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02-13-2010, 01:06 AM | #226 |
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sure doesn't look like AMS Evo has much of suspension travel on their suspension setup..
and their Evo X is one of the most dominating car on the circuit. Sure i know you can't compare street car to race car. Race track have far better road surface. but my point is you can't judge quality and performance just base on the coilover stoke length. Here another one showing inside mounting of the rear suspension on the evo X I don't know much about Evo X looks like stock location to me.
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Last edited by Kenji815; 02-13-2010 at 02:01 AM. |
02-13-2010, 01:11 AM | #227 |
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I have no idea how many times I have to repeat this...
1) Just because you can get away with it on a racecar doesn't mean you can get away with it on a normal car. Race cars can do clever things like rewelding the suspension pickup points to totally change the geometry of the suspension (in this case, for all you know, they could have moved the suspension pickup points such that the pictured tire positioning represents several inches of droop) 2) You can do things wrong and still be fast. You'd just be faster if you did them right. |
02-13-2010, 02:22 AM | #228 |
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That AMS car is running spring rates at or near 1000 lbs/in in the rear (different motion ratio than GD impreza though) and yes, it does still have some compliance. Decent bump and droop travel considering the spring rates if you look through the rest of the the car's pictures after the car is fully built.
This thread is so frustrating....a lot of nitpicking from all over the place that is not constructive. There is nothing inherently wrong with a dual height adjustable coilover design functionally, it's just that in practice for Subarus they unfortunately use such short bodies and shaft lengths that you generally can't get a good ride height with good bump AND droop travel. Advanced suspensions are designed from the ground up for a target ride height range, so they can be built with shortened bodies that are not dual adjustable and you're still fine in terms bump and droop travel. IF say they were dual adjustable but with the same total travel, you might have another adjustment to make and in conjunction with helpers you could really fine tune available bump and droop at a given ride height...if you wanted to. Travel is important...it's important to have as much as you can use. If you're building a car that is driven to the street and in and out of driveways and gas stations, then yes you want more travel and it can still be really fun and handle well. If you're building a racecar that never sees the street, runs 600 lbs/in spring rates, and the biggest bump it sees is the kerbing at the track (which can still be significant), then maybe you don't need as much travel as the other car. If you're building a car that sees something in between...well than maybe something in between is the way to go. There are always compromises....in my experience it's much better for handling and ride quality to have a little more travel than you think you need. But 10 inches of travel on a track car with 700 lbs/in springs is going to give you problems, first and foremost being fitting that into the wheel well and having a spring that stiff that fits the shock not raising the car to monster truck height. - Andrew |
02-13-2010, 02:36 AM | #229 |
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^ really well said Andrew. I think the major problem on this forum is that some think that a certain way of tuning is absolute. And it really isn't it, just opinions and personal theories.
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02-13-2010, 03:09 AM | #230 |
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No, that's exactly the point. 90% of it isn't opinions and personal preference. There's a right way and a wrong way for almost all of this stuff. That last 10% that is personal preference and opinion is so much more advanced than anything that's going on on NASIOC that it doesn't even enter into the conversation.
