suspension tuning question

[tab1324]

I've got an 82 XJ and it is my first bike so pardon the ignorance of this question.... What exactly do the 'dial' measurements on the fork and rear shocks do? I assume it's for firmness of ride or rebound or something. My fronts were set on 2 and when I'd hit my front brake or roll off the throttle at higher rpms, the front end would sink quite a bit - more than I would expect to be normal - but then again it's my first bike.

Tom B.

[Jerry]

Damping is a method of controlling springs. There are two components: compression, which resists the spring movement when the wheel is traveling up or compressing the spring, and rebound, where the spring is trying to force the wheel back to its original position.

The XJ adjusable damping controls low-speed spring movement. (Suspension travel speed, not over-the-ground speed.) A setting of 1 is the least restrictive (softest) setting and 4 is the most restrictive (hardest) setting. While it is not necessary for the front and rear settings to match, the settings must match side to side. Both fronts, or rears, must be set to the same setting or your handling will be compromised. Braking, acceleration, and travel over rolling bumps are all low-speed suspension movments.

The XJ complicates things by having air-adjustable forks and rear shocks. Air pressure also affects how much force it will take to get the suspension to move. Front minimum (and recommended starting point) is 5.7 PSI, with a maximum setting of 17 psi. More pressure results in a siffer, less pliant suspension. Rear suspension should be no less than 14 psi (recommended) with a max of 57 psi.

Getting the right settings for your style, weight, spring condition, and installed accessories (windshield, bags) is a matter of trial and error. I would start with the factory recommended air pressures and try different damping settings, then up the pressures and see how the bike feels until you find a combination of pressure/damping that works well for you.

Being 260 pounds and with Vetter fairing and hard bags installed, I run 28 pounds in the rear shocks. I had Progressive fork springs installed and run no air in the front. Front Damping is set to 1 and back is set at 2. I do a combination of super-slab cruising and modeately twisting back roads; the pressure/damping I use works well in both types of riding.

PS...a bicycle tire air pump works well to change air pressures. Be careful; the volume is small. It can be hard to use an air hose to change pressure by small incriments, plus it is easy to blow the front seals with to much pressure. The XJ uses a balanced air system, meaning the front forks have a "T" connection so the 1 fill point feeds both forks. Rear shocks also have a "T" so pressure is evenly split between them from the 1 fill point. Front valve is on left fork tube just under the handlebars, rear is on the top of the left shock.

[Jerry]

Sorry, should have mentined the fill valves are under chrome screw-off caps.