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02-03-2010, 11:50 PM | #265 |
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02-04-2010, 12:39 AM | #266 | |
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There are other offerings on the market that I do hear negative feedback on when it comes to knock back. All I can say is that over many years of development, there are certain tweaks that can be made to avoid it altogether. Well, at least until a wheel bearing starts to go! The AP Racing calipers used in the Ferrari Challenge Stradale series in Europe are sold in two variants: Tight course (no knock back, but with some very light drag) and high speed course (no drag with some knock back allowed). Teams will run different calipers depending on which track they are running at. |
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02-06-2010, 07:52 PM | #267 |
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Where can I order the AP BBK (front and rear) for the E92 M3?
I'm considering between AP and the Alcon Super Kit (380mm) Last edited by prodigue; 02-06-2010 at 07:59 PM.. |
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02-06-2010, 08:43 PM | #268 |
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I got mine from RennSpec.
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02-06-2010, 09:37 PM | #269 |
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I purchased mine from WheelSto.
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02-09-2010, 02:16 PM | #270 |
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Chris B - your help here has helped me decide to go AP - many thanks.
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02-09-2010, 11:49 PM | #271 |
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Curious what features are in the AP calipers for knockback. Ironically, I ran your AP knockback springs in my stoptech's. They helped, but did not completely eliminate the horrible knockback from the weak nissan hubs. Nothing like coming out of the corkscrew and having your pedal go the floor at the next brake zone.
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02-10-2010, 12:57 AM | #272 |
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02-10-2010, 08:37 AM | #273 |
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02-10-2010, 11:09 AM | #274 | |
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I can't go into all the details, but many years of seal and groove machining variations have essentially eliminated knockback. We often hear that complaint on the ST kits (especially from the Subaru WRX crowd -- much worse than the Nissans), which has *thus far* been cured 100% of the time after moving up to AP. Chris |
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02-11-2010, 01:38 PM | #276 |
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Thorney Motor Sport in the UK does AP Racing.
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02-11-2010, 02:19 PM | #277 |
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Chris: How about a more detailed description of "knock back"? What is a design causes it, what does it really feel like. What is really happening with the various wheel and brake components. What designs reduce or eliminate it and how does that work? Thanks in advance.
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02-11-2010, 08:37 PM | #278 | |
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In reality, a whole bunch of stuff is going on to reduce brake system effectiveness and feedback to the driver. The object of the game is to mitigate all these nuisances so the driver doesn't notice the deck is stacked slightly against him. An issue that has significant ill effects is pad knockback. This is when some action or another has pushed the pads back away from the rotor. Since there is no residual pressure in the brake lines (nor do we want any), the pads will stay away -- or "knocked back" -- until the driver pushes the pedal again. Only now, the first part of the now very soft pedal travel gets used up moving enough fluid to bring the pads back in contact with the rotor. Once in contact, line pressure will begin building to make the brakes work again. It is a very uneasy feeling to suddenly have a soft pedal when it was all good just a moment ago. If there are no mechanisms in place to bring the pads back in contact with the rotor, the pedal problem reveals it's ugly head. Major causes of pad knockback: 1. Wheel bearing flex: Under heavy cornering, all wheel bearings flex. Some just a little and some way too much! Since the rotor is attached to the hub/spindle assembly, the rotor goes where the inner race of the bearings go. The caliper is fixed to the upright, which stays in line with the outer races of the bearings. When the bearings flex in a left hand turn, the rotors will tilt to the right with respect to the upright. This pushes the pads on the right (front left inner and front right outer) back into the caliper slightly. A right turn does the same to the opposite pads. 2. Cornering G-force: In some professional formulas I've been involved in that use significant downforce, cornering loads are often well over 3g's. If a pad weighs a 1/2 pound, that is now an equivalent of 1-1/2+ pounds pushing the pistons back into the caliper (plus the damned bearing flex!). 