Krunko

thanks to whoever can answer this...

LanceS13

It lowers the center of gravity.  It reduces the torque applied to the car's longitudinal rotation allowing all four tires to do closer to the same work to keep the car planted in the corners.....anybody want to explain this better?
A side-effect of lowering springs is increased spring rate, which decreases body roll.

tnord

it increases all aspects of handling........essentially acceleration in all directions......forward (accelerating)
backward (braking) left & right

now how it does this is something that can be described in a paragraph or in a 900 page report

essentially, it's all about weight transfer.
lower/stiffer springs reduce the amount of weight (force) that is transferred (applied) towards the outside of the car

for example; lets say we are driving a car that weighs 100lbs. lets also assume that our car has lateral acceleration capabilities of 1.0g. remember that 1 g is equal to the force of gravity on the car, which is as we said, 100lbs. remember that objects in motion wish to stay in motion. even when we want to turn the car, the car still wants to go straight.  lets say we are turning the car right.  when we begin to turn the car, at say 25 mph, a force is applied to the outside of the car(for all practical purposes this force is applied perpendicular to the direction the car is traveling at the time). assume that at 25mph on this particular corner, 100lbs (1g) is applied perpendicular to our direction of travel, our maximum cornering capability.
now lets say we change our suspension (springs). with this same speed, 25mph, on this same corner, now only 80lbs of force is applied towards the outside.  because we still have 20lbs of force left, we can do one of two things, turn sharper, or speed up. assuming you're on the proper line, the best choice is to go faster.

i know this is an extremely crude explanation of what happens, and i'm sure i made some mistakes. but i think it gives a general understanding of what goes on without getting into geometry, tires, and front/back weight transfer. i just really wish i had a drawing to help with the understanding.

(Edited by tnord at 5:24 pm on Feb. 20, 2002)

LanceS13

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from tnord on 6<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'>3 pm on Feb. 20, 2002
now how it does this is something that can be described in a paragraph or in a 900 page report</td></tr></table><span id='postcolor'>
hehe...exactly
I can't really explain it w/o a drawing either.


(Edited by LanceS13 at 12:13 am on Feb. 21, 2002)

dosborn

does this guy KNOW HOW TO PARTY OR WHAT?<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/confused.gif" border="0" valign="absmiddle" alt='???'>??

Gismo R

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from tnord on 6<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'>3 pm on Feb. 20, 2002
essentially, it's all about weight transfer.
lower/stiffer springs reduce the amount of weight (force) that is transferred (applied) towards the outside of the car</td></tr></table><span id='postcolor'>
I'm not so sure that's 100% accurate. True it's all about weight transfer, but there is always the same amout of force applied to the outside of the &quot;same&quot; car taking the same turn at the same velocity with no matter what springs you have on there. The stiffer the spring means the more force it takes to compress and expand the sring(the have a higher spring constant the stiffer the spring). So there is still that same amount of force being applied but the spring is just not compressing as much as, say a stock spring would. Springs with higher spring constants (more difficult to compress) would not allow for as much roll, or weight transfer, as stock springs would. This would keep all four tires more firmly planted to the surface, therefore creating more friction points between your tires and the road. A car that has springs that are not as stiff would tend to roll while taking a shape turn at a moderate speed. This would cause the springs to compress due to the wieght transfer, and therefore would be less balanced through the turn, making the outside tires handle most of the cars wieght.
opps, what you said is correct. I read it wrong sorry.

(Edited by Gismo R at 12:28 am on Feb. 21, 2002)

tnord

you're right gismo.........i was just trying to keep it simple, even though the very nature of the topic is very complex

what i meant was the force applied to the tires, i'm no physics major or engineer, but my understanding is that with stiffer springs the springs absorb more of the burden than before, essentially transferring less force to the tires

Gismo R

Yeah I realized what you were saying whenever I got done submitting the post, (my bad). What you said is correct to my knowlege, and by the way I am studing engineering. And yeah a suspension system is very complex when you look at the physics of it. The ultimate suspension would be a system that counter acts the wieght transfer allowing for essentially no roll at all. I think I read some where that BMW or someone designed such a thing, but BMW wouldn't put it on their cars because they wanted the driver to be able to feel the handling limits of the car.

