Something I never thought to ask regarding handling

Somewhat... I do recall that my dad's old IH Scout II (100" wheelbase) was not particularly stable at high (relative, it wouldn't actually go that fast) speeds, but that's an extreme example. Probably the sloppy steering box/linkage and fast steering ratio didn't help.

nate

It certainly increases the polar moment of inertia. That increases stability at the expense of maneuverability.

At the risk of being a pedant, I know what you're trying to say, but disagree with your terminology. The polar moment of inertia is determined solely by the way the mass of the vehicle is distributed relative to the center of mass. If you take two otherwise identical vehicles and lengthen or shorten the wheelbase of one, what that will do is increase or decrease the torque developed around the center of mass by a similar side (slip) force on the tires. The polar moment of inertia will remain basically unchanged, save for that caused by physically moving the suspension components.

nate

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Hmm. I think the ratio of wheelbase:average-track also figures into the equation. That is, how much longer the wheelbase is relative to track.

My wife finds my '08 Optima to be a one-hand, 70mph, stable, secure driving experience compared to the '05 Malibu sedan I turned in in December. That car was a white-nuckle experience for her - both hands firmly gripping the wheel and barely exceeding 60(!). And that's with less than 40,000 miles and alignment done at the beginning of '08.

2006.5 > 08 Kia Optima: Wheelbase: 107.1" Avg Track: 61.5 wb:t ratio: 1.75:1 F/R weight: 61/39%

2004 > 07 Chevy Malibu(LS Sedan): Wheelbase: 106.3" Avg Track: 59.7" wb:t ratio: 1.78:1 F/R weight: 59/41%

By all measures, the MALIBU should out-handle the Kia! It's wheelbase was longer relative to average track(that is, less "square"), and the front-rear weight distrib was slightly more equitable(as equitable as you could get in front-wheel drive cars). R&T even pissed on the Kia's handling:

- which really makes me wonder what THEY consider good handling. But no - my wife and I feel far more secure driving the Optima - slightly tighter steering center, less wander, more solid fit & finish.

Heh. I rented a 2005 Malibu a few years ago for a trip to Florida. Had the same experience as your wife, and after about 100 miles I was

*really* thinking about turning around and taking it back. Instead I bought a tire gauge and found the left front has 10psi. Couldn't tell by looking at the low-profile tires. After putting 30 all around it was a one finger drive the rest of the trip, and the finger hardly got any work. It was odd in that it didn't just pull to the left as you would expect, but was all over the road. Might be the steering geometry is just real sensitive to tire inputs.

--Vic

_______________ If you are trying to imply that my tire pressures may have been off/ unequal, stand corrected: I check the pressures in mine and my wife's car on a WEEKLY basis - forget about monthly(!), and I keep both set

2psi above Kia and Toyota specs due to the excessive shoulder wear I've noticed at exactly spec(30psi on both cars, and on the old Malibu mind you). 32psi does the trick - a slightly firmer ride, yet still smooth and tight on the steering. I don't think the HumVees in Iraq have their tires pressures checked THAT frequently. ;)

As far as pulling to the left, the last car I drove that *didn't* pull to the left was my good ole 1981 Buick Century. My '96 Contour, '03 Impala, and '05 Malibu all pulled left within a few seconds of loosening my grip on the steeringwheel. The Kia pulls to the right, but only after letting go of the steering wheel for at least 10sec - that's spot on in my book!

-CC

Yes, the longer the wheelbase the more stable the vehicle with regards to handling. Center of gravity also has a HUGE affect on stability. Both make the amount of leverage required for the vehicle to de-stabilize rise. Want an easy experiment? Take a brick and a granite tile and 4 marbles. Now take the brick and stand it on end and cluster the marbles in a square under the end so they hold the weight. You now have a "vehicle" with a very high COG. Note that it is easy to tip it in any direction. Take the same brick and lay it down with the marbles at each corner, That gives you a "vehicle" with a lower COG and more wheelbase. Notice it is much harder to tip? Switch to the granite tile and place the marbles at the corners, place the brick in the middle. Now you have a VERY stable "vehicle"

It all is simple physics. In an auto you can find the same methods used easily. Take a look at a Jeep CJ with 6" suspension lift and 4" body lift (very common for rock crawlers and mudders) Take off those large HEAVY tires you normally see and install stock rubber, care to guess how fast you could turn a corner? For the opposite end look at a Saleen S7, LOW ground clearance, WIDE sticky tires, seating and drive line all mounted very low. Capable of over 1.1G on a skid pad an a slalom course at 70+ mph!!!

The Jeep has a short wheelbase with high COG, The Saleen has a long wheelbase with a low COG.

Want a larger extreme, take a look at a HEMMT, 33 feet long 8 wheel drive less than 8 feet tall and able to handle driving angles that make you want to climb out the doors on the uphill side!!!

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No offense taken. It's just that others have "implied" that something I am doing is wrong by inferring with their own experiences. As far as the alignment shop goes, it is a local one. I do not use Town Fair or Sears or any other national business because of an experience I had in one of those places. I told them that the steering on one of those cars I mentioned - since out of memory - was loosy-goosey with poor return, and all they did was bump the tire pressure up from factory (30) to the max listed on the tire(35psi). Sure, that tightened up the steering, but it felt like I was driving a BASKETBALL!

lol...Since then I've been going to the aforementioned alignment shop. Of course, their alignment machine computer says "Set at factory - non- adj." for any vehicle made since 1990 when it comes to Caster or Camber, and they also suggest taking it to a body shop for bent parts. When I ask them how a vehicle's alignment could possibly be in spec even with bent parts, all they can do is shrug and give me that "I'dun'know" smile. Other than the pulling to the left, their alignments produce a smooth, low rolling resistance ride. They've cut as much as 2-4$ off my weekly gas fill-ups.

-CC

I implied nothing. But you can infer what you want. Just stated the facts of my experience. I'll add the car had 5000 miles, and I put about 3000 more on it. Had the 4-cyl Ecotec. Drove perfectly fine once I had 30 psi in the left front. White-knuckle with 10 psi in the left front. Wandered all over, needing constant correction. While I'm here I'll also add that out of curiosity I looked and the Malibu has no serious knocks on handling. So if you think it's normal for it being a "white-knuckle" experience driving one at highway speed, you're wrong. You might want to look for a different alignment shop.

--Vic

I think Nate's technically right, but since wheelbase and overall vehicle length tend to go together, Don's observation is generally true. A LONG vehicle has a high moment of inertia regardless of its wheelbase. If you hung a long vehicle on a little-bitty wheelbase, it would still be a little more stable (directionally) than putting the same weight in between the wheels. But it wouldn't handle for suck. ;-) Taking the long vehicle and pushing the wheels out to the corners retains the stability, AND makes it handle a little better. But truth be told, its almost a second-order effect until you get into aggressive handling. A long vehicle and a short vehicle can both be made to feel stable and handle acceptably in daily driving. If the Malibu was that unstable, it was because something was wrong or it was just a bad design. Having driven a few Malibu rentals myself, I can't say I ever noticed anything like that- I found them very pleasing (if boring) cars. The only "white knuckle" rental I've had recently was a 40,000 mile Honda Accord. I expect to see more beaters like that in the future as rental car companies hold onto their fleets longer and longer :-/