CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS
Non-Audio Stuff => Car Talk => Topic started by: ROK on August 13, 2013, 02:04:09 PM
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Opinions?
I want to get some Eibach springs but my friends (who also happen to get air bags in their cars and drop them to an inch off the ground) keep telling me to get coils since I'd want to lower it more than what springs can do for me...
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Umm...well, if u want to lower the car more than springs can do.....what was the question again?
What are you trying to do? Drop (how much?), go faster, reduce roll, increase compliance or stiffness? More information needed...
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Umm...well, if u want to lower the car more than springs can do.....what was the question again?
What are you trying to do? Drop (how much?), go faster, reduce roll, increase compliance or stiffness? More information needed...
I just want to get rid of that terrible wheel gap in my car without rubbing. However, I feel that my car could use some stiffening up and reduce that body roll ugh.
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The question whether to lower the suspension in a car is primarily the issue...
Most people do this for aesthetic reasons, not understanding that the geometry of the suspension is thus altered... furthermore the use of spacers to get the wheels "looking better", or to use wider tires and rims than the manufacturer recommended.
In my opinion lowering the vehicle with lowering springs (retaining the original shock absorbers) is completely wrong and in some cases may prove even dangerous... the reason being that the stock shock absorber might not work properly if it is somewhat compressed, because the remaining length might not have enough bump/rebound and even might bottom out.
Coilovers are better in this respect, because they take into consideration the lowering and pre tension of the coil, at same time bump and rebound adjustments make it easier to match with the weight and type of roads you are going to use the vehicle, plus the variety of spring tensions might make it compatible with your vehicle.
There is a very good reason for a manufacturer to choose the height of the suspension, spring tension, and bump/rebound... this is because road vehicles are supposed to drive on roads, and roads have a variety of surface and quality of tarmac... furthermore there must be a level of comfort.
Track day cars, will usually be driven only on track, and they can be lowered quite a bit, and the srping tensions can be very high... such a vehicle although very competent and safe on the track, it is by no means safe on the road, because the road has a vastly greater variability in quality, ie bumps, potholes, unevenness etc...
I went into these variables very briefly,... my general recommendation to you is firstly,...to leave the car alone and don't mess with it..., secondly if you do want to mess with it, make sure you have a good understanding of what i explained to you above and then get yourself coilovers from a REPUTABLE brand (stay away from cheap Chinese brands), that most users of your vehicle seem to like and have come to an agreement what adjustments should be made...
When you have have installed them, take your time to relearn your car, preferably in a safe environment such as a race track (not the oval type)... make notes of what you like and dislike, and then proceed into final adjustments...
On the matter of body roll... it is inherent in the car's design (suspension geometry)... reducing body roll, would not make your car have better grip, nor will it make your car more agile... it will only affect how you feel about the car under these conditions, and in many cases it might make you feel more confident than you should... your car would be less gradual and more sudden...
Sport cars are designed from the beginning to have the suspension characteristics they have, one cannot transform a day to day saloon car into a sport car...
Hope you found these few points helpful, and good luck with your lowering project!! p;)
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Agree wholeheartedly will all points above though there are a few exceptions:
1-The effect of lowering springs is relative to each cars particular design, so some will handle it better than others. A FRS will handle a one inch drop a lot better than a 90's Nissan Sentra which is one of the worst designed suspensions in automotive history and pretty much an accident waiting to happen w/ lowering springs.
2-There are ways to offset the effect via roll-center adjusters which correct back toward a stock geometry. There are also particular tophats that can be used to allow for lowering springs but retain or improve the compression range of the dampers despite using shorter springs. This all equals money.
3-Before picking wheels/tires, figure out the spring coilover question first as you'll have to account for clearance issues relative to the new suspension components.
4-I'm going to have to disagree a bit on the body roll issue. Lateral inertia definitely affects grip and cornering. Most drivers will never realize this in actuality because you need the speed, environment and ballz to do so w/o killing anyone, namely yourself. That said, physics does apply side to side independent of what's going on front to rear. Two examples. One, a lifted truck is easy to experience the ill effects of body roll on grip, four tires on the road are better than two. Reduced roll height is an easy way to manage leverage and torque upon the top of a vehicle by lowering the CoG. It shifts the mass lower, the leverage is reduced. Two, Porsche active engine mounts. That's a lot of money and technology to actively compensate for the inertial effects upon the engine when cornering if grip is not impacted. Reducing center of gravity is a very real handling benefit, just as real as stiffening front springs to prevent nose dive during braking. An inverted pendulum is a bad sports car. So the question is, can do this safely w/o making your car actually drive worse. Yes you can.
