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jamal posted:the rate and distribution of weight transfer is the important thing. I totally get that. But I bet, prior to your making the point, 95% of people here (and in AI) would have defined weight transfer as the rate of actual_weight_transfer, which would obviously lead to confusion. And of course the rate does involve shocks and roll bars. The debate over the best settings for those, of course, must rage on forever.
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Apr 23, 2012 08:04
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jamal posted:the same total amount happens for a given cornering force regardless of the suspension setup. When you are going around a corner at a certain speed the only way to change the amount of weight tranfer is to change the track, the height of the center of gravity, or the weight of the car. Period. This is a concept that needs to be understood before we can go any farther, and I'm not saying much else about this stuff until we are all in agreement. Sources would be Ford WRC rally team, Ross Dunkerton and Murray Coote, who knows more about suspensions than just about anyone on earth. Even Sebastian Loeb but he's an rear end in a top hat. You might notice that rallying has a much different view of weight transfer, this is true. There is a huge disconnect between the two disciplines as the former is dealing with much more fixed variables and even goes too far in restricting it, while the second relies on it or you crash. You are incorrect in how to change weight transfer. The area I bolded is not the way to do it, but the RESULT of doing it, more specifically how much weight actually gets to the tyre. And this is where the disconnect comes about as you are saying how much might occur, I'm depending on what actually happens. You seem to be approaching it from the wrong direction. The way I know I can change the weight transfer is belt the brakes. Whoops, why am I spinning off backwards, did I unload the rear? A hard suspension WILL resist weight from transferring. This is as you state simple physics as the front requires more force to compress and more actual weight to bear down on the front tyres - the whole system is interconencted so that even if you apply x amount of force to the front, the suspension applies y amount of force in return and forces the weight to hold where it is and the rear to also remain in it's place. IF you allow the front end to be soft you may get to the point where the resistance breaks down and the rear end is allowed to rise and even leave the ground - this isnt that uncommon which is why you have brake bias adjustments - and the entire weight of the car is now on the front tyres. Now for simple example - IF a person in a STI comes barrelling into a corner, lets say we want to brake as hard as possible. (Remember, I have done this test, this isnt out of a book) Because lets say the ground is gravel and I need to sweep the poo poo off the road. So lets say z amount of effort has to be applied to the tyres to enable the car to dig in. I set everything to hard, x force down on the suspension is met by y return force by the suspension, the weight is transfered forward - but only enough to make z-w, w being the actual force applied to the tyres as the actual weight has remained too much on the rear. I go off. I repeat, this is not out of a book, this is actual testing of theory as the swaybar idea to begin with did not work in my head. I now soften the suspension by removing the sway bar, now giving me a lower y force that can be applied. I come in again, same speed, choose a slightly different line (because I have removed gravel from the first run so I want to avoid it to make this test fair) and hammer the brakes. THIS time x force is met by y but THIS time there's not enough to prevent the rear from lifting.... gently caress that is distracting, guy next to me on the train is watching some show and the woman reclining next to the pool has incredible legs. ...... Where was I? Okay so this time the rear has lifted, resulting in actual real weight being put onto the front wheels and hence the w value is quite a deal higher, resulting in z being achieved. And I turn corner. Wow those legs ARE distracting. The fact is that while those legs are good, you most certainly can change weight transfer and because that we are dealing with a highly complex system, neat drawing in books dont work and in fact much of those books (which I have read) doesn't translate where you have suspensions that need to work well outside of the ranges that those writers have dealt with. So while in general I am talking about results and a starting point of a wildly different discipline and you are I think talking about x - y(?), the point is that it's actually a simple experiment to show that you most certainly can change the actual weight transferred to any given wheel and the proof in the end is rallying works and we all this weekend scratched our heads wondering why you said as you did, because as said, weight transfer - as in the actual result - is what allows us to make a corner at all esp in loose gravel. Or even look at an old Escort on tarmac as it basically lays all it's weight on one wheel in hard cornering. I can do some rough sketches with lots of arrows if anyone wants, which I think is required. quote:And thus is at definitional odds with that steady state definition above The steady state definition is too simple and if you use it, you will crash. I guarenttee it. You MUST think much more boradly and not use book definitions but actual hard real world results and realize the whole system is extremely complex, it is not a simple clean equation at all. One of the problems the simple equation has to deal with is left foot braking, a technique EXPLICTLY designed to change the manner of how a car changes it's weight distribution.
