youngjun91

Hi all,

I have a technical question that I've posted elsewhere, but thought to try here also. I ordered Swift Spec R springs expecting that I could use my AP2 (MY04) shocks with them since lots of people on this forum as well as Swift themself claims that they match decently well. In fact, it seems, there is a particularly fast guy in California in the Racing forum that has exactly this setup. So I thought it was OK, until I looked up the spring rates:

front, back (lb/in)
CR springs: 392/347
Swift Spec R: 420/392 (linear, not progressive)
MY04: 261/280

It seems that the CR and Swift springs are really really close in stiffness/rate. In fact, they are only off by 7% and 13% respectively with the Swift springs being just slightly stiffer.

So then naturally I figured that the CR shocks should be an almost perfect match for the Swift springs since the shock damping for the CR shocks should be perfectly matched to the CR springs (which in turn is almost the same as the Swift springs). Make sense so far? I don't know exactly what formula Honda or sports cars manufacturers in general use for damping. Is it critically damped, or 65% of critical damping? Anyone know the exact damping rate? Anyway, I was in the process of buying either new or slightly used CR shocks, but then I figured I should do some homework first.

The MY04 springs are 33% and 19% less stiff (front and rear respectively) than the CR spring rates. I called Swift (in the U.S.) about this and they said that they have received good feedback from AP2 owners and a small number of CR owners that their springs worked well with both stock shock setups.

My question is “how could that be”? Here’s another graph to look at. Look at page 52: http://blog.kw-suspension.com/wp-con...k-shootout.pdf You’ll see how much more damping there is on the CR shock compared to the AP2 shock, especially on the front. It makes sense because there is a greater difference on the stiffness of the front spring compared to the rear spring when you compare CR vs. AP2 spring stiffness.

This would leave me to believe that the CR shock especially in the front would be a great match (almost perfect in fact) for the Swift spring in the front. Of course in the rear, the CR shock would again be an almost perfect match for the Swift spring, but the AP2 shock is pretty close in damping force, so it would probably be OK here.

Anyone have any well formulated thoughts on this? I am trying to tune especially for HPDE, but I also autox and occasionally drive the car to work also. I could have jumped right to KWv3’s off the bat, but I liked the idea of trying the budget route first.

My overall question is, which shock would be the best mach for the Swift Spec R springs? Should I get CR shocks (at least the fronts), try the AP2 shocks first, Koni-off-the-shelf, Koni revalved ($150 extra per shock), Biltstein (Swift told me less than $100 revalve per shock). Swift also told me that it’s really rebound that’s critical and he thought that the blog.kw-suspension.com had the compression and rebound flipped by accident. If that’s the case, is the Koni-off-the-shelf a good match since the rebound is adjustable (but I don’t like the rumor I hear that there is less force on compression compared to APx). Some may ask - why not just use the CR springs and buy a fully proven matched set? The only reason would be because I slightly favor the lower Spec R height.

Anyone with CR stock shocks and Swift Springs have any decent HPDE/track/autox experience they could share?

Thanks for reading,
Young

takchi

Swift Springs were designed on CR shocks. The spring rate is at the very limit for AP1 & AP2 OEM shocks, but works best on CR shocks according to Swift Springs.

adrs2k

What he said

I should have my swifts on this weekend or next.

youngjun91

Thank you. I may have heard that also from the Swift representative, but we talked about so many things that that fact may have gotten lost in the data exchange. Where did you hear this? How can I confirm? Please let me know as I may be about to plunk down another 800 on new CR shocks. I will probably give the Swift rep one more call.

If this is true, I'm surprised more CR folks aren't switching to the Swift Spec R's. It'd be such a cheap mod for you guys, unless there are significant disadvantages also, like lag in steering response due to changed roll center, or wanting to keep everything OEM and pure. But there is definitely an advantage in a lowered center of gravity, which if you're a track or autox person, is not something to be sneezed at.

takchi

I was told this by a Swift Spring representative. I chose not to do this mod because I didn't want to mess with the changed suspension geometry. Now that I already have the rear RCAs, I may run Swift Spec R springs in the future if I am to ever sell my coilovers.

Go2

Spec Rs FTW

youngjun91

I just talked to Swift and he basically said the same thing, that is, that the CR was what was used to develop the Swift Spec R spring. So, there you go CR owners, a spring that may be optimized for your shocks. I might just pick up the CR shocks. Anyone have a set they'd like to sell?

adrs2k

Thanks for the info

I will be installing my Swifts tomorrow night and will do a full picture review and write up. Driving impressions will be limited though until my alignment gets done the following week and I am not sure if I will have time to hit the canyons to weigh in on my findings either.

RylisPro

Greatly anticipating your review
The cost of the springs aren't bad $314 but add at least another $100 for install and alignment
I am waiting to see if all they hype of these springs are actually worth the $414 bucks haha

Especially since I decided my CR doesn't really need anymore modifications

adrs2k

I paid $299 shipped for the springs.
I do the install myself.
Science of Speed charges $85 for alignment.

So for me its pretty darn cheap!

I will do some actual before and after measurements as well.