Hello folks,

I've been scouring teh intarwebs for some guidance on this but haven't found much.

I want to know how to decide where to tune a loaded shock's piston position (with the car at rest on level ground). In other words, what is an optimal ratio/amount of bump vs. droop travel from rest? I already know how to adjust this, I'm just looking on some objective data/logic about what to set it to.

The simple logic seems to be to set things up so that you have equal available bump and droop travel. But I suspect the actual answer is more complicated and depends on whether you have enough spring to stay out of the bumps stops, typical road conditions, drive-axle, etc.

Anyone have any resources or specific experience with this topic?

 

Suspension can see massive loads from bumps in compression, but on extension it only sees the force in the spring. The road can push up on the spring/damper, but it can't pull down! So you would ideally want more bump travel than rebound. On motorcycles, you typically set up for 2x to 3x as much bump travel vs. rebound from static. What's ideal depends on usage, but 2x as much bump as rebound is probably about "right". That doesn't mean, however, that you should reduce available droop to achieve a 2:1 ratio.

Practically speaking, I would say that you should give yourself as much compression travel as you can (while minimizing tire to body/chassis contact) at your desired ride height, and maximize droop travel available, whatever ratio that gives. If you need more bump travel from there, you have to raise the car.

 

Thanks, ZDan, that's exactly the kind of input I was looking for. Let's assume I am limited only by the available travel in the damper. My ride height and fender room are independent variables because I have threaded shock bodies and plenty of fender clearance.

Sounds like I want the minimum available shock piston droop to avoid lifting a wheel. Maybe it's time to bust out a dynamics calculator and get some weight transfer estimates so I have an idea what a minimal amount of loading might be front and rear at 1.2 G or so. From there I can estimate where the piston would be at that point, add some extra for dips and start from there.

 

I did some more digging and 2:1 and 1.5:1 seem to be common ratios so I will start there. I'm worried I will end up with rear wheel lift at that ratio because my rear shocks are very travel-limited, but time will tell.