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Apr 23, 2012 09:35
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Cat Terrist posted:The steady state definition is too simple and if you use it, you will crash. I guarenttee it. You MUST think much more boradly and not use book definitions but actual hard real world results and realize the whole system is extremely complex, it is not a simple clean equation at all. Well, I think most suspension engineers are competent enough to model car dynamics as time-dependent systems. Even in the early days of analog computing, engineers knew to model suspensions (per corner, since that's way simpler) as 2nd order systems, implemented with inductor/resistor/capacitor circuits. I'm not gonna argue that the real world might not match up to models, but I think plenty of people here are capable of grasping the complex models that might be involved.
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Apr 23, 2012 09:45
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kimbo305 posted:Well, I think most suspension engineers are competent enough to model car dynamics as time-dependent systems. Even in the early days of analog computing, engineers knew to model suspensions (per corner, since that's way simpler) as 2nd order systems, implemented with inductor/resistor/capacitor circuits. I'm not gonna argue that the real world might not match up to models, but I think plenty of people here are capable of grasping the complex models that might be involved. The issue here tho is that a subset of tarmac guys are saying this is the theory and a another subset of tarmac and the gravel rally guys are saying WTF, this contradicts what we do. I wasnt lying when I said I had a bunch of rally lads over and we were discussing a few ideas and we discussed this very topic. It really does fly in the face of everything we try to do to make weight transfer work for us and to get as much of it as possible. But as I am want to do I am doing a Cat Handling analogue to think it through - this isnt as silly as it sounds, I used cats to fix handling problems before. In this case I'm using Maddie (mum cat, handles like a Mazda6) and Ed (Rally Escort oversteer and paw lift) to work through what I want to say later and even to do some math. It sounds dumb but it helps you understand the concepts if you break them down and apply them to a cat.
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Apr 23, 2012 12:42
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Seat Safety Switch, can you help a brother out?DrakeriderCa posted:For those who recall my last post, I was looking at Foresters. I found one, looked at it, and I like it. This is the car:
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Apr 23, 2012 13:16
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jamal posted:i would just get a perrin inlet so you don't have to take off the manifold and not bother with that stuff. no reason to replace fuel rails until like 500hp. alright sir thank you. Amandyke posted:This just recently happened to me as well. Got the perrin installed and all is well (aside from it needing the tune tweaked as there was also a leak in the BOV gasket, both leaks likely have been there for a very long time... before the last tune touch up I had.) Yeah I'm working with my mech and tuner concurrently over this issue. My car was a teensy bit low on power on the dyno last week which I'm assuming was inlet related. Hopefully.
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Apr 23, 2012 13:57
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Ribsauce posted:I actually have another stupid question. I had a Yakama rack on my car but I hated having the "feet" stuck in my door and the drat thing scratched my paint up so I got rid of it. Is it possible to put a permanent roof rack installed and about how much does that cost? I really like my car but I absolutely need a roof rack by the summer for my hobbies* and if I can only go Yakama/Thule style I might just sell it and get an SUV or something. Unfortunately, the car is now 7 years old so it is a little late to sink a bunch of money into an improvement like that, although this car would probably last me 10 more years the way I drive (like an old lady). I tend to think of those as being permanent. Just leave the feet on there and don't gently caress with it. If paint scratches bother you, get a scratch repair kit from this guy and pick up some sugru and apply like so.
