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Joel Gat

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    Arizona
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    2006 Baja, 2019 Miata Off Roader

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  1. Hello, At gmail.com, I'm carguy. I agree that in the totally un-real-world situation of a single braking event with perfect conditions, perfect road surface, etc., with a perfectly matched brake system that is designed around the specific spring rates and ride height, etc., of the car, threshold braking will be better. As soon as you move to the un-ideal real world, though... First, you'd be surprised - the cost of a properly designed ABS system is extremely expensive. I know first hand from the guys that did the brake system design for GM until recently, that they were approached by GM and asked to make a custom ABS program to account for the tires and chassis setup that the factory race teams were using, and in the end, it was decided that GM could not afford to give that custom programming to their teams... So most teams are running with suboptimal ABS programs that are designed around stock tires, stock weight balance, stock weight transfer, stock brake bias, etc., despite all those parameters being changed. Modern ABS systems are quite robust, including the Subaru one, though, as one expert told me, speaking about the WRX ABS, "I am sure the Subaru system is optimized for some set of conditions - I just have no idea what those conditions might be." Subaru ABS is strangely hypersensitive to bumps, which is not what you'd expect from a "rally car heritage." I 100% agree with this statement. There is a reason that StopTech brakes are on more podium cars in World Challenge and Grand Am these days... with a properly balanced brake system, you can work wonders in the braking zone. The fact that the exact same brake kit you buy for your street car is on cars winning World Challenge race cars (yep, even those WC cars are running stock rear brakes, often), is quite telling. Get the bias / balance right, and you have a winner. Get it right and the brakes work as good as it gets, whether you have ABS on or disabled. And the electronics work by reducing braking somewhere. You'd be much better off with peak braking without reducing the braking, which is why it's so important to have the front-rear bias done right. Some of these BBK companies are basically slapping the same 2-3 piston sizes they have on a million different car kits and they're saying they developed their kits scientifically... sure! The science being "1. Post a lot on the internet, 2. ???, 3. Profit!" Amen. Joel, still with stock brakes on both Subarus, though testing new pads on the STi for one of the brake manufacturers.
  2. Hello, Praedet, EBD is a simple system that just compares relative slips and probably uses some kind of maximum slip LUT. So, yeah, it's fine with whatever brake mods you make, with the usual yadda yadda about not being optimized for non 100% stock systems. LittleBlueGT: I only have half a decade of professional motorsports experience and only 3 years of that was as a funded factory team crew chief (Subaru of America), so I don't know everything, but I do know that in road racing, we'd take 100 lbs to get ABS any day. I've never seen a driver who posted slower times with ABS and usually, the improvement in times is significant. Joel
  3. Hello, Talked to Tim at StopTech... someone with a brake kit would have to supply piston sizes - they don't publish that ever since a huge range of their products were copied by another brake manufacturer... As for pad mu, he said the pads they use don't have a published mu, but anyway, the published mus are about as useful as dyno-hp numbers when it comes to comparing pads. Every pad manufacturer uses their own mu's and one company's 0.3 might be much stickier than another's 0.6. That goes back to someone else's post - perhaps it's better to list mechanical advantages and then have pad mu's as a seperate chart? Or someone shlep a bunch of pads somewhere for mu-testing And finally, on ABS, ABS is always better than no-ABS, ideal conditions or not, because the "threshold" you're braking towards on the right front tire is drastically different than the threshold at the left rear tire. If you want to beat ABS, you need 4 brake pedals, four appendages, and a really good butt-dyno so you can get all four wheels at their thresholds. If you exceed at any corner, you suddenly lose most of the braking at that corner. Finally, as far as I know, EBD measures front and rear slip angles and uses the ABS to modify the front / rear bias by unclamping the rears, regardless of lockup - solely based on current slip angles. IE, without waiting for lockups, if the rears are decelerating too quickly relative to the fronts, they may be about to lock up, so release them to maintain better front bias. Joel
  4. Hello, Quick stop for more info: Relative front torques, StopTech BBQ for Outbacks: For the OB2.5i and 3.0R, 89.4%. For the 2.5XT, 90.1%. For the LGT, it's a totally different BBK, so Tim says the front brake torque is 99.0% of stock, ignoring friction. I will ping him for the piston sizes, effective rotor diameter, and mu. Joel