DSC

Would that just turn it into a dependant suspension again?

Jeff240sx

The lead pipe coilovers!!!
What a ride it would be...

But seriously.. no.. its not dependant suspension. &nbsp; Those #### bavarians think of everything. &nbsp;First, the electronic throttlebody, then electronic valves, and now the suspension. &nbsp;I read that it would actually lean the tires into the turn too. &nbsp;It would be a cushy ride, but the only thing that would tell you you're goin too fast is the tires screaming in agony.
-Jeff

cmathews

As far as electronic suspensions go, they are the best setup. All modern suspension designs are a comprimise. The best handling cars generally have the crappiest ride, while the ones that have the most compliant ride can't make a 90 degree turn at 5mph. Tire wear and drivability are also considerations (ie toe out can make the car turn in better, but wears out the tires quickly). The electronic suspensions were used on Formula 1 cars, although I don't remember when. The design worked beautifully. The only problem lied in tire technology. Race tires are designed to heat up due to sliding friction and other forces. The electronic suspension worked so well that the tires on a car with electronic suspension never heated up enough (slip angle was drasticly reduced). They could not get a tire company to make them custom tires, so the project was scrapped. The system was perfect other than that-- it only used a few horses to work. I have heard rumors that GT cars used them for a while. Caddilac uses a cheap one-off of this type of suspension (ride leveling). Between this and all wheel drive, you could drastically reduce tire wear and cornering ability while using very few horses to power the systems. I personally hate things like ABS and Traction control, but it is because consumers in america rarely get a system that is better than a good driver. They are better than the average american driver, but who cares about them. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'> I am a mechanical engineering student planning on going into racecar design, so this stuff interests me a lot.

If there are any minor errors, I am sorry, but this is my understanding of the whole system.

***
I did forget to mention that the system eliminates body roll completely while going smoothly over bumps of any size.

(Edited by cmathews at 10:42 am on Feb. 21, 2002)

Krunko

So theoretically my car will have better acceleration after it is lowered with a decent suspension setup?

I know that if this is true it probably isn't a big enough difference to notice...i'm assuming.

AJ

umm,, not really... (someone correct me if i'm wrong) but u will have WORSE acceleration in a dragstrip type race. &nbsp;Your car will force less weight back on the driving tires = worse traction = can't drive as hard if you have decently high hp. &nbsp;This is for rear wheel drive cars, front and all wheel will be better with stiffer springs..

tnord

but while under acceleration less weight will be transfered to the rear, keeping more force on the front of the car, allowing for better turn in

MorganS13

i've heard from some guys with supras and adjustable shocks that they get their best times and most traction by softening the rear shocks up so there's more weight transfer when drag racing. &nbsp;another plus for getting adjustables

tnord

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from MorganS13 on 1:11 pm on Feb. 21, 2002
i've heard from some guys with supras and adjustable shocks that they get their best times and most traction by softening the rear shocks up so there's more weight transfer when drag racing. another plus for getting adjustables</td></tr></table><span id='postcolor'>

yeah.......but who cares about drag racing, if you wanna run drag races, buy a stinkin camaro

MorganS13

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">yeah.......but who cares about drag racing, if you wanna run drag races, buy a stinkin camaro</td></tr></table><span id='postcolor'>

i was sayin that cause there was a question regarding how it would affect drag type races... &nbsp;adjustable shocks just give u more control so u can adjust your setup depending on what type of track u were goin to that day (drag or Auto-x). &nbsp;i didn't buy my car for drag races...

240racer

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from Gismo R on 12:24 am on Feb. 21, 2002
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from tnord on 6<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wow.gif" border="0" valign="absmiddle" alt=':0'>3 pm on Feb. 20, 2002
essentially, it's all about weight transfer.
lower/stiffer springs reduce the amount of weight (force) that is transferred (applied) towards the outside of the car</td></tr></table><span id='postcolor'>
I'm not so sure that's 100% accurate. True it's all about weight transfer, but there is always the same amout of force applied to the outside of the &quot;same&quot; car taking the same turn at the same velocity with no matter what springs you have on there. The stiffer the spring means the more force it takes to compress and expand the sring(the have a higher spring constant the stiffer the spring). So there is still that same amount of force being applied but the spring is just not compressing as much as, say a stock spring would. Springs with higher spring constants (more difficult to compress) would not allow for as much roll, or weight transfer, as stock springs would.
</td></tr></table><span id='postcolor'>

