Effects and factors of wheelbase in the design of a motor vehicle

There are two concepts to understand (which I think you might already get to an extent). As the wheel base length grows, stability is gained, but you lose maneuverability. You also risk the greater chance of the vehicle becoming high-centered (ground rubbing the center of the vehicle) when traversing bumps in the road unless you increase the ride height of the vehicle or in some way gain more ground clearance, but then you lose some stability due to a higher center of gravity. Conversely, as the wheel base length shrinks, stability is lost, but you gain in maneuverability. Some of the stability can be regained through widening the wheel track (distance between the tires on a given axle).

There are many different reasons why a manufacturer would adjust the wheel base on a vehicle.

• Use: If a vehicle is to be used off-road (4-wheel drive) purposes, the wheelbase will not be made as long as the longer it is, the easier it will be to get high-centered. If a vehicle is meant for high speed cornering, the vehicle will be lower to the ground and the wheelbase will be longer, with wheels set more forward and back relative to the end of the vehicle.
• Aesthetics: How does the designer want a vehicle to look when it's put together?
• Manufacturing Costs: When you lengthen a vehicle, costs (such as frame/suspension strengthening and stiffening) come into play, which can drastically change cost.
• Viability: Does the vehicle actually need a longer wheelbase to function properly? This goes hand-in-hand with what was said earlier.
• Interior Space: As you lengthen the wheelbase, the interior space can be increased.
• Weight Distribution: Wheelbase has a great affect on weight distribution, depending on where the axle centers are located in the vehicle.
• Weight: As you lengthen a wheelbase while keeping the same distance in front/back of the wheels, your vehicle weight will increase to "fill in the gap" between the wheels, as well as what is needed to strengthen the vehicle to be able to handle the extra forces put on it to support it. If you do not overall lengthen the vehicle when increasing the wheelbase, the weight will not increase, but you will lose in other areas, such as trunk (boot) space in the rear.

One other thing with relationship to motorcycles:

• Torque Stability: If the wheelbase is not sufficient where there is an excess of power/torque, the front tire will always want to raise during a power filled takeoff. To counter act this, longer trailing arms will be added which creates a longer lever with the same amount of weight, thus giving the bike more stability on takeoff. (This is counteracting the want of the bike to do a "wheelie" during takeoff).

These are the basic reasons for selecting a wheelbase by a manufacturer, but there is no magic "formula" for a wheelbase. A manufacturer must decide for itself why it would want to use a wheelbase of a certain length. They will take all of the factors into account and use what it determines as best for the vehicle design, use, aesthetics, viability, and cost factors.