Zender

I couldn't find anyone comparing the sport suspension to a lowered F-Sport coil only suspension. All the posts just say it's same as stock or a little stiffer than stock etc. But the stock SPORT suspension is stiffer than the stock suspension already so I am wondering what is the ride difference compared to the stock SPORT suspension.

Thanks.

Zender

I guess I know why I couldn't ever find the info...

passnu2

iTrader: (33)

yea this area is always dead....

PM member Vikdiddy as he has the Fsport springs and Struts. he can maybe help give you some info or guidance.

CAIFAN_64

iTrader: (1)

I would assume that is the same!!! both are 1" drop

ba-b4

^^^ ummm don't think so..The Sport suspension springs are linear springs and give 1/2" drop. F sport springs are progressive springs with 1" drop.

CAIFAN_64

iTrader: (1)

^^^ sorry I dont know much about springs!! whtas the difference between linear springs and progressive springs??

ba-b4

here ya go

http://www.tuninglinx.com/html/suspension-springs.html

carchitect

iTrader: (1)

I've installed the F-sport springs on an IS350 @ with with the Bilstein F-sport shocks. My IS350 is a sport pack and came with the sport suspension.

As mentioned above the sport suspension is like the OEM suspension in that it has a linear rate spring. The sport suspension is a stiffer spring and a shock that has been revalved to work in tandem with the sport springs.

The Bilstein have a separate spring perch. This makes them more prone to making noises. The OEM spring seat is welded to the body of the shock. The bilstein shock's rod (in the rear) doesn't fit the bump stop washer 100% either. We needed to make a small washer to fit it. Something bilstein should've looked into. These are just things I've noticed about them.

I run the F-sport sway bars on my vehicle and this did indeed bring the vehicle to lay flatter in the turns.

Driving impression. The progressive springs will absorb a lot more of the rough road like the ripple effect feedback than the sport springs. The sport springs will feel a lot more comfortable in the heavier bump in the roads like road patches over potholes.

During cornering its a whole different game. The F-sport springs give you more body roll since the progressive rate springs are good at doing so. Linear rate springs like the sport suspension keep the body roll to a minimum.

The sport suspension purchase would be the most expensive option but (IMO) is the better of the two. There is a reason the IS-F doesn't use progressive rate springs. The HKS hypermax III CLX which is the best coilover setup of the ISx50 is also a linear rate coilover kit. No susprises there either.

-Joe

mikez

That website in the person above your's post states that the progressive springs have a tad of body roll at first, but as the coils collasp, the spring rate increases and the spring becomes stiff under hard cornering reducing roll.

Unless you are saying that the sports spring are stiffer than F sport even when the F sports are compressed.

Zender

Ok now I am confused...

I just want to know if the ride will be better or worse with F-Sport springs ONLY vs the stock Sport suspension setup.

I am not looking at replacing anything other than the springs.

Also, one of the above posts said that the sport suspension is already .5" lower than the normal suspension... so would the F-Sport springs only lower me another .5" instead of 1"? Car seems to have a lot wheel well space and a .5" drop would be enough I think if the above is true.

Thanks

carchitect

iTrader: (1)

The following are spring rates info i've received :-

(N/mm)
OEM normal suspension IS250: F 45 R 49
OEM normal suspension IS350: F 46 R 51
OEM suspension IS250 AWD : F 46 R 49
IS-F suspension : F 86 R 74
F-sport : F 47-66 R 40-70

I don't have the specs for the sport suspension on either the 250 or the 350. I'll find out and let you know. Based of road feel, my sport suspension feels like the suspension of the IS-F. If the rate is the same as the IS-F the rate of the spring will be stiffer than the either the soft or hard spring on the progressive rate f-sport spring.

carchitect

iTrader: (1)

The ride will be more bouncier with the f-sport springs instead of the sport springs. The car will have more body roll as well. The vehicle will feel softer and it will drop another 1/2" over the sport springs on the front and 1" in the rear.

I lowered my front with billet spacers I had machined to fit the lower ball joint and knuckle. The car's suspension wasn't altered by doing so. The ride quality ramained. The car does look even front to rear wheel well gap. PM me for details.

lobuxracer

iTrader: (2)

How did you drop the upper control arm? I can see it being easy to drop the car with a ball joint spacer, but without lowering the upper control arm the same amount, you'll change the camber curves and basically re-engineer the suspension. It might be OK, it might not depending on what you're trying to achieve. Did you run the numbers through a calculator to figure the new roll center and roll couple?

carchitect

iTrader: (1)

No I didn't. I had a feeling I'd get that questioned asked by you someday when I'd open my mouth. No one else would ever thing about stuff like that. The drop in the front is only 1/2". Its a billet spacer that is precisely machined to fit into between the knuckle and lower ball joint. The upper arm does drop inwards some due to this. The front camber went from -0.6 to -0.8 and the toe required readjusting. If anything the vehicle should camber in more during high speed turns and body roll. The caster was unchanged. The roll center shouldn't be affected much since the lower arm is positioned in the exact same location like it was before the drop. Another advantage of this was not having to readjust the ride height control sensors for the beam level control. But I did have to readjust the headlights to lightup the road properly. From the driver's seat the vehicle doesn't feel any different. Only slightly lower.

VikH

iTrader: (5)

What? I find this very very hard to believe.