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The way to get good ride quality and performance:
1. Travel
2. Quality valving
3. Reasonable spring rates
All of those are important. If you REALLY screw up 1 of them you're in trouble.
So let's start with travel. From the factory these cars have pretty decent TOTAL travel. But a lot of that is droop (extension) travel and not compression (bump) travel. You're almost on the bumpstops at rest by design. With most lowering springs, you're already compressing the bumpstops before you hit a bump. It's a serious limiting factor when it comes to both performance and comfort if you want more than a mild drop on lowering springs.
You obviously need travel to soak up bumps and for mechanical grip (harsh spikes in load from bottomed out shocks is bad). It's important for comfort and handling.
Coilovers are usually designed with a drop in mind from the start, so that's good. You sometimes get more bump travel at a lower ride height...at the expense of limited droop travel. Both are important. Unfortunately travel numbers are rarely advertised by anyone. Our RCE coilovers have about 142mm of total travel in front, about the same as same as OEM and more than most coilovers. You end up with more compression travel than stock at our recommended ride heights with a still good amount of droop.
You'll often see separate ride height and spring preload adjustability advertised. This is IMO almost always misunderstood and misused even by suspension companies. MCA in Australia is one of the few places I've seen that gets that it's more about ratio of bump to droop travel than anything else (and in practice it's usually a cost-saving measure).
Valving is also something you don't see in marketing and can be difficult to interpret anyway. Things like linear, digressive, and progressive valving are generalizations that are tossed around but there's much more to it. Digressive is usually thought of as the ticket for street and circuit driving, but there's a lot of nuance beyond that. There are plenty of crappy shocks out there with digressive pistons, or shocks with good quality components that are just valved poorly. For comfort, the enemy is mostly excessive rebound...especially with limited travel. Rebound is the force from the damper that tries to hold up the wheel after it compresses. It acts against the spring extending and has to be designed with that in mind. Lots of rebound with a softer spring can lead to packing down, which means the damper is holding the wheel up too much. The wheel doesn't extend in time for the next bump, so you have even more limited bump travel and it just gets worse.
This is by far the most complicated part. It takes some math to figure out where to start and with the way dampers function over different kinds of inputs...it can do well in certain situations and worse in others. An adjuster can help dial things in but sometimes you're limited in your range OR there is no 1 good setting (the range might be from soft and crappy to stiff and crappy, with nothing but crap in between). Shocks are complicated.
Spring rates are IMO kind of the least important of the three, but all 3 do have to work together. A really good set up can have spring rates 3 x as stiff as stock and still ride better than stock if it has good valving and travel. But they have to be dialed in. There are rules of thumb about appropriate spring rates for different applications and tire choices that are usually a good start. Stickier tires need stiffer springs is the short version. But a lot of those formulas are just that...a good start. Testing and experience will have you shifting things a little in either direction to get the most out of the car on track or to find a good compromise for different usages.
Anyway, that's just the start of things really. Happy to answer questions here or by PM or give us a call to chat. We have our own springs and coilovers, and also sell a few other brands that we have learned to like in our almost 20 years in Subaru suspension. We're also not afraid to say when another company makes a good product that we don't sell. We just like good suspension.
- Andrew
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