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08-20-2008, 08:44 PM | #155 |
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I believe 5th is a direct drive, meaning power is transmitted down the main shaft without torque being transferred to another shaft.
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08-20-2008, 08:49 PM | #156 |
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OK, I see, that would be slightly more efficient, lighter, and eliminate bending moments. Anyway, they could have still made 3rd and 4th slightly shorter though. Also, looking at gear ratios on sports cars, there are tranmissions out there that don't use direct drive such as the Gallordo and the F430.
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08-20-2008, 09:27 PM | #157 | |
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the very same reasons you noted for the brembo brakes... I bet 99% never drive at 9/10th's...we THINK we do, but someone like Hans Stuck would show us the folly of our logic M3 Reno_Fernley 111 EVO track 109 I've yet to see a track test >115, let alone 140! the big brake craze is like chia pets...why? because people will buy them...there is no tangible benefit, these are street cars...the floating caliper is better for street cars...BMW knows this...they used fixed calipers before they were 'vogue'...the actual cost difference? negligable...a couple of $ per caliper, when 1000's are being made...and I'm not sure to which advantage... the Bosch handbook clearly states that foating calipers are better (and gives the reasons), and modern design has mitigated any inherent disadvantage... if it was all about performance, why paint the calipers? it only traps heat and drives it into the piston and fluid...it produces an R value...F1 cars aren't painted, they are 'raw', in addition they are not machined smooth... an irregular surface has more surface area, hence better radiation... the ONLY benefit for painted, ancy calipers is marketing...most BMW owners transcend that level of (un)sophistication |
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08-20-2008, 09:47 PM | #158 | |
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60-0 downhill or flat, kinetic, 1/2 (88)^2 ~ 3872 (ignore m, it's constant) potential g delta h, assume a stopping distance of 112 ft at 10% grade (pretty steep) U ~ 11 x 32 or 353 total energy ~ 353 + 3872 ~4225...so the added energy is only 8.4% of the total... as I said, it would make negligable difference... increasing the speed < 5% would be about the same effect... as far as mass of the disc increasing vs distance/work, the only additonal energy would be that stored by the flywheel effect due to gravity (inertia) W = distance x F, F = braking force which is the same, so any difference (if any) would be negligable... distance = W/F since force is constant, and the work is only marginally increase, the distance is not greatly increased... straight out of the Bosch book page 616 I also noticed they list all required DOT and TUV brake tests for certification...not one requires incline testing... |
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08-20-2008, 10:02 PM | #159 | |||
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I'm not sure what info you are talking about or where this is coming from. the M3 will exceed 130mph on the straights of 90% of the decent sized tracks in the US. Heck, my old S2000 would hit 120 at sebring, road atlanta, etc. Have you ever driven on a real roadcourse? I'm not trying to pick at you, I'm just curious. Quote:
I agree floating calipers are better for dealing with the vagaries of real life like pad material, warped rotors, water, etc., but that isn't as important when you replace your rotors for every track weekend. Quote:
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08-20-2008, 10:43 PM | #160 |
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I insist that this thread should be in the Track/AutoX forum.
My S2000 (I had two of them) would reach 120 mph at Pocono North with just 240 Hp (stock car). My 380 Hp GT3 at Cali Speedway (ROVAL) ran 151 mph (Traqmate data verified), and 147 mph at Pocono North, and 153 mph at Watkins Glen, and 140+ mph at Lime Rock. Look on the chart below the top speed achieved by the wrong geared M3 with manual transmission:
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08-20-2008, 11:25 PM | #161 |
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That is a great article, its sitting in my room right now. As much as I believe that there are plenty of tracks where the M3 will be hitting 130, which it certainly does at willow springs. They did have pro's driving these cars at the tracks and I think the one with the M3 hitting 148 is an oval with major banking. Not that I wouldn't track my car there, but I think banked ovals are in the minority for track days. On the flipside, the lower Vmax scores are from a coned auto-x event. Auto-x events are notorious for being extremely tight courses and having low speeds, due to area confinements. I still think that the majority of road courses would let a 400hp car hit well over 100mph.
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08-21-2008, 01:36 AM | #162 | ||
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08-21-2008, 03:58 PM | #163 |
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I'm no expert or professional driver:
I have 1 mil miles in BMW/Porsches, 500k in M3's alone my first Porsche was in 1977, first BMW in 1981... at least 40+ driving schools, several DoD, etc. I used to race (club) 911's and 2002's...snow, ice, dirt/gravel, tarmac I have at least 200k 'just for shytes & giggles' miles...back roads, etc. I'm a novice...I admit it...it keeps me from doing stupid things I would not be faster with Brembos vs oem on any M3...especially on the street... you want a track car? get a 944 or 325 and strip it down/build it up... but for most classes, stock brakes are required...iirc, sliding/1 piston on both as far as cost being the reason BMW made their choice: anybody know the following pricing? e92 M3 front caliper/carrier/rotor (it's >$900 for the e46 M3 ZCP per side!) e87 135i front caliper/rotor just curious... |
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08-21-2008, 04:03 PM | #164 |
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I don't know the answers to your question, but during a local BMW event, when Larry Koch was asked why they went for the current caliper design on the M3, he mentioned that it allows for rotor expansion, and then pointed out that it also costs less with a smile.