You were right on the ball before that last statement. &nbsp;The springs do not affect weight transfer, however, they do reduce body roll. &nbsp;The real reason we don't want body roll is not weight transfer, but rather camber change and transient response. &nbsp;If the camber changes with roll on either a strut or 4-bar suspension the camber always gets worse and that causes less cornering force. &nbsp;Also, the time it takes to roll the car slows its response in quick multiple corners, this would not affect anything in a long steady corner. &nbsp;So lots of body roll does not automatically mean less cornering force. &nbsp;Also, to answer the original question, lowering your cg reduces both body roll and weight transfer. &nbsp;Weight transfer however is more important then body roll to me. &nbsp;However, in some auto-x situations weight transfer is sacrificed for the quick handling of no body roll. &nbsp;Reducing body roll usually decreases ultimate cornering grip, but you have to do it somewhat for response. &nbsp;Front drive cars often lift a rear wheel, which obviously has less traction than it did when it was on the ground, but the car is faster around the course because it took less time to lift the wheel then it would have to roll the body and leave it on the ground. &nbsp;
Adam

Jeff240sx

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from AJ on 1:46 pm on Feb. 21, 2002
umm,, not really... (someone correct me if i'm wrong) but u will have WORSE acceleration in a dragstrip type race. Your car will force less weight back on the driving tires = worse traction = can't drive as hard if you have decently high hp. This is for rear wheel drive cars, front and all wheel will be better with stiffer springs..
</td></tr></table><span id='postcolor'>

Im not so sure I'm getting this right...
Having sloppy suspension... wouldn't that be like running with a backpack on? &nbsp;If it's tight, you'll still have that weight there, and can run fast. &nbsp;But then you loosen it, and the backpack wants to stay where it was, and you now have a force to move that doesn't want to, and you will ultimatly run slower... &nbsp;Does that make sense?
If not... then back to car talk.
The weight is still gonna go back to the rear wheels, but it wont seem so, because the springs are harder to compress. &nbsp;If it took 500lbs to fully bottom out the rear, &nbsp;and you transfer the 500lbs back, your suspension bottoms out and you KNOW all the weight is on the tires. &nbsp;But then you get 1000lb springs, you will only go down 1/2 suspension travel, but still have the 500lbs shifting to the rear, so it won't seem that the weight is there... but it is.
It seems that acceleration should be faster with stiff suspension to me.
But... I may be wrong.
-Jeff

DSC

wouldn't that throw out the window everything they are supposed to do for cornering then?

Gismo R

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from 240racer on 8:27 pm on Feb. 21, 2002
The springs do not affect weight transfer, however, they do reduce body roll. </td></tr></table><span id='postcolor'>
Yeah thats right. Weight transfer is caused by a centrifugal force, which is generated by the car taking the turn. The stiffer springs just simply push harder against the car wanting to roll. And I also forgot to mention the fact that they improve steering response. Thanks for the correction. But one most also take into consideration that a suspension that sits to low will fail to perform as well as it should.

LanceS13

No. (to DSC)
Listen to 240racer...however, I'm not sure I agree with the last statements in his post. (*edit: never mind, I misunderstood)
Weight transfer is good if you know how to use it to your advantage. The same force will applied to the ground regardless.
Body roll is bad....that's what stiffer springs reduce...not weight transfer. Body roll numbs the cars response in transitions. In a sence, body roll slows weight transfer. When you're turning right, you have more force on the left side tires. Then you have a transition to the left. Softer springs would absorb more of the force and cause slower weight transfer...even though the ultimate weight transfer would be the same. Stiffer springs would allow the weight to be transfered from the left side tires to the top of the left springs (quicker expansion) over to the right springs and into right tires (by less compression) faster. Allowing for quicker, more responsive handling.

