pistons, 2x 31.8mm pistons and 2x 38.1mm pistons. Thats per side a piston area of 2507mm² Compared to the OEM one cilinder caliper that 11,1% decrease (1 side) and the 135i caliper has a 13.8% decrease (1 side). You wont convince me that that 2,7% difference is the border between having a fantastic BBK and having a worthless BBK. I think there's a reason that the piston area from a AP bbk (designed, tried and tested on the z4m) and the 135i caliper (Brembo designed caliper) are so incredible close. It's only 69mm² difference per side.
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Last edited by GuidoK; 11-11-2015 at 04:57 PM.. |
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11-11-2015, 04:26 PM | #12 | |
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And if those same people who track their E46 M/Z4 M with 135i calipers tell you they'd prefer the 135i caliper to say, a properly engineered AP Racing, StopTECH, Brembo, or any other reputable brake vendor that supplies a properly ratio'ed caliper set, they'd be lying. Those that do the 135i conversion probably do it for compromising reasons. Either they can source it cheap, and don't worry about the super stiff pedal that makes it super hard to modulate properly, or they're doing it for some other reasons (i.e. shifting bias to the rear, ability to run larger pad offset the loss of ability to modulate brakes, or they simply have no idea). The 135i caliper by itself is not a upgrade to the sliding calipers on the MZ4. The internal seals are poorly designed and it's a terrible choice for track applications. My friend who supplied me the specs of the 135i caliper cracked several pistons within a few sessions. I would advise to stay away from the 135i caliper as an upgrade for the E46 M3/Z4 M, especially for track guys. Now, if you're upgrading for looks...That's another matter entirely. Those in the know wouldn't touch that caliper for moderate to heavy track use with a 1,000' stick.
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11-11-2015, 04:47 PM | #13 |
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Brake kit is coming in tomorrow, so I will take some measurements and we can resume discussion then
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11-11-2015, 05:06 PM | #14 | |||
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that is not the proper physics explanation. Quote:
So your theory is flawed as you just said that the AP racing set is properly engineered/ratio'ed Quote:
They come stock with epdm(nbr?) seals because that is much more durable and less prone to tear. That is the seal material you'd want for street wear&dirt
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11-12-2015, 11:45 AM | #15 |
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I admire your ambition here. However, that's a pretty big undertaking when the E86M isn't really an underbraked car to begin with. Plus, with all of the known working aftermarket kits, this is really just an academic "because I can" exercise.
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11-12-2015, 12:12 PM | #16 |
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On the other hand.... I made my own rear calipers fit (135i calipers) and everybody was screaming dont do it, only big companies should do brakes etc etc, you will get a dangerous car...
Well... needless to say it performs flawlessly. I mean on a fairly comparative car using the rear calipers (as they were ment to)..... And now a few years later you see that the aftermarket has finally caught up and yes they now also can supply rear brackets etc to make 135i calipers fit for z4/z4m.....finally only 3 years too late. So I see this project from daemonblitz (using F series performance brakes) the same way. He's just the aftermarket sector ahead This set is by the looks of it also substantially cheaper than a front/rear set from one of the aftermarket manufacturers. Which is also important (if money wasn't a subject we'd all be driving around with $20k carbon brembo GT sets ) And of course if you have the technical skill to fabricate brackets or adapt brake shoes or brake disks etc (whatever it needs to make this kit fit), you also have the clarity of mind that for the first testdrives you do that on an empty road and you do some max. brake test to see if the abs kicks in and to see that you dont have lockup at the rear (so that the brake balance is right). That goes without saying. That is not something you have to explain to somebody who has hands on engineering skills. (that is something you should do every time you do work on your brakes ) Whether you need it or not is a different question but that goes for every bbk. But I suspect that the 4 piston calipers are lighter than the stock steel ones, or house a larger pad. That is mostly the case with bbk's, they're either lighter or you get more friction material. Bigger disks are obviously heavier (both already have an inner aluminium hat).
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Last edited by GuidoK; 11-12-2015 at 12:31 PM.. |
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11-12-2015, 12:39 PM | #17 |
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11-12-2015, 12:46 PM | #18 |
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Some motorsport tuner on german ebay I think.
Forgot his name. With non m z4 you get highly modified e-brake shoes (I assume just like I did mine) I don't know if the ad is still there.
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11-18-2015, 09:14 AM | #19 |
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It seems this is vary complicated ( moving away from stock Brakes to brakes not intended for your vehicle). Second, if your looking to improve braking, I would assume you will be tracking (otherwise why would you want to upgrade brakes?)
Therefore, IMHO, it seems insane (to me) to put your safety and the safety of others in jeopardy using a untested braking system not designed for your vehicle because you can purchase it for a "Crazy" price ( if your not an expert in this area). To what end? Knocking off a fraction of a second per lap?? This comes from a guy (Me) who had a cobalt SS with an ill-prepared braking system crash into my 4 month-old 2012 Boss 302.I If your looking to increase braking performance, IMO, this is not the place to cut corners and save money. Just my 2¢ Last edited by Bossdog; 11-18-2015 at 09:24 AM.. |
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11-19-2015, 12:36 PM | #20 | |
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I honestly did not expect this much negative feedback on this project. It is still in the early stages, I have yet to even see if the rotor itself will bolt up without coming too close to the spindle, which I wont be able to test until the car is out of storage. In hindsight, I probably should have just waited until it was done or not posted about it at all.
Bossdog, yes it is not a straight forward plug and play mod, and the end purpose is for tracking. I can see your concern about retrofitting a BBK not designed for this car, but I would not call it an untested braking system, the calipers are Brembo 4 pot and 2 pot. It is however a BBK that was made for a larger, heavier car. In regards to safety, this is not something that I am doing on my own in my garage during my spare time, it will be a custom job that will be done by professionals. I do not intend to put anyone's safety in jeopardy. I am sorry to hear about your unfortunate crash, but the whole point of retrofitting this properly is to ensure that the car is not "ill prepared". Quote:
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11-19-2015, 01:04 PM | #21 |
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I think its an ambitious project, and I would never take it on. But I wish you luck and hopefully the project won't give you to much of a hard time. You could be onto something here. Be sure to post your results.
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11-19-2015, 04:43 PM | #22 | |
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Best of Luck, I'm sure you will learn much. We all love to watch from the cheap seats when someone on the community tries something new |
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