I'm just now learning about "the way cars work". Something's been erking my curiousity. I keep hearing the term "4 wheel independent suspension"...

What's that mean and why is it so good/bad?

------------------
-matthew "Whyt Nyte" d.
84 SE
"You are not special.
You are not a beatiful and unique snowflake.
You are the same decaying organic matter as everyone else."

It means each wheel moves up & down independently of each other. Most cars have independent front suspensions, but not the rear. A good example would be most muscle cars (Camaros, Mustangs, etc.). Most have a live rear axle (except some newer models). Picture a car taking a very sharp corner, like in an SCCA type of event......a car with 4 wheel independent suspension will fare a little better.....those without independent rear will have the outside rear wheel lifted off the ground in a tight corner, whereas the 4 wheel independent car will keep all 4 wheels on the ground.
Basicaly, having 4 wheel independent suspension is a good thing!

I hope this helps......this isn't my best area of expertise.

Basically what Mrfiero said is true, to some exceptions.

The rear inside wheel on either system (more specifically on independant systems, believe it or not) is the one that's likely to come off of the ground, because it is independant. with a solid rear axle that rear wheel basically can't come unplanted, because the other side is keeping it from doing so. This never to say it can't be done, just that it's kind of rare to see it. If you've ever watched Touring car racing, or even Celebrity Celica/Neon challenges, those cars always have their rear inside wheel hiked up off of the ground because they're so stiff with their independant setups.

Independant is better for the reason that mrfiero described. Each wheel, moving independantly, is left undisturbed. With a live rear axle, whatever the left wheel feels will get transmitted over to the right wheel. So, if you hit a patch of potholes, with some on the right and most on the left, the suspension will be somewhat skatey due to the fact that the rear wheels aren't able to move independantly and cope with each pothole on an individual basis. Instead, they both have to feel the shock and this translates to the right wheel being jostled around by the left wheel's movement, and hence allows the back end to get squirly due to loss of traction on both wheels.

Hope you guys got all that. if someone knows I'm wrong somewhere please feel free to correct me.

------------------
1987 Toyota MR2 N/A 5 speed
http://www.atlantamr2s.com
http://www.geocities.com/darionscard

Notable mods: Sus tech springs and sway bars, Toyota strut tower brace, KYB strut inserts, HKS exhaust, NGK plugs/wires, Momo Racer wheels (14x6), Custom intake, Kenwood 12" speaker in front trunk, Jensen amp.

I'm confused now. How can the inside wheel lift in a hard turn? Assume that a Neon takes a hard left turn.....the right rear would be the one to lift (the outside in reference to the direction of the turn).

In this same hard left turn, more weight is transferred to the left wheels than the right. This forces the left wheels down and the right up. The right rear wheel from a car with a live rear axle will actually lift off the ground the same distance that the left rear gets pushed down, or compressed.

Imagine a live rear axle as a "teeter-totter".....when one side is down the other is up. An independent rear can still experience lifting, but generally all 4 wheels stay in contact with the road.

Is this right or do I have my wires crossed?

Got your wires crossed, man.

In a hard left turn, most of the weight of the car will be transferred to the right(outside) side, which is why the body will roll to the right. The lack of weight on the left(inside) side of the car means that side is more likely to lift. The inside rear is the one that usually does, because there is also weight transfer towards the front when you're slowing down from the turn.

Look at the driver side rear wheel of this car:

Don't quote me on this, but I think I live rear axle design is less likely to lift wheels off the ground, due to them being connected.. I know it's a better design for a drag car. Less issues with wheel hop and things like that.

The ratio of the sprung weight to the unsprung weight of any vehicle affects the ride and performance of the suspension. The sprung weight is all the weight of the parts that move, the unsprung weight is the weight of the rest of the vehicle. One advantage of 4-wheel independent suspension is the sprung weight is much less, this alone improves the ride and performance.

Oh, good -- an opportunity to pontificate!

Why do cars have suspension? That is, why aren't wheels attached directly to the body like a farm cart?

Many reasons, including:

• To isolate passengers and cargo from bumps
  
• To keep wheels in contact with pavement
  

Generally, independent suspension does this better than solid-axle suspension.

Picture a pair of wheels connected by an axle, like the rear wheels of a Camaro, pickup truck, or almost all older American cars: |--O--|. When one wheel rides over a bump, the entire axle tilts, changing the angle of the other wheel with respect to the pavement. Usually this is bad thing, particularly when it causes the other wheel to un-stick in the middle of a hard corner.

Also, a solid axle assembly often is heavier than independent suspension, which is bad for the ratio of sprung-to-unsprung weight, as noted above. And indpendent suspension allows placement of an engine between the wheels instead of above the axle, which gives the car a lower center of mass.

On the bad side, independent suspension is more complex and expensive than a solid axle.

I hope this helps . . .

[This message has been edited by MrPBody (edited 12-03-2000).]

also I don't *think* or have never heard of being able to adjust camber on the solid axle type setup. With independant suspension setups you're allowed a greater range of tuning options like camber and toe.

Thanks......it was REALLY late when I wrote that and couldn't think clearly.

That's what I get for staying up so late!

Camber and caster on the rear of my Ciera GT (solid axle), it adjusted with wedged-shaped slims between the bearing and mounting plate. Alignment shops hate having to do it, but when they quote "four wheel alignment", they better get the shims out (not that it moves again once the alignment is done).

Watch "My Cousin Vinny" for more information on this topic.

------------------
85 SE 2M6

LMAO

Actually, A solid state axle is better for a flat corner (in theory) than independent suspension, because the body is free to roll while the axle stays put. However, independent suspension is better in real life because there is no such thing as a 'flat' corner, they all have some bumps. On a solid axle, the bumps affect both wheels while on independent suspension they only affect the wheel hitting the bumps. Thus, indie. susp. helps the wheels stay down in relation to bumps in the road. One advantage that a solid axle has is the lack of bump steer (although a well designed indie system shouldn't have any either..)

Just in case anyone has the wrong idea about this I wanted to expound on the 4-wheel independant suspension's tendancy to lift the inside rear tire.

IF you're nuts enough to go around a corner this fast (racing is ok... city streets, well I hope you can afford the ticket/body shop) you'll find that indeed you can lift the inside rear tire if your shocks and springs are stiff enough.

Sounds bad in comparison to a solid rear axle that will 'see-saw' and keep the inside tire down, right? Wrong.

As the outside suspension compresses, the inside suspension decompresses, allowing the inside tire to drop down. In a solid rear axle car, the force applied to the outside tire translates across the axle and actually forces the inside wheel down farther. This makes up the difference where the independant suspension can lift off the street. However, while the solid axle car keeps it's tire down, there isn't enough weight on that wheel to allow it to apply any useable traction.

In other words, when you see a car on TV going around the corner with it's rear tire in the air, it's pretty much using the three tires it can get traction from, and the fourth tire (the one in the air) wouldn't provide enough traction for the pit crew to worry about trying to keep it down on the ground.

If you put a big enough anti-sway bar on the back, you'd never lift the inside rear tire regardless of what kind of supsension you had. But if you did that, your car would oversteer dangerously in high-speed corners.

(If your car can't "sit down hard" on the outside rear wheel, the centrifugal force would become more lateral, and chances are your tires wouldn't be able to grip, causing the back end to fishtail out, thus oversteer.)

So lifting that tire isn't a bad thing unless you're doing it in front of the local PD. (Unfortunately, it does make your car look like it's looking for a fire hydrant to pee on.)

Just be thankful that Fiero's have so much weight in the back end to help keep those tires down, saving us from that silly 'rear leg up' look.