Reaction Coilovers & Swift Springs

[socalvn]

So lately I'm finding my ride on city streets to be kinda bouncy, so I want to install Swift springs on the front Reaction Coilovers for mostly spirited City driving and freeway no track although occasionally I do pretend like I'm on the track.

Hoping Volfy can chime in here knowing your well experienced in this area, mabee with a special recommendation for spring rate? I'm driving the 2.5T
Thanks to all for commenting

 

[Snowwhite]

can you turn up the rebound damping on the coilovers? that should reduce bouncing.

 

[socalvn]

can you turn up the rebound damping on the coilovers? that should reduce bouncing.

Yes but I just fell like a better spring rate would help more

 

[Volfy]

I wrote a lot about Swift spring selection and install on Riaction coilovers. There is no need to repeat all of it, since you probably already read it here:

Riaction Coilover Installed

Just like the title says installed Riaction Coilovers no more saggy lowering springs got all 4 corners done divorced coilovers in the rear separate spring with adjustable top hat. just the front was about a 2 1/2 hour project corners balanced to 20 inches.

stingerforum.org

As for what spring rate to choose... I'll just expound on two important points:

1. The biggest limiting factor is whether you can change the rear spring rates to match. Riaction, as of yet, does not offer an option to the "OEM" 10kgf/mm springs. The 8kgf/mm front spring rate Riaction ships with their coilover kits is a good match for that. With the "OEM" Riaction springs, my Stinger was fairly neutral steering on both corner entry and steady state. If I had gone with a higher front spring rate, say 10kgf/mm, that would increase the car's tendency to understeer. I don't want that. Depending on your car's setup (tire sizing, anti-roll bar, shock settings, ride height, etc.), your car's cornering attitude could be different, and a different front/rear spring rate balance could work better.

I've tried to find an alternate source for rear springs that would fit, but have so far come up empty.

2. Also, the spring rate at the front or rear should be matched with the damping rate setup. Unless you opt for the two-way adjustable versions, the shock adjustments are on REBOUND only. Compression damping is fixed in the valve stack. Out of the box, the Riaction valve stacks are optimized for the 8k/10k spring rates. You can vary the spring rate a little and the shocks would still match reasonably well. However, the more you increase or decrease the spring rate from Riaction's "OEM" setup, the more you should consider sending the shocks back to Riaction to get re-valved to match. I believe they charge $85 per corner for this service, which is actually quite reasonable. It's only $10 more than their rebuild service. Discuss with their tech what you're doing, and they'll re-work your valve stack to suit. Do bear in mind the same front/rear balance rule (mentioned above) applies to shock stiffness as well.

Realistically speaking, the 8k/10k setup works quite well for street driving... maybe even a bit stiffer for those who prefer a softer ride. Guys like us who value handling prowess don't mind, of course, and are willing to put up with it on the daily. Still, unless the car will see a lot of track time, I don't see any reason to go much stiffer... unless you're a masochist. Besides, doing so without stiffening up the rest of the suspension joints with urethane bushings is rather pointless. The stiffer springs and shocks will further stress those other weak links and tweak the suspension alignment out of whack when you push the car hard. Stinger was designed - and equipped - as a gran turismo. Not a track machine. The more you try to tune it into one, the more parts you'll have to replace/modify.

Same thing happens to guys that are into engine mods, when increased HP starts stressing out the driveline and breaking parts.

 

[Volfy]

can you turn up the rebound damping on the coilovers? that should reduce bouncing.

Yes, but you only want enough to keep the suspension from pogoing. Too much rebound damping, and you could run into problems like rebound stacking over successive suspension compressions (e.g., when driving over rough roads, or through fast slaloms).

As a general rule, you want as little rebound damping as you can get away with.