All cars are a compromise of sorts, nothing wrong w/ an owner shifting the balance to be more in tune w/ their preferences if they know what they are doing. It is even possible to improve dynamics and comfort/compliance if you have the specific know how and wallet required. Granted these are rarely the cases.
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I have to kindly insist on point 4, that the lateral inertia of the car going through a sharp corner, is identical whatever the suspension height, or the body roll... grip has to do with the ability of the tires to remain in contact with the tarmac, and assuming the inertia is the same (speed times mass)... the car that maintains the maximum tire to tarmac contact is the car with the better grip...
In lowered (only with lowering springs) cars shocks do not work optimum, their bump/rebound characteristics are altered for the worse... which in fact a lowered car might have LESS grip in a corner... because the (now compressed) shock absorber might not be able to apply the same pressure on the wheel/tire..
Same applies to severe braking, you may have a more sudden dip (although shallower) because of diminished bump, of front shocks, and you may also experience tail lightness because of diminished rebound on rear wheels...
The body roll is a parameter that is inherent and i would also say desirable in a street car, (except for comfort) to make the driver (everyday driver) aware of the increased speed or bend sharpness...
I have managed only very slight better lap times in similar cars with only differences the suspension height, (with the same shock absorbers), and that was only because of a little more confidence provided from the lowered car, and not in actuality of better grip...
I have very little knowledge of American cars, but surely the same applies to all manufacturers,... that, considerable thought is put into the suspension designs because normal people are going to drive them, and not only race drivers.
On the other hand if you are going to drive within the legal speed limits and carefully... you may may go lower only with springs...
The best though is to go coilovers.
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I have to kindly insist on point 4, that the lateral inertia of the car going through a sharp corner, is identical whatever the suspension height, or the body roll... grip has to do with the ability of the tires to remain in contact with the tarmac, and assuming the inertia is the same (speed times mass)... the car that maintains the maximum tire to tarmac contact is the car with the better grip...
Only to a point, and that's the point. At some point, relative to height and speed, inertial mass at the top will impact the grip/deflection of the tires contact patch which will be relative to the suspension geometry in question. Where the car comes from doesn't matter, what it's suspension looks like does. Obviously a proper SLA setup will compensate better than a poorly designed Mac strut. Speed is also impacted wrt higher CoG in both transition speed and drag. A lower car reacts quicker and occupies less overall area. Your point is valid to a point, it not a universal principle at all to say ride height doesn't matter. It's simple physics that a car's height increases side load on a turn the higher it sits. This is easy to test by measuring lateral G test on a SUV w/ sport and raised suspensions on the same car. Really, you only need to look at a simple arithmetic equation wrt polar moment of inertia. It's the same principle you'd use to figure out how much mass you are moving at the same rotational speed as you plus size a rim. The math is the math, we aren't dealing with electrons in the quantum verse here.
Effects of a lever/mechanical advantage:
https://www.google.com/search?q=lever+mechanical+advantage&client=firefox-a&hs=cuM&rls=org.mozilla:en-US:official&tbm=isch&tbo=u&source=univ&sa=X&ei=bwYNUrD7IuKbygHP0YGYDA&ved=0CDgQsAQ&biw=1920&bih=1015 (https://www.google.com/search?q=lever+mechanical+advantage&client=firefox-a&hs=cuM&rls=org.mozilla:en-US:official&tbm=isch&tbo=u&source=univ&sa=X&ei=bwYNUrD7IuKbygHP0YGYDA&ved=0CDgQsAQ&biw=1920&bih=1015)
I appreciate your point though but it is simply because your tires and suspension are good enough to compensate for the speed you are willing to push. At some point/speed, an added inch or two of ride height will cost you time and grip. That's just a physical law whether or not any particular car or driver actually realizes this point in person is somewhat irrelevant to the fact. Somewhat, because you can say 95% of typical drivers will never see this point in their lifetime.