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08-21-2008, 04:08 PM | #165 | |
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but my guess, it's ~ the same cost as any rotor... it's aluminum, iron, x-drilled and floating on cast in place pins...big too the only thing it lacks, it's not rebuildable... it's the calipers I'm curious about they cost $540 per side on the ZCP...I bet the 135i's don't cost any more... I bet the e9x M3's are at least $650 or they would not have used them on a lower target price car unless they are trying to appeal to a certain demographics 'taste' |
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08-21-2008, 04:47 PM | #166 |
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now here's some BMW brakes...lol http://www.itv-f1.com/News_Article.aspx?id=43660
seriously though, capture the kinetic energy for reuse... infinite modulation, absolutely control...much easier to control an electric signal than a mechanical/hydraulic circuit... ecu could control the throttle/brake in synch...driver steers and uses one pedal, the throttle no heat generated, or at least much less... I wonder what it looks like? a motor/generator on the axle? or or a rotor disc (like the brake disc) spinning thru a stator toroid/magnet... |
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08-21-2008, 05:20 PM | #167 | |
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The following page might give you a sense of the retail prices of the caliper assembly in Europe: http://bmwfans.info/original/E92/Cou...4/ill-34_1618/ The same site should have retail pricing info on other BMW models as well.
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08-21-2008, 06:03 PM | #168 | |
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they don't have the 135i listed yet... |
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08-21-2008, 08:52 PM | #169 | |
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No, I want my high performance ///M car to be able to do the same thing my $30K subaru can do... run a large selection of pads, that can be changed easily, and not taper them so they wind up costing twice as much in the long run. When the calipers start spreading, and pads are lasting half as long as they should, we'll hear from the track people who will move to fixed calipers/multi-piston set-ups. I only hope, financially, that I'm not one of them...
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08-21-2008, 08:56 PM | #170 | |
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and there is a healthy selection of pads for the e46, there will be for the e92 in due time it takes 5 minutes to change pads...per side... but better change rotors too, cause they're gonna suck on the street after being thrashed the pads do not taper, it's one advantage of the system... solid bushings will reduce it even more 'track people' <1% of the cars total mileage...get a track car...you can get one for less than a set of brembos, track wheels/tires... you guys make 60k sound like a lot of money... wtf? "Arcadian, I've fought countless times, yet I've never met an adversary who could offer me what we Spartans call "A Beautiful Death." I can only hope, with all the world's warriors gathered against us, there might be one down there who's up to the task." Μολὼν λαβέ!! |
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08-21-2008, 10:04 PM | #171 |
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there are so many variables in the brake system performance equation, that looking at calipers is moot: my order
tires driver pad compound pedal/master cylinder/system hydraulic balance control systems, abs, etc. rotor diameter calipers rotor dia is critical...look at an M3 vs a 997...huge difference why so important? brake torque is the stopping force, T = r F r = rotor radius, F = brake force or hydraulic pressure x piston area = pad area x piston pressure now if r is bigger, F is smaller for a given T...still with me? now friction = Ff = u F...see, if F is smaller, so is friction force for the same stopping power (brake torque)...if friction force is smaller, so is the heat density... and it makes sense, the path/area around the rotor is larger... it makes no sense to look at 1 component in a complex system... there's a quote floating around by the chief engineer on the GT-R project...that calipers are moot, it's rotor diameter that makes the difference...and they are huge on the GT-R, 4 x 15" |
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08-22-2008, 10:17 AM | #172 | |
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Bruce |
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08-22-2008, 11:39 AM | #173 | ||
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http://www.bimmerfest.com/forums/sho...7&postcount=16
Link above shows pretty bad taper and some bushings that are supposed to help this non-existant taper Reduce what?...you just said there is no taper. So what is it? Is there taper, like evey other slider experiences when used hard on a track or is there no taper and those solid bushings are just BS? Quote:
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08-22-2008, 12:38 PM | #174 | |
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they have to...the disc is rotating in one direction primarily... although the area is larger, that means little especially if the mean radius of the centroid of their area is smaller... Ff = u N you see area in that equation? what this means for a constant rate of decleration (brake torque) the pressure on the rotor is the same (all else being constant) it's the material that matters, not the area... a larger pad may wear less, but not stop better or heat less... what is more important is the size (mass and surface area) of the disc most of the heat goes into the disc, NOT the pads...it's ENGINEERED that way...you could stop a train with a large enough disc and a properly designed 1 sq in pad and touch the pad when done, it would only be warm... Q = -kA(dT/dx) take a look at the relative difference of the pads areas... as you can see heat conduction is linear with the area, NOT squared... so a small difference in area means nothing if the material is suitable... this is all about bling...otherwise they would not epoxy coat the calipers... |
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08-22-2008, 03:36 PM | #175 | |
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I actually don't think we disagree all that much about most of this stuff as, again, we are talking minor differences. But this statement is just funny. I don't know where you get some of these crazy ideas to prove your points. I've seen pads get so hot that they change color and literally cook the rubber seals around the pistons. You ever change pads in the middle of an endurance race? You have to wear oven mits as they are literally hundreds of degrees. |
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08-22-2008, 04:36 PM | #176 | |
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a nickle jammed under a train wheel will prevent it from moving as you know, trains are electric...the diesel drives a genset, and there is an electric motor in each 'truck'...a gear tranny could not stand up to starting a train... but the torque curve of the motor is so smooth it could not 'lift' the ~200 tons the height of a nickle I think in strange ways...I was born an engineer who happened to get an education...not a normal person who chose to be an engineer oh, I'm sure the pads are very hot...but the rotors glow cherry red... I've only had 1 pad failure in all my miles, on my e36 the front right material cracked and seperated from the backing...the pads were new and not really being thrashed...they were PF metal masters iirc |
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