3. Vibration and/or shock: In some rally or off-road vehicles, the violent nature of the road surface can jar the pads back into the calipers. 4. Rotor runout: If the rotor is starting to wear unevenly or is no longer in near-perfect alignment with the hat or hat section, the friction surfaces can start to slightly knock the pads away from the rotor. 5. Rotor coning: When some rotors are very hot and run at very high speeds, they will expand in a non-uniform manner. They will start to "cone" around the hat section. This is one of the primary reasons all real race cars use floating, 2-piece rotors. On the street, there are more options to fix this, such as the strap drive system. Fixes: 1. Design and develop components that reduce or eliminate pad knockback. They may cost a little more, but well worth it. AP has been doing this for years by experimenting with seals, seal grooves, anti-knockback springs behind the pistons and other stuff. Larger, stiffer bearings are a huge expense for most vehicles. Even so, some of the WRX (5-100mm lug pattern) guys move up to the STI hubs (5-114.3mm lugs). The larger, stiffer STI bearings are worth the hassle. Audi A4, Lexus IS300 and late-model Pontiac GTO are more examples of less than ideal wheel bearings. 2. Tap the pedal with the left foot after cornering heavily and before you intend to use the brakes again. This is fun to watch on the track when you are behind someone battling this condition. Well, you might not be behind them for long as most passing occurs under braking. I vote for solution #1. OK, this wasn't such a short answer, but I hope it helps. I'm out for a 3-day weekend, so keep on motorin'! May you all enjoy yours, especially if you are working your way closer towards your next deeper brake marker...4...3...2...1(!). Chris Last edited by AP Racing - Chris_B; 02-11-2010 at 08:40 PM.. Reason: Clarity? |
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02-12-2010, 12:16 PM | #279 |
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^ Great, thanks.
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E92 M3 | Space Gray on Fox Red | M-DCT | CF Roof | RAC RG63 Wheels | Brembo 380mm BBK | | Vorsteiner Ti Exhaust | Matte Black Grilles/Side Gills/Rear Emblem/Mirrors | | Alekshop Back up Camera | GP Thunders | BMW Aluminum Pedals | Elite Angels | | XPEL Full Front Wrap | Hardwired V1 | Interior Xenon Light Kit | |
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03-09-2010, 10:59 AM | #280 |
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So I want to get some OEM 18s for my winter set up.
I think it was on this thread, that EU style OEM 18s clear the APs without a spacer, and the North American spec OEM 18s do not. I contacted Tischer BMW and they say style 219 has one part number, for here and there. So are the style 260 the EU ones? I don't want to run spacers. Any help would be appreciated. Thanks. EDIT----After some digging. Evan@Tischer was able to come up with the style 260 part numbers. These are the EU spec 18s. 36102283750, fronts, 419.32 each 36102283751, rears, 457.30 each.
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03-09-2010, 05:46 PM | #281 |
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Another Q.
Will the rear OEM 18s clear the front AP BBK with out a spacer? 18x9.5 et23. Im will most likely get style 260, not style 219(EU VS NA), so it might have a touch more clearance, if any at all.
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03-09-2010, 06:10 PM | #283 | |
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I was set to go with Brembo first, but I found more feedback on AP kit, so I ended up going with AP.
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03-09-2010, 06:32 PM | #285 | |
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AP 368/356 kit is more expensive then Brembo's 365/35 kit. Not by much though.
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03-09-2010, 06:42 PM | #286 | |
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Stillen is the supplier of the systems being referred to here and has been in the brake upgrade business for over 20 years now. They are an AP development partner and system integrator. For some systems, Stillen supplies components back to AP. Ironically, Stillen was the one to introduce Brembo to the North American aftermarket, effectively creating the industry segment long before most people knew what a BBK was. They made the switch to AP Racing around 1996. The Stillen/AP Racing kits and the AP Racing Formula UK kits are available through at least four forum-supporting vendors. Chris |
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