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Having frequented tracks, and owning a track day car, i must insist on my points because i have explained adequately, that i am speaking about the SAME car with STOCK shocks (and of course the same size rims and type of tyres)... the lowered car MIGHT handle WORSE...
I think this is simple enough...
Now on the other points you make about suspension geometry might be valid, but the inherent geometry of cars designed to be street cars, can only be MINIMALLY altered (talking about height)... and is not measured in many inches... only a few,... if only one or two maximum, and ALWAYS in conjuction with the appropriate coils and shock absorbers that will handle the altered height.
In any event i hope people that read this and want to "pimp their rides" do so carefully...
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Wow! I'm glad this thread is going well and is actually has proper information. Good information for the OP Anaxilus and Chris1967.
If the OP just wants aesthetics there is always the factory route. I assume a BMW of some sort suggested by his avatar. I'm pretty sure there is a sport, zhp, M (or whatever they call it now) version of pretty much every BMW which usually includes proper suspension changes.
That usually costs a pretty penny and a nice set of eibach or h&r's with a fresh set of bilsteins could do the trick.
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Having frequented tracks, and owning a track day car, i must insist on my points because i have explained adequately, that i am speaking about the SAME car with STOCK shocks (and of course the same size rims and type of tyres)... the lowered car MIGHT handle WORSE...
I think this is simple enough...
Now on the other points you make about suspension geometry might be valid, but the inherent geometry of cars designed to be street cars, can only be MINIMALLY altered (talking about height)... and is not measured in many inches... only a few,... if only one or two maximum, and ALWAYS in conjuction with the appropriate coils and shock absorbers that will handle the altered height.
In any event i hope people that read this and want to "pimp their rides" do so carefully...
What's a street car? A Camry, Corvette or Porsche Boxster?? The last two come with variants w/ 1-1.5" drops from the factory using the same suspension geometry. Others like TRD will sell lowering springs w/ full factory warranty and support. W/ proper adjustability in the suspension in question, proper alignment can be preserved after modding. Even then, aftermarket lower control arms, and camberplates/tophats can deal w/ any issues. Roll-center adjusters fix raised roll centers from lowered suspensions, proper coilover design and top hats also compensate for preserving rebound and compression stroke is designed right.
So if you know what you are doing, you CAN lower a car and improve performance. Manufacturers and race teams do this, it's not snake oil but like everything is relative.
But yes, done wrong, most people w/ incomplete knowledge can/will make their car handle worse, slower, more dangerously. Done right however, you can improve speed, feel and even ride comfort at the same time. My friends track Integra rides like it's on rails around corners but feels better than most Cadillacs just cruising on the street. That car is so dialed in it's ridiculous.
Might want to look at what 'M' sport options are available for your car. You don't have to buy a complete M to get the M suspension package.
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A street car is a car that is designed to tackle with SAFETY,ALL sorts of surfaces, including mild gravel, and bumpy roads, and all this with some kind of comfort.
Maybe where you live my friend, all roads are flat, with good maintained tarmac, with proper angles in the turns, etc...
Where i live, this is not the case... pot holes, saddle bumps, eroded tarmac... etc...
In your arguments you are using the term "lowering" without taking into consideration that in order to do so the absorbers AND coils have to be matched to maintain drive-ability (and safety)... but the lower you go the smoother the road should be in order for the suspension to work, and vice versa... rally cars have tall suspensions...yet their ability to corner (in the roads they are driven) is far superior than an equivalent "lowered" versions.
Yes Porsche Boxster does have a lowered version but this is with different shock/coil combination for one, and i seriously doubt it can will corner better in the roads i drive in, than lets say a Mitsubishi EVO X (which is a superb driving machine)... in a track though (smooth surfaces) the Boxster will be quicker.
When i use the term geometry it is conjunction with the real world, and this is why it was designed, to be safe and effective in various conditions...that is why the height is important to be maintained...
So all things should be in perspective, to the road surface the vehicle is going to be driven on, they cannot be viewed as separate values.
It is not rocket science to lower a car a agree with you... but in my opinion all these thing we are discussing should be taken into consideration.