  5. Hello, Okay, last week I dropped off my car at StopTech to let them have it for a week (hey, they're only a short 700 mile round-trip detour from home and SWA is dirt cheap). They did their thing and came up with a kit for the OXT. First, yes, the 328mm kits fit under the stock OXT wheels (pictured). Yes, there's radial clearance room for the 332mm kit, but not axial - you would need a 2-3mm hubcentric spacer. Second, I don't care for drilled rotors and I think Red doesn't fit the totally-stock outwards appearance of my OXT, so I had them take off the test-mule kit (yes, I believe _that_ strongly that a BBK is not necessary until you get the suspension and tires and head out to the track). Forget looking at gift horses in the mouth... I'll take slotted rotors and black calipers when I get around to buying a set. http://www.stoptech.com/images/Tim/obxt1.JPG http://www.stoptech.com/images/Tim/obxt2.JPGhttp://www.stoptech.com/images/Tim/obxt3.JPG I asked for a bunch of data from them, it'll be forthcoming. I'm on the road still (posting via EVDO - gotta love this wireless broadband while driving in the middle of nowhere!), so I can get more info as needed and post it later. Ignoring friction, the StopTech BBK makes 89.4% of stock front brake torque. Once you account for the recommended pads, however, it's roughly 96% of stock front brake torque. What additional data do you need for the charts or for general knowledge? Joel
  6. Hello, Now I agree with you completely That sounds more like what I would expect. Hahah... can't help you there... we just had a post-St. Patty's Day drinking celebration (any excuse, eh?). Damn Naja's in Redondo Beach, CA - 77 different beers on tap, 107 different bottled beers. But yeah, suspension compression slightly affects weight transfer, but the effect is pretty small compared to the shift you get from the CG being above the ground. So it might be a few more percent. Joel Joel
  7. Hello, I wholeheartedly agree! Great thread... I do have some comments on Dan's post. I'm hung over right now, so I'm going to pose questions rather than pretend to have the facts in my aching head I'm not sure the effect is as big as you're saying. Without trying to hurt my brain with physics, the weight still transfers forward, and the lack of dive affects that transfer subtly, but doesn't prevent it from happening. I think? I certainly know that you would never want 50/50 bias in racing! Any imperfection in the ground, the chassis setup, the driver's inputs, etc., would send the car spinning. You always want the fronts to do the majority of the work, even if you could prevent that from happening. Understeer is stable, oversteer is not... Locking up the fronts means you continue in the direction you were traveling before (because a locked tire has less traction than a tire with slip). Locking up the rear means the rear stops decellerating as quickly as the front and the rear comes around. That's even the case with ABS - if the rears are being released more than the fronts, then the rear wants to travel faster than the front and the only way to do that is to come around. And forget trail braking if the rears are doing half of the work... That's pretty much true of any Subaru. Though... if you have good twisties to drive on, I can certainly fade stock pads without trying hard. Pads and lines would improve feel and provide all the braking you need for anything but the track (even in the twisties, aside from a really long downhill, you usually have time for the brakes to cool, and you shouldn't be braking so hard that you generate too much heat to dissappate. But honestly, I would guess that something liky 75% of BBK sales are more about looks than about performance I'm not sure... If the stock pads grip well enough to get you to the threashold of the tires, then certainly this is the case. Can the stock pads hold the car at the threshold of the tires (esp if you have good tires on), even with a haul down from 100 mph? I'm not sure - I've never tried. I would imagine, though, that at some speed, you'll exceed the heat range of the stock pads in a single stop... meaning you'd generate more heat if you had better pads. But under 80 mph or whatever, I'm sure that Dan is correct. Joel
  8. Hello, Oh, no doubt the stock pads can't stand heat. But before you get out of their heat range, they're not bad - not 30% worse than aftermarket street pads. The rated mu of a pad assumes it is at the correct heat range. A good race pad might maintain a high mu over a wider heat range, and must have a good mu at a heat that might melt a stock pad, but it probably has a poor mu at cold temperatures, and on the other hand, any street pad has to have a good mu at cold temps. You're cruising on the freeway, not using your brakes, the rotors and pads are at ambient air temperature, and a dummy in front of you decides to slam on his brakes for no reason (seems to be common around here, too). You slam on your brakes. You better have the best possible mu at this moment, right now, right here, right from ambient cold. And the OEM knows that. And the OEM pads are ideal for this exact type of situation. Add three more 60 mph stops and the OE pad turns into butter. A good performance pad might