mrsardar

First off I currently have IS 350 with Sport PKG suspension and I was thinking about putting on the F-sport springs. I know that there is minor drop with OEM Sport PKG suspension from the standard OEM suspension. but how much more of a drop will i get when i put on the F-Sport springs?

Secondly I heard that if you are using your OEM shocks when putting on the F-Sport spring one shouldn't have to many miles on the shock. I am not sure if this is a true statement but can someone please verify if this info is correct?

If it is true, I have about 40K miles on my car and I hope i can use my stock shocks.

IS-SV

I took am in the same situation with a IS350 on sport pkg suspension at 24K miles, and I'm considering f-sport springs..... Dealer has a IS250 w/springs/shocks, I'll see if they let me drive it.

Kurtz

iTrader: (1)

The sport springs give a 1/2 inch drop in front.

The F-sports give a 1 inch drop all around.

So you'll see a 1/2 inch added front drop, and 1 inch drop rear.

NOTE: The sport springs are linear, the F-sports are progressive.

Progressive springs are an attempt to compromise between soft and firm spring rates, and as with most compromises they're not the best at either.

IS-SV

Have you had a chance to drive a IS with the F-sport springs yet?

Kurtz

iTrader: (1)

Nope... but I've driven other cars with progressive springs (my wifes supra among them) and always preferred linear ones.

I'm pretty happy with the sport suspension springs on my IS and have no plans to change em.

IS-SV

I've driven Eibach's too, I too wasn't impressed.

I'll see if I can try that IS250 w/f-sports at dealer next week.

Kurtz

iTrader: (1)

I'm about 99% sure the Eibach Prokit springs are the same springs as the F-sport ones.

See for example-
https://www.clublexus.com/forums/sus...f-sport-3.html

mrsardar

So you are saying that the f-sport spring is softer then the sport pkg spring?

IS-SV

Rightoh.

Not very likely, therefore percentage would be significantly less than 99%.

Kurtz

iTrader: (1)

They are softer some of the time and firmer some of the time.

That's the nature of non-linear springs... their rate changes.

Spring rate F-sport springs:
F-sport : F 47-66 R 40-70

(there's a range because the rate changes)

46 and 51 front/rear are the stock springs

Nobody seems to know the spring rate on the sport springs, but they're stiffer than the stock ones (while still being linear) so they'd be stiffer than the F-sports intially, and less stiff once the F-sports reach higher firmness.

VikH

iTrader: (5)

I thought the sport springs dropped 10 mm from stock? If so, then the drop from stock is 0.4". Since I do not have straight springs, I cannot comment on sportiness. I would add that the lower center of gravity with F-Sport springs will add a new variable to the equation. Lower COG can help with handling.

Why are you getting springs? Better looks? Performance? You may want to look into coilovers if you want better performance.

Kurtz

iTrader: (1)

My bad, it is indeed (by the book) exactly 10 mm, so 0.4 inches instead of 0.5 inches

mrsardar

I thought of getting the F-sport spring since i am getting the F-sport wheels and thinking it might look better and as far as performance goes i am not excepting to much out of the F-sport spring from what i already have on the car.

But i have to say the f-sport sway bars did reduce the body roll a lot.

IS-SV

Good question, especially since some of us are happy with the ride/handling compromise of the OEM sport suspension.

In my opinion, the goals with the F-sport springs is the following:

1. slightly lower ride height, for better appearance especially w/19" wheels
2. slightly improved handling
3. minimal impact on ride quality, or maintaining decent ride quality of OEM sport suspension.

Feel free to give feedback w/F-sport springs on items above.

Coilovers are more expensive, will give the lower look with the clearance problems that come with a very low ride height, improve handling, and cause more ride deterioration.

IS-SV

From the Edmunds review of IS250 modded w/F-Sport suspension, etc.

"We couldn't believe it either. But the best part is the F Sport's highway ride. If you bought an IS-F, you're probably a regular at the chiropractor by now, but this IS actually rides well, and there's even less impact harshness than in a stock IS 250.

Credit goes to Bilstein for the impressive all-round tuning of the F Sport dampers. They are wonderfully matched with the shorter, progressive-rate springs (1 inch shorter in front; 0.7 inch shorter in the rear). Since the 2008 Lexus IS 250's stock springs are not progressive, the springs are initially more compliant, which helps deliver that silky ride, but they firm up nicely deeper in their travel and keep the sedan off its bump stops."