Physics Behind Short Wheelbase

[jefferios]

I'm looking for someone who can help explain to me why having a short wheelbase makes the ride more bumpy. Regarding the smart, I think the ride is fine, but I just am seeking knowledge on why this occurs.

I looked at some science behind the wheelbase in general, and equations on how and where weight will transfer too, but it said nothing about the ride quality.

Here are two equations I found relating to the front and rear tires:



Those equations only discuss weight...

Feel free to be technical if it helps!

[BigWarpGuy]

Perhaps since the vehicle is -relatively - light weight that it reacts more to bumps in the road than does a heavier car?

[smartHHO]

I am thinking weight has some part to it, but it also is the suspension. Look at a Cadillac, how soft the suspension is, but yet it is a smooth ride. Or a Lexus, the ride is very nice. The smart does not have some high end suspension system, if it did, then the car would start getting into the very high price range. The Smart is what it is, Cheap, economical gas saving machine. Nothing more nothing less. Fun to drive, and you can drive a lot on less money.

[KillerBee]

An interesting query my friend. I am not a scientist but I will offer my opinion.

Perhaps some of the reason is because of the stubby front end. Relatively speaking the front wheels of a Smart are close to the driver. As soon as you hit a bump (or pothole) that force is felt almost immediately as upward (or downward) motion. As soon as you recover from that, the rear wheels encounter the same obstacle and the process repeats. When you add in multiple obstacles, the feelings are multiplied. Because this happens so quickly, it all feels very bumpy (or choppy as I like to call it).
For comparison, think of a limo with a very long wheelbase and the relative distance between the driver and each axle. The car would "float" over the same obstacles easier. Think of big 1960's Buicks, Lincolns etc that were referred to as "Land-Yachts".
Another way to look at it would be to think of a teeter-totter. The driver is at the fulcrum point. A Smart would be a very short teeter-totter and a limo would be twice as long (or longer). Imagine the difference when you raised the shorter TT to 2' off the ground from one end to the other repeatedly vs. rocking the longer one 2' off the ground back and forth. The shorter one would seem bumpier.

Suspension and weight can be mostly (but not entirely) ruled out. Cars are designed taking all of that into consideration, larger cars having stiffer, yet more plush suspension. That being said, the Smart is an economy car and may have a suspension setup that is designed for neither luxury or performance.

Tires must be viewed as part of the equation. The Smart uses a low profile tire. This means there isn't much sidewall (read air volume) between the wheel and the road. This can contribute to a harsh, jolting ride.

Pete

[sberger]

After a ton of research, here is the formula:

Pothole > Wheelbase = Big Bump

Now you know!!!!

[jetfuel]

Originally Posted by sberger

After a ton of research, here is the formula:

Pothole > Wheelbase = Big Bump

Now you know!!!!

jetfuel

[forestacademy]

Two Words

School Bus

While the smart is bumpy and lightweight, I think the same can be said for the back of a school bus.

THe front of the bus is not so bad, where the weight is, but the back is very bumpy.
Not a short wheel base on the bus.

THe back of an older Explorer was unberable while the driver sat comfortabley in front near the engine once again.

I guess what im saying in this ramble is since the smart is a rear engine car and the driver is up front, the driver is in the bumpy part of the car.

[theguywiththelongestname]

here's a cool explanation about wheelbase and RC model cars:
How changing the wheelbase on your rc vehicle can affect handling.

[msjohnson1974]

Originally Posted by sberger

After a ton of research, here is the formula:

Pothole > Wheelbase = Big Bump

Now you know!!!!

Correction:

For Each Pothole
IF Pothole.NotDodged Then
IF Pothole.Size >= smart.WheelBase Then
smart.Jolt(HARD)
Coffee.Spill(Most)
Driver.Curse(F_Bomb)
ELSE
smart.Jolt(NotAsHard)
Coffee.Spill(Some)
Driver.Curse()
END IF
END IF
Next Pothole

[bigcritter]

I've read a few books about the smart, and evidently when the first "City Cars" were built, the front & rear tires were the same size, and the width of the rear axle was the same as the front. The suspension was also softer. They began having problems with rollovers in Germany & other parts of Europe, so they had to redesign the chassis to eliminate the problem. That's when they went to the wider/longer rear axle, wider rear tires, and a stiffer suspension......as well as an upgraded ESP system. So while that really doesn't have anything to do with the "short" wheelbase, it does partly explain why the ride is a little harsh! :>) As I also mentioned in a different post, the bumps can be bad & teeth jarring, but the DIPS are what really rock my world, and NOT in a pleasant way!! :>(