(Edited by LanceS13 at 10:32 pm on Feb. 21, 2002)

Gismo R

Oh yeah, there is still the same amount of wieght being transfered to the rear tires, reguardless of what springs you have on your car. Actually stiffer springs might help drag times, but thats because wieght is being transfered more quickly. A stiffer spring wouldn't lag behind the wieght transfer as bad as soft springs would.

DSC

ok, I think I pretty much get it but if you reduce body roll wouldn't you keep the weight more even? so you take a right turn real hard and you change your L/R weight to 60/40 instead of 50/50 whereas if you had a stiffer spring it would reduce the body roll (keeping the car flatter) and make it more like 55/45. Now I know the numbers are very inacurate but its gets my question out there. Granted the latteral force would still be the same, but it seems you would keep the car more level...thus reducing the ammout of weight on the outside tires. &nbsp;or in drag, rear tires.

misnomer

DSC: No

Stiffer springs reduce body roll, this is true. They don't effect how much wieght shifts though. Basically, a stiffer spring takes more wieght to compress it, thusly lessening body roll. Same amount of wieght goes on the spring, but a stiffer spring won't compress as much.
Get it?
Got it?
Good.

LanceS13

Think in terms of &nbsp;force...not weight. &nbsp;The actual mass of the car isn't shifting, but the part of the car absorbing/transferring the most force does.

LanceS13

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote </td></tr><tr><td id="QUOTE">Quote: from Gismo R on 10:21 pm on Feb. 21, 2002
But one most also take into consideration that a suspension that sits to low will fail to perform as well as it should.
</td></tr></table><span id='postcolor'>
this is only true if suspension travel is inadequate

DSC

ahh, ok, thanks a bunch guys. &nbsp;Makes sence now...

White240sx

I'll throw what I can in here. I only browsed over the posts so don't blast me if things have already been said, or if I’m beating a dead horse.;)

Stiff springs will help your car corner better, but too stiff and when you hit some bumpy tarmac the car will shoot off into the sand. This is why sway bars are your friend. They work to increase your spring rate when you corner but they won't stiffen your car up so that it can’t absorb any bumps. Wide wheel tracks also will allow you to achieve a lot of lateral grip with out running super stiff springs as well (universal spacers are recommended for people running stockers). So running 17x7 +40 wheels isn't going to do you any good if you want optimal handling.

As far as weight transfer is concerned, that’s where height adjustable coilovers come in. People will agree that 50/50 front/rear balance is best for optimal handling, but what about left/right weight bias? This is what those HA coilovers are for (not to &quot;slam&quot; your car as pop culture would have you believe). Get a set of scales and see how weight is transferred between the left and right side. Then you do the calculations to figure the average and from that you adjust the corner weights accordingly. When you are done, the sum of the diagonal corner weights should be equal.

Lowering springs. There are drawbacks to lowering springs; they shorten your suspension travel, which can cause you to hit off the bumpstops frequently. Also some suspension geometrys drastically change as they move up and down, hence bump steer. When you lower your car you now set the &quot;ambient&quot; suspension setting with all new camber/castor/toe angles. Especially when you have a highly tuned factory set-up such as the Nissan rear multi-link. This is why there are all of those expensive adjustable suspension arms on the market, so that you can tune in desirable settings that are proportional to the changes you made with the springs and socks.

So in finality, suspension tuning is as complex as engine tuning. At first it may seem as simple as intake+exhaust=power, just like it may seem that springs+struts=formula 1 car. But the more you lean, the more you realize about the seemingly infinite amount of forces involved, and things are a million times more complex than you imagined them.

cmathews

The comments about weight transfer warrant a comment. When using stiffer springs, don't worry about the weight transfering to the outside tires-- worry about what the inside tires are doing. If the body rolls a lot, the inside tires aren't doing much, with less body roll they do a lot more. This isn't because there is less weight transfer to the outside. On a very basic level you should think of weight transfer to the outside tires as being a constant regardless of spring rates (this is not entirely accurate, but is close enough for our purposes). &nbsp;You will get the benifit of a quicker response (quicker turning response time) and greater turning force by the inside tires (greater maximum turning force).

The case of Drag racing is different because of some specialized needs and techniques that differentiate it from any other type of racing. (ie - 5 psi in the rear slicks to get the best grip) I would explain what those things are but 1) I don't drag race and 2) I don't remember what they are and why.