For BMW... cheap solution Eibach/Bilstein, better solution Bilstein PSS9, or KW Variant3... check these out before looking into any "M" solutions
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A street car is a car that is designed to tackle with SAFETY,ALL sorts of surfaces, including mild gravel, and bumpy roads, and all this with some kind of comfort.
Maybe where you live my friend, all roads are flat, with good maintained tarmac, with proper angles in the turns, etc...
Where i live, this is not the case... pot holes, saddle bumps, eroded tarmac... etc...
In your arguments you are using the term "lowering" without taking into consideration that in order to do so the absorbers AND coils have to be matched to maintain drive-ability (and safety)... but the lower you go the smoother the road should be in order for the suspension to work, and vice versa... rally cars have tall suspensions...yet their ability to corner (in the roads they are driven) is far superior than an equivalent "lowered" versions.
Yes Porsche Boxster does have a lowered version but this is with different shock/coil combination for one, and i seriously doubt it can will corner better in the roads i drive in, than lets say a Mitsubishi EVO X (which is a superb driving machine)... in a track though (smooth surfaces) the Boxster will be quicker.
When i use the term geometry it is conjunction with the real world, and this is why it was designed, to be safe and effective in various conditions...that is why the height is important to be maintained...
So all things should be in perspective, to the road surface the vehicle is going to be driven on, they cannot be viewed as separate values.
It is not rocket science to lower a car a agree with you... but in my opinion all these thing we are discussing should be taken into consideration.
For BMW... cheap solution Eibach/Bilstein, better solution Bilstein PSS9, or KW Variant3... check these out before looking into any "M" solutions
LOL! You have never driven on the 5 freeway in southern California apparently. The US has the worst roads in the world apart from a third world banana republic, maybe a 500 mile stretch of road through the plains of Kansas would be smooth, not California. I've removed chunks of asphalt from the road under hard braking the asphalt is so cheap and crap here.
You are really confusing a lot of issues here and unnecessarily. Again, you are oversimplifying and simply not accounting for real world examples.
1-No I'm not discounting anything, neither are the spring makers. Aftermarket springs are generally equal to or higher rate than stock. OE dampers tend to be softer, you are not going to get into trouble because of stock damper rates buying a proper Eibach, TRD, Swift or HR lowering spring kit and, this is simply not true and doesn't make any sense. Not to mention they have already calculated the acceptable range of spring rates for the dampers in question, it's not some backyard hick w/ a Still throwing darts at a bunch of numbers and using a blow torch to cut down some springs. Stock valving in the dampers can accomodate a wider range that you think and most are dual tube, not monotube. Look at the FRZ/BRZ. Dramatically different rates but same damper rates from the factory. Ideally you would change spring rates for each track.
2-No, just no....a lowered rally car on a track would be faster than a tall rally car. They are only taller because they need clearance driving over dirt roads in Cyprus. That ride height also changes based on the circuits conditions, it is not static. They use coilovers, not factory settings. They also use skinny tires in bad weather. Are you going to suggest we all put 150 section width on our wheels w/ metal studs to go faster around a track? Come on.
3-You keep assuming a lowered car can not retain or improve on suspension travel or ride comfort. While generally true based on half assed planning and hacks, this is not absolutely true, not at all. Pretty much every stock suspension can be improved if done right. They pretty much come flawed from the factory simply because they picking the cheapest compromise the bean counters/accountants will allow. There are so many compromises they have to make in selecting damper and spring rates like allowing for various tire compounds across the country and various wheel/tire size packages as options. Factory settings have a huge envelope to play around with. This is far from ideal in either speed or comfort.
4-I find it ironic that we recommended various coilovers and kits to begin with and you were against the idea. But not you recommend going w/ those same aftermarket solutions over solutions provided by 'M' the same people that actually make the car and designed it to be used in what you call 'real world' conditions. I'm not sure I follow your logic. By your train of thinking I'd think M offered the best solution because BMW actually built the car, considered all the variables, offer the suspension on their factory cars (M3/5. etc) and support it w/ a warranty and liability falls on them if they install it.