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Apr 23, 2012 14:09
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DrakeriderCa posted:Seat Safety Switch, can you help a brother out? Unfortunately I have no idea about that strange vibration you're experiencing; most of the time non-driveline vibrations are an exhaust heat shield that's gotten "whanged" and needs to be cut off or bent back. It may also be as simple as a poorly balanced wheel or a tie-rod that's worn out. Sometimes it's also interior trim rattling, but those are usually pretty obvious and repeat at multiples of the same frequency of chassis vibration. Hopefully the shop can repro and figure out what it is. The period on it is so long that I'm suspecting it's related to the body in some way. That's a handsome car. Sounds like Rally Subaru might have a decent amount of records as to what small things the car was brought in for (between services) previously as well, so you should try and get ahold of those. Seat Safety Switch fucked around with this message at 14:13 on Apr 23, 2012 |
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Apr 23, 2012 14:11
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Seat Safety Switch posted:Sorry I missed the earlier post. Sounds good, thanks. The current owners have most of the records but I'm having the inspection done at Rally, so I'll ask them about that too.
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Apr 23, 2012 15:24
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Cat Terrist posted:The steady state definition is too simple and if you use it, you will crash. I guarenttee it. the steady state example is getting used because it is simple. if you fail statics (I got an a), they don't let you take dynamics.
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Apr 23, 2012 19:40
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I moved from 150 ft elevation to 6000 ft this week. I notice that my Defi racer boost gauge reads weaker vacuum and higher boost. That makes sense for gauge pressure, but is there a way to recalibrate it? It's showing 1.2 bar instead of barely over one.
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Apr 24, 2012 20:00
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Quick non-suspension related question. I've noticed recently that my wrx likes to pull (somewhat frighteningly) hard right (more of a rotational force) if I step on the brakes with any sort of force. I notice it rather well when going 50mph+ and it's caused a pucker or two when I was breaking from higher speeds. After pumping the brakes a bit it goes back to stopping straight. I've got my front wheels off right now and was looking at the rotors/pads (lots of life left) and didn't see any unusual wear patterns. The rubber boots on the 14mm bolts look to be in good condition, I haven't pulled the calipers off yet but wanted to see if anyone had encountered the same issue. Or knew what to do to remedy it.
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Apr 24, 2012 23:57
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When was the last time you bled your brakes? That sounds like a hydraulic issue to me.
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Apr 25, 2012 00:00
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could be an alignment issue or a worn tie rod/ball joint, or it could be a bad wheel bearing. a bearing on the way out will cause pad knockback, so when you get on the brakes the caliper has a gap to take up between the pad and rotor before it starts working. so if one side is bad and the other is good the side with a good bearing will generate a lot more braking force.
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Apr 25, 2012 00:03
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Cat Terrist posted:A hard suspension WILL resist weight from transferring. This is as you state simple physics as the front requires more force to compress and more actual weight to bear down on the front tyres - the whole system is interconencted so that even if you apply x amount of force to the front, the suspension applies y amount of force in return and forces the weight to hold where it is and the rear to also remain in it's place. IF you allow the front end to be soft you may get to the point where the resistance breaks down and the rear end is allowed to rise and even leave the ground - this isnt that uncommon which is why you have brake bias adjustments - and the entire weight of the car is now on the front tyres. ok, so say I have a car with 200lb springs and a car with 400lb springs. and I weigh 200lb and sit on the corner of the cars. The car with the soft springs compresses 1" and the car with stiff springs compresses 1/2" I still weigh the same regardless of how far the suspension compresses. now, say I take both those cars out and get on the brakes so they slow down at 0.5g. Both of them are slowing down at the same rate. The suspension on the softer car compresses twice as much. The weight transfer is exactly the same. jamal fucked around with this message at 00:18 on Apr 25, 2012 |
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Apr 25, 2012 00:11
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Seat Safety Switch posted:When was the last time you bled your brakes? That sounds like a hydraulic issue to me. Brakes were bled a few months ago. I inspected the lines going to the calipers, no cracks or fluid leakage is evident on them. jamal posted:could be an alignment issue or a worn tie rod/ball joint, or it could be a bad wheel bearing. a bearing on the way out will cause pad knockback, so when you get on the brakes the caliper has a gap to take up between the pad and rotor before it starts working. so if one side is bad and the other is good the side with a good bearing will generate a lot more braking force. Alignment was just recently done (and will be done again on thursday when the koni's go in). Just gave the wheels Ye Olde Shake Test and didn't feel any slop on the horizontal or vertical. Are there any other checks I could do? Tie rods look ok on both sides from a cursory glance (no obvious tears or dry looking rubber on the pillow balls). My initial thought is that it could be the slide pins... Amandyke fucked around with this message at 00:29 on Apr 25, 2012 |
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Apr 25, 2012 00:19
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yeah it could be that too if the caliper is sticking a bit. I would just pull them out, clean them, and give them a coat of brake grease and see if it helps. Be careful with the boots so you don't tear one. They just pop out when you pull on them.
