Discussion and questions related to the course Motorsport Wheel Alignment Fundamentals
In "What to Adjust" module of the Motorsport Wheel Alignment Fundamentals course, around time stamp 0:50, Andre mentioned about using zip tie to measure bump travel to make sure our suspension is not bottoming out.
1. Without visual aid, I have to imagine that he means to wrap a zip tie around the damper part that will goes inside the damper body when the damper is compressed, and see how much it moves. Is this what he meant?
2. Can we use this method to measure if we have enough rebound travel?
3. He also said the solution to suspension bottoming out is either raising the ride height or installing stiffer springs, so how do I pair the correct combination of spring rate and the damper? How stiff a damper I need and how to check its compatiblity with a certain spring rate. Come to think about it, I'm not even sure if damper stiffness is a thing or not.
1/ yes, around the damper shaft. For checking if it's hitting the bump stop(s), place a small amount of grease on the stop, it'll be clear by the smearing if there's contact.
2/ no, think about it. ;-)
3/ I'm not sure there is guide, as such, as with up to 4 different adjustments to the damper rate (some off road dampers have even more), vehicle variations, application variations, etc. there is a lot to take into account. You may need to try trial and error starting with your current dampers' middle adjustment(s) and working from there. However, if you're yet to buy the package, they are usually close to what you need if sold together. Anyone aware of a useful guide?
Thanks Gord for the excellent answer :)
All good questions!
1. You're correct, it's just a zip tie around the shaft to see what the maximum compression is for each damper.
2. Unfortunately not, it only tells us the maximum compression, nothing about the droop travel.
3. You specify your dampers based on some calculations for the spring stiffness and mass for that corner of the car. For specifying basic damping, you're usually talking in terms of a damping ratio, which lets you calculate the required damping forces for your application. It isn't a very complicated process to calculate this, but too much for a forum post! We will be releasing a suspension tuning course in 2021 that will likely cover this process though!