And why does it lead to poor automotive performance? I’m trying to expand my knowledge of motoring and the motoring press seems to frown on such things.
From AXLES:
The performance issue would be in comparison to an independent rear suspension where the rear drive wheels are independently sprung. IRS tends to handle cornering at speed better.
For something like drag racing you’re actually probably better off with a live axle.
And yeah, that definition linked to seems like it could include IRS, but I believe the popular usage is to distinguish between a solid axle and IRS.
I trust we’ll know soon if that’s in error.
A live axle is where the axle tubes and center differnetial is all one assembly, solidly attached to the wheels. The axle assembly moves independently of the rest of the car, but the wheels attached to the axle move together.
The opposite is IRS, independent rear suspension. Each wheel can move independently. The center differnetial is mounted to the chassis, and does not move with the wheels.
Each design has strong and weak points.
Live axles inherently handle high torque better. You will not find dragsters with IRS.
Live axles have less power loss. IRS has more universal joints transferring power, and more angles the power has to traverse.
Live axles are generally less expensive to produce and maintain.
IRS has less unsprung weight. This is mass connected to the wheels, not the body of the car. Less unsprung weight makes for a better ride over quick bumps (pot-holes). It also improves handling over uneven surfaces.
IRS allows rear wheel alignment changes. With a live axle, the wheels are fixed to the axle assembly.
It is a popular belief that solid (live) rear axles handle bad, but that is not necessarily true. Many road race cars use solid axles. Trans Am racers come to mind. Solid axles do not limit handling on a smooth race track. The more uneven (bumpy) the track is, the better the IRS will be.
Markus
Live axles give better articulation in extremely rough terrain (e.g., rock crawling). If you look at serious off-roaders you’ll see that live axles usually have both wheels on the ground, while IRS have one hanging in the air. Many rabid Jeep fans were frothing angry when DaimlerChrysler put IRS on the Liberty and discontinued the Cherokee.