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Apr 25, 2012 00:48
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Jamal - Subaru technician, advice guru, and parts salesman.
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Apr 25, 2012 01:00
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now I just need to take a sexy picture for the calendar here are a couple I found  
jamal fucked around with this message at 01:21 on Apr 25, 2012 |
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Apr 25, 2012 01:10
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jamal posted:You could try and go up the ladder to SOA. But I really dislike the stock pistons anyhow. Cobb is the place to go down there. Yimisport is probably my second choice. Took your advice and went to Yimisport, good bunch of guys. I just got the car back today after just over one month and just under $4k and now get to break in a 4th engine.
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Apr 25, 2012 05:33
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jamal posted:now, say I take both those cars out and get on the brakes so they slow down at 0.5g. Both of them are slowing down at the same rate. The suspension on the softer car compresses twice as much. The weight transfer is exactly the same. If the surface is loose (say, gravel), would the stiffer springs have the effect of more rapidly reacting and pushing into the gravel? That is, from the same pedal action at the brake, you get more bite into the dirt and thus possibly better deceleration. This reaction time is of course dependent on spring constant. I know the above is dynamic/transient and not measuring a steady state 0.5g deceleration. That situation seems to map more easily to braking down at the end of a long straight on a track.
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Apr 25, 2012 05:34
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kimbo305 posted:If the surface is loose (say, gravel), would the stiffer springs have the effect of more rapidly reacting and pushing into the gravel? That is, from the same pedal action at the brake, you get more bite into the dirt and thus possibly better deceleration. This reaction time is of course dependent on spring constant. The problem with going too stiff is that weight transfer happens too quickly and abruptly and shocks the tire. The interaction between the tire and the road surface is most important, and the more gradually a tire is loaded, the better it will grip. So a big part of suspension tuning is finding a compromise. On one hand it has to be as soft as possible to load the tire gradually and to allow it to follow bumps and imperfections. You also have to keep it stiff enough to prevent excessive body motion, poor dynamic alignment, compensate for downforce, and make the car more responsive to direction changes. So when suspension is too stiff and you hammer the brakes, you are very quickly adding all that extra load, bypassing the small window of an ideal slip angle, and the tire starts to slide. With a softer setup you get more travel and more time for the tire to be loaded and the result is more grip. On dirt and gravel you not only have less grip but you have a rough, uneven surface, so the softness is not just about making things happen more slowly in a lower grip sutuation but also keeping the tire in good contact with the ground. What CT and I are not disagreeing about is how to set up a car (well not completely). It just seems like he is getting the basics completely wrong, declaring that it doesn't work in practice, and doing the opposite. Which is actually right. Lazor posted:Took your advice and went to Yimisport, good bunch of guys. I just got the car back today after just over one month and just under $4k and now get to break in a 4th engine. Good to hear, I've been friends with the Pauls for a long time now and actually spent a weekend working there back in the day. We used to always send each other funny care packages plus Paul L. the tuner there is a fellow Canadian. jamal fucked around with this message at 09:06 on Apr 25, 2012 |
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Apr 25, 2012 06:24
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So I was under the 04 FXT the other day and noticed something strange going on with the control arms... Thankfully there's a recall, so I won't have to foot the bill. And Subaru is even nice enough to give me a loaner car in the mean time. On the downside, the parts are supposedly on a 2+ month back order.  Does anyone know if there's actually that much of a delay? This Chrysler 200 loaner is painfully boring. Also, check your control arms now.
