Harley Softail M8 Shock Absorber
Low Rider is the most badass Harley-Davidson motorcycle, which appeared in 1977 on the FX platform. It later moved to the FXR and Dyna frames, and since 2018 it has been built on the Softail M8 platform. Initially, Low Rider was a light motorcycle with a minimum seat height, because of short shock absorbers and a deep seat. It was very popular and became the best-selling Harley-Davidson.
The first models based on FX and FXR were equipped with forward controls and a two-disc front brake in combination with alloy wheels on the sporty S versions. In 1993, Low Rider switched to a larger Dyna frame and was equipped with mid-controls that still remain.
The modern Low Rider based on Softail M8 is equipped with a hidden mono shock absorber and a double seat with a deep bucket. The S version, produced since 2020, is equipped with a rigid inverted fork, dual front disc brakes and a larger engine — this is fully in line with the spirit and concept of the original.
We like street style with a club-culture lean, where stunts and active riding are a big part. The clubstyle always has long shock absorbers and a step-up rear seat. This not only provides a sport look, but also increases clearance and shortens wheelbase, which provides better riding performance.
The easiest way to raise the tail is to install a standard 13.1" shock absorber from Fat Bob or Street Bob. But we decided to try the air shock absorber Legend Revo Air, which allows adjusting the length, even on the go.
The Softail M8 uses shock absorbers of two lengths: 12.6" and 13.1"; the Low Rider S uses the 12.6".
Air shock absorber has obvious advantages: the ability to change the length, clearance and stiffness, and adjust the sag to different weight loads. There are also disadvantages: complex installation due to the wiring in the handlebar and the compressor installation, and the need to keep the air intake filter in the compressor clean so that it does not suck in dust.
Legend uses metal joints instead of silent blocks on all its shock absorbers. Such joints effectively release the tension of the damper rod, which extends the service life of the seals and reduces the friction of the piston and the rod.
The Legend shock absorber damper has a monotube design, where the oil is under pressure due to a chamber with compressed nitrogen, separated from the oil by a floating piston. It ensures stable operation under intense load (for example, on a bad road) and greater resistance to bottoming out during impacts. The rebound adjustment allows you to adjust the hydraulic resistance and how fast the shock absorber extends after compression.
The weight of an air shock absorber with a compressor is the same as the weight of a standard shock absorber with a hydraulic preload adjustment unit.
Installation
When installing, it is important that the air line is not under tension, especially at the joints, and does not rub against the motorcycle.
Power and control wires also shouldn't rub each other or break. The red wire (plus) is just under the shock absorber, and it should not touch it during pumping and lowering.
Our new handlebar T-Bar LA Choppers Kage Fighter has a small hole for the Legend control wire, so the control had to be modified. We cut out a hole for the wire in the switch body. We did not show this in the video, because it is possible to install it without any modifications, but then the wire is pressed and may be damaged.
Adjustment
In terms of design, the air shock absorber springs are different from the usual shock absorber ones. For the air shocks the stiffness is regulated by the pressure. On an ordinary coil-over shock, the spring is metal and its stiffness is constant. So if you need to adjust the stiffness to the weight load, you have to change the spring. By adjusting the preload, it is possible to compress the spring in a small range and increase the stiffness, while the spring length decreases and its characteristic changes. The hydraulic damper, which absorbs the energy of shocks, can be the same in both shock absorbers types.
The high price of the air kit is fully justified if the weight load is changed often. Harley-Davidson installs a remote hydraulic preload adjuster on Fat Bob, Fat Boy and Sport Glide — and it's convenient to sit on the motorcycle while adjusting. But on the Low Rider S, this adjuster is located under the seat, which makes the adjustment difficult.
On touring bikes, pressure sensors with a gauge are used, so you can adjust necessary settings to different loads (for example, with and without a passenger). On Softails, the rear fender is not covered with side bags, so it is possible to set the sag visually through the gap between the fender and the rear tire.
The sag setting in the Legend manual is approximate. The working range of the pressure and shock absorber's length is much less than the maximum (nominal) one, but still more than the length adjustment on any coil shock absorber, where the length is adjustable within a maximum of 15 mm, and the spring stiffness is constant.
You can purchase and install suspension components in our workshop. We work with Legend Suspension, Bitubo, Ohlins, Wilbers, Progressive Suspension, RaceTech, Hyperpro.
