Motorsport Wheel Alignment: Live Axle
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Live Axle
02.20
| 00:00 | - A solid axle or beam axle is a type of dependent suspension design where the two wheels are connected laterally by a common shaft or axle. |
| 00:09 | When the axle being referred to is used to transmit power, it's known as a live axle, however this technique is often used at the rear of a front wheel drive car where it's called a beam axle. |
| 00:20 | While historically this was a common suspension arrangement, particularly in the rear of rear wheel drive cars, the number of disadvantages of a solid axle, mean that the suspension designs for modern performance based cars have moved towards independent design options. |
| 00:36 | One of the key aspects with a solid axle design is that typically the camber and toe are set due to the axle geometry and they can't be adjusted. |
| 00:46 | For every rule, there's always an exception however and in specially designed live axles for race use, it is actually possible to incorporate camber and toe changes through the use of a floating hub. |
| 00:58 | These aren't common though, so in most instances we can consider toe and camber to be non adjustable. |
| 01:05 | The live axle also requires a method of locating it laterally and longitudinally in the chassis. |
| 01:11 | There are a variety of possibilities here and at its simplest, this can be achieved with leaf springs. |
| 01:18 | In a performance application it's more common to use coil springs combined with four trailing arms for longitudinal location. |
| 01:25 | This is known as a four link. |
| 01:28 | Lateral location of the axle can be handled in a number of ways which we'll deal with in the next module. |
| 01:34 | Since both wheels are fixed together, one of the downsides of a live axle is that if one wheel traverses a bump, this will affect the angle between the other wheel and the ground. |
| 01:45 | This can reduce the available grip if the inside wheel traverses a bump during cornering because the outside wheel effectively moves into positive camber. |
| 01:53 | The weight of the live axle is another disadvantage as this is part of the car's unsprung weight. |
| 01:59 | The higher the unsprung weight, the harder it is for the wheels and tyres to respond quickly to undulations or bumps in the road which compromises traction and affects ride quality. |
| 02:11 | The advantage of the live axle however is simplicity, both in the design as well as the manufacturing. |