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Apr 25, 2012 06:42
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you could always get some aluminum sti arms off the forums or ebay
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Apr 25, 2012 06:44
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jamal posted:What CT and I are not disagreeing about is how to set up a car (well not completely). It just seems like he is getting the basics completely wrong, declaring that it doesn't work in practice, and doing the opposite. Which is actually right. jamal posted:On dirt and gravel you not only have less grip but you have a rough, uneven surface, so the softness is not just about making things happen more slowly in a lower grip sutuation but also keeping the tire in good contact with the ground.
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Apr 25, 2012 09:46
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Lazor posted:Took your advice and went to Yimisport, good bunch of guys. I just got the car back today after just over one month and just under $4k and now get to break in a 4th engine. drat. Now I don't feel so bad about the money I've spent on my car.
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Apr 26, 2012 01:25
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Finally had the time to install the konis/RCE yellows today, instant night/day difference.   What is the general bleed/break-in time for new dampers? Thanks again for the killer deal, jamal!
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Apr 27, 2012 00:15
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sweet setup. People say wait a bit for the springs to settle before alignment, but the amount of change is very very small so it's not that big of a deal.
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Apr 27, 2012 03:53
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McSpatula posted:Finally had the time to install the konis/RCE yellows today, instant night/day difference. Mine's at the shop right now getting it's inserts installed. 
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Apr 27, 2012 04:01
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Amandyke posted:Quick non-suspension related question. I've noticed recently that my wrx likes to pull (somewhat frighteningly) hard right (more of a rotational force) if I step on the brakes with any sort of force. I notice it rather well when going 50mph+ and it's caused a pucker or two when I was breaking from higher speeds. After pumping the brakes a bit it goes back to stopping straight. I've got my front wheels off right now and was looking at the rotors/pads (lots of life left) and didn't see any unusual wear patterns. The rubber boots on the 14mm bolts look to be in good condition, I haven't pulled the calipers off yet but wanted to see if anyone had encountered the same issue. Or knew what to do to remedy it. I'm actually having a very similar issue with my 06 WRX, but the brakes have not been bled. Should I start there before trying the rest of the advice you all gave?
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Apr 27, 2012 15:21
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Inlet replaced today. Next up is the front 02 sensor. Spending money on this car has rapidly turned from fun to exhausting.
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Apr 30, 2012 00:50
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Replaced my front passenger bearing hub on my GT at 46k miles this weekend and now I can hear the driver's side going out.  Any special reason why I shouldn't stick with the OEM hub?
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Apr 30, 2012 19:00
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If you're talking about a Legacy GT and it's an 05-09, there's a TSB that extends the warranty for the rear wheel bearings to 100k. I've had two rear wheel bearings and a front replaced under the extended warranty. Subaru knows the bearings are a problem. The TSB number is 03-58-08; you might get lucky and get the front covered as well. Wheel bearings are generally covered under the standard powertrain warranty, so even if they don't let you sneak in under the TSB, you might have some time or mileage left on yours. I'd stick with the OEM part; they've fixed it.