The Impreza chassis is a highly compromised design. The dimensions of the chassis, the location of the suspension pickup points, and the geometry of the suspension links put very harsh limits on what it is and isn't possible to do with an Impreza. So much so that the majority of the time, there's only one or two solutions that, really, are able to be used successfully. Sure, you can pick a different solution that maybe is fast on a Civic or a Supra, but you're going to be slower than the guy who picked one of the right ways for the Impreza chassis. Another thing that goes wrong in these threads is that much of the audience takes the wrong message away. For instance, in here there's been a lot of ragging on DA and SA coils and the differences between them. Neither DA nor SA is inherently a bad design choice. The problem is that all the cheap DA and SA options for the Impreza chassis are badly designed. They're not bad because they're DA or because they're SA, they're bad because the designer made a bad choice (often in the name of cutting costs). For example, DA coils get a bad rap. There's nothing wrong with DA coils. However, the cheap DA coils actually sold for the Impreza tend to suck because the designer spec'd a short body, a short stroke, and a stiff spring so that the same damper will fit the widest range of cars. The DA functionality is then used as a bandaid to cover up the fact that the damper isn't right for the car. So, the real message a bunch of us are trying to convey is "Buy the best design you can for your money" what a lot of people seem to hear is "You can't have a DA/SA/NA design that's any good." I'll leave you with two things to think about. I think we can all agree that Lotus knows a thing or two about chassis setup. It can be reasonably argued that they're the best in the suspension design business. Take a look at two of their newest offerings: The Evora has inches more suspension travel than other supercars. Every single review of it has commented on how well it rides, how well it handles, how much grip there is, and how unbelievably easy to drive it is. The 2010 Exige Cup has a user-adjustable suspension, including height adjustment. Lotus wanted to provide the user with the largest amount of height adjustment that stayed within the range of best performance. On a car with a suspension that would be more tolerant of height changes than ours, they're allowing the use 10mm of total adjustment. |
02-13-2010, 07:49 AM | #231 | ||
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02-13-2010, 12:22 PM | #232 | |
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Also about the evora argument doesnt quite work. for how good the evora is, its more of a commuter super car then something made for pure performance, bushings are softer for a more comfortable ride and what not. and in comparison if you look at a alms porsche, it has VERY little droop. You even look at the sierra sierra evo, which uses take off suspension off a formula car.. they seem to know what they're doing, but again the coilover was a short bodied take off from a formula atlantic car, just revalved and fabricated to fit. It all depends on what the car is used for. Yes droop and travel are important but depending on what the car is used for, more travel isnt always needed (high aero, pure track car). |
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02-13-2010, 07:35 PM | #233 |
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hehehe.. Looks like my D2 coils with 15k/13k ...
Luckily, I haven't killed myself yet. Great discussion in this thread. Technical, yes but a lot of truth to be told. Read up and think folks! |
02-14-2010, 12:02 AM | #234 | |
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Why are all the test videos of racing coilovers made on bumpy streets instead of race tracks? Why does Phil from Element do so well on crappy BCs? I'd rather see a kid slam his car on Megan's than slam his car on Motons and never take it to the track. I think the problem is that you're targeting an audience that DGAF. |
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02-14-2010, 12:32 AM | #235 | ||
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02-14-2010, 02:40 AM | #236 | ||
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02-14-2010, 02:43 AM | #237 | |
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How do you figure? People have repeatedly brought up "the way it's done on racecars" in this thread in an attempt to somehow justify doing it to street cars.
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02-14-2010, 04:13 AM | #238 |
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Holy mother of a thread batman!
I like it. I figure I'd toss out some reference points. --Stock struts-- Full extension: 18" (wheel center to fender) At bumpstop: 14" (two finger gap) Compressed: 12.5" (zero fingers) This represents the range of travel the strut has from full extension to full compression. And yes, zero finger gap = fully compressed suspension. I've tossed 2000 lbs. in the back of my car and it doesn't go lower then this. --Terminology-- Droop: extension of travel past resting position. ex. if a tire dropped into a pothole, this is how far it would drop relative to stock ride height. Bump: compression of travel past resting position. ex. driving a tire up on a curb and compressing that one strut. Compliance: the ability to conform to changes. ex. offroading and keeping all tires on the ground. --Normal driving-- Under normal driving conditions the suspension will operate out both directions from its resting position. Some droop and bump travel will be needed to conform to the road surface changes (compliance). How much compliance needed will depend upon the road conditions. A very smooth road will need little. A rough road will need a lot. On a softer suspension setup, more travel will readily be used up: car stays in one spot suspension flops around. With stiff springs, the car will flow more with the road changes making for a rougher ride but also less need for suspension compliance. Random bumps and dips can