lobuxracer

iTrader: (2)

They have different geometry. The suspension links are different lengths and the bushings are different. It's pretty obvious in the service manual and in the parts lists.

JROD08ISF

I get it all that but wouldn’t that be more felt in steering and feedback?

Compression, Rebound and Stability are felt from suspension components.

Edited.. this seemed like a good article to reference. Forgive me I’m a noob.
https://nasaspeed.news/tech/suspensi...s-on-handling/

When the suspension moves, the shock absorber is designed to control movements of the suspension and chassis, working in conjunction with the springs. The springs actually absorb shocks over bumps and help control body roll. The shocks control the oscillations of the springs, determining how fast the spring compresses or extends. Stiffer shock rates slow spring movements while a softer shock rate allows the spring to move faster. A shock is far too soft if it allows the springs to oscillate, or bounce, more than one full cycle. A shock is far too stiff if it limits suspension travel. A shock that is too stiff can cause the tire contact patch to bounce off the road surface over bumps or jack weight in the car after body roll occurs, even pulling the tire off the track surface for an instant.

So.. What I think I’m feeling is the Swift Springs are too soft. This seems to echo what others have said, and they obviously know more than me.

the advertised swift spring rates are firmer than stock, just seems not right paired with Bilsteins.

lobuxracer

iTrader: (2)

No. The links are primarily responsible for providing the geometry to keep the tire in contact with the racing surface. The shocks and springs are there to deal with the inevitable changes in force applied to the tires under braking, turning, and dealing with irregularities in the surface. There's way more to this than that article can cover; it's just too short. Suffice it to say everything starts with the geometry and maintaining good geometry. If the suspension links are not helping this, they need to change. The original configuration of the IS F's rear suspension generates a lot of toe change as the suspension cycles. Changing the length of the links helps minimize this. Toe change isn't necessarily a bad thing, but you want it to change to help the car, not make it harder to go fast. So, the later models have a better design from the factory because they incorporate what Lexus learned with this suspension over the years, and particularly when they ran the IS F in endurance races. I've often thought if I wanted a fundamentally better car with rubber bushings, I'd be way ahead to get a complete rear subframe from an '11 or later just for the revised suspension pieces. I'll end up doing something very similar with the plan I have, but I'm not going with rubber bushings.

JROD08ISF

Thanks Lance.

lobuxracer

iTrader: (2)

The last thing you said is on point. The damper and the spring have a natural frequency. Street cars like 0.8 Hz, racecars like 2.4 Hz. Not all, not everytime, but those are where chassis tuners start with a virgin setup. It's pretty likely the springs and dampers are mismatched. It would be ideal to know what springs Bilstein used when they set up the damping so you could at least start from a known position. The other thing is, Swift isn't well known for delivering the rate printed on the box the springs were shipped it. You'd be wise to test them to see if they really are matched and delivering what the box said they should. The people I know and trust tell me Hypercoil delivers what's printed on the box, and not many others.

AlOtaBblGm

I love the Bilsteins and OEM springs on my 08. To me it's ideal for street performance compromise. The Tokico's were far too harsh on even slightly rougher roads.

BS ISF

I have had Bilsteins on for about a year and 15K miles. I love them for what they are. They handle better than the stock shocks in every category ie: braking, cornering, etc... The biggest benefit for me was they handle bumps and potholes way softer than OEM. The harshness on bumps is drastically reduced. I didn't want to lower my car being in Chicago and the roads are brutal so if you don't want a drop these are a great replacement.

JROD08ISF

Took the Swifts Springs off today... 1000x times better on OEM Springs.. Much more stable, compliant and the Bilsteins are miles better than stock 2008 dampers. I am confident again behind the wheel.

Reminding me why I fell in love with the car, Just have to deal with reverse rake.

Jwconeil

There really isn’t a cheap way to lower the car and do it right. I came to terms with that. Stock height for now. Saving for Ohlins.

JROD08ISF

BMW F80’s in stock form look equally ridiculous, helped me come to terms with the wheel gap.

Jwconeil

I wouldn’t mind the visuals so much if the car would keep four wheels on the earth in hard, tight turns, which disengages the torsen .

LILEVO

iTrader: (1)

In the coming weeks I'm upgrading my 2012 to the 2013/14 power steering ECU, springs/struts, and going to a 17" wheel for ET streets. The difference might be minor or not even noticable, but I'm curious to compare.

ChpEng

iTrader: (1)

Did you find a 17in wheel which fits over the front brakes, or just rear?

LILEVO

iTrader: (1)

Haven't looked. Just concerned with the rears for slicks. These are the ones to buy: AV2017905H35BK, 17x9 Black Wheel AVID1 AV20 5x4.5 35

Slowlane

Nice
Whats the difference 2012 to the 2013/14 power steering ECU and whats involved?