In case it matters, I am talking specifically about motorcycle suspensions, although I assume the principles are the same.
Everyone says that when you get serious about track day riding, you first upgrade your suspension. All else comes after.
For the record, I couldn’t find anything online answering my question.
In: Engineering
In your specific example, a “good” suspension is the one the rater prefers. If they prefer a softer suspension, then that’s a “good suspension”. If the prefer a firmer suspension, you got it – that’s good to them.
There is no universal “good”, just what the rider prefers for the terrain/track they usually encounter
From the factory they are built to be smooth and handle a variety of riders with a certain amount of “sag”. It won’t be even or perfect for everyone, and a lot of them have adjustable features to set the “rider sag”. It’s not particularly important for street or regular off road riding. But in a race where you push the bike to it’s limits the last thing you want is something like your front wheel lifting because you are too light for the forks, or bottoming out because you are too heavy. You get springs that are built to better handle your specific weight and make fine adjustments on the preload so that when riding you stay evenly within the range of travel offered by your suspension. In other words the oem stuff installed at the factory targets a comfortable ride for as many people as possible, upgrades for track target predictability and stability for you specifically. At least as far as my knowledge goes for motorcycle suspensions.
To add, stiffness of the springs is one variable, another is the rate of damping provided by the shock absorbers. Changing these variables can have large effects on the dynamics of the vehicle in various situations. Tuning these variables is seeking an optimal balance.
The purpose of a factory suspension system is to balance comfort for the rider as well as keeping the wheel in contact with the road, for all manner of rider weights.
The purpose of an aftermarket, performance-based suspension system is to focus on keeping the wheel in contact with the road in nearly all conditions. Rider comfort is a distant second. The first part of this ins installing springs appropriate to the rider’s weight. Another significant factor is a suspension system that allows for tuning of how quickly the wheel absorbs bumps in the road surface, as well as how quickly the wheel recovers from those bumps.
Basically everything else is going to rely on the suspension to be “good”. You want the shocks to absorb enough energy that they can take the pounding you intend to give them, depending on what type of bike/surface you’re working with, but not so strong they’ll bounce you back up, you want the springs to help take the roughness out of it, and keep the wheels in contact as much as possible, and you might want some degree of adjustability so you can change it based on surface/conditions. This is also all going to want to be done as light as possible, which is another thing you’re upgrading by going beyond stock.
The suspension itself is simple, it’s two forms of compression that work together to cover each other’s downsides, and you’re using two of them to get the cheapest/lightest/best balance of what they both do, that’s really all it comes down to. When you’re buying stock, they’re having to take into account a lot more of the cheap part, a lot less of the light part, and a lot more potential longevity and complexity. By swapping it out, you’re getting what you personally want, without needing to design something for thousands of variables.
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