use significant amounts of travel, as much as the change in height of the imperfection. A 3000 lb. chassis can't move isntantly, so the suspension is forced to soak up the imperfection. If it's a two inch bump in the road, it will use up 2 inches of bump travel. If enough is not available, the suspension will bottom out and a very high force impact will be sent to the chassis instead. A LOT of ride harshness comes from this. Bump stops play an intermediate role but can only help so much and the moderate ramp up of spring force can only dampen the impact force some. Much of the harshness remains. Adequate bump travel can prevent this from ever occuring. It is interesting how much suspension travel you actually use on a daily basis. For example, my Forester is currently 30% stiffer then a stock STI. It still ends up using most of its range of travel on my roads. I have actually gone stiffer but with more bump travel and gotten a sizably more compliant ride. --Racing-- Under racing conditions, the car will roll under high cornering forces and squat and dive under hard acceleration and braking. A sizable amount of suspension travel is needed doing this. The softer the suspension, the more travel gets used. Even a relatively firm setup (stock STI) will still use about 2" of travel (outside: bump, inside: rebound) under steady state cornering. If a bump exists in the road during this corner, additional travel is needed. Inadequate travel can upset the car and compromise handling. More compliance means the car will remain stable over more adverse terrain while under hard driving. Enough compliance needs to be in place in order to keep the car stable and safe for the given track/course. Without modifying the stock geometry, one can only gain bump travel by raising the ride height. CG rises up too which increases roll. Stiffer springs and sway bars can be used to force less roll and less compliance need. However the course surface will be the ultimate limiting factor. The surface will define how much compliance is needed (absolute requirement). Then the car needs just enough compliance to work well but provide as low and as stiff a setup as allowable to maximize grip and handling. Every track/course will have different absolutes. Sometimes stability is the difference between holding the throttle down or being forced to brake or in worst case, from losing control and crashing. |
02-14-2010, 08:30 AM | #239 | |
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Sure it does. People keep forgetting that the majority of buyers for these products are for street use yet certain people keep pushing the track issue as it if means it works on the streets.
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I've stated it myself, there are people in fast cars on crappy suspension just like there are slow cars on awesome suspension...it's only part of the total equation. |
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02-14-2010, 10:12 AM | #240 | |
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The following photos by Kyle Crawford: High dollar AMS droop (stock pickup points) My no budget droop (Element custom valving, does not add droop that I know of) I guess you could say Ryan Gates is doing it wrong, but his trophies say that he's doing enough. |
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02-14-2010, 10:51 AM | #241 |
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That car actually has a decent amount of droop for a race car, about the same as what I have with my JRZs. No amount of droop will help in that particular corner, unless you happen to come across a damper with about a foot and a half of stroke
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02-14-2010, 11:15 AM | #242 |
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no, I wasn't talking about the stunt drive, I meant for you to look at the droop while it's unsprung in the air. that would be funny having a foot and a half of droop though
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02-14-2010, 11:53 AM | #243 |
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just for fun... here is a picture of my M Roadster which is on TC Kline coilovers which use a set of custom valved d/a konis. (car has very different motion ratios, etc from my wrx)
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02-14-2010, 12:25 PM | #244 |
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Nice jack.
-Duncan |
02-14-2010, 01:11 PM | #245 | |
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2) As has been said repeatedly, you can be doing it wrong and still go fast, you'd just go faster if you were doing it right. I have to say thank you to all the clueless posters in this thread. I have a bunch of friends over last night. Most of them are recent RIT graduates from their FSAE race team. They laughed their asses off at this thread. It made a good drinking game. |
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02-14-2010, 01:19 PM | #246 | |
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So many members are now going to have nightmares of nerds laughing at a computer monitor because they don't have enough droop on their cheap coils to get the fastest lap time driving to get groceries. |
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02-14-2010, 01:25 PM | #247 |
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02-14-2010, 01:29 PM | #248 |
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That's pretty sad.
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02-14-2010, 01:45 PM | #249 | |
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I had the grammar department over to laugh at the punctuation in this thread. |
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02-14-2010, 02:30 PM | #250 | |
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I was able to buy 300 double cheeseburgers for the money I saved on my coilovers. I will get more happiness out of life from 300 cheeseburgers than I will with 1 second faster lap times because I have mad tyte droop. |
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