Benefits (in general, not only volvo):
– Wheel arch width: Adding coilovers to a damper strut increases the radius by about an inch each side. So removing the coilovers could give you an extra 2″ between the wheelarches – rather useful for vans, estate, SUV bootspace
– Floor height: It may also be possible to lower the floor height – again good for bootspace.
– Load distribution. The weight of the car has to be transferred to the wheel hub carriers. In a coilover design this generally means down into the floor structure, then back up the wheelarches, and into the top of the spring. That means some significant structure up there. With a transverse leaf, you should be able to take it straight from the floor into the spring. Loads at the top of the damper (without coil) are much lower. So you should be able to simplify the structure considerably, saving weight.
– Hub mounting: If you have a driveshaft running straight through the centre of the hub, it’s rather in the way for that damper/spring unit. If the coil spring is playing a part in defining the damper strut length, this could be quite a problem.
You could mount the strut to the hub above the driveshaft, But this would result in a very high wheelarch (packaging, load distribution risks)
You could mount it lower, but off-centre (fore or aft). But because of the extra diameter of the coilover, it would be considerably more off-centre than just a damper unit. That introduces a load trying to rotate the hub in bump – loading up bushes and trying to move the wheel position. That’s unnecessary loads that need to be countered (weight) and unnecessary wheel movement (loss of grip/handling).
However, a leaf could be mounted directly above or below the driveshafts – no off-centre loads, no artificially induced wheel movements.
– Subframes: It’s quite common to construct the complete suspension onto a subframe. It can be easier to install, easier to set up, and easier to control Noise, Vibration & Harshness (NVH) with dedicated bushes between subframe and chassis. In some cases, a transverse leaf is far better suited to this. Load paths and packaging can be well-suited to a compact, simple sub-structure.
– Corvette and Volvo uses composite leaf spring, so there should be some weight saving comparing to steel coils
– Wheel arch width: Adding coilovers to a damper strut increases the radius by about an inch each side. So removing the coilovers could give you an extra 2″ between the wheelarches – rather useful for vans, estate, SUV bootspace
– Floor height: It may also be possible to lower the floor height – again good for bootspace.
– Load distribution. The weight of the car has to be transferred to the wheel hub carriers. In a coilover design this generally means down into the floor structure, then back up the wheelarches, and into the top of the spring. That means some significant structure up there. With a transverse leaf, you should be able to take it straight from the floor into the spring. Loads at the top of the damper (without coil) are much lower. So you should be able to simplify the structure considerably, saving weight.
– Hub mounting: If you have a driveshaft running straight through the centre of the hub, it’s rather in the way for that damper/spring unit. If the coil spring is playing a part in defining the damper strut length, this could be quite a problem.
You could mount the strut to the hub above the driveshaft, But this would result in a very high wheelarch (packaging, load distribution risks)
You could mount it lower, but off-centre (fore or aft). But because of the extra diameter of the coilover, it would be considerably more off-centre than just a damper unit. That introduces a load trying to rotate the hub in bump – loading up bushes and trying to move the wheel position. That’s unnecessary loads that need to be countered (weight) and unnecessary wheel movement (loss of grip/handling).
However, a leaf could be mounted directly above or below the driveshafts – no off-centre loads, no artificially induced wheel movements.
– Subframes: It’s quite common to construct the complete suspension onto a subframe. It can be easier to install, easier to set up, and easier to control Noise, Vibration & Harshness (NVH) with dedicated bushes between subframe and chassis. In some cases, a transverse leaf is far better suited to this. Load paths and packaging can be well-suited to a compact, simple sub-structure.
– Corvette and Volvo uses composite leaf spring, so there should be some weight saving comparing to steel coils
Downsides:
– price to replace
– in some applications some difficulties with wheel alignment
– for tuners problematic to lower their ride or change easily and cheap suspension stiffness