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Apr 30, 2012 22:19
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Are Subaru clutches stiff across the board? I drove an 06 Legacy GT with an ACT Stage 2 clutch, which the owner said was somewhat stiffer than stock. But drat, that was the stiffest clutch I'd ever felt. From memory, it was stiffer than the clutch in my SVT Focus, which every autocross instructor that went into it said was the stiffest they'd felt. So working backwards, the stock Legacy clutch must be on the stiff side. The owner said WRX clutches were pretty heavy, too.
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May 1, 2012 01:01
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08 Legacy GT. That TSB is only good for 05-06 model years. I still have some powertrain warranty left but honestly, it's like a 140 bucks for the parts to be at my door and an hour on a Sunday to do it. Better than the two hour round trip to the Subaru dealer to sit around and wait for them to do it.
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May 1, 2012 01:01
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kimbo305 posted:Are Subaru clutches stiff across the board? I drove an 06 Legacy GT with an ACT Stage 2 clutch, which the owner said was somewhat stiffer than stock. But drat, that was the stiffest clutch I'd ever felt. From memory, it was stiffer than the clutch in my SVT Focus, which every autocross instructor that went into it said was the stiffest they'd felt. My RS and my 05 Leggy were normal. The race mustang is stiffer.
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May 1, 2012 01:05
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kimbo305 posted:Are Subaru clutches stiff across the board? I drove an 06 Legacy GT with an ACT Stage 2 clutch, which the owner said was somewhat stiffer than stock. But drat, that was the stiffest clutch I'd ever felt. From memory, it was stiffer than the clutch in my SVT Focus, which every autocross instructor that went into it said was the stiffest they'd felt. I don't know what "Stage 2" means for a clutch, but single disc ACT clutches are always heavier than stock. The 2600 ACT in my Talon will seriously build up the muscles in your left leg. It's HEAVY. Every time I had to take it in for an alignment I had to drive it onto the machine after painfully watching the goomba "who does this all the time" stall the car repeatedly.
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May 1, 2012 01:37
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BoostCreep posted:I don't know what "Stage 2" means for a clutch, but single disc ACT clutches are always heavier than stock. The 2600 ACT in my Talon will seriously build up the muscles in your left leg. It's HEAVY. Every time I had to take it in for an alignment I had to drive it onto the machine after painfully watching the goomba "who does this all the time" stall the car repeatedly. I think stage designations delineate the levels torque the clutch is designed to handle, within a brand line. Never really thought about how any of the clutch design could affect pressure/effort. I had a "stage 4" Clutchmasters clutch in a Focus once and it was super light. After I got out of the Legacy, I drove my Vette and did the thing where you're afraid you just punched through the floorpan with your foot (could happen with a balsa wood floor).
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May 1, 2012 01:42
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Bud Manstrong posted:If you're talking about a Legacy GT and it's an 05-09, there's a TSB that extends the warranty for the rear wheel bearings to 100k. I've had two rear wheel bearings and a front replaced under the extended warranty. Subaru knows the bearings are a problem. The TSB number is 03-58-08; you might get lucky and get the front covered as well. Wheel bearings are generally covered under the standard powertrain warranty, so even if they don't let you sneak in under the TSB, you might have some time or mileage left on yours. I'd stick with the OEM part; they've fixed it. On my loving car I lost 3 front wheel bearings (admittedly 1 had to do with trying to have my left front wheel occupy the same space as a curb) and exactly 0 rear wheel bearings. I wish that included all of them.
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May 1, 2012 05:08
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kimbo305 posted:I think stage designations delineate the levels torque the clutch is designed to handle, within a brand line. Never really thought about how any of the clutch design could affect pressure/effort. I had a "stage 4" Clutchmasters clutch in a Focus once and it was super light. It really depends on the clutch design. Dual disc clutches usually have lighter pedal feel since they don't increase friction from pressure alone, while clutches that rely on increased clamping force like the ACT 2100, 2600, and 2900lb clutches will directly transmit that force to your leg. Personally I prefer the ACT style clutches because I get more feedback from the direct pressure connection as opposed to relying on mechanical trickery.
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May 1, 2012 05:34
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