have close to the same mu but better heat tolerance, so might last through 6 stops like that in a row (but might not perform as well on the first stop). A good race pad will suck and eat a bunch of your rotor on the first 3 or 4 of those, but then should last through another 10 of them in rapid succession. Given the goals of the OEM - max performance in that one to three panic stops - you can bet that the actual mu of the pad is quite good and quite near what you'll get out of performance pads. They sacrifice longevity at heat for instant gratification and some reduced dusting and noise. That said, there are other factors at play, the worst of which is the tire, which, unfortunately, affects everything, right down to the maximum deceration allowable by the ABS. The ABS is tuned to let the wheel slow down no faster than the OE tire could slow down under the best of conditions (grippy warm asphalt). Any time you can slow the wheel down faster, the ABS won't let you, which doesn't matter for low mu surfaces, but does matter in a performance scenario. But that's off topic. My point is only that I think the mu numbers in this thread are off. Joel
  9. Hello, Oh, one other comment: I don't know the mu numbers for the stock pads or the aftermarket pads, but I certainly don't think the jump is as drastic as posted here. My personal experience is that you do not get a 10% or more increase in brake torque with a set of street pads. You might get a small jump - but in a single application of the brakes, do you really feel that huge of a difference that you (as in anyone in the thread) think there's a 30% increase in brake torque? I dunno... it sounds fishy to me... Joel
  10. Hello, Just to raise a quick point - in racing the WRX for SoA, we used the stock brakes initially, because our rules didn't allow BBKs. With the appropriate PFC pads, while the car was ballasted to 3300 lbs, we never once experienced brake fade. The clamping force generated by the stock brakes was more than sufficient. The heat capacity of the system, however, left things to be desired, and despite using krytox grease (originally designed to lube the wheel bearings on those carts that smelters use to bring molten ore out of the oven (ie, really freaking hot)) we melted the plastic bearing retainers inside the wheel bearings... every single time we went on track. The BBK (StopTech) put an end to melting the wheelbearings, reduced our rotor and pad consumption rate, prevented melted steering ball joints, etc. It also improved modulation and feel, which was critical given that we weren't allowed to run ABS. I will have more to add to this great thread a little later... Joel
  11. Hello, [edit: previous question deleted] I'm a dummy. Ok, now I get it. You have the headphone thing in the dash... Joel
  12. Hello, jp928, there's a better option. The same option that centerpunch, jazzymt, and others have come up with for the lack of a line-level input into the OE stereo: if enough people don't like the way it works, someone with the right know-how can create a fix that anyone interested in can then apply. I think it's great to discuss the major weaknesses of these systems so that fixes can eventually be made. I have jazzymt's input board and am installing it this weekend. For $35, I resolved a major complaint I had about a nearly $30k car! Now, if someone can give me cold air AC and not just the AC compressor on Defrost for $35, WOOT WOO! I'm interested... Joel
  13. Hello, jp928, yeah I got that... but what if I don't need max defrost? What if I need cool air, warmer than outside, but not hot, while still being dry, so that I can drive a couple hundred miles without fog on my windshield? I just hate when marketing think they're being smarter than the consumer and they make things better by getting rid of choices that have existed for decades. Ahh well... it's not like people take AWD Subaru Outbacks in the cold or anything, eh? Joel
  14. Hello, I see several people here have the same problem I have. 65 is NOT max AC if you are in defrost (blowing on the windshield) mode. In defrost, the compressor comes on, but the air comes in at what feels like about 70 degrees, which can be pretty warm if you've been backpacking in the cold... Heavy breathing, warm breath, means lots of fog, so I turn on the defrost, and get baked. I have to turn the defrost on full and open the windows, or blast my feet with freezing air if I turn to defrost+feet mode. If my shoes are all muddy from backpacking, I'll take them off and drive barefoot to dry off my feet... What a pain. I just want defrost with cold AC. Joel
  15. Hello, Cool beans. Payment sent... Can't wait! So while I'm in there, any other things that I should be playing around with? Anything I should be looking at while I have the radio out? I'm thinking of switching the cig lighter to constant power so that I can attach accessories while I'm at base camp. I'm also thinking of bringing some switched and some constant power lines to connectors and leaving them around the area of the green test connectors so that I have taps when I need them. I'll probably hardwire in power taps for the XM at this time, too. Any other thoughts? Thanks, Joel
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