 

[socalvn]

I wrote a lot about Swift spring selection and install on Riaction coilovers. There is no need to repeat all of it, since you probably already read it here:

Riaction Coilover Installed

Just like the title says installed Riaction Coilovers no more saggy lowering springs got all 4 corners done divorced coilovers in the rear separate spring with adjustable top hat. just the front was about a 2 1/2 hour project corners balanced to 20 inches.

stingerforum.org

As for what spring rate to choose... I'll just expound on two important points:

1. The biggest limiting factor is whether you can change the rear spring rates to match. Riaction, as of yet, does not offer an option to the "OEM" 10kgf/mm springs. The 8kgf/mm front spring rate Riaction ships with their coilover kits is a good match for that. With the "OEM" Riaction springs, my Stinger was fairly neutral steering on both corner entry and steady state. If I had gone with a higher front spring rate, say 10kgf/mm, that would increase the car's tendency to understeer. I don't want that. Depending on your car's setup (tire sizing, anti-roll bar, shock settings, ride height, etc.), your car's cornering attitude could be different, and a different front/rear spring rate balance could work better.

I've tried to find an alternate source for rear springs that would fit, but have so far come up empty.

2. Also, the spring rate at the front or rear should be matched with the damping rate setup. Unless you opt for the two-way adjustable versions, the shock adjustments are on REBOUND only. Compression damping is fixed in the valve stack. Out of the box, the Riaction valve stacks are optimized for the 8k/10k spring rates. You can vary the spring rate a little and the shocks would still match reasonably well. However, the more you increase or decrease the spring rate from Riaction's "OEM" setup, the more you should consider sending the shocks back to Riaction to get re-valved to match. I believe they charge $85 per corner for this service, which is actually quite reasonable. It's only $10 more than their rebuild service. Discuss with their tech what you're doing, and they'll re-work your valve stack to suit. Do bear in mind the same front/rear balance rule (mentioned above) applies to shock stiffness as well.

Realistically speaking, the 8k/10k setup works quite well for street driving... maybe even a bit stiffer for those who prefer a softer ride. Guys like us who value handling prowess don't mind, of course, and are willing to put up with it on the daily. Still, unless the car will see a lot of track time, I don't see any reason to go much stiffer... unless you're a masochist. Besides, doing so without stiffening up the rest of the suspension joints with urethane bushings is rather pointless. The stiffer springs and shocks will further stress those other weak links and tweak the suspension alignment out of whack when you push the car hard. Stinger was designed - and equipped - as a gran turismo. Not a track machine. The more you try to tune it into one, the more parts you'll have to replace/modify.

Same thing happens to guys that are into engine mods, when increased HP starts stressing out the driveline and breaking parts.

Thank you for the detailed response other options to consider most of the time it drives beautiful just on certain roads that are in poor condition that's typical of any suspension

 

[Volfy]

Thank you for the detailed response other options to consider most of the time it drives beautiful just on certain roads that are in poor condition that's typical of any suspension

As I briefly mentioned in the other thread, for general road riding, the biggest advantage upgrading to Swift springs is improved linearity and load handling. When I had the Riaction "OEM" springs on, they were bottoming out (coil collapsing partially or completely) going over large bumps. That was with only me, the driver, in the car. If I had a car full of passengers and cargo, it would be even worse.

Also, it is more than just cargo load. Brake dive will also compress the front springs. So does lateral acceleration (i.e. cornering load). Lowering the car helps to reduce weight transfer, both longitudinally and laterally. However, lowering ride height also lowers the roll center. Too much of that, and the car loses its naturally roll resistance. A car lowered too much could actually roll more than if kept at stock ride height. This might be counter-intuitive, but it is very much true. Look up "roll center correction kit", and you'll see companies selling them to minimize exactly that problem.

If any one particular suspension mod is not quite performing as you expected, it's very important to evaluate/analyze WHY before deciding on the next step.

In my case, it didn't take but 1-1/2 months of running on the Riaction kit as is, before I figured out what was going on and how I could fix it. Your suspension setup is a good bit different than mine, so you'd have to figure out your case individually. Coilovers are a powerful tool for suspension tuning. More adjustments means more ways to get it right and, unfortunately, just as many ways to get it wrong.