I think I'll just leave it here as comparing a Boxster and Evo is hinting at going down a road not worth traveling. I appreciate that you track your car, so do I and many others that use coilovers on the street. Including manufacturers. Tracking your car is helpful but not a validation to be a the last authority on anything. Whether you think my degree in automotive technology, ASE certification and specialization in engine and chassis management mean anything is up to you. It shouldn't need an appeal to authority because everything I said is mathematically and physically sound and has been repeatedly proven. You made a decent point in relative terms to ride height under certain 'typical' conditions but have really taken what should have been a clear simple post and gone way too far w/ it IMO trying to mak it into some absolute rule, "Never lower a street car at all."
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OP probably won't push it hard enough to even notice. It sounds to me like OP is after looks. Pimp it out like a ghetto car! I would think twice about a drop over 1" though.
OP, coilovers are nice, but only useful if you race. Lots of folks do coilovers, for looks. It's a waste of money and time adjusting it, and tweaking it with no methodology (like ghetto cars). I'd just do a minor drop. Eibach Pro-Kit should be fine, in general.
Cutting through the fluff, see what kits are available from reputable dealers/manufacturers if you want more. Just changing the spring is generally bad if you slam it. See what Dinan has to offer, or the M suspension for your car. There's a balance between all components. Over compensating on one will leave an issue with other parts.
Also, if you're pushing it hard enough to feel the limits of your BMW (if I assume M3), on the street, then you've got a death wish.
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I am really taken back by your reply... i find it a little too aggressive...
I didn't mean to sound like an authority, and i am sorry if it sounded to you like that... i have had many fast cars with many many different suspension combinations... and have had done a few track schools... that's all... i don't design cars like you (i am a specialist dentist... nothing to do with cars i am afraid)...
I spoke in general fashion, from my not so small experience... and not trying to be a know it all...
I am sorry if i offended you or the forum...
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I am really taken back by your reply... i find it a little too aggressive...
I didn't mean to sound like an authority, and i am sorry if it sounded to you like that... i have had many fast cars with many many different suspension combinations... and have had done a few track schools... that's all... i don't design cars like you (i am a specialist dentist... nothing to do with cars i am afraid)...
I spoke in general fashion, from my not so small experience... and not trying to be a know it all...
I am sorry if i offended you or the forum...
Not at all. Sorry if it came off like that. I just didn't know where you were going and the argument started getting circular which tends to get under under my skin a bit. No need to apologize or take anything the wrong way. People tend to speak in generalities but express them as absolutes grammatically which is a bit of my philosophy background reading into things too specifically, like a computer. Par for the course trying to communicate on the Internet. Don't worry, we are all pirates here. :)p5 You get karma points for speaking your mind. :)p1
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Opinions?
I want to get some Eibach springs but my friends (who also happen to get air bags in their cars and drop them to an inch off the ground) keep telling me to get coils since I'd want to lower it more than what springs can do for me...
Getting back to your question (and away from the physics/law of inertia/etc), I'd suggest the Bilsteins PSS10 coilovers... if you're the kind that switches wheels every so often to achieve a different look, keep your ride "hellaflush", you'd want some adjustability in both height and comfort. The PSS10s can take a beating and built a lot better than cheaper suspension brands. And when you dial in the height just right, it really looks nice, especially on an E46 M3 (had a friend with this setup and he went up and down the state getting Eurotuner coverage). You owe it to your Bimmer than just Eibachs! :&
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I am really taken back by your reply... i find it a little too aggressive...
I didn't mean to sound like an authority, and i am sorry if it sounded to you like that... i have had many fast cars with many many different suspension combinations... and have had done a few track schools... that's all... i don't design cars like you (i am a specialist dentist... nothing to do with cars i am afraid)...
I spoke in general fashion, from my not so small experience... and not trying to be a know it all...
I am sorry if i offended you or the forum...
Not at all. Sorry if it came off like that. I just didn't know where you were going and the argument started getting circular which tends to get under under my skin a bit. No need to apologize or take anything the wrong way. People tend to speak in generalities but express them as absolutes grammatically which is a bit of my philosophy background reading into things too specifically, like a computer. Par for the course trying to communicate on the Internet. Don't worry, we are all pirates here. :)p5 You get karma points for speaking your mind. :)p1
Thanks Analixus, no problem!! :)p1
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Wow, just remembered this thread, came into it and was kind of shocked. So much information to absorb...
Thanks you guys, I'll be looking into it more and if I need help